Optional C++ namespaces (#4759)

Co-authored-by: Michael Winkelmann <michael@winkelmann.site>

api/cpp/cmake/SlintMacro.cmake

@@ -11,6 +11,19 @@ set_property(CACHE DEFAULT_SLINT_EMBED_RESOURCES PROPERTY STRINGS
 #     INITIALIZE_FROM_VARIABLE DEFAULT_SLINT_EMBED_RESOURCES)
 
 function(SLINT_TARGET_SOURCES target)
+    # Parse the NAMESPACE argument
+    cmake_parse_arguments(SLINT_TARGET_SOURCES "" "NAMESPACE" "" ${ARGN})
+
+    if (DEFINED SLINT_TARGET_SOURCES_NAMESPACE)
+        # Remove the NAMESPACE argument from the list
+        list(FIND ARGN "NAMESPACE" _index)
+        list(REMOVE_AT ARGN ${_index})
+        list(FIND ARGN "${SLINT_TARGET_SOURCES_NAMESPACE}" _index)
+        list(REMOVE_AT ARGN ${_index})
+        # If the namespace is not empty, add the --cpp-namespace argument
+        set(_SLINT_CPP_NAMESPACE_ARG "--cpp-namespace=${SLINT_TARGET_SOURCES_NAMESPACE}")
+    endif()
+
     foreach (it IN ITEMS ${ARGN})
         get_filename_component(_SLINT_BASE_NAME ${it} NAME_WE)
         get_filename_component(_SLINT_ABSOLUTE ${it} REALPATH BASE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
@@ -28,6 +41,7 @@ function(SLINT_TARGET_SOURCES target)
                 --style ${_SLINT_STYLE}
                 --embed-resources=${embed}
                 --translation-domain="${target}"
+                ${_SLINT_CPP_NAMESPACE_ARG}
             DEPENDS Slint::slint-compiler ${_SLINT_ABSOLUTE}
             COMMENT "Generating ${_SLINT_BASE_NAME}.h"
             DEPFILE ${CMAKE_CURRENT_BINARY_DIR}/${_SLINT_BASE_NAME}.d

api/cpp/docs/cmake_reference.md

@@ -5,23 +5,26 @@
 ## `slint_target_sources`
 
 ```
-slint_target_sources(<target> <files>....)
+slint_target_sources(<target> <files>.... [NAMESPACE namespace])
 ```
 
 Use this function to tell cmake about the .slint files of your application, similar to the builtin cmake [target_sources](https://cmake.org/cmake/help/latest/command/target_sources.html) function.
 The function takes care of running the slint-compiler to convert `.slint` files to `.h` files in the build directory,
 and extend  the include directories of your target so that the generated file is found when including it in your application.
 
+The optional NAMESPACE argument will put the generated components in the given C++ namespace.
 
 Given a file called `the_window.slint`, the following example will create a file called `the_window.h` that can
-be included from your .cpp file.
+be included from your .cpp file. Assuming the `the_window.slint` contains a component `TheWindow`, the output
+C++ class will be put in the namespace `ui`, resulting to `ui::TheWindow`.
 
 ```cmake
 add_executable(my_application main.cpp)
 target_link_libraries(my_application PRIVATE Slint::Slint)
-slint_target_sources(my_application the_window.slint)
+slint_target_sources(my_application the_window.slint NAMESPACE ui)
 ```
 
+
 ## Resource Embedding
 
 By default, images from [`@image-url()`](slint-reference:src/language/syntax/types#images) or fonts that your Slint files reference are loaded from disk at run-time. This minimises build times, but requires that the directory structure with the files remains stable. If you want to build a program that runs anywhere, then you can configure the Slint compiler to embed such sources into the binary.

examples/todo/cpp/CMakeLists.txt

@@ -10,4 +10,4 @@ endif()
 
 add_executable(todo main.cpp)
 target_link_libraries(todo PRIVATE Slint::Slint)
-slint_target_sources(todo ../ui/todo.slint)
+slint_target_sources(todo ../ui/todo.slint NAMESPACE todo_ui)

examples/todo/cpp/main.cpp

@@ -5,7 +5,8 @@
 
 int main()
 {
-    auto demo = MainWindow::create();
+    auto demo = todo_ui::MainWindow::create();
+    using todo_ui::TodoItem;
 
     auto todo_model = std::make_shared<slint::VectorModel<TodoItem>>(std::vector {
             TodoItem { "Implement the .slint file", true },

internal/compiler/generator.rs

@@ -18,15 +18,15 @@ use crate::namedreference::NamedReference;
 use crate::object_tree::{Component, Document, ElementRc};
 
 #[cfg(feature = "cpp")]
-mod cpp;
+pub mod cpp;
 
 #[cfg(feature = "rust")]
 pub mod rust;
 
-#[derive(Copy, Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 pub enum OutputFormat {
     #[cfg(feature = "cpp")]
-    Cpp,
+    Cpp(cpp::Config),
     #[cfg(feature = "rust")]
     Rust,
     Interpreter,
@@ -37,7 +37,9 @@ impl OutputFormat {
     pub fn guess_from_extension(path: &std::path::Path) -> Option<Self> {
         match path.extension().and_then(|ext| ext.to_str()) {
             #[cfg(feature = "cpp")]
-            Some("cpp") | Some("cxx") | Some("h") | Some("hpp") => Some(Self::Cpp),
+            Some("cpp") | Some("cxx") | Some("h") | Some("hpp") => {
+                Some(Self::Cpp(cpp::Config::default()))
+            }
             #[cfg(feature = "rust")]
             Some("rs") => Some(Self::Rust),
             _ => None,
@@ -50,7 +52,7 @@ impl std::str::FromStr for OutputFormat {
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         match s {
             #[cfg(feature = "cpp")]
-            "cpp" => Ok(Self::Cpp),
+            "cpp" => Ok(Self::Cpp(cpp::Config::default())),
             #[cfg(feature = "rust")]
             "rust" => Ok(Self::Rust),
             "llr" => Ok(Self::Llr),
@@ -74,8 +76,8 @@ pub fn generate(
 
     match format {
         #[cfg(feature = "cpp")]
-        OutputFormat::Cpp => {
-            let output = cpp::generate(doc);
+        OutputFormat::Cpp(config) => {
+            let output = cpp::generate(doc, config);
             write!(destination, "{}", output)?;
         }
         #[cfg(feature = "rust")]

internal/compiler/generator/cpp.rs

@@ -8,6 +8,12 @@
 
 use std::fmt::Write;
 
+/// The configuration for the C++ code generator
+#[derive(Clone, Debug, Default, PartialEq)]
+pub struct Config {
+    pub namespace: Option<String>,
+}
+
 fn ident(ident: &str) -> String {
     if ident.contains('-') {
         ident.replace('-', "_")
@@ -76,6 +82,7 @@ mod cpp_ast {
     pub struct File {
         pub includes: Vec<String>,
         pub after_includes: String,
+        pub namespace: Option<String>,
         pub declarations: Vec<Declaration>,
         pub definitions: Vec<Declaration>,
     }
@@ -85,6 +92,11 @@ mod cpp_ast {
             for i in &self.includes {
                 writeln!(f, "#include {}", i)?;
             }
+            if let Some(namespace) = &self.namespace {
+                writeln!(f, "namespace {} {{", namespace)?;
+                INDENTATION.with(|x| x.set(x.get() + 1));
+            }
+
             write!(f, "{}", self.after_includes)?;
             for d in &self.declarations {
                 write!(f, "\n{}", d)?;
@@ -92,6 +104,11 @@ mod cpp_ast {
             for d in &self.definitions {
                 write!(f, "\n{}", d)?;
             }
+            if let Some(namespace) = &self.namespace {
+                writeln!(f, "}} // namespace {}", namespace)?;
+                INDENTATION.with(|x| x.set(x.get() - 1));
+            }
+
             Ok(())
         }
     }
@@ -515,8 +532,8 @@ fn handle_property_init(
 }
 
 /// Returns the text of the C++ code produced by the given root component
-pub fn generate(doc: &Document) -> impl std::fmt::Display {
-    let mut file = File::default();
+pub fn generate(doc: &Document, config: Config) -> impl std::fmt::Display {
+    let mut file = File { namespace: config.namespace.clone(), ..Default::default() };
 
     file.includes.push("<array>".into());
     file.includes.push("<limits>".into());

internal/compiler/lib.rs

@@ -94,6 +94,9 @@ pub struct CompilerConfiguration {
 
     /// The domain used as one of the parameter to the translate function
     pub translation_domain: Option<String>,
+
+    /// C++ namespace
+    pub cpp_namespace: Option<String>,
 }
 
 impl CompilerConfiguration {
@@ -142,6 +145,18 @@ impl CompilerConfiguration {
 
         let enable_component_containers = enable_experimental_features;
 
+        let cpp_namespace = match output_format {
+            #[cfg(feature = "cpp")]
+            crate::generator::OutputFormat::Cpp(config) => match config.namespace {
+                Some(namespace) => Some(namespace),
+                None => match std::env::var("SLINT_CPP_NAMESPACE") {
+                    Ok(namespace) => Some(namespace),
+                    Err(_) => None,
+                },
+            },
+            _ => None,
+        };
+
         Self {
             embed_resources,
             include_paths: Default::default(),
@@ -154,6 +169,7 @@ impl CompilerConfiguration {
             accessibility: true,
             enable_component_containers,
             translation_domain: None,
+            cpp_namespace,
         }
     }
 }

tests/cases/exports/cpp_namespace.slint

@@ -0,0 +1,36 @@
+// Copyright © SixtyFPS GmbH <info@slint.dev>
+// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-1.1 OR LicenseRef-Slint-commercial
+
+//cpp-namespace: my::ui
+//ignore: rust,js
+struct TestStruct {
+    condition: bool,
+}
+
+enum TestEnum {
+    A,
+    B,
+    C
+}
+
+export component TestCase inherits Rectangle {
+    in-out property <TestStruct> test_struct;
+    in-out property <TestEnum> test_enum;
+}
+
+/*
+```cpp
+auto handle = my::ui::TestCase::create();
+const my::ui::TestCase &instance = *handle;
+my::ui::TestStruct test_struct {.condition = false};
+test_struct.condition = true;
+instance.set_test_struct(test_struct);
+assert(instance.get_test_struct() == test_struct);
+instance.set_test_enum(my::ui::TestEnum::A);
+auto test_enum = instance.get_test_enum();
+test_enum = my::ui::TestEnum::B;
+instance.set_test_enum(test_enum);
+assert(instance.get_test_enum() == my::ui::TestEnum::B);
+```
+
+*/

tests/driver/cpp/cppdriver.rs

@@ -16,9 +16,14 @@ pub fn test(testcase: &test_driver_lib::TestCase) -> Result<(), Box<dyn Error>>
         .map(|(k, v)| (k.to_string(), std::path::PathBuf::from(v)))
         .collect::<std::collections::HashMap<_, _>>();
 
+    let cpp_namespace = test_driver_lib::extract_cpp_namespace(&source);
+
     let mut diag = BuildDiagnostics::default();
     let syntax_node = parser::parse(source.clone(), Some(&testcase.absolute_path), None, &mut diag);
-    let mut compiler_config = CompilerConfiguration::new(generator::OutputFormat::Cpp);
+    let output_format =
+        generator::OutputFormat::Cpp(generator::cpp::Config { namespace: cpp_namespace });
+
+    let mut compiler_config = CompilerConfiguration::new(output_format.clone());
     compiler_config.include_paths = include_paths;
     compiler_config.library_paths = library_paths;
     let (root_component, diag, _) =
@@ -31,7 +36,7 @@ pub fn test(testcase: &test_driver_lib::TestCase) -> Result<(), Box<dyn Error>>
 
     let mut generated_cpp: Vec<u8> = Vec::new();
 
-    generator::generate(generator::OutputFormat::Cpp, &mut generated_cpp, &root_component)?;
+    generator::generate(output_format, &mut generated_cpp, &root_component)?;
 
     if diag.has_error() {
         let vec = diag.to_string_vec();

tests/driver/driverlib/lib.rs

@@ -238,3 +238,23 @@ fn test_extract_ignores() {
     let r = extract_ignores(source).collect::<Vec<_>>();
     assert_eq!(r, ["cpp", "rust", "nodejs"]);
 }
+
+pub fn extract_cpp_namespace(source: &str) -> Option<String> {
+    lazy_static::lazy_static! {
+        static ref RX: Regex = Regex::new(r"//cpp-namespace:\s*(.+)\s*\n").unwrap();
+    }
+    RX.captures(source).map(|mat| mat.get(1).unwrap().as_str().trim().to_string())
+}
+
+#[test]
+fn test_extract_cpp_namespace() {
+    assert!(extract_cpp_namespace("something").is_none());
+
+    let source = r"
+    //cpp-namespace: ui
+    Blah {}
+";
+
+    let r = extract_cpp_namespace(source);
+    assert_eq!(r, Some("ui".to_string()));
+}

tools/compiler/main.rs

@@ -62,6 +62,10 @@ struct Cli {
     /// Translation domain
     #[arg(long = "translation-domain", action)]
     translation_domain: Option<String>,
+
+    /// C++ namespace
+    #[arg(long = "cpp-namespace", name = "C++ namespace")]
+    cpp_namespace: Option<String>,
 }
 
 fn main() -> std::io::Result<()> {
@@ -74,7 +78,18 @@ fn main() -> std::io::Result<()> {
         diag.print();
         std::process::exit(-1);
     }
-    let mut compiler_config = CompilerConfiguration::new(args.format);
+
+    let mut format = args.format.clone();
+
+    if args.cpp_namespace.is_some() {
+        if !matches!(format, generator::OutputFormat::Cpp(..)) {
+            eprintln!("C++ namespace option was set. Output format will be C++.");
+        }
+        format =
+            generator::OutputFormat::Cpp(generator::cpp::Config { namespace: args.cpp_namespace });
+    }
+
+    let mut compiler_config = CompilerConfiguration::new(format.clone());
     compiler_config.translation_domain = args.translation_domain;
 
     // Override defaults from command line:
@@ -102,10 +117,10 @@ fn main() -> std::io::Result<()> {
     let diag = diag.check_and_exit_on_error();
 
     if args.output == std::path::Path::new("-") {
-        generator::generate(args.format, &mut std::io::stdout(), &doc)?;
+        generator::generate(format, &mut std::io::stdout(), &doc)?;
     } else {
         generator::generate(
-            args.format,
+            format,
             &mut BufWriter::new(std::fs::File::create(&args.output)?),
             &doc,
         )?;