Use fallback modifiers for tablet on Wayland

Another platform where the modifiers in the tablet events are garbage
apparently, so we use the same workaround as we do on Android and
Emscripten.

Also include the platform into the tablet event log, since that's
relevant stuff for it.

ChangeLog

@@ -11,6 +11,7 @@ Unreleased Version 2.2.2-pre
  * Fix: Don't default Android to fingerpaint when a pen is present.
  * Fix: Work around a crash on Android that sometimes occurs when putting your palm on the screen, which somehow leads to touch events with zero contact points. Thanks Mav for reporting.
  * Fix: Uncap aspect ratio on older Android versions. Thanks Molderche for reporting.
+ * Fix: Work around modifier keys not registering when using a tablet on Wayland. Thanks Absolute Goober for reporting.
 
 2024-11-06 Version 2.2.2-beta.4
  * Fix: Solve rendering glitches with selection outlines that happen on some systems. Thanks xxxx for reporting.

src/desktop/mainwindow.cpp

@@ -2387,6 +2387,7 @@ void MainWindow::toggleTabletEventLog()
 				DP_event_log_write_meta("Drawpile: %s", cmake_config::version());
 				DP_event_log_write_meta("Qt: %s", QT_VERSION_STR);
 				DP_event_log_write_meta("OS: %s", qUtf8Printable(QSysInfo::prettyProductName()));
+				DP_event_log_write_meta("Platform: %s", qUtf8Printable(QGuiApplication::platformName()));
 				DP_event_log_write_meta("Input: %s", tabletinput::current());
 				const desktop::settings::Settings &settings = dpApp().settings();
 				DP_event_log_write_meta("Tablet enabled: %d", settings.tabletEvents());

src/desktop/scene/canvasview.cpp

@@ -194,6 +194,10 @@ CanvasView::CanvasView(QWidget *parent)
 	, m_showTransformNotices(true)
 	, m_hoveringOverHud{false}
 	, m_renderSmooth(false)
+#ifdef Q_OS_LINUX
+	, m_waylandWorkarounds(
+		  QGuiApplication::platformName() == QStringLiteral("wayland"))
+#endif
 {
 	viewport()->setAcceptDrops(true);
 	viewport()->setAttribute(Qt::WA_AcceptTouchEvents);
@@ -2619,6 +2623,12 @@ CanvasView::getTabletModifiers(const QTabletEvent *tabev) const
 	Q_UNUSED(tabev);
 	return getFallbackModifiers();
 #else
+#	ifdef Q_OS_LINUX
+	// Tablet event modifiers aren't reported properly on Wayland.
+	if(m_waylandWorkarounds) {
+		return getFallbackModifiers();
+	}
+#	endif
 	return tabev->modifiers();
 #endif
 }

src/desktop/scene/canvasview.h

@@ -451,6 +451,9 @@ private slots:
 #ifdef __EMSCRIPTEN__
 	bool m_enableEraserOverride = false;
 #endif
+#ifdef Q_OS_LINUX
+	bool m_waylandWorkarounds;
+#endif
 };
 
 }

src/desktop/view/canvascontroller.cpp

@@ -168,6 +168,10 @@ CanvasController::CanvasController(CanvasScene *scene, QWidget *parent)
 	, m_brushBlendMode(DP_BLEND_MODE_NORMAL)
 	, m_touch(new TouchHandler(this))
 	, m_toolState(int(tools::ToolState::Normal))
+#ifdef Q_OS_LINUX
+	, m_waylandWorkarounds(
+		  QGuiApplication::platformName() == QStringLiteral("wayland"))
+#endif
 {
 	desktop::settings::Settings &settings = dpApp().settings();
 	settings.bindCanvasViewBackgroundColor(
@@ -2077,6 +2081,12 @@ CanvasController::getTabletModifiers(const QTabletEvent *event) const
 	Q_UNUSED(event);
 	return getFallbackModifiers();
 #else
+#	ifdef Q_OS_LINUX
+	// Tablet event modifiers aren't reported properly on Wayland.
+	if(m_waylandWorkarounds) {
+		return getFallbackModifiers();
+	}
+#	endif
 	return event->modifiers();
 #endif
 }

src/desktop/view/canvascontroller.h

@@ -422,6 +422,9 @@ class CanvasController : public QObject {
 	bool m_saveInProgress = false;
 
 	bool m_hoveringOverHud = false;
+#ifdef Q_OS_LINUX
+	bool m_waylandWorkarounds;
+#endif
 };
 
 }