Add a function to mark translated strings as dirty

api/cpp/cbindgen.rs

@@ -933,7 +933,7 @@ macro_rules! declare_features {
     };
 }
 
-declare_features! {interpreter backend_qt freestanding renderer_software renderer_skia experimental}
+declare_features! {interpreter backend_qt freestanding renderer_software renderer_skia experimental gettext}
 
 /// Generate the headers.
 /// `root_dir` is the root directory of the slint git repo

api/cpp/include/slint.h

@@ -1258,6 +1258,27 @@ inline SharedString translate(const SharedString &original, const SharedString &
 
 } // namespace private_api
 
+#ifdef SLINT_FEATURE_GETTEXT
+/// Forces all the strings that are translated with `@tr(...)` to be re-evaluated.
+/// This is useful if the language is changed at runtime.
+/// The function is only available when Slint is compiled with `SLINT_FEATURE_GETTEXT`.
+///
+/// Example
+/// ```cpp
+///     my_ui->global<LanguageSettings>().on_french_selected([] {
+///        // trick from https://www.gnu.org/software/gettext/manual/html_node/gettext-grok.html
+///        setenv("LANGUAGE", langs[l], true);
+///        extern int _nl_msg_cat_cntr;
+///        ++_nl_msg_cat_cntr;
+///        slint::update_all_translations();
+///    });
+/// ```
+inline void update_all_translations()
+{
+    cbindgen_private::slint_translations_mark_dirty();
+}
+#endif
+
 #if !defined(DOXYGEN)
 cbindgen_private::Flickable::Flickable()
 {

examples/printerdemo/cpp/CMakeLists.txt

@@ -11,3 +11,9 @@ endif()
 add_executable(printerdemo main.cpp)
 target_link_libraries(printerdemo PRIVATE Slint::Slint)
 slint_target_sources(printerdemo ../ui/printerdemo.slint)
+
+find_package(Intl)
+if(Intl_FOUND)
+    target_compile_definitions(printerdemo PRIVATE HAVE_GETTEXT SRC_DIR="${CMAKE_CURRENT_SOURCE_DIR}")
+    target_link_libraries(printerdemo PRIVATE Intl::Intl)
+endif()

examples/printerdemo/cpp/main.cpp

@@ -2,8 +2,14 @@
 // SPDX-License-Identifier: MIT
 
 #include "printerdemo.h"
+#include "slint.h"
 
+#include <cstdlib>
 #include <ctime>
+#ifdef HAVE_GETTEXT
+#    include <locale>
+#    include <libintl.h>
+#endif
 
 struct InkLevelModel : slint::Model<InkLevel>
 {
@@ -23,6 +29,11 @@ struct InkLevelModel : slint::Model<InkLevel>
 
 int main()
 {
+#ifdef HAVE_GETTEXT
+    bindtextdomain("printerdemo", SRC_DIR "/../lang");
+    std::locale::global(std::locale(""));
+#endif
+
     auto printer_demo = MainWindow::create();
     printer_demo->set_ink_levels(std::make_shared<InkLevelModel>());
     printer_demo->on_quit([] { std::exit(0); });
@@ -65,5 +76,16 @@ int main()
         }
     });
 
+#if defined(HAVE_GETTEXT) && defined(SLINT_FEATURE_GETTEXT)
+    printer_demo->global<PrinterSettings>().on_change_language([](int l) {
+        static const char *langs[] = { "en", "fr" };
+        setenv("LANGUAGE", langs[l], true);
+        // trick from https://www.gnu.org/software/gettext/manual/html_node/gettext-grok.html
+        extern int _nl_msg_cat_cntr;
+        ++_nl_msg_cat_cntr;
+        slint::update_all_translations();
+    });
+#endif
+
     printer_demo->run();
 }

examples/printerdemo/lang/fr/LC_MESSAGES/printerdemo.po

@@ -1,16 +1,13 @@
 # Copyright © SixtyFPS GmbH <info@slint.dev>
 # SPDX-License-Identifier: MIT
 #
-# Olivier Goffart <ogoffart@bepointbe.be>, 2023.
 msgid ""
 msgstr ""
 "Project-Id-Version: \n"
 "Report-Msgid-Bugs-To: \n"
 "POT-Creation-Date: 2024-04-17 03:03+0000\n"
 "PO-Revision-Date: 2023-06-09 07:56+0200\n"
-"Last-Translator: Olivier Goffart <ogoffart@bepointbe.be>\n"
-"Language-Team: German <kde-i18n-de@kde.org>\n"
-"Language: de_DE\n"
+"Language: fr_FR\n"
 "MIME-Version: 1.0\n"
 "Content-Type: text/plain; charset=UTF-8\n"
 "Content-Transfer-Encoding: 8bit\n"

examples/printerdemo/rust/Cargo.toml

@@ -23,6 +23,11 @@ name = "printerdemo_lib"
 slint = { path = "../../../api/rs/slint", features = ["backend-android-activity-05"] }
 chrono = { version = "0.4", default-features = false, features = ["clock", "std"]}
 
+# Disable gettext on macOS due to https://github.com/Koka/gettext-rs/issues/114
+[target.'cfg(not(any(target_os = "macos", target_os = "android")))'.dependencies]
+slint = { path = "../../../api/rs/slint", features=["gettext"] }
+
+
 [build-dependencies]
 slint-build = { path = "../../../api/rs/build" }
 

examples/printerdemo/rust/lib.rs

@@ -102,6 +102,21 @@ pub fn main() {
         },
     );
 
+    // Disable gettext on macOS due to https://github.com/Koka/gettext-rs/issues/114
+    #[cfg(not(any(target_os = "macos", target_os = "android")))]
+    {
+        slint::init_translations!(concat!(env!("CARGO_MANIFEST_DIR"), "/../lang/"));
+        main_window.global::<PrinterSettings>().on_change_language(|l| {
+            let lang = match l {
+                0 => "en",
+                1 => "fr",
+                _ => return,
+            };
+            std::env::set_var("LANGUAGE", lang);
+            slint::init_translations!(concat!(env!("CARGO_MANIFEST_DIR"), "/../lang/"));
+        })
+    }
+
     main_window.run().unwrap();
 }
 

examples/printerdemo/ui/common.slint

@@ -170,6 +170,7 @@ export component SpinBox inherits Rectangle {
 export component ComboBox inherits Rectangle {
     in-out property <string> value;
     in property <[string]> choices;
+    callback selected(int);
 
     border-radius: 3px;
     border-width: 2px;
@@ -235,6 +236,7 @@ export component ComboBox inherits Rectangle {
                 item-area := TouchArea {
                     clicked => {
                         root.value = value;
+                        root.selected(idx);
                     }
                 }
             }

examples/printerdemo/ui/printerdemo.slint

@@ -4,11 +4,11 @@
 import { DemoPalette, Page } from "common.slint";
 import { HomePage } from "./home_page.slint";
 import { InkLevel, InkPage } from "./ink_page.slint";
-import { SettingsPage } from "./settings_page.slint";
+import { SettingsPage, PrinterSettings } from "./settings_page.slint";
 import { PrinterQueue } from "./printer_queue.slint";
 
 // re-export for the native code
-export { PrinterQueue }
+export { PrinterQueue, PrinterSettings }
 
 import "./fonts/NotoSans-Regular.ttf";
 import "./fonts/NotoSans-Bold.ttf";

examples/printerdemo/ui/settings_page.slint

@@ -3,6 +3,10 @@
 
 import { DemoPalette, Page, SpinBox, ComboBox, CheckBox, Label } from "common.slint";
 
+export global PrinterSettings {
+    callback change-language(int);
+}
+
 export component SettingsPage inherits Page {
     header: @tr("Settings");
 
@@ -65,10 +69,11 @@ export component SettingsPage inherits Page {
 
             Rectangle {}
 
-            Label { text: @tr("Paper Type"); }
+            Label { text: @tr("Language"); }
             ComboBox {
-                value: @tr("Standard");
-                choices: [@tr("Standard"), @tr("Non-standard")];
+                value: @tr("English");
+                choices: [@tr("English"), @tr("French")];
+                selected(x) => { PrinterSettings.change-language(x); }
             }
         }
         Row {

internal/core/context.rs

@@ -5,6 +5,7 @@ use crate::api::PlatformError;
 use crate::platform::{EventLoopProxy, Platform};
 #[cfg(all(not(feature = "std"), feature = "unsafe-single-threaded"))]
 use crate::thread_local;
+use crate::Property;
 #[cfg(not(feature = "std"))]
 use alloc::boxed::Box;
 use alloc::rc::Rc;
@@ -17,6 +18,9 @@ thread_local! {
 pub(crate) struct SlintContextInner {
     pub(crate) platform: Box<dyn Platform>,
     pub(crate) window_count: core::cell::RefCell<isize>,
+    /// This property is read by all translations, and marked dirty when the language change
+    /// so that every translated string gets re-translated
+    pub(crate) translations_dirty: core::pin::Pin<Box<Property<()>>>,
 }
 
 /// This context is meant to hold the state and the backend.
@@ -28,7 +32,11 @@ pub struct SlintContext(pub(crate) Rc<SlintContextInner>);
 impl SlintContext {
     /// Create a new context with a given platform
     pub fn new(platform: Box<dyn Platform + 'static>) -> Self {
-        Self(Rc::new(SlintContextInner { platform, window_count: 0.into() }))
+        Self(Rc::new(SlintContextInner {
+            platform,
+            window_count: 0.into(),
+            translations_dirty: Box::pin(Property::new_named((), "SlintContext::translations")),
+        }))
     }
 
     /// Return an event proxy

internal/core/translations.rs

@@ -192,6 +192,10 @@ pub fn translate(
 
 #[cfg(all(target_family = "unix", feature = "gettext-rs"))]
 fn translate_gettext(string: &str, ctx: &str, domain: &str, n: i32, plural: &str) -> String {
+    crate::context::GLOBAL_CONTEXT.with(|ctx| {
+        let Some(ctx) = ctx.get() else { return };
+        ctx.0.translations_dirty.as_ref().get();
+    });
     fn mangle_context(ctx: &str, s: &str) -> String {
         format!("{}\u{4}{}", ctx, s)
     }
@@ -220,6 +224,13 @@ fn translate_gettext(string: &str, ctx: &str, domain: &str, n: i32, plural: &str
     }
 }
 
+pub fn mark_all_translations_dirty() {
+    crate::context::GLOBAL_CONTEXT.with(|ctx| {
+        let Some(ctx) = ctx.get() else { return };
+        ctx.0.translations_dirty.mark_dirty();
+    })
+}
+
 #[cfg(feature = "gettext-rs")]
 /// Initialize the translation by calling the [`bindtextdomain`](https://man7.org/linux/man-pages/man3/bindtextdomain.3.html) function from gettext
 pub fn gettext_bindtextdomain(_domain: &str, _dirname: std::path::PathBuf) -> std::io::Result<()> {
@@ -230,6 +241,7 @@ pub fn gettext_bindtextdomain(_domain: &str, _dirname: std::path::PathBuf) -> st
         START.call_once(|| {
             gettextrs::setlocale(gettextrs::LocaleCategory::LcAll, "");
         });
+        mark_all_translations_dirty();
     }
     Ok(())
 }
@@ -240,10 +252,8 @@ mod ffi {
     use super::*;
     use crate::slice::Slice;
 
+    /// Perform the translation and formatting.
     #[no_mangle]
-    /// Returns a nul-terminated pointer for this string.
-    /// The returned value is owned by the string, and should not be used after any
-    /// mutable function have been called on the string, and must not be freed.
     pub extern "C" fn slint_translate(
         to_translate: &mut SharedString,
         context: &SharedString,
@@ -255,4 +265,10 @@ mod ffi {
         *to_translate =
             translate(to_translate.as_str(), &context, &domain, arguments.as_slice(), n, &plural)
     }
+
+    /// Mark all translated string as dirty to perform re-translation in case the language change
+    #[no_mangle]
+    pub extern "C" fn slint_translations_mark_dirty() {
+        mark_all_translations_dirty();
+    }
 }

xtask/src/cppdocs.rs

@@ -90,6 +90,7 @@ pub fn generate(show_warnings: bool) -> Result<(), Box<dyn std::error::Error>> {
         renderer_software: true,
         renderer_skia: true,
         experimental: false,
+        gettext: true,
     };
     cbindgen::gen_all(&root, &generated_headers_dir, enabled_features)?;