sola/qwindowkit.git

			@@ -9,6 +9,28 @@
			namespace QWK {

			#if QWINDOWKIT_CONFIG(ENABLE_WINDOWS_SYSTEM_BORDER)
			// https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowsbackingstore.cpp#L42
			// In QtWidgets applications, when repainting happens, QPA at the last calls
			// QWindowsBackingStore::flush() to draw the contents of the buffer to the screen, we need to
			// call GDI drawing the top border after that.

			// After debugging, we know that there are two situations that will lead to redrawing.
			//
			// 1. Windows sends a WM_PAINT message, after which Qt immediately generates a QExposeEvent or
			// QResizeEvent and send it to the corresponding QWidgetWindow instance, calling "flush" at the
			// end of its handler.
			//
			// 2. When a timer or user input triggers Qt to redraw spontaneously, the corresponding
			// QWidget receives a QEvent::UpdateRequest event and also calls "flush" at the end of its
			// handler.
			//
			// The above two cases are mutually exclusive, so we just need to intercept the two events
			// separately and draw the border area after the "flush" is called.

			// https://github.com/qt/qtbase/blob/e26a87f1ecc40bc8c6aa5b889fce67410a57a702/src/plugins/platforms/windows/qwindowswindow.cpp#L2440
			// Note that we can not draw the border right after WM_PAINT comes or right before the WndProc
			// returns, because Qt calls BeginPaint() and EndPaint() itself. We should make sure that we
			// draw the top border between these two calls, otherwise some display exceptions may arise.

			class WidgetBorderHandler : public QObject, public NativeEventFilter, public SharedEventFilter {
			public:
			@@ -21,6 +43,8 @@
			// Must extend top frame to client area
			static QVariant defaultMargins = QVariant::fromValue(QMargins(0, 1, 0, 0));
			ctx->setWindowAttribute(QStringLiteral("extra-margins"), defaultMargins);

			// Enable dark mode by default, otherwise the frame borders are white
			ctx->setWindowAttribute(QStringLiteral("dark-mode"), true);

			ctx->installNativeEventFilter(this);
			@@ -41,6 +65,37 @@
			} else {
			widget->setContentsMargins({});
			}
			}

			inline void resumeWidgetEvent(QWidget w, QEvent event) {
			// Friend class helping to call `event`
			class HackedWidget : public QWidget {
			public:
			friend class QWK::WidgetBorderHandler;
			};

			// Let the widget paint first
			static_cast<HackedWidget *>(w)->event(event);

			// Due to the timer or user action, Qt will redraw some regions spontaneously,
			// even if there is no WM_PAINT message, we must wait for it to finish redrawing
			// and then update the top border area.
			ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
			}

			inline void resumeWindowEvent(QWindow window, QEvent event) {
			// Friend class helping to call `event`
			class HackedWindow : public QWindow {
			public:
			friend class QWK::WidgetBorderHandler;
			};

			// Let Qt paint first
			static_cast<HackedWindow *>(window)->event(event);

			// Upon receiving the WM_PAINT message, Qt will redraw the entire view, and we
			// must wait for it to finish redrawing before drawing this top border area.
			ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
			}

			protected:
			@@ -83,28 +138,22 @@
			Q_UNUSED(obj)

			auto window = widget->windowHandle();
			if (event->type() == QEvent::Expose) {
			// Qt will absolutely send a QExposeEvent to the QWindow when it receives a
			// WM_PAINT message. When the control flow enters the expose handler, Qt must
			// have already called BeginPaint() and it's the best time for us to draw the

			// Qt will absolutely send a QExposeEvent or QResizeEvent to the QWindow when it
			// receives a WM_PAINT message. When the control flow enters the expose handler, Qt
			// must have already called BeginPaint() and it's the best time for us to draw the
			// top border.

			// Since a QExposeEvent will be sent immediately after the QResizeEvent, we can simply
			// ignore it.
			if (event->type() == QEvent::Expose) {
			auto ee = static_cast<QExposeEvent *>(event);
			if (isNormalWindow() && window->isExposed() && !ee->region().isNull()) {
			// Friend class helping to call `event`
			class HackedWindow : public QWindow {
			public:
			friend class QWK::WidgetBorderHandler;
			};

			// Let Qt paint first
			static_cast<HackedWindow *>(window)->event(event);

			// Upon receiving the WM_PAINT message, Qt will redraw the entire view, and we
			// must wait for it to finish redrawing before drawing this top border area.
			ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
			if (window->isExposed() && !ee->region().isNull()) {
			resumeWindowEvent(window, event);
			return true;
			}
			}

			return false;
			}

			@@ -114,20 +163,7 @@
			case QEvent::UpdateRequest: {
			if (!isNormalWindow())
			break;

			// Friend class helping to call `event`
			class HackedWidget : public QWidget {
			public:
			friend class QWK::WidgetBorderHandler;
			};

			// Let the widget paint first
			static_cast<HackedWidget *>(widget)->event(event);

			// Due to the timer or user action, Qt will redraw some regions spontaneously,
			// even if there is no WM_PAINT message, we must wait for it to finish redrawing
			// and then update the top border area.
			ctx->virtual_hook(AbstractWindowContext::DrawWindows10BorderHook2, nullptr);
			resumeWidgetEvent(widget, event);
			return true;
			}