chore: vendor clipboard into go package

packages/tui/clipboard/.github/FUNDING.yml

@@ -0,0 +1,12 @@
+# These are supported funding model platforms
+
+github: [changkun] # Replace with up to 4 GitHub Sponsors-enabled usernames e.g., [user1, user2]
+patreon: # Replace with a single Patreon username
+open_collective: # Replace with a single Open Collective username
+ko_fi: # Replace with a single Ko-fi username
+tidelift: # Replace with a single Tidelift platform-name/package-name e.g., npm/babel
+community_bridge: # Replace with a single Community Bridge project-name e.g., cloud-foundry
+liberapay: # Replace with a single Liberapay username
+issuehunt: # Replace with a single IssueHunt username
+otechie: # Replace with a single Otechie username
+custom: # Replace with up to 4 custom sponsorship URLs e.g., ['link1', 'link2']

packages/tui/clipboard/.github/workflows/clipboard.yml

@@ -0,0 +1,71 @@
+# Copyright 2021 The golang.design Initiative Authors.
+# All rights reserved. Use of this source code is governed
+# by a MIT license that can be found in the LICENSE file.
+#
+# Written by Changkun Ou <changkun.de>
+
+name: clipboard
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  platform_test:
+    env:
+      DISPLAY: ':0.0'
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        go: ['1.24.x']
+    steps:
+    - name: Install and run dependencies (xvfb libx11-dev)
+      if: ${{ runner.os == 'Linux' }}
+      run: |
+        sudo apt update
+        sudo apt install -y xvfb libx11-dev x11-utils libegl1-mesa-dev libgles2-mesa-dev
+        Xvfb :0 -screen 0 1024x768x24 > /dev/null 2>&1 &
+        # Wait for Xvfb
+        MAX_ATTEMPTS=120 # About 60 seconds
+        COUNT=0
+        echo -n "Waiting for Xvfb to be ready..."
+        while ! xdpyinfo -display "${DISPLAY}" >/dev/null 2>&1; do
+          echo -n "."
+          sleep 0.50s
+          COUNT=$(( COUNT + 1 ))
+          if [ "${COUNT}" -ge "${MAX_ATTEMPTS}" ]; then
+            echo "  Gave up waiting for X server on ${DISPLAY}"
+            exit 1
+          fi
+        done
+        echo "Done - Xvfb is ready!"
+
+    - uses: actions/checkout@v2
+    - uses: actions/setup-go@v2
+      with:
+        stable: 'false'
+        go-version: ${{ matrix.go }}
+
+    - name: Build (${{ matrix.go }})
+      run: |
+        go build -o gclip cmd/gclip/main.go
+        go build -o gclip-gui cmd/gclip-gui/main.go
+
+    - name: Run Tests with CGO_ENABLED=1 (${{ matrix.go }})
+      if: ${{ runner.os == 'Linux' || runner.os == 'macOS'}}
+      run: |
+        CGO_ENABLED=1 go test -v -covermode=atomic .
+
+    - name: Run Tests with CGO_ENABLED=0 (${{ matrix.go }})
+      if: ${{ runner.os == 'Linux' || runner.os == 'macOS'}}
+      run: |
+        CGO_ENABLED=0 go test -v -covermode=atomic .
+
+    - name: Run Tests on Windows (${{ matrix.go }})
+      if: ${{ runner.os == 'Windows'}}
+      run: |
+        go test -v -covermode=atomic .

packages/tui/clipboard/.gitignore

@@ -0,0 +1,15 @@
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+
+# Test binary, built with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Dependency directories (remove the comment below to include it)
+# vendor/

packages/tui/clipboard/Dockerfile

@@ -0,0 +1,13 @@
+# Copyright 2021 The golang.design Initiative Authors.
+# All rights reserved. Use of this source code is governed
+# by a MIT license that can be found in the LICENSE file.
+#
+# Written by Changkun Ou <changkun.de>
+
+FROM golang:1.24
+RUN apt-get update && apt-get install -y \
+      xvfb libx11-dev libegl1-mesa-dev libgles2-mesa-dev \
+    && apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
+WORKDIR /app
+COPY . .
+CMD [ "sh", "-c", "./tests/test-docker.sh" ]

packages/tui/clipboard/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2021 Changkun Ou <contact@changkun.de>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

packages/tui/clipboard/README.md

@@ -0,0 +1,162 @@
+# clipboard [![PkgGoDev](https://pkg.go.dev/badge/golang.design/x/clipboard)](https://pkg.go.dev/golang.design/x/clipboard) ![](https://changkun.de/urlstat?mode=github&repo=golang-design/clipboard) ![clipboard](https://github.com/golang-design/clipboard/workflows/clipboard/badge.svg?branch=main)
+
+Cross platform (macOS/Linux/Windows/Android/iOS) clipboard package in Go
+
+```go
+import "golang.design/x/clipboard"
+```
+
+## Features
+
+- Cross platform supports: **macOS, Linux (X11), Windows, iOS, and Android**
+- Copy/paste UTF-8 text
+- Copy/paste PNG encoded images (Desktop-only)
+- Command `gclip` as a demo application
+- Mobile app `gclip-gui` as a demo application
+
+## API Usage
+
+Package clipboard provides cross platform clipboard access and supports
+macOS/Linux/Windows/Android/iOS platform. Before interacting with the
+clipboard, one must call Init to assert if it is possible to use this
+package:
+
+```go
+// Init returns an error if the package is not ready for use.
+err := clipboard.Init()
+if err != nil {
+      panic(err)
+}
+```
+
+The most common operations are `Read` and `Write`. To use them:
+
+```go
+// write/read text format data of the clipboard, and
+// the byte buffer regarding the text are UTF8 encoded.
+clipboard.Write(clipboard.FmtText, []byte("text data"))
+clipboard.Read(clipboard.FmtText)
+
+// write/read image format data of the clipboard, and
+// the byte buffer regarding the image are PNG encoded.
+clipboard.Write(clipboard.FmtImage, []byte("image data"))
+clipboard.Read(clipboard.FmtImage)
+```
+
+Note that read/write regarding image format assumes that the bytes are
+PNG encoded since it serves the alpha blending purpose that might be
+used in other graphical software.
+
+In addition, `clipboard.Write` returns a channel that can receive an
+empty struct as a signal, which indicates the corresponding write call
+to the clipboard is outdated, meaning the clipboard has been overwritten
+by others and the previously written data is lost. For instance:
+
+```go
+changed := clipboard.Write(clipboard.FmtText, []byte("text data"))
+
+select {
+case <-changed:
+      println(`"text data" is no longer available from clipboard.`)
+}
+```
+
+You can ignore the returning channel if you don't need this type of
+notification. Furthermore, when you need more than just knowing whether
+clipboard data is changed, use the watcher API:
+
+```go
+ch := clipboard.Watch(context.TODO(), clipboard.FmtText)
+for data := range ch {
+      // print out clipboard data whenever it is changed
+      println(string(data))
+}
+```
+
+## Demos
+
+- A command line tool `gclip` for command line clipboard accesses, see document [here](./cmd/gclip/README.md).
+- A GUI application `gclip-gui` for functionality verifications on mobile systems, see a document [here](./cmd/gclip-gui/README.md).
+
+
+## Command Usage
+
+`gclip` command offers the ability to interact with the system clipboard
+from the shell. To install:
+
+```bash
+$ go install golang.design/x/clipboard/cmd/gclip@latest
+```
+
+```bash
+$ gclip
+gclip is a command that provides clipboard interaction.
+
+usage: gclip [-copy|-paste] [-f <file>]
+
+options:
+  -copy
+        copy data to clipboard
+  -f string
+        source or destination to a given file path
+  -paste
+        paste data from clipboard
+
+examples:
+gclip -paste                    paste from clipboard and prints the content
+gclip -paste -f x.txt           paste from clipboard and save as text to x.txt
+gclip -paste -f x.png           paste from clipboard and save as image to x.png
+
+cat x.txt | gclip -copy         copy content from x.txt to clipboard
+gclip -copy -f x.txt            copy content from x.txt to clipboard
+gclip -copy -f x.png            copy x.png as image data to clipboard
+```
+
+If `-copy` is used, the command will exit when the data is no longer
+available from the clipboard. You can always send the command to the
+background using a shell `&` operator, for example:
+
+```bash
+$ cat x.txt | gclip -copy &
+```
+
+## Platform Specific Details
+
+This package spent efforts to provide cross platform abstraction regarding
+accessing system clipboards, but here are a few details you might need to know.
+
+### Dependency
+
+- macOS: require Cgo, no dependency
+ - Linux: require X11 dev package. For instance, install `libx11-dev` or `xorg-dev` or `libX11-devel` to access X window system.
+   Wayland sessions are currently unsupported; running under Wayland
+   typically requires an XWayland bridge and `DISPLAY` to be set.
+- Windows: no Cgo, no dependency
+- iOS/Android: collaborate with [`gomobile`](https://golang.org/x/mobile)
+
+### Screenshot
+
+In general, when you need test your implementation regarding images,
+There are system level shortcuts to put screenshot image into your system clipboard:
+
+- On macOS, use `Ctrl+Shift+Cmd+4`
+- On Linux/Ubuntu, use `Ctrl+Shift+PrintScreen`
+- On Windows, use `Shift+Win+s`
+
+As described in the API documentation, the package supports read/write
+UTF8 encoded plain text or PNG encoded image data. Thus,
+the other types of data are not supported yet, i.e. undefined behavior.
+
+## Who is using this package?
+
+The main purpose of building this package is to support the
+[midgard](https://changkun.de/s/midgard) project, which offers
+clipboard-based features like universal clipboard service that syncs
+clipboard content across multiple systems, allocating public accessible
+for clipboard content, etc.
+
+To know more projects, check our [wiki](https://github.com/golang-design/clipboard/wiki) page.
+
+## License
+
+MIT | &copy; 2021 The golang.design Initiative Authors, written by [Changkun Ou](https://changkun.de).

packages/tui/clipboard/clipboard.go

@@ -0,0 +1,155 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+/*
+Package clipboard provides cross platform clipboard access and supports
+macOS/Linux/Windows/Android/iOS platform. Before interacting with the
+clipboard, one must call Init to assert if it is possible to use this
+package:
+
+	err := clipboard.Init()
+	if err != nil {
+		panic(err)
+	}
+
+The most common operations are `Read` and `Write`. To use them:
+
+	// write/read text format data of the clipboard, and
+	// the byte buffer regarding the text are UTF8 encoded.
+	clipboard.Write(clipboard.FmtText, []byte("text data"))
+	clipboard.Read(clipboard.FmtText)
+
+	// write/read image format data of the clipboard, and
+	// the byte buffer regarding the image are PNG encoded.
+	clipboard.Write(clipboard.FmtImage, []byte("image data"))
+	clipboard.Read(clipboard.FmtImage)
+
+Note that read/write regarding image format assumes that the bytes are
+PNG encoded since it serves the alpha blending purpose that might be
+used in other graphical software.
+
+In addition, `clipboard.Write` returns a channel that can receive an
+empty struct as a signal, which indicates the corresponding write call
+to the clipboard is outdated, meaning the clipboard has been overwritten
+by others and the previously written data is lost. For instance:
+
+	changed := clipboard.Write(clipboard.FmtText, []byte("text data"))
+
+	select {
+	case <-changed:
+		println(`"text data" is no longer available from clipboard.`)
+	}
+
+You can ignore the returning channel if you don't need this type of
+notification. Furthermore, when you need more than just knowing whether
+clipboard data is changed, use the watcher API:
+
+	ch := clipboard.Watch(context.TODO(), clipboard.FmtText)
+	for data := range ch {
+		// print out clipboard data whenever it is changed
+		println(string(data))
+	}
+*/
+package clipboard // import "golang.design/x/clipboard"
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"sync"
+)
+
+var (
+	// activate only for running tests.
+	debug          = false
+	errUnavailable = errors.New("clipboard unavailable")
+	errUnsupported = errors.New("unsupported format")
+	errNoCgo       = errors.New("clipboard: cannot use when CGO_ENABLED=0")
+)
+
+// Format represents the format of clipboard data.
+type Format int
+
+// All sorts of supported clipboard data
+const (
+	// FmtText indicates plain text clipboard format
+	FmtText Format = iota
+	// FmtImage indicates image/png clipboard format
+	FmtImage
+)
+
+var (
+	// Due to the limitation on operating systems (such as darwin),
+	// concurrent read can even cause panic, use a global lock to
+	// guarantee one read at a time.
+	lock      = sync.Mutex{}
+	initOnce  sync.Once
+	initError error
+)
+
+// Init initializes the clipboard package. It returns an error
+// if the clipboard is not available to use. This may happen if the
+// target system lacks required dependency, such as libx11-dev in X11
+// environment. For example,
+//
+//	err := clipboard.Init()
+//	if err != nil {
+//		panic(err)
+//	}
+//
+// If Init returns an error, any subsequent Read/Write/Watch call
+// may result in an unrecoverable panic.
+func Init() error {
+	initOnce.Do(func() {
+		initError = initialize()
+	})
+	return initError
+}
+
+// Read returns a chunk of bytes of the clipboard data if it presents
+// in the desired format t presents. Otherwise, it returns nil.
+func Read(t Format) []byte {
+	lock.Lock()
+	defer lock.Unlock()
+
+	buf, err := read(t)
+	if err != nil {
+		if debug {
+			fmt.Fprintf(os.Stderr, "read clipboard err: %v\n", err)
+		}
+		return nil
+	}
+	return buf
+}
+
+// Write writes a given buffer to the clipboard in a specified format.
+// Write returned a receive-only channel can receive an empty struct
+// as a signal, which indicates the clipboard has been overwritten from
+// this write.
+// If format t indicates an image, then the given buf assumes
+// the image data is PNG encoded.
+func Write(t Format, buf []byte) <-chan struct{} {
+	lock.Lock()
+	defer lock.Unlock()
+
+	changed, err := write(t, buf)
+	if err != nil {
+		if debug {
+			fmt.Fprintf(os.Stderr, "write to clipboard err: %v\n", err)
+		}
+		return nil
+	}
+	return changed
+}
+
+// Watch returns a receive-only channel that received the clipboard data
+// whenever any change of clipboard data in the desired format happens.
+//
+// The returned channel will be closed if the given context is canceled.
+func Watch(ctx context.Context, t Format) <-chan []byte {
+	return watch(ctx, t)
+}

packages/tui/clipboard/clipboard_android.c

@@ -0,0 +1,80 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build android
+
+#include <android/log.h>
+#include <jni.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define LOG_FATAL(...) __android_log_print(ANDROID_LOG_FATAL, \
+    "GOLANG.DESIGN/X/CLIPBOARD", __VA_ARGS__)
+
+static jmethodID find_method(JNIEnv *env, jclass clazz, const char *name, const char *sig) {
+	jmethodID m = (*env)->GetMethodID(env, clazz, name, sig);
+	if (m == 0) {
+		(*env)->ExceptionClear(env);
+		LOG_FATAL("cannot find method %s %s", name, sig);
+		return 0;
+	}
+	return m;
+}
+
+jobject get_clipboard(uintptr_t jni_env, uintptr_t ctx) {
+	JNIEnv *env = (JNIEnv*)jni_env;
+	jclass ctxClass = (*env)->GetObjectClass(env, (jobject)ctx);
+	jmethodID getSystemService = find_method(env, ctxClass, "getSystemService", "(Ljava/lang/String;)Ljava/lang/Object;");
+
+	jstring service = (*env)->NewStringUTF(env, "clipboard");
+	jobject ret = (jobject)(*env)->CallObjectMethod(env, (jobject)ctx, getSystemService, service);
+	jthrowable err = (*env)->ExceptionOccurred(env);
+
+	if (err != NULL) {
+		LOG_FATAL("cannot find clipboard");
+		(*env)->ExceptionClear(env);
+		return NULL;
+	}
+	return ret;
+}
+
+char *clipboard_read_string(uintptr_t java_vm, uintptr_t jni_env, uintptr_t ctx) {
+	JNIEnv *env = (JNIEnv*)jni_env;
+	jobject mgr = get_clipboard(jni_env, ctx);
+	if (mgr == NULL) {
+		return NULL;
+	}
+
+	jclass mgrClass = (*env)->GetObjectClass(env, mgr);
+	jmethodID getText = find_method(env, mgrClass, "getText", "()Ljava/lang/CharSequence;");
+
+	jobject content = (jstring)(*env)->CallObjectMethod(env, mgr, getText);
+	if (content == NULL) {
+		return NULL;
+	}
+
+	jclass clzCharSequence = (*env)->GetObjectClass(env, content);
+	jmethodID toString = (*env)->GetMethodID(env, clzCharSequence, "toString", "()Ljava/lang/String;");
+	jobject s = (*env)->CallObjectMethod(env, content, toString);
+
+	const char *chars = (*env)->GetStringUTFChars(env, s, NULL);
+	char *copy = strdup(chars);
+	(*env)->ReleaseStringUTFChars(env, s, chars);
+	return copy;
+}
+
+void clipboard_write_string(uintptr_t java_vm, uintptr_t jni_env, uintptr_t ctx, char *str) {
+	JNIEnv *env = (JNIEnv*)jni_env;
+	jobject mgr = get_clipboard(jni_env, ctx);
+	if (mgr == NULL) {
+		return;
+	}
+
+	jclass mgrClass = (*env)->GetObjectClass(env, mgr);
+	jmethodID setText = find_method(env, mgrClass, "setText", "(Ljava/lang/CharSequence;)V");
+
+	(*env)->CallVoidMethod(env, mgr, setText, (*env)->NewStringUTF(env, str));
+}

packages/tui/clipboard/clipboard_android.go

@@ -0,0 +1,102 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build android
+
+package clipboard
+
+/*
+#cgo LDFLAGS: -landroid -llog
+
+#include <stdlib.h>
+char *clipboard_read_string(uintptr_t java_vm, uintptr_t jni_env, uintptr_t ctx);
+void clipboard_write_string(uintptr_t java_vm, uintptr_t jni_env, uintptr_t ctx, char *str);
+
+*/
+import "C"
+import (
+	"bytes"
+	"context"
+	"time"
+	"unsafe"
+
+	"golang.org/x/mobile/app"
+)
+
+func initialize() error { return nil }
+
+func read(t Format) (buf []byte, err error) {
+	switch t {
+	case FmtText:
+		s := ""
+		if err := app.RunOnJVM(func(vm, env, ctx uintptr) error {
+			cs := C.clipboard_read_string(C.uintptr_t(vm), C.uintptr_t(env), C.uintptr_t(ctx))
+			if cs == nil {
+				return nil
+			}
+
+			s = C.GoString(cs)
+			C.free(unsafe.Pointer(cs))
+			return nil
+		}); err != nil {
+			return nil, err
+		}
+		return []byte(s), nil
+	case FmtImage:
+		return nil, errUnsupported
+	default:
+		return nil, errUnsupported
+	}
+}
+
+// write writes the given data to clipboard and
+// returns true if success or false if failed.
+func write(t Format, buf []byte) (<-chan struct{}, error) {
+	done := make(chan struct{}, 1)
+	switch t {
+	case FmtText:
+		cs := C.CString(string(buf))
+		defer C.free(unsafe.Pointer(cs))
+
+		if err := app.RunOnJVM(func(vm, env, ctx uintptr) error {
+			C.clipboard_write_string(C.uintptr_t(vm), C.uintptr_t(env), C.uintptr_t(ctx), cs)
+			done <- struct{}{}
+			return nil
+		}); err != nil {
+			return nil, err
+		}
+		return done, nil
+	case FmtImage:
+		return nil, errUnsupported
+	default:
+		return nil, errUnsupported
+	}
+}
+
+func watch(ctx context.Context, t Format) <-chan []byte {
+	recv := make(chan []byte, 1)
+	ti := time.NewTicker(time.Second)
+	last := Read(t)
+	go func() {
+		for {
+			select {
+			case <-ctx.Done():
+				close(recv)
+				return
+			case <-ti.C:
+				b := Read(t)
+				if b == nil {
+					continue
+				}
+				if bytes.Compare(last, b) != 0 {
+					recv <- b
+					last = b
+				}
+			}
+		}
+	}()
+	return recv
+}

packages/tui/clipboard/clipboard_darwin.go

@@ -0,0 +1,266 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build darwin && !ios
+
+package clipboard
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	lastChangeCount int64
+	changeCountMu   sync.Mutex
+)
+
+func initialize() error { return nil }
+
+func read(t Format) (buf []byte, err error) {
+	switch t {
+	case FmtText:
+		return readText()
+	case FmtImage:
+		return readImage()
+	default:
+		return nil, errUnsupported
+	}
+}
+
+func readText() ([]byte, error) {
+	// Check if clipboard contains string data
+	checkScript := `
+	try
+		set clipboardTypes to (clipboard info)
+		repeat with aType in clipboardTypes
+			if (first item of aType) is string then
+				return "hastext"
+			end if
+		end repeat
+		return "notext"
+	on error
+		return "error"
+	end try
+	`
+
+	cmd := exec.Command("osascript", "-e", checkScript)
+	checkOut, err := cmd.Output()
+	if err != nil {
+		return nil, errUnavailable
+	}
+
+	checkOut = bytes.TrimSpace(checkOut)
+	if !bytes.Equal(checkOut, []byte("hastext")) {
+		return nil, errUnavailable
+	}
+
+	// Now get the actual text
+	cmd = exec.Command("osascript", "-e", "get the clipboard")
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, errUnavailable
+	}
+	// Remove trailing newline that osascript adds
+	out = bytes.TrimSuffix(out, []byte("\n"))
+
+	// If clipboard was set to empty string, return nil
+	if len(out) == 0 {
+		return nil, nil
+	}
+	return out, nil
+}
+func readImage() ([]byte, error) {
+	// AppleScript to read image data from clipboard as base64
+	script := `
+	try
+		set theData to the clipboard as «class PNGf»
+		return theData
+	on error
+		return ""
+	end try
+	`
+
+	cmd := exec.Command("osascript", "-e", script)
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, errUnavailable
+	}
+
+	// Check if we got any data
+	out = bytes.TrimSpace(out)
+	if len(out) == 0 {
+		return nil, errUnavailable
+	}
+
+	// The output is in hex format (e.g., «data PNGf89504E...»)
+	// We need to extract and convert it
+	outStr := string(out)
+	if !strings.HasPrefix(outStr, "«data PNGf") || !strings.HasSuffix(outStr, "»") {
+		return nil, errUnavailable
+	}
+
+	// Extract hex data
+	hexData := strings.TrimPrefix(outStr, "«data PNGf")
+	hexData = strings.TrimSuffix(hexData, "»")
+
+	// Convert hex to bytes
+	buf := make([]byte, len(hexData)/2)
+	for i := 0; i < len(hexData); i += 2 {
+		b, err := strconv.ParseUint(hexData[i:i+2], 16, 8)
+		if err != nil {
+			return nil, errUnavailable
+		}
+		buf[i/2] = byte(b)
+	}
+
+	return buf, nil
+}
+
+// write writes the given data to clipboard and
+// returns true if success or false if failed.
+func write(t Format, buf []byte) (<-chan struct{}, error) {
+	var err error
+	switch t {
+	case FmtText:
+		err = writeText(buf)
+	case FmtImage:
+		err = writeImage(buf)
+	default:
+		return nil, errUnsupported
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	// Update change count
+	changeCountMu.Lock()
+	lastChangeCount++
+	currentCount := lastChangeCount
+	changeCountMu.Unlock()
+
+	// use unbuffered channel to prevent goroutine leak
+	changed := make(chan struct{}, 1)
+	go func() {
+		for {
+			time.Sleep(time.Second)
+			changeCountMu.Lock()
+			if lastChangeCount != currentCount {
+				changeCountMu.Unlock()
+				changed <- struct{}{}
+				close(changed)
+				return
+			}
+			changeCountMu.Unlock()
+		}
+	}()
+	return changed, nil
+}
+
+func writeText(buf []byte) error {
+	if len(buf) == 0 {
+		// Clear clipboard
+		script := `set the clipboard to ""`
+		cmd := exec.Command("osascript", "-e", script)
+		if err := cmd.Run(); err != nil {
+			return errUnavailable
+		}
+		return nil
+	}
+
+	// Escape the text for AppleScript
+	text := string(buf)
+	text = strings.ReplaceAll(text, "\\", "\\\\")
+	text = strings.ReplaceAll(text, "\"", "\\\"")
+
+	script := fmt.Sprintf(`set the clipboard to "%s"`, text)
+	cmd := exec.Command("osascript", "-e", script)
+	if err := cmd.Run(); err != nil {
+		return errUnavailable
+	}
+	return nil
+}
+func writeImage(buf []byte) error {
+	if len(buf) == 0 {
+		// Clear clipboard
+		script := `set the clipboard to ""`
+		cmd := exec.Command("osascript", "-e", script)
+		if err := cmd.Run(); err != nil {
+			return errUnavailable
+		}
+		return nil
+	}
+
+	// Create a temporary file to store the PNG data
+	tmpFile, err := os.CreateTemp("", "clipboard*.png")
+	if err != nil {
+		return errUnavailable
+	}
+	defer os.Remove(tmpFile.Name())
+
+	if _, err := tmpFile.Write(buf); err != nil {
+		tmpFile.Close()
+		return errUnavailable
+	}
+	tmpFile.Close()
+
+	// Use osascript to set clipboard to the image file
+	script := fmt.Sprintf(`
+	set theFile to POSIX file "%s"
+	set theImage to read theFile as «class PNGf»
+	set the clipboard to theImage
+	`, tmpFile.Name())
+
+	cmd := exec.Command("osascript", "-e", script)
+	if err := cmd.Run(); err != nil {
+		return errUnavailable
+	}
+	return nil
+}
+func watch(ctx context.Context, t Format) <-chan []byte {
+	recv := make(chan []byte, 1)
+	ti := time.NewTicker(time.Second)
+
+	// Get initial clipboard content
+	var lastContent []byte
+	if b := Read(t); b != nil {
+		lastContent = make([]byte, len(b))
+		copy(lastContent, b)
+	}
+
+	go func() {
+		defer close(recv)
+		defer ti.Stop()
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ti.C:
+				b := Read(t)
+				if b == nil {
+					continue
+				}
+
+				// Check if content changed
+				if !bytes.Equal(lastContent, b) {
+					recv <- b
+					lastContent = make([]byte, len(b))
+					copy(lastContent, b)
+				}
+			}
+		}
+	}()
+	return recv
+}

packages/tui/clipboard/clipboard_ios.go

@@ -0,0 +1,80 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build ios
+
+package clipboard
+
+/*
+#cgo CFLAGS: -x objective-c
+#cgo LDFLAGS: -framework Foundation -framework UIKit -framework MobileCoreServices
+
+#import <stdlib.h>
+void clipboard_write_string(char *s);
+char *clipboard_read_string();
+*/
+import "C"
+import (
+	"bytes"
+	"context"
+	"time"
+	"unsafe"
+)
+
+func initialize() error { return nil }
+
+func read(t Format) (buf []byte, err error) {
+	switch t {
+	case FmtText:
+		return []byte(C.GoString(C.clipboard_read_string())), nil
+	case FmtImage:
+		return nil, errUnsupported
+	default:
+		return nil, errUnsupported
+	}
+}
+
+// SetContent sets the clipboard content for iOS
+func write(t Format, buf []byte) (<-chan struct{}, error) {
+	done := make(chan struct{}, 1)
+	switch t {
+	case FmtText:
+		cs := C.CString(string(buf))
+		defer C.free(unsafe.Pointer(cs))
+
+		C.clipboard_write_string(cs)
+		return done, nil
+	case FmtImage:
+		return nil, errUnsupported
+	default:
+		return nil, errUnsupported
+	}
+}
+
+func watch(ctx context.Context, t Format) <-chan []byte {
+	recv := make(chan []byte, 1)
+	ti := time.NewTicker(time.Second)
+	last := Read(t)
+	go func() {
+		for {
+			select {
+			case <-ctx.Done():
+				close(recv)
+				return
+			case <-ti.C:
+				b := Read(t)
+				if b == nil {
+					continue
+				}
+				if bytes.Compare(last, b) != 0 {
+					recv <- b
+					last = b
+				}
+			}
+		}
+	}()
+	return recv
+}

packages/tui/clipboard/clipboard_ios.m

@@ -0,0 +1,20 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build ios
+
+#import <UIKit/UIKit.h>
+#import <MobileCoreServices/MobileCoreServices.h>
+
+void clipboard_write_string(char *s) {
+    NSString *value = [NSString stringWithUTF8String:s];
+    [[UIPasteboard generalPasteboard] setString:value];
+}
+
+char *clipboard_read_string() {
+    NSString *str = [[UIPasteboard generalPasteboard] string];
+    return (char *)[str UTF8String];
+}

packages/tui/clipboard/clipboard_linux.go

@@ -0,0 +1,277 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build linux && !android
+
+package clipboard
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	// Clipboard tools in order of preference
+	clipboardTools = []struct {
+		name      string
+		readCmd   []string
+		writeCmd  []string
+		readImg   []string
+		writeImg  []string
+		available bool
+	}{
+		{
+			name:     "xclip",
+			readCmd:  []string{"xclip", "-selection", "clipboard", "-o"},
+			writeCmd: []string{"xclip", "-selection", "clipboard"},
+			readImg:  []string{"xclip", "-selection", "clipboard", "-t", "image/png", "-o"},
+			writeImg: []string{"xclip", "-selection", "clipboard", "-t", "image/png"},
+		},
+		{
+			name:     "xsel",
+			readCmd:  []string{"xsel", "--clipboard", "--output"},
+			writeCmd: []string{"xsel", "--clipboard", "--input"},
+			readImg:  []string{"xsel", "--clipboard", "--output"},
+			writeImg: []string{"xsel", "--clipboard", "--input"},
+		},
+		{
+			name:     "wl-clipboard",
+			readCmd:  []string{"wl-paste", "-n"},
+			writeCmd: []string{"wl-copy"},
+			readImg:  []string{"wl-paste", "-t", "image/png", "-n"},
+			writeImg: []string{"wl-copy", "-t", "image/png"},
+		},
+	}
+
+	selectedTool   int = -1
+	toolMutex      sync.Mutex
+	lastChangeTime time.Time
+	changeTimeMu   sync.Mutex
+)
+
+func initialize() error {
+	toolMutex.Lock()
+	defer toolMutex.Unlock()
+
+	if selectedTool >= 0 {
+		return nil // Already initialized
+	}
+
+	// Check which clipboard tool is available
+	for i, tool := range clipboardTools {
+		cmd := exec.Command("which", tool.name)
+		if err := cmd.Run(); err == nil {
+			clipboardTools[i].available = true
+			if selectedTool < 0 {
+				selectedTool = i
+			}
+		}
+	}
+
+	if selectedTool < 0 {
+		return fmt.Errorf(`%w: No clipboard utility found. Install one of the following:
+
+For X11 systems:
+	apt install -y xclip
+	# or
+	apt install -y xsel
+
+For Wayland systems:
+	apt install -y wl-clipboard
+
+If running in a headless environment, you may also need:
+	apt install -y xvfb
+	# and run:
+	Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1 &
+	export DISPLAY=:99.0`, errUnavailable)
+	}
+
+	return nil
+}
+
+func read(t Format) (buf []byte, err error) {
+	toolMutex.Lock()
+	tool := clipboardTools[selectedTool]
+	toolMutex.Unlock()
+
+	switch t {
+	case FmtText:
+		return readText(tool)
+	case FmtImage:
+		return readImage(tool)
+	default:
+		return nil, errUnsupported
+	}
+}
+
+func readText(tool struct {
+	name      string
+	readCmd   []string
+	writeCmd  []string
+	readImg   []string
+	writeImg  []string
+	available bool
+}) ([]byte, error) {
+	// First check if clipboard contains text
+	cmd := exec.Command(tool.readCmd[0], tool.readCmd[1:]...)
+	out, err := cmd.Output()
+	if err != nil {
+		// Check if it's because clipboard contains non-text data
+		if tool.name == "xclip" {
+			// xclip returns error when clipboard doesn't contain requested type
+			checkCmd := exec.Command("xclip", "-selection", "clipboard", "-t", "TARGETS", "-o")
+			targets, _ := checkCmd.Output()
+			if bytes.Contains(targets, []byte("image/png")) && !bytes.Contains(targets, []byte("UTF8_STRING")) {
+				return nil, errUnavailable
+			}
+		}
+		return nil, errUnavailable
+	}
+
+	return out, nil
+}
+
+func readImage(tool struct {
+	name      string
+	readCmd   []string
+	writeCmd  []string
+	readImg   []string
+	writeImg  []string
+	available bool
+}) ([]byte, error) {
+	if tool.name == "xsel" {
+		// xsel doesn't support image types well, return error
+		return nil, errUnavailable
+	}
+
+	cmd := exec.Command(tool.readImg[0], tool.readImg[1:]...)
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, errUnavailable
+	}
+
+	// Verify it's PNG data
+	if len(out) < 8 || !bytes.Equal(out[:8], []byte{0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A}) {
+		return nil, errUnavailable
+	}
+
+	return out, nil
+}
+
+func write(t Format, buf []byte) (<-chan struct{}, error) {
+	toolMutex.Lock()
+	tool := clipboardTools[selectedTool]
+	toolMutex.Unlock()
+
+	var cmd *exec.Cmd
+	switch t {
+	case FmtText:
+		if len(buf) == 0 {
+			// Write empty string
+			cmd = exec.Command(tool.writeCmd[0], tool.writeCmd[1:]...)
+			cmd.Stdin = bytes.NewReader([]byte{})
+		} else {
+			cmd = exec.Command(tool.writeCmd[0], tool.writeCmd[1:]...)
+			cmd.Stdin = bytes.NewReader(buf)
+		}
+	case FmtImage:
+		if tool.name == "xsel" {
+			// xsel doesn't support image types well
+			return nil, errUnavailable
+		}
+		if len(buf) == 0 {
+			// Clear clipboard
+			cmd = exec.Command(tool.writeCmd[0], tool.writeCmd[1:]...)
+			cmd.Stdin = bytes.NewReader([]byte{})
+		} else {
+			cmd = exec.Command(tool.writeImg[0], tool.writeImg[1:]...)
+			cmd.Stdin = bytes.NewReader(buf)
+		}
+	default:
+		return nil, errUnsupported
+	}
+
+	if err := cmd.Run(); err != nil {
+		return nil, errUnavailable
+	}
+
+	// Update change time
+	changeTimeMu.Lock()
+	lastChangeTime = time.Now()
+	currentTime := lastChangeTime
+	changeTimeMu.Unlock()
+
+	// Create change notification channel
+	changed := make(chan struct{}, 1)
+	go func() {
+		for {
+			time.Sleep(time.Second)
+			changeTimeMu.Lock()
+			if !lastChangeTime.Equal(currentTime) {
+				changeTimeMu.Unlock()
+				changed <- struct{}{}
+				close(changed)
+				return
+			}
+			changeTimeMu.Unlock()
+		}
+	}()
+
+	return changed, nil
+}
+
+func watch(ctx context.Context, t Format) <-chan []byte {
+	recv := make(chan []byte, 1)
+	ti := time.NewTicker(time.Second)
+
+	// Get initial clipboard content
+	var lastContent []byte
+	if b := Read(t); b != nil {
+		lastContent = make([]byte, len(b))
+		copy(lastContent, b)
+	}
+
+	go func() {
+		defer close(recv)
+		defer ti.Stop()
+
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ti.C:
+				b := Read(t)
+				if b == nil {
+					continue
+				}
+
+				// Check if content changed
+				if !bytes.Equal(lastContent, b) {
+					recv <- b
+					lastContent = make([]byte, len(b))
+					copy(lastContent, b)
+				}
+			}
+		}
+	}()
+	return recv
+}
+
+// Helper function to check clipboard content type for xclip
+func getClipboardTargets() []string {
+	cmd := exec.Command("xclip", "-selection", "clipboard", "-t", "TARGETS", "-o")
+	out, err := cmd.Output()
+	if err != nil {
+		return nil
+	}
+	return strings.Split(string(out), "\n")
+}

packages/tui/clipboard/clipboard_nocgo.go

@@ -0,0 +1,25 @@
+//go:build !windows && !darwin && !linux && !cgo
+
+package clipboard
+
+import "context"
+
+func initialize() error {
+	return errNoCgo
+}
+
+func read(t Format) (buf []byte, err error) {
+	panic("clipboard: cannot use when CGO_ENABLED=0")
+}
+
+func readc(t string) ([]byte, error) {
+	panic("clipboard: cannot use when CGO_ENABLED=0")
+}
+
+func write(t Format, buf []byte) (<-chan struct{}, error) {
+	panic("clipboard: cannot use when CGO_ENABLED=0")
+}
+
+func watch(ctx context.Context, t Format) <-chan []byte {
+	panic("clipboard: cannot use when CGO_ENABLED=0")
+}

packages/tui/clipboard/clipboard_test.go

@@ -0,0 +1,336 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+package clipboard_test
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"image/color"
+	"image/png"
+	"os"
+	"reflect"
+	"runtime"
+	"testing"
+	"time"
+
+	"golang.design/x/clipboard"
+)
+
+func init() {
+	clipboard.Debug = true
+}
+
+func TestClipboardInit(t *testing.T) {
+	t.Run("no-cgo", func(t *testing.T) {
+		if val, ok := os.LookupEnv("CGO_ENABLED"); !ok || val != "0" {
+			t.Skip("CGO_ENABLED is set to 1")
+		}
+		if runtime.GOOS == "windows" {
+			t.Skip("Windows does not need to check for cgo")
+		}
+
+		if err := clipboard.Init(); !errors.Is(err, clipboard.ErrCgoDisabled) {
+			t.Fatalf("expect ErrCgoDisabled, got: %v", err)
+		}
+	})
+	t.Run("with-cgo", func(t *testing.T) {
+		if val, ok := os.LookupEnv("CGO_ENABLED"); ok && val == "0" {
+			t.Skip("CGO_ENABLED is set to 0")
+		}
+		if runtime.GOOS != "linux" {
+			t.Skip("Only Linux may return error at the moment.")
+		}
+
+		if err := clipboard.Init(); err != nil && !errors.Is(err, clipboard.ErrUnavailable) {
+			t.Fatalf("expect ErrUnavailable, but got: %v", err)
+		}
+	})
+}
+
+func TestClipboard(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		if val, ok := os.LookupEnv("CGO_ENABLED"); ok && val == "0" {
+			t.Skip("CGO_ENABLED is set to 0")
+		}
+	}
+
+	t.Run("image", func(t *testing.T) {
+		data, err := os.ReadFile("tests/testdata/clipboard.png")
+		if err != nil {
+			t.Fatalf("failed to read gold file: %v", err)
+		}
+		clipboard.Write(clipboard.FmtImage, data)
+
+		b := clipboard.Read(clipboard.FmtText)
+		if b != nil {
+			t.Fatalf("read clipboard that stores image data as text should fail, but got len: %d", len(b))
+		}
+
+		b = clipboard.Read(clipboard.FmtImage)
+		if b == nil {
+			t.Fatalf("read clipboard that stores image data as image should success, but got: nil")
+		}
+
+		img1, err := png.Decode(bytes.NewReader(data))
+		if err != nil {
+			t.Fatalf("write image is not png encoded: %v", err)
+		}
+		img2, err := png.Decode(bytes.NewReader(b))
+		if err != nil {
+			t.Fatalf("read image is not png encoded: %v", err)
+		}
+
+		w := img2.Bounds().Dx()
+		h := img2.Bounds().Dy()
+
+		incorrect := 0
+		for i := 0; i < w; i++ {
+			for j := 0; j < h; j++ {
+				wr, wg, wb, wa := img1.At(i, j).RGBA()
+				gr, gg, gb, ga := img2.At(i, j).RGBA()
+				want := color.RGBA{
+					R: uint8(wr),
+					G: uint8(wg),
+					B: uint8(wb),
+					A: uint8(wa),
+				}
+				got := color.RGBA{
+					R: uint8(gr),
+					G: uint8(gg),
+					B: uint8(gb),
+					A: uint8(ga),
+				}
+
+				if !reflect.DeepEqual(want, got) {
+					t.Logf("read data from clipbaord is inconsistent with previous written data, pix: (%d,%d), got: %+v, want: %+v", i, j, got, want)
+					incorrect++
+				}
+			}
+		}
+
+		if incorrect > 0 {
+			t.Fatalf("read data from clipboard contains too much inconsistent pixels to the previous written data, number of incorrect pixels: %v", incorrect)
+		}
+	})
+
+	t.Run("text", func(t *testing.T) {
+		data := []byte("golang.design/x/clipboard")
+		clipboard.Write(clipboard.FmtText, data)
+
+		b := clipboard.Read(clipboard.FmtImage)
+		if b != nil {
+			t.Fatalf("read clipboard that stores text data as image should fail, but got len: %d", len(b))
+		}
+		b = clipboard.Read(clipboard.FmtText)
+		if b == nil {
+			t.Fatal("read clipboard taht stores text data as text should success, but got: nil")
+		}
+
+		if !reflect.DeepEqual(data, b) {
+			t.Fatalf("read data from clipbaord is inconsistent with previous written data, got: %d, want: %d", len(b), len(data))
+		}
+	})
+}
+
+func TestClipboardMultipleWrites(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		if val, ok := os.LookupEnv("CGO_ENABLED"); ok && val == "0" {
+			t.Skip("CGO_ENABLED is set to 0")
+		}
+	}
+
+	data, err := os.ReadFile("tests/testdata/clipboard.png")
+	if err != nil {
+		t.Fatalf("failed to read gold file: %v", err)
+	}
+	chg := clipboard.Write(clipboard.FmtImage, data)
+
+	data = []byte("golang.design/x/clipboard")
+	clipboard.Write(clipboard.FmtText, data)
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*2)
+	defer cancel()
+
+	select {
+	case <-ctx.Done():
+		t.Fatalf("failed to receive clipboard change notification")
+	case _, ok := <-chg:
+		if !ok {
+			t.Fatalf("change channel is closed before receiving the changed clipboard data")
+		}
+	}
+	_, ok := <-chg
+	if ok {
+		t.Fatalf("changed channel should be closed after receiving the notification")
+	}
+
+	b := clipboard.Read(clipboard.FmtImage)
+	if b != nil {
+		t.Fatalf("read clipboard that should store text data as image should fail, but got: %d", len(b))
+	}
+
+	b = clipboard.Read(clipboard.FmtText)
+	if b == nil {
+		t.Fatalf("read clipboard that should store text data as text should success, got: nil")
+	}
+
+	if !reflect.DeepEqual(data, b) {
+		t.Fatalf("read data from clipbaord is inconsistent with previous write, want %s, got: %s", string(data), string(b))
+	}
+}
+
+func TestClipboardConcurrentRead(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		if val, ok := os.LookupEnv("CGO_ENABLED"); ok && val == "0" {
+			t.Skip("CGO_ENABLED is set to 0")
+		}
+	}
+
+	// This test check that concurrent read/write to the clipboard does
+	// not cause crashes on some specific platform, such as macOS.
+	done := make(chan bool, 2)
+	go func() {
+		defer func() {
+			done <- true
+		}()
+		clipboard.Read(clipboard.FmtText)
+	}()
+	go func() {
+		defer func() {
+			done <- true
+		}()
+		clipboard.Read(clipboard.FmtImage)
+	}()
+	<-done
+	<-done
+}
+
+func TestClipboardWriteEmpty(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		if val, ok := os.LookupEnv("CGO_ENABLED"); ok && val == "0" {
+			t.Skip("CGO_ENABLED is set to 0")
+		}
+	}
+
+	chg1 := clipboard.Write(clipboard.FmtText, nil)
+	if got := clipboard.Read(clipboard.FmtText); got != nil {
+		t.Fatalf("write nil to clipboard should read nil, got: %v", string(got))
+	}
+	clipboard.Write(clipboard.FmtText, []byte(""))
+	<-chg1
+
+	if got := clipboard.Read(clipboard.FmtText); string(got) != "" {
+		t.Fatalf("write empty string to clipboard should read empty string, got: `%v`", string(got))
+	}
+}
+
+func TestClipboardWatch(t *testing.T) {
+	if runtime.GOOS != "windows" {
+		if val, ok := os.LookupEnv("CGO_ENABLED"); ok && val == "0" {
+			t.Skip("CGO_ENABLED is set to 0")
+		}
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*2)
+	defer cancel()
+
+	// clear clipboard
+	clipboard.Write(clipboard.FmtText, []byte(""))
+	lastRead := clipboard.Read(clipboard.FmtText)
+
+	changed := clipboard.Watch(ctx, clipboard.FmtText)
+
+	want := []byte("golang.design/x/clipboard")
+	go func(ctx context.Context) {
+		t := time.NewTicker(time.Millisecond * 500)
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-t.C:
+				clipboard.Write(clipboard.FmtText, want)
+			}
+		}
+	}(ctx)
+	for {
+		select {
+		case <-ctx.Done():
+			if string(lastRead) == "" {
+				t.Fatalf("clipboard watch never receives a notification")
+			}
+			t.Log(string(lastRead))
+			return
+		case data, ok := <-changed:
+			if !ok {
+				if string(lastRead) == "" {
+					t.Fatalf("clipboard watch never receives a notification")
+				}
+				return
+			}
+			if !bytes.Equal(data, want) {
+				t.Fatalf("received data from watch mismatch, want: %v, got %v", string(want), string(data))
+			}
+			lastRead = data
+		}
+	}
+}
+
+func BenchmarkClipboard(b *testing.B) {
+	b.Run("text", func(b *testing.B) {
+		data := []byte("golang.design/x/clipboard")
+
+		b.ReportAllocs()
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			clipboard.Write(clipboard.FmtText, data)
+			_ = clipboard.Read(clipboard.FmtText)
+		}
+	})
+}
+
+func TestClipboardNoCgo(t *testing.T) {
+	if val, ok := os.LookupEnv("CGO_ENABLED"); !ok || val != "0" {
+		t.Skip("CGO_ENABLED is set to 1")
+	}
+	if runtime.GOOS == "windows" {
+		t.Skip("Windows should always be tested")
+	}
+
+	t.Run("Read", func(t *testing.T) {
+		defer func() {
+			if r := recover(); r != nil {
+				return
+			}
+			t.Fatalf("expect to fail when CGO_ENABLED=0")
+		}()
+
+		clipboard.Read(clipboard.FmtText)
+	})
+
+	t.Run("Write", func(t *testing.T) {
+		defer func() {
+			if r := recover(); r != nil {
+				return
+			}
+			t.Fatalf("expect to fail when CGO_ENABLED=0")
+		}()
+
+		clipboard.Write(clipboard.FmtText, []byte("dummy"))
+	})
+
+	t.Run("Watch", func(t *testing.T) {
+		defer func() {
+			if r := recover(); r != nil {
+				return
+			}
+			t.Fatalf("expect to fail when CGO_ENABLED=0")
+		}()
+
+		clipboard.Watch(context.TODO(), clipboard.FmtText)
+	})
+}

packages/tui/clipboard/clipboard_windows.go

@@ -0,0 +1,551 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build windows
+
+package clipboard
+
+// Interacting with Clipboard on Windows:
+// https://docs.microsoft.com/zh-cn/windows/win32/dataxchg/using-the-clipboard
+
+import (
+	"bytes"
+	"context"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"image"
+	"image/color"
+	"image/png"
+	"reflect"
+	"runtime"
+	"syscall"
+	"time"
+	"unicode/utf16"
+	"unsafe"
+
+	"golang.org/x/image/bmp"
+)
+
+func initialize() error { return nil }
+
+// readText reads the clipboard and returns the text data if presents.
+// The caller is responsible for opening/closing the clipboard before
+// calling this function.
+func readText() (buf []byte, err error) {
+	hMem, _, err := getClipboardData.Call(cFmtUnicodeText)
+	if hMem == 0 {
+		return nil, err
+	}
+	p, _, err := gLock.Call(hMem)
+	if p == 0 {
+		return nil, err
+	}
+	defer gUnlock.Call(hMem)
+
+	// Find NUL terminator
+	n := 0
+	for ptr := unsafe.Pointer(p); *(*uint16)(ptr) != 0; n++ {
+		ptr = unsafe.Pointer(uintptr(ptr) +
+			unsafe.Sizeof(*((*uint16)(unsafe.Pointer(p)))))
+	}
+
+	var s []uint16
+	h := (*reflect.SliceHeader)(unsafe.Pointer(&s))
+	h.Data = p
+	h.Len = n
+	h.Cap = n
+	return []byte(string(utf16.Decode(s))), nil
+}
+
+// writeText writes given data to the clipboard. It is the caller's
+// responsibility for opening/closing the clipboard before calling
+// this function.
+func writeText(buf []byte) error {
+	r, _, err := emptyClipboard.Call()
+	if r == 0 {
+		return fmt.Errorf("failed to clear clipboard: %w", err)
+	}
+
+	// empty text, we are done here.
+	if len(buf) == 0 {
+		return nil
+	}
+
+	s, err := syscall.UTF16FromString(string(buf))
+	if err != nil {
+		return fmt.Errorf("failed to convert given string: %w", err)
+	}
+
+	hMem, _, err := gAlloc.Call(gmemMoveable, uintptr(len(s)*int(unsafe.Sizeof(s[0]))))
+	if hMem == 0 {
+		return fmt.Errorf("failed to alloc global memory: %w", err)
+	}
+
+	p, _, err := gLock.Call(hMem)
+	if p == 0 {
+		return fmt.Errorf("failed to lock global memory: %w", err)
+	}
+	defer gUnlock.Call(hMem)
+
+	// no return value
+	memMove.Call(p, uintptr(unsafe.Pointer(&s[0])),
+		uintptr(len(s)*int(unsafe.Sizeof(s[0]))))
+
+	v, _, err := setClipboardData.Call(cFmtUnicodeText, hMem)
+	if v == 0 {
+		gFree.Call(hMem)
+		return fmt.Errorf("failed to set text to clipboard: %w", err)
+	}
+
+	return nil
+}
+
+// readImage reads the clipboard and returns PNG encoded image data
+// if presents. The caller is responsible for opening/closing the
+// clipboard before calling this function.
+func readImage() ([]byte, error) {
+	hMem, _, err := getClipboardData.Call(cFmtDIBV5)
+	if hMem == 0 {
+		// second chance to try FmtDIB
+		return readImageDib()
+	}
+	p, _, err := gLock.Call(hMem)
+	if p == 0 {
+		return nil, err
+	}
+	defer gUnlock.Call(hMem)
+
+	// inspect header information
+	info := (*bitmapV5Header)(unsafe.Pointer(p))
+
+	// maybe deal with other formats?
+	if info.BitCount != 32 {
+		return nil, errUnsupported
+	}
+
+	var data []byte
+	sh := (*reflect.SliceHeader)(unsafe.Pointer(&data))
+	sh.Data = uintptr(p)
+	sh.Cap = int(info.Size + 4*uint32(info.Width)*uint32(info.Height))
+	sh.Len = int(info.Size + 4*uint32(info.Width)*uint32(info.Height))
+	img := image.NewRGBA(image.Rect(0, 0, int(info.Width), int(info.Height)))
+	offset := int(info.Size)
+	stride := int(info.Width)
+	for y := 0; y < int(info.Height); y++ {
+		for x := 0; x < int(info.Width); x++ {
+			idx := offset + 4*(y*stride+x)
+			xhat := (x + int(info.Width)) % int(info.Width)
+			yhat := int(info.Height) - 1 - y
+			r := data[idx+2]
+			g := data[idx+1]
+			b := data[idx+0]
+			a := data[idx+3]
+			img.SetRGBA(xhat, yhat, color.RGBA{r, g, b, a})
+		}
+	}
+	// always use PNG encoding.
+	var buf bytes.Buffer
+	png.Encode(&buf, img)
+	return buf.Bytes(), nil
+}
+
+func readImageDib() ([]byte, error) {
+	const (
+		fileHeaderLen = 14
+		infoHeaderLen = 40
+		cFmtDIB       = 8
+	)
+
+	hClipDat, _, err := getClipboardData.Call(cFmtDIB)
+	if err != nil {
+		return nil, errors.New("not dib format data: " + err.Error())
+	}
+	pMemBlk, _, err := gLock.Call(hClipDat)
+	if pMemBlk == 0 {
+		return nil, errors.New("failed to call global lock: " + err.Error())
+	}
+	defer gUnlock.Call(hClipDat)
+
+	bmpHeader := (*bitmapHeader)(unsafe.Pointer(pMemBlk))
+	dataSize := bmpHeader.SizeImage + fileHeaderLen + infoHeaderLen
+
+	if bmpHeader.SizeImage == 0 && bmpHeader.Compression == 0 {
+		iSizeImage := bmpHeader.Height * ((bmpHeader.Width*uint32(bmpHeader.BitCount)/8 + 3) &^ 3)
+		dataSize += iSizeImage
+	}
+	buf := new(bytes.Buffer)
+	binary.Write(buf, binary.LittleEndian, uint16('B')|(uint16('M')<<8))
+	binary.Write(buf, binary.LittleEndian, uint32(dataSize))
+	binary.Write(buf, binary.LittleEndian, uint32(0))
+	const sizeof_colorbar = 0
+	binary.Write(buf, binary.LittleEndian, uint32(fileHeaderLen+infoHeaderLen+sizeof_colorbar))
+	j := 0
+	for i := fileHeaderLen; i < int(dataSize); i++ {
+		binary.Write(buf, binary.BigEndian, *(*byte)(unsafe.Pointer(pMemBlk + uintptr(j))))
+		j++
+	}
+	return bmpToPng(buf)
+}
+
+func bmpToPng(bmpBuf *bytes.Buffer) (buf []byte, err error) {
+	var f bytes.Buffer
+	original_image, err := bmp.Decode(bmpBuf)
+	if err != nil {
+		return nil, err
+	}
+	err = png.Encode(&f, original_image)
+	if err != nil {
+		return nil, err
+	}
+	return f.Bytes(), nil
+}
+
+func writeImage(buf []byte) error {
+	r, _, err := emptyClipboard.Call()
+	if r == 0 {
+		return fmt.Errorf("failed to clear clipboard: %w", err)
+	}
+
+	// empty text, we are done here.
+	if len(buf) == 0 {
+		return nil
+	}
+
+	img, err := png.Decode(bytes.NewReader(buf))
+	if err != nil {
+		return fmt.Errorf("input bytes is not PNG encoded: %w", err)
+	}
+
+	offset := unsafe.Sizeof(bitmapV5Header{})
+	width := img.Bounds().Dx()
+	height := img.Bounds().Dy()
+	imageSize := 4 * width * height
+
+	data := make([]byte, int(offset)+imageSize)
+	for y := 0; y < height; y++ {
+		for x := 0; x < width; x++ {
+			idx := int(offset) + 4*(y*width+x)
+			r, g, b, a := img.At(x, height-1-y).RGBA()
+			data[idx+2] = uint8(r)
+			data[idx+1] = uint8(g)
+			data[idx+0] = uint8(b)
+			data[idx+3] = uint8(a)
+		}
+	}
+
+	info := bitmapV5Header{}
+	info.Size = uint32(offset)
+	info.Width = int32(width)
+	info.Height = int32(height)
+	info.Planes = 1
+	info.Compression = 0 // BI_RGB
+	info.SizeImage = uint32(4 * info.Width * info.Height)
+	info.RedMask = 0xff0000 // default mask
+	info.GreenMask = 0xff00
+	info.BlueMask = 0xff
+	info.AlphaMask = 0xff000000
+	info.BitCount = 32 // we only deal with 32 bpp at the moment.
+	// Use calibrated RGB values as Go's image/png assumes linear color space.
+	// Other options:
+	// - LCS_CALIBRATED_RGB = 0x00000000
+	// - LCS_sRGB = 0x73524742
+	// - LCS_WINDOWS_COLOR_SPACE = 0x57696E20
+	// https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-wmf/eb4bbd50-b3ce-4917-895c-be31f214797f
+	info.CSType = 0x73524742
+	// Use GL_IMAGES for GamutMappingIntent
+	// Other options:
+	// - LCS_GM_ABS_COLORIMETRIC = 0x00000008
+	// - LCS_GM_BUSINESS = 0x00000001
+	// - LCS_GM_GRAPHICS = 0x00000002
+	// - LCS_GM_IMAGES = 0x00000004
+	// https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-wmf/9fec0834-607d-427d-abd5-ab240fb0db38
+	info.Intent = 4 // LCS_GM_IMAGES
+
+	infob := make([]byte, int(unsafe.Sizeof(info)))
+	for i, v := range *(*[unsafe.Sizeof(info)]byte)(unsafe.Pointer(&info)) {
+		infob[i] = v
+	}
+	copy(data[:], infob[:])
+
+	hMem, _, err := gAlloc.Call(gmemMoveable,
+		uintptr(len(data)*int(unsafe.Sizeof(data[0]))))
+	if hMem == 0 {
+		return fmt.Errorf("failed to alloc global memory: %w", err)
+	}
+
+	p, _, err := gLock.Call(hMem)
+	if p == 0 {
+		return fmt.Errorf("failed to lock global memory: %w", err)
+	}
+	defer gUnlock.Call(hMem)
+
+	memMove.Call(p, uintptr(unsafe.Pointer(&data[0])),
+		uintptr(len(data)*int(unsafe.Sizeof(data[0]))))
+
+	v, _, err := setClipboardData.Call(cFmtDIBV5, hMem)
+	if v == 0 {
+		gFree.Call(hMem)
+		return fmt.Errorf("failed to set text to clipboard: %w", err)
+	}
+
+	return nil
+}
+
+func read(t Format) (buf []byte, err error) {
+	// On Windows, OpenClipboard and CloseClipboard must be executed on
+	// the same thread. Thus, lock the OS thread for further execution.
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	var format uintptr
+	switch t {
+	case FmtImage:
+		format = cFmtDIBV5
+	case FmtText:
+		fallthrough
+	default:
+		format = cFmtUnicodeText
+	}
+
+	// check if clipboard is avaliable for the requested format
+	r, _, err := isClipboardFormatAvailable.Call(format)
+	if r == 0 {
+		return nil, errUnavailable
+	}
+
+	// try again until open clipboard successed
+	for {
+		r, _, _ = openClipboard.Call()
+		if r == 0 {
+			continue
+		}
+		break
+	}
+	defer closeClipboard.Call()
+
+	switch format {
+	case cFmtDIBV5:
+		return readImage()
+	case cFmtUnicodeText:
+		fallthrough
+	default:
+		return readText()
+	}
+}
+
+// write writes the given data to clipboard and
+// returns true if success or false if failed.
+func write(t Format, buf []byte) (<-chan struct{}, error) {
+	errch := make(chan error)
+	changed := make(chan struct{}, 1)
+	go func() {
+		// make sure GetClipboardSequenceNumber happens with
+		// OpenClipboard on the same thread.
+		runtime.LockOSThread()
+		defer runtime.UnlockOSThread()
+		for {
+			r, _, _ := openClipboard.Call(0)
+			if r == 0 {
+				continue
+			}
+			break
+		}
+
+		// var param uintptr
+		switch t {
+		case FmtImage:
+			err := writeImage(buf)
+			if err != nil {
+				errch <- err
+				closeClipboard.Call()
+				return
+			}
+		case FmtText:
+			fallthrough
+		default:
+			// param = cFmtUnicodeText
+			err := writeText(buf)
+			if err != nil {
+				errch <- err
+				closeClipboard.Call()
+				return
+			}
+		}
+		// Close the clipboard otherwise other applications cannot
+		// paste the data.
+		closeClipboard.Call()
+
+		cnt, _, _ := getClipboardSequenceNumber.Call()
+		errch <- nil
+		for {
+			time.Sleep(time.Second)
+			cur, _, _ := getClipboardSequenceNumber.Call()
+			if cur != cnt {
+				changed <- struct{}{}
+				close(changed)
+				return
+			}
+		}
+	}()
+	err := <-errch
+	if err != nil {
+		return nil, err
+	}
+	return changed, nil
+}
+
+func watch(ctx context.Context, t Format) <-chan []byte {
+	recv := make(chan []byte, 1)
+	ready := make(chan struct{})
+	go func() {
+		// not sure if we are too slow or the user too fast :)
+		ti := time.NewTicker(time.Second)
+		cnt, _, _ := getClipboardSequenceNumber.Call()
+		ready <- struct{}{}
+		for {
+			select {
+			case <-ctx.Done():
+				close(recv)
+				return
+			case <-ti.C:
+				cur, _, _ := getClipboardSequenceNumber.Call()
+				if cnt != cur {
+					b := Read(t)
+					if b == nil {
+						continue
+					}
+					recv <- b
+					cnt = cur
+				}
+			}
+		}
+	}()
+	<-ready
+	return recv
+}
+
+const (
+	cFmtBitmap      = 2 // Win+PrintScreen
+	cFmtUnicodeText = 13
+	cFmtDIBV5       = 17
+	// Screenshot taken from special shortcut is in different format (why??), see:
+	// https://jpsoft.com/forums/threads/detecting-clipboard-format.5225/
+	cFmtDataObject = 49161 // Shift+Win+s, returned from enumClipboardFormats
+	gmemMoveable   = 0x0002
+)
+
+// BITMAPV5Header structure, see:
+// https://docs.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapv5header
+type bitmapV5Header struct {
+	Size          uint32
+	Width         int32
+	Height        int32
+	Planes        uint16
+	BitCount      uint16
+	Compression   uint32
+	SizeImage     uint32
+	XPelsPerMeter int32
+	YPelsPerMeter int32
+	ClrUsed       uint32
+	ClrImportant  uint32
+	RedMask       uint32
+	GreenMask     uint32
+	BlueMask      uint32
+	AlphaMask     uint32
+	CSType        uint32
+	Endpoints     struct {
+		CiexyzRed, CiexyzGreen, CiexyzBlue struct {
+			CiexyzX, CiexyzY, CiexyzZ int32 // FXPT2DOT30
+		}
+	}
+	GammaRed    uint32
+	GammaGreen  uint32
+	GammaBlue   uint32
+	Intent      uint32
+	ProfileData uint32
+	ProfileSize uint32
+	Reserved    uint32
+}
+
+type bitmapHeader struct {
+	Size          uint32
+	Width         uint32
+	Height        uint32
+	PLanes        uint16
+	BitCount      uint16
+	Compression   uint32
+	SizeImage     uint32
+	XPelsPerMeter uint32
+	YPelsPerMeter uint32
+	ClrUsed       uint32
+	ClrImportant  uint32
+}
+
+// Calling a Windows DLL, see:
+// https://github.com/golang/go/wiki/WindowsDLLs
+var (
+	user32 = syscall.MustLoadDLL("user32")
+	// Opens the clipboard for examination and prevents other
+	// applications from modifying the clipboard content.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-openclipboard
+	openClipboard = user32.MustFindProc("OpenClipboard")
+	// Closes the clipboard.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-closeclipboard
+	closeClipboard = user32.MustFindProc("CloseClipboard")
+	// Empties the clipboard and frees handles to data in the clipboard.
+	// The function then assigns ownership of the clipboard to the
+	// window that currently has the clipboard open.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-emptyclipboard
+	emptyClipboard = user32.MustFindProc("EmptyClipboard")
+	// Retrieves data from the clipboard in a specified format.
+	// The clipboard must have been opened previously.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getclipboarddata
+	getClipboardData = user32.MustFindProc("GetClipboardData")
+	// Places data on the clipboard in a specified clipboard format.
+	// The window must be the current clipboard owner, and the
+	// application must have called the OpenClipboard function. (When
+	// responding to the WM_RENDERFORMAT message, the clipboard owner
+	// must not call OpenClipboard before calling SetClipboardData.)
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setclipboarddata
+	setClipboardData = user32.MustFindProc("SetClipboardData")
+	// Determines whether the clipboard contains data in the specified format.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-isclipboardformatavailable
+	isClipboardFormatAvailable = user32.MustFindProc("IsClipboardFormatAvailable")
+	// Clipboard data formats are stored in an ordered list. To perform
+	// an enumeration of clipboard data formats, you make a series of
+	// calls to the EnumClipboardFormats function. For each call, the
+	// format parameter specifies an available clipboard format, and the
+	// function returns the next available clipboard format.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-isclipboardformatavailable
+	enumClipboardFormats = user32.MustFindProc("EnumClipboardFormats")
+	// Retrieves the clipboard sequence number for the current window station.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getclipboardsequencenumber
+	getClipboardSequenceNumber = user32.MustFindProc("GetClipboardSequenceNumber")
+	// Registers a new clipboard format. This format can then be used as
+	// a valid clipboard format.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-registerclipboardformata
+	registerClipboardFormatA = user32.MustFindProc("RegisterClipboardFormatA")
+
+	kernel32 = syscall.NewLazyDLL("kernel32")
+
+	// Locks a global memory object and returns a pointer to the first
+	// byte of the object's memory block.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-globallock
+	gLock = kernel32.NewProc("GlobalLock")
+	// Decrements the lock count associated with a memory object that was
+	// allocated with GMEM_MOVEABLE. This function has no effect on memory
+	// objects allocated with GMEM_FIXED.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-globalunlock
+	gUnlock = kernel32.NewProc("GlobalUnlock")
+	// Allocates the specified number of bytes from the heap.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-globalalloc
+	gAlloc = kernel32.NewProc("GlobalAlloc")
+	// Frees the specified global memory object and invalidates its handle.
+	// https://docs.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-globalfree
+	gFree   = kernel32.NewProc("GlobalFree")
+	memMove = kernel32.NewProc("RtlMoveMemory")
+)

packages/tui/clipboard/cmd/gclip-gui/AndroidManifest.xml

@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+Copyright 2021 The golang.design Initiative Authors.
+All rights reserved. Use of this source code is governed
+by a MIT license that can be found in the LICENSE file.
+
+Written by Changkun Ou <changkun.de>
+-->
+<manifest
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	package="design.golang.clipboard.gclip"
+	android:versionCode="1"
+	android:versionName="1.0">
+
+
+	<!-- In order to access the clipboard, the application manifest must
+	     specify the permission requirement. See the following page for
+	     details.
+	     http://developer.android.com/guide/topics/manifest/manifest-intro.html#perms -->
+	<uses-permission android:name="android.permission.CLIPBOARD" />
+
+	<application android:label="gclip" android:debuggable="true">
+	<activity android:name="org.golang.app.GoNativeActivity"
+		android:label="Gclip"
+		android:configChanges="orientation|keyboardHidden">
+		<meta-data android:name="android.app.lib_name" android:value="Gclip" />
+		<intent-filter>
+			<action android:name="android.intent.action.MAIN" />
+			<category android:name="android.intent.category.LAUNCHER" />
+		</intent-filter>
+	</activity>
+	</application>
+</manifest>

packages/tui/clipboard/cmd/gclip-gui/README.md

@@ -0,0 +1,31 @@
+# gclip-gui
+
+This is a very basic example for verification purpose that demonstrates
+how the [golang.design/x/clipboard](https://golang.design/x/clipboard)
+can interact with macOS/Linux/Windows/Android/iOS system clipboard.
+
+The gclip GUI application writes a string to the system clipboard
+periodically then reads it back and renders it if possible.
+
+Because of the system limitation, on mobile devices, only string data is
+supported at the moment. Hence, one must use clipboard.FmtText. Other supplied
+formats result in a panic.
+
+This example is intentded as cross platform application. To build it, one
+must use [gomobile](https://golang.org/x/mobile). You may follow the instructions
+provided in the [GoMobile wiki](https://github.com/golang/go/wiki/Mobile) page.
+
+
+- For desktop: `go build -o gclip-gui`
+- For Android: `gomobile build -v -target=android -o gclip-gui.apk`
+- For iOS:     `gomobile build -v -target=ios -bundleid design.golang.gclip-gui.app`
+
+## Screenshots
+
+| macOS | iOS | Windows | Android | Linux |
+|:-----:|:---:|:-------:|:-------:|:-----:|
+|![](../../tests/testdata/darwin.png)|![](../../tests/testdata/ios.png)|![](../../tests/testdata/windows.png)|![](../../tests/testdata/android.png)|![](../../tests/testdata/linux.png)|
+
+## License
+
+MIT | © 2021 The golang.design Initiative Authors, written by [Changkun Ou](https://changkun.de).

packages/tui/clipboard/cmd/gclip-gui/main.go

@@ -0,0 +1,236 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build android || ios || linux || darwin || windows
+
+// This is a very basic example for verification purpose that
+// demonstrates how the golang.design/x/clipboard can interact
+// with macOS/Linux/Windows/Android/iOS system clipboard.
+//
+// The gclip GUI application writes a string to the system clipboard
+// periodically then reads it back and renders it if possible.
+//
+// Because of the system limitation, on mobile devices, only string
+// data is supported at the moment. Hence, one must use clipboard.FmtText.
+// Other supplied formats result in a panic.
+//
+// This example is intentded as cross platform application.
+// To build it, one must use gomobile (https://golang.org/x/mobile).
+// You may follow the instructions provided in the GoMobile's wiki page:
+// https://github.com/golang/go/wiki/Mobile.
+//
+// - For desktop:
+//
+// 	go build -o gclip-gui
+//
+// - For Android:
+//
+// 	gomobile build -v -target=android -o gclip-gui.apk
+//
+// - For iOS:
+//
+// 	gomobile build -v -target=ios -bundleid design.golang.gclip-gui.app
+//
+package main
+
+import (
+	"fmt"
+	"image"
+	"image/color"
+	"log"
+	"os"
+	"sync"
+	"time"
+
+	"golang.design/x/clipboard"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/font/basicfont"
+	"golang.org/x/image/math/fixed"
+	"golang.org/x/mobile/app"
+	"golang.org/x/mobile/event/lifecycle"
+	"golang.org/x/mobile/event/paint"
+	"golang.org/x/mobile/event/size"
+	"golang.org/x/mobile/exp/gl/glutil"
+	"golang.org/x/mobile/geom"
+	"golang.org/x/mobile/gl"
+)
+
+type Label struct {
+	sz     size.Event
+	images *glutil.Images
+	m      *glutil.Image
+	drawer *font.Drawer
+
+	mu   sync.Mutex
+	data string
+}
+
+func NewLabel(images *glutil.Images) *Label {
+	return &Label{
+		images: images,
+		data:   "Hello! Gclip.",
+		drawer: nil,
+	}
+}
+
+func (l *Label) SetLabel(s string) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	l.data = s
+}
+
+const (
+	lineWidth  = 100
+	lineHeight = 120
+)
+
+func (l *Label) Draw(sz size.Event) {
+	l.mu.Lock()
+	s := l.data
+	l.mu.Unlock()
+	imgW, imgH := lineWidth*basicfont.Face7x13.Width, lineHeight*basicfont.Face7x13.Height
+	if sz.WidthPx == 0 && sz.HeightPx == 0 {
+		return
+	}
+	if imgW > sz.WidthPx {
+		imgW = sz.WidthPx
+	}
+
+	if l.sz != sz {
+		l.sz = sz
+		if l.m != nil {
+			l.m.Release()
+		}
+		l.m = l.images.NewImage(imgW, imgH)
+	}
+	// Clear the drawing image.
+	for i := 0; i < len(l.m.RGBA.Pix); i++ {
+		l.m.RGBA.Pix[i] = 0
+	}
+
+	l.drawer = &font.Drawer{
+		Dst:  l.m.RGBA,
+		Src:  image.NewUniform(color.RGBA{0, 100, 125, 255}),
+		Face: basicfont.Face7x13,
+		Dot:  fixed.P(5, 10),
+	}
+	l.drawer.DrawString(s)
+	l.m.Upload()
+	l.m.Draw(
+		sz,
+		geom.Point{X: 0, Y: 50},
+		geom.Point{X: geom.Pt(imgW), Y: 50},
+		geom.Point{X: 0, Y: geom.Pt(imgH)},
+		l.m.RGBA.Bounds(),
+	)
+}
+
+func (l *Label) Release() {
+	if l.m != nil {
+		l.m.Release()
+		l.m = nil
+		l.images = nil
+	}
+}
+
+// GclipApp is the application instance.
+type GclipApp struct {
+	app app.App
+
+	ctx gl.Context
+	siz size.Event
+
+	images *glutil.Images
+	l      *Label
+
+	counter int
+}
+
+// WatchClipboard watches the system clipboard every seconds.
+func (g *GclipApp) WatchClipboard() {
+	go func() {
+		tk := time.NewTicker(time.Second)
+		for range tk.C {
+			// Write something to the clipboard
+			w := fmt.Sprintf("(gclip: %d)", g.counter)
+			clipboard.Write(clipboard.FmtText, []byte(w))
+			g.counter++
+			log.Println(w)
+
+			// Read it back and render it, if possible.
+			data := clipboard.Read(clipboard.FmtText)
+			if len(data) == 0 {
+				continue
+			}
+
+			// Set the current clipboard data as label content and render on the screen.
+			r := fmt.Sprintf("clipboard: %s", string(data))
+			g.l.SetLabel(r)
+			g.app.Send(paint.Event{})
+		}
+	}()
+}
+
+func (g *GclipApp) OnStart(e lifecycle.Event) {
+	g.ctx, _ = e.DrawContext.(gl.Context)
+	g.images = glutil.NewImages(g.ctx)
+	g.l = NewLabel(g.images)
+	g.app.Send(paint.Event{})
+}
+
+func (g *GclipApp) OnStop() {
+	g.l.Release()
+	g.images.Release()
+	g.ctx = nil
+}
+
+func (g *GclipApp) OnSize(size size.Event) {
+	g.siz = size
+}
+
+func (g *GclipApp) OnDraw() {
+	if g.ctx == nil {
+		return
+	}
+	defer g.app.Send(paint.Event{})
+	defer g.app.Publish()
+	g.ctx.ClearColor(0, 0, 0, 1)
+	g.ctx.Clear(gl.COLOR_BUFFER_BIT)
+	g.l.Draw(g.siz)
+}
+
+func init() {
+	err := clipboard.Init()
+	if err != nil {
+		panic(err)
+	}
+}
+
+func main() {
+	app.Main(func(a app.App) {
+		gclip := GclipApp{app: a}
+		gclip.app.Send(size.Event{WidthPx: 800, HeightPx: 500})
+		gclip.WatchClipboard()
+		for e := range gclip.app.Events() {
+			switch e := gclip.app.Filter(e).(type) {
+			case lifecycle.Event:
+				switch e.Crosses(lifecycle.StageVisible) {
+				case lifecycle.CrossOn:
+					gclip.OnStart(e)
+				case lifecycle.CrossOff:
+					gclip.OnStop()
+					os.Exit(0)
+				}
+			case size.Event:
+				gclip.OnSize(e)
+			case paint.Event:
+				gclip.OnDraw()
+			}
+		}
+	})
+}

packages/tui/clipboard/cmd/gclip/README.md

@@ -0,0 +1,40 @@
+# gclip
+
+`gclip` command offers the ability to interact with the system clipboard
+from the shell. To install:
+
+```bash
+$ go install golang.design/x/clipboard/cmd/gclip@latest
+```
+
+```bash
+$ gclip
+gclip is a command that provides clipboard interaction.
+usage: gclip [-copy|-paste] [-f <file>]
+options:
+  -copy
+        copy data to clipboard
+  -f string
+        source or destination to a given file path
+  -paste
+        paste data from clipboard
+examples:
+gclip -paste                    paste from clipboard and prints the content
+gclip -paste -f x.txt           paste from clipboard and save as text to x.txt
+gclip -paste -f x.png           paste from clipboard and save as image to x.png
+cat x.txt | gclip -copy         copy content from x.txt to clipboard
+gclip -copy -f x.txt            copy content from x.txt to clipboard
+gclip -copy -f x.png            copy x.png as image data to clipboard
+```
+
+If `-copy` is used, the command will exit when the data is no longer
+available from the clipboard. You can always send the command to the
+background using a shell `&` operator, for example:
+
+```bash
+$ cat x.txt | gclip -copy &
+```
+
+## License
+
+MIT | &copy; 2021 The golang.design Initiative Authors, written by [Changkun Ou](https://changkun.de).

packages/tui/clipboard/cmd/gclip/main.go

@@ -0,0 +1,131 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+package main // go install golang.design/x/clipboard/cmd/gclip@latest
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+
+	"golang.design/x/clipboard"
+)
+
+func usage() {
+	fmt.Fprintf(os.Stderr, `gclip is a command that provides clipboard interaction.
+
+usage: gclip [-copy|-paste] [-f <file>]
+
+options:
+`)
+	flag.PrintDefaults()
+	fmt.Fprintf(os.Stderr, `
+examples:
+gclip -paste                    paste from clipboard and prints the content
+gclip -paste -f x.txt           paste from clipboard and save as text to x.txt
+gclip -paste -f x.png           paste from clipboard and save as image to x.png
+
+cat x.txt | gclip -copy         copy content from x.txt to clipboard
+gclip -copy -f x.txt            copy content from x.txt to clipboard
+gclip -copy -f x.png            copy x.png as image data to clipboard
+`)
+	os.Exit(2)
+}
+
+var (
+	in   = flag.Bool("copy", false, "copy data to clipboard")
+	out  = flag.Bool("paste", false, "paste data from clipboard")
+	file = flag.String("f", "", "source or destination to a given file path")
+)
+
+func init() {
+	err := clipboard.Init()
+	if err != nil {
+		panic(err)
+	}
+}
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	if *out {
+		if err := pst(); err != nil {
+			usage()
+		}
+		return
+	}
+	if *in {
+		if err := cpy(); err != nil {
+			usage()
+		}
+		return
+	}
+	usage()
+}
+
+func cpy() error {
+	t := clipboard.FmtText
+	ext := filepath.Ext(*file)
+
+	switch ext {
+	case ".png":
+		t = clipboard.FmtImage
+	case ".txt":
+		fallthrough
+	default:
+		t = clipboard.FmtText
+	}
+
+	var (
+		b   []byte
+		err error
+	)
+	if *file != "" {
+		b, err = os.ReadFile(*file)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to read given file: %v", err)
+			return err
+		}
+	} else {
+		b, err = io.ReadAll(os.Stdin)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to read from stdin: %v", err)
+			return err
+		}
+	}
+
+	// Wait until clipboard content has been changed.
+	<-clipboard.Write(t, b)
+	return nil
+}
+
+func pst() (err error) {
+	var b []byte
+
+	b = clipboard.Read(clipboard.FmtText)
+	if b == nil {
+		b = clipboard.Read(clipboard.FmtImage)
+	}
+
+	if *file != "" && b != nil {
+		err = os.WriteFile(*file, b, os.ModePerm)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to write data to file %s: %v", *file, err)
+		}
+		return err
+	}
+
+	for len(b) > 0 {
+		n, err := os.Stdout.Write(b)
+		if err != nil {
+			return err
+		}
+		b = b[n:]
+	}
+	return nil
+}

packages/tui/clipboard/example_test.go

@@ -0,0 +1,56 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+//go:build cgo
+
+package clipboard_test
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"golang.design/x/clipboard"
+)
+
+func ExampleWrite() {
+	err := clipboard.Init()
+	if err != nil {
+		panic(err)
+	}
+
+	clipboard.Write(clipboard.FmtText, []byte("Hello, 世界"))
+	// Output:
+}
+
+func ExampleRead() {
+	err := clipboard.Init()
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(string(clipboard.Read(clipboard.FmtText)))
+	// Output:
+	// Hello, 世界
+}
+
+func ExampleWatch() {
+	err := clipboard.Init()
+	if err != nil {
+		panic(err)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second*2)
+	defer cancel()
+
+	changed := clipboard.Watch(context.Background(), clipboard.FmtText)
+	go func(ctx context.Context) {
+		clipboard.Write(clipboard.FmtText, []byte("你好，world"))
+	}(ctx)
+	fmt.Println(string(<-changed))
+	// Output:
+	// 你好，world
+}

packages/tui/clipboard/export_test.go

@@ -0,0 +1,14 @@
+// Copyright 2021 The golang.design Initiative Authors.
+// All rights reserved. Use of this source code is governed
+// by a MIT license that can be found in the LICENSE file.
+//
+// Written by Changkun Ou <changkun.de>
+
+package clipboard
+
+// for debugging errors
+var (
+	Debug          = debug
+	ErrUnavailable = errUnavailable
+	ErrCgoDisabled = errNoCgo
+)

packages/tui/clipboard/go.mod

@@ -0,0 +1,13 @@
+module golang.design/x/clipboard
+
+go 1.24
+
+require (
+	golang.org/x/image v0.28.0
+	golang.org/x/mobile v0.0.0-20250606033058-a2a15c67f36f
+)
+
+require (
+	golang.org/x/exp/shiny v0.0.0-20250606033433-dcc06ee1d476 // indirect
+	golang.org/x/sys v0.33.0 // indirect
+)

packages/tui/clipboard/go.sum

@@ -0,0 +1,8 @@
+golang.org/x/exp/shiny v0.0.0-20250606033433-dcc06ee1d476 h1:Wdx0vgH5Wgsw+lF//LJKmWOJBLWX6nprsMqnf99rYDE=
+golang.org/x/exp/shiny v0.0.0-20250606033433-dcc06ee1d476/go.mod h1:ygj7T6vSGhhm/9yTpOQQNvuAUFziTH7RUiH74EoE2C8=
+golang.org/x/image v0.28.0 h1:gdem5JW1OLS4FbkWgLO+7ZeFzYtL3xClb97GaUzYMFE=
+golang.org/x/image v0.28.0/go.mod h1:GUJYXtnGKEUgggyzh+Vxt+AviiCcyiwpsl8iQ8MvwGY=
+golang.org/x/mobile v0.0.0-20250606033058-a2a15c67f36f h1:/n+PL2HlfqeSiDCuhdBbRNlGS/g2fM4OHufalHaTVG8=
+golang.org/x/mobile v0.0.0-20250606033058-a2a15c67f36f/go.mod h1:ESkJ836Z6LpG6mTVAhA48LpfW/8fNR0ifStlH2axyfg=
+golang.org/x/sys v0.33.0 h1:q3i8TbbEz+JRD9ywIRlyRAQbM0qF7hu24q3teo2hbuw=
+golang.org/x/sys v0.33.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=

packages/tui/clipboard/test_linux_nocgo.sh

@@ -0,0 +1,109 @@
+#!/bin/bash
+# Test script for Linux CGO-free clipboard implementation
+
+echo "Testing Linux clipboard implementation without CGO..."
+
+# Check for required tools
+echo "Checking for clipboard tools..."
+for tool in xclip xsel wl-copy; do
+    if command -v $tool &> /dev/null; then
+        echo "✓ $tool is installed"
+    else
+        echo "✗ $tool is not installed"
+    fi
+done
+
+# Create test program
+cat > test_linux_clipboard.go << 'EOF'
+package main
+
+import (
+    "fmt"
+    "log"
+    "os"
+    "golang.design/x/clipboard"
+)
+
+func main() {
+    err := clipboard.Init()
+    if err != nil {
+        log.Fatal("Failed to initialize clipboard:", err)
+    }
+    
+    // Test text
+    fmt.Println("\n=== Testing Text Clipboard ===")
+    testText := []byte("Hello from CGO-free Linux clipboard!")
+    clipboard.Write(clipboard.FmtText, testText)
+    fmt.Println("Wrote text:", string(testText))
+    
+    readText := clipboard.Read(clipboard.FmtText)
+    fmt.Println("Read text:", string(readText))
+    
+    if string(testText) == string(readText) {
+        fmt.Println("✓ Text clipboard test passed")
+    } else {
+        fmt.Println("✗ Text clipboard test failed")
+    }
+    
+    // Test empty write
+    fmt.Println("\n=== Testing Empty Write ===")
+    clipboard.Write(clipboard.FmtText, []byte{})
+    emptyRead := clipboard.Read(clipboard.FmtText)
+    if emptyRead == nil || len(emptyRead) == 0 {
+        fmt.Println("✓ Empty write test passed")
+    } else {
+        fmt.Println("✗ Empty write test failed, got:", string(emptyRead))
+    }
+    
+    // Test image if requested
+    if len(os.Args) > 1 && os.Args[1] == "image" {
+        fmt.Println("\n=== Testing Image Clipboard ===")
+        
+        // Try to read test image
+        imageData, err := os.ReadFile("tests/testdata/clipboard.png")
+        if err != nil {
+            fmt.Println("Could not read test image:", err)
+            return
+        }
+        
+        clipboard.Write(clipboard.FmtImage, imageData)
+        fmt.Println("Wrote image data, length:", len(imageData))
+        
+        readImage := clipboard.Read(clipboard.FmtImage)
+        if readImage != nil {
+            fmt.Println("Read image data, length:", len(readImage))
+            if len(imageData) == len(readImage) {
+                fmt.Println("✓ Image clipboard test passed")
+            } else {
+                fmt.Println("✗ Image lengths don't match")
+            }
+        } else {
+            fmt.Println("✗ Failed to read image from clipboard")
+        }
+        
+        // Test that reading text from image clipboard returns nil
+        textFromImage := clipboard.Read(clipboard.FmtText)
+        if textFromImage == nil {
+            fmt.Println("✓ Reading text from image clipboard correctly returned nil")
+        } else {
+            fmt.Println("✗ Reading text from image clipboard should return nil, got:", string(textFromImage))
+        }
+    }
+}
+EOF
+
+# Run tests with CGO disabled
+echo -e "\n=== Running with CGO_ENABLED=0 ==="
+CGO_ENABLED=0 go run test_linux_clipboard.go
+
+echo -e "\n=== Running with CGO_ENABLED=0 and image test ==="
+CGO_ENABLED=0 go run test_linux_clipboard.go image
+
+# Run actual tests
+echo -e "\n=== Running go test with CGO_ENABLED=0 ==="
+CGO_ENABLED=0 go test -v -run TestClipboard
+
+# Clean up
+rm -f test_linux_clipboard.go
+
+echo -e "\nTest script completed!"

packages/tui/clipboard/tests/Makefile

@@ -0,0 +1,15 @@
+# Copyright 2021 The golang.design Initiative Authors.
+# All rights reserved. Use of this source code is governed
+# by a MIT license that can be found in the LICENSE file.
+#
+# Written by Changkun Ou <changkun.de>
+
+all: test
+
+test:
+	go test -v -count=1 -covermode=atomic ..
+
+test-docker:
+	docker build -t golang-design/x/clipboard ..
+	docker run --rm --name cb golang-design/x/clipboard
+	docker rmi golang-design/x/clipboard

packages/tui/clipboard/tests/test-docker.sh

@@ -0,0 +1,11 @@
+# Copyright 2021 The golang.design Initiative Authors.
+# All rights reserved. Use of this source code is governed
+# by a MIT license that can be found in the LICENSE file.
+#
+# Written by Changkun Ou <changkun.de>
+
+# require apt-get install xvfb
+Xvfb :99 -screen 0 1024x768x24 > /dev/null 2>&1 &
+export DISPLAY=:99.0
+
+go test -v -covermode=atomic ./...