Add bindings for QtMsgType, QMessageLogContext and qt_message_output

This allows Rust and CXX-Qt applications to send messages to the Qt
logger.

CHANGELOG.md

@@ -26,6 +26,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add cxx-qt-lib-extras crate which contains: `QCommandLineOption`, `QCommandLineParser`, `QElapsedTimer`, `QApplication`
 - Serde support for `QString` (requires "serde" feature on cxx-qt-lib)
 - A new QuickControls module, which exposes `QQuickStyle`. This module is enabled by default and is behind the `qt_quickcontrols` feature.
+- Support for `QMessageLogContext` and sending log messages to the Qt message handler.
 
 ### Changed
 

crates/cxx-qt-lib/build.rs

@@ -136,6 +136,7 @@ fn main() {
         "core/qstringlist",
         "core/qt",
         "core/qtime",
+        "core/qtlogging",
         "core/qurl",
         "core/qvariant/mod",
         "core/qvariant/qvariant_bool",
@@ -254,6 +255,7 @@ fn main() {
         "core/qstring",
         "core/qstringlist",
         "core/qtime",
+        "core/qtlogging",
         "core/qurl",
         "core/qvariant/qvariant",
         "core/qvector/qvector",

crates/cxx-qt-lib/include/core/qtlogging.h

@@ -0,0 +1,48 @@
+// clang-format off
+// SPDX-FileCopyrightText: 2024 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+// clang-format on
+// SPDX-FileContributor: Joshua Goins <[email protected]>
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0
+#pragma once
+
+#include "rust/cxx.h"
+#include <QDebug>
+#include <QtCore/qlogging.h>
+
+int
+qmessagelogcontext_line(const QMessageLogContext& context);
+
+void
+qmessagelogcontext_set_line(QMessageLogContext& context, const int line);
+
+const char*
+qmessagelogcontext_file(const QMessageLogContext& context);
+
+void
+qmessagelogcontext_set_file(QMessageLogContext& context, const char* file);
+
+const char*
+qmessagelogcontext_function(const QMessageLogContext& context);
+
+void
+qmessagelogcontext_set_function(QMessageLogContext& context,
+                                const char* function);
+
+const char*
+qmessagelogcontext_category(const QMessageLogContext& context);
+
+void
+qmessagelogcontext_set_category(QMessageLogContext& context,
+                                const char* category);
+
+// Define namespace otherwise we hit a GCC bug
+// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56480
+namespace rust {
+
+template<>
+struct IsRelocatable<QMessageLogContext> : ::std::true_type
+{
+};
+
+} // namespace rust

crates/cxx-qt-lib/src/core/mod.rs

@@ -98,6 +98,9 @@ pub use qvariant::{QVariant, QVariantValue};
 mod qvector;
 pub use qvector::{QVector, QVectorElement};
 
+mod qtlogging;
+pub use qtlogging::{qt_message_output, QMessageLogContext, QtMsgType};
+
 #[cxx::bridge]
 mod ffi {
     #[namespace = "rust::cxxqtlib1"]

crates/cxx-qt-lib/src/core/qtlogging.cpp

@@ -0,0 +1,68 @@
+// clang-format off
+// SPDX-FileCopyrightText: 2024 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+// clang-format on
+// SPDX-FileContributor: Joshua Goins <[email protected]>
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0
+#include "cxx-qt-lib/qtlogging.h"
+
+#include "../assertion_utils.h"
+
+// QMessageLogContext has three "const char*" members for line, category, etc
+// https://codebrowser.dev/qt5/qtbase/src/corelib/global/qlogging.h.html#QMessageLogContext
+assert_alignment_and_size(QMessageLogContext,
+                          alignof(intptr_t),
+                          sizeof(intptr_t) * 4);
+
+static_assert(::std::is_trivially_copyable<QMessageLogContext>::value,
+              "QMessageLogContext must be trivially copyable");
+
+int
+qmessagelogcontext_line(const QMessageLogContext& context)
+{
+  return context.line;
+}
+
+void
+qmessagelogcontext_set_line(QMessageLogContext& context, const int line)
+{
+  context.line = line;
+}
+
+const char*
+qmessagelogcontext_file(const QMessageLogContext& context)
+{
+  return context.file;
+}
+
+void
+qmessagelogcontext_set_file(QMessageLogContext& context, const char* file)
+{
+  context.file = file;
+}
+
+const char*
+qmessagelogcontext_function(const QMessageLogContext& context)
+{
+  return context.function;
+}
+
+void
+qmessagelogcontext_set_function(QMessageLogContext& context,
+                                const char* function)
+{
+  context.function = function;
+}
+
+const char*
+qmessagelogcontext_category(const QMessageLogContext& context)
+{
+  return context.category;
+}
+
+void
+qmessagelogcontext_set_category(QMessageLogContext& context,
+                                const char* category)
+{
+  context.category = category;
+}

crates/cxx-qt-lib/src/core/qtlogging.rs

@@ -0,0 +1,146 @@
+// SPDX-FileCopyrightText: 2024 Klarälvdalens Datakonsult AB, a KDAB Group company <[email protected]>
+// SPDX-FileContributor: Joshua Goins <[email protected]>
+//
+// SPDX-License-Identifier: MIT OR Apache-2.0
+use cxx::{type_id, ExternType};
+use std::ffi::c_char;
+use std::ffi::CStr;
+use std::marker::PhantomData;
+
+#[cxx::bridge]
+mod ffi {
+    /// The level the message is sent to the message handler at.
+    #[repr(i32)]
+    enum QtMsgType {
+        /// A debug message.
+        QtDebugMsg = 0,
+        /// An info message.
+        QtInfoMsg = 4,
+        /// A warning message.
+        QtWarningMsg = 1,
+        /// A fatal message.
+        QtFatalMsg = 3,
+        /// A critical message.
+        QtCriticalMsg = 2,
+    }
+
+    unsafe extern "C++" {
+        include!("cxx-qt-lib/qstring.h");
+        type QString = crate::QString;
+
+        include!("cxx-qt-lib/qtlogging.h");
+        type QMessageLogContext<'a> = crate::QMessageLogContext<'a>;
+        type QtMsgType;
+
+        /// Outputs a message in the Qt message handler.
+        fn qt_message_output(msgType: QtMsgType, context: &QMessageLogContext, string: &QString);
+
+        #[cxx_name = "qmessagelogcontext_line"]
+        #[doc(hidden)]
+        fn line(context: &QMessageLogContext) -> i32;
+
+        #[cxx_name = "qmessagelogcontext_set_line"]
+        #[doc(hidden)]
+        fn set_line(context: &mut QMessageLogContext, line: i32);
+
+        #[cxx_name = "qmessagelogcontext_file"]
+        #[doc(hidden)]
+        unsafe fn file(context: &QMessageLogContext) -> *const c_char;
+
+        #[cxx_name = "qmessagelogcontext_set_file"]
+        #[doc(hidden)]
+        unsafe fn set_file(context: &mut QMessageLogContext, file: *const c_char);
+
+        #[cxx_name = "qmessagelogcontext_function"]
+        #[doc(hidden)]
+        unsafe fn function(context: &QMessageLogContext) -> *const c_char;
+
+        #[cxx_name = "qmessagelogcontext_set_function"]
+        #[doc(hidden)]
+        unsafe fn set_function(context: &mut QMessageLogContext, function: *const c_char);
+
+        #[cxx_name = "qmessagelogcontext_category"]
+        #[doc(hidden)]
+        unsafe fn category(context: &QMessageLogContext) -> *const c_char;
+
+        #[cxx_name = "qmessagelogcontext_set_category"]
+        #[doc(hidden)]
+        unsafe fn set_category(context: &mut QMessageLogContext, category: *const c_char);
+    }
+
+    #[namespace = "rust::cxxqtlib1"]
+    unsafe extern "C++" {
+        include!("cxx-qt-lib/common.h");
+
+        #[doc(hidden)]
+        #[rust_name = "qmessagelogcontext_default"]
+        fn construct() -> QMessageLogContext<'static>;
+    }
+}
+
+/// The QMessageLogContext struct defines the context passed to the Qt message handler.
+#[repr(C)]
+#[derive(Clone, Copy)]
+pub struct QMessageLogContext<'a> {
+    version: i32,
+    line: i32,
+    file: *const c_char,
+    function: *const c_char,
+    category: *const c_char,
+    _phantom: PhantomData<&'a c_char>,
+}
+
+impl Default for QMessageLogContext<'_> {
+    fn default() -> Self {
+        ffi::qmessagelogcontext_default()
+    }
+}
+
+impl<'a> QMessageLogContext<'a> {
+    pub fn new(
+        line: i32,
+        file: &'a *const c_char,
+        function: &'a *const c_char,
+        category: &'a *const c_char,
+    ) -> QMessageLogContext<'a> {
+        let mut context = QMessageLogContext::default();
+        unsafe {
+            ffi::set_line(&mut context, line);
+            ffi::set_file(&mut context, *file);
+            ffi::set_function(&mut context, *function);
+            ffi::set_category(&mut context, *category);
+        }
+
+        context
+    }
+
+    /// The line number given to the message handler.
+    pub fn line(&self) -> i32 {
+        ffi::line(self)
+    }
+
+    /// The file path given to the message handler.
+    pub fn file(&self) -> &CStr {
+        unsafe { CStr::from_ptr(ffi::file(self)) }
+    }
+
+    /// The name of the function given to the message handler.
+    pub fn function(&self) -> &CStr {
+        unsafe { CStr::from_ptr(ffi::function(self)) }
+    }
+
+    /// The category given to the message handler.
+    pub fn category(&self) -> &CStr {
+        unsafe { CStr::from_ptr(ffi::category(self)) }
+    }
+}
+
+// Safety:
+//
+// Static checks on the C++ side ensure that QMessageLogContext is trivial.
+unsafe impl ExternType for QMessageLogContext<'_> {
+    type Id = type_id!("QMessageLogContext");
+    type Kind = cxx::kind::Trivial;
+}
+
+pub use ffi::{qt_message_output, QtMsgType};