Merge pull request #83 from mappu/miqt-lockosthread

Call runtime.LockOSThread() automatically for the Qt main thread

README.md

@@ -89,6 +89,8 @@ Qt class inherited types are projected as a Go embedded struct. For example, to
 
 - When a Qt subclass adds a method overload (e.g. `QMenu::addAction(QString)` vs `QWidget::addAction(QAction*)`), the base class version is shadowed and can only be called via `myQMenu.QWidget.AddAction(QAction*)`.
 
+The Go runtime migrates goroutines between OS threads, but Qt expects fixed OS threads to be used for each QObject. When you first call `qt.NewQApplication` in MIQT, that will be considered the [Qt main thread](https://doc.qt.io/qt-6/thread-basics.html#gui-thread-and-worker-thread) and will automatically signal the Go runtime to bind to a fixed OS thread using `runtime.LockOSThread()`.
+
 Some C++ idioms that were difficult to project were omitted from the binding. But, this can be improved in the future.
 
 ### Q6. Can I use Qt Designer and the Qt Resource system?

cmd/genbindings/emitgo.go

@@ -272,6 +272,12 @@ func (gfs *goFileState) emitParametersGo2CABIForwarding(m CppMethod) (preamble s
 
 			tmp = append(tmp, "argc, &argv[0]")
 
+			// Additional quirk for QApplication constructor: bind to OS thread
+			gfs.imports["runtime"] = struct{}{}
+			preamble += "\n"
+			preamble += "runtime.LockOSThread() // Prevent Go from migrating the main Qt thread\n"
+			preamble += "\n"
+
 		} else if skipNext {
 			// Skip this parameter, already handled
 			skipNext = false

qt/gen_qapplication.go

@@ -61,6 +61,9 @@ func NewQApplication(args []string) *QApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QApplication_new(argc, &argv[0])
 	return newQApplication(ret)
 }
@@ -74,6 +77,9 @@ func NewQApplication2(args []string, param3 int) *QApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QApplication_new2(argc, &argv[0], (C.int)(param3))
 	return newQApplication(ret)
 }

qt/gen_qcoreapplication.go

@@ -59,6 +59,9 @@ func NewQCoreApplication(args []string) *QCoreApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QCoreApplication_new(argc, &argv[0])
 	return newQCoreApplication(ret)
 }
@@ -72,6 +75,9 @@ func NewQCoreApplication2(args []string, param3 int) *QCoreApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QCoreApplication_new2(argc, &argv[0], (C.int)(param3))
 	return newQCoreApplication(ret)
 }

qt/gen_qguiapplication.go

@@ -53,6 +53,9 @@ func NewQGuiApplication(args []string) *QGuiApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QGuiApplication_new(argc, &argv[0])
 	return newQGuiApplication(ret)
 }
@@ -66,6 +69,9 @@ func NewQGuiApplication2(args []string, param3 int) *QGuiApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QGuiApplication_new2(argc, &argv[0], (C.int)(param3))
 	return newQGuiApplication(ret)
 }

qt6/gen_qapplication.go

@@ -53,6 +53,9 @@ func NewQApplication(args []string) *QApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QApplication_new(argc, &argv[0])
 	return newQApplication(ret)
 }
@@ -66,6 +69,9 @@ func NewQApplication2(args []string, param3 int) *QApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QApplication_new2(argc, &argv[0], (C.int)(param3))
 	return newQApplication(ret)
 }

qt6/gen_qcoreapplication.go

@@ -59,6 +59,9 @@ func NewQCoreApplication(args []string) *QCoreApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QCoreApplication_new(argc, &argv[0])
 	return newQCoreApplication(ret)
 }
@@ -72,6 +75,9 @@ func NewQCoreApplication2(args []string, param3 int) *QCoreApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QCoreApplication_new2(argc, &argv[0], (C.int)(param3))
 	return newQCoreApplication(ret)
 }

qt6/gen_qguiapplication.go

@@ -53,6 +53,9 @@ func NewQGuiApplication(args []string) *QGuiApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QGuiApplication_new(argc, &argv[0])
 	return newQGuiApplication(ret)
 }
@@ -66,6 +69,9 @@ func NewQGuiApplication2(args []string, param3 int) *QGuiApplication {
 	for i := range args {
 		argv[i] = C.CString(args[i])
 	}
+
+	runtime.LockOSThread() // Prevent Go from migrating the main Qt thread
+
 	ret := C.QGuiApplication_new2(argc, &argv[0], (C.int)(param3))
 	return newQGuiApplication(ret)
 }