Ignore spontaneous tablet events in canvas instead

Rather than doing it with an event filter, because that apparently
doesn't work properly and still lets spontaneous events through. They're
now ignored in the canvas controller/canvas view instead.

ChangeLog

@@ -18,6 +18,7 @@ Unreleased Version 2.2.2-pre
  * Fix: Don't carry over HUD button presses to dock UI in small screen mode. Thanks Meru for reporting.
  * Feature: Make list action buttons in settings dialog clearer, adding an edit button for canvas shortcuts. Thanks Maffi for suggesting.
  * Fix: Work around broken transparency when copying images between canvases on Wayland. Thanks Absolute Goober for reporting.
+ * Fix: Properly ignore system tablet events when using KisTablet drivers on Windows. Thanks Doc 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/CMakeLists.txt

@@ -316,6 +316,7 @@ target_sources(drawpile PRIVATE
 	utils/qtguicompat.h
 	utils/recents.cpp
 	utils/recents.h
+	utils/tabletfilter.h
 	utils/touchhandler.cpp
 	utils/touchhandler.h
 	utils/widgetutils.cpp

src/desktop/main.h

@@ -93,6 +93,7 @@ class DrawpileApp final : public QApplication {
 	void setDockTitleBarsHidden(bool hidden);
 	void focusCanvas();
 	void shortcutsChanged();
+	void tabletDriverChanged();
 
 protected:
 	bool event(QEvent *e) override;

src/desktop/scene/canvasview.cpp

@@ -206,7 +206,12 @@ CanvasView::CanvasView(QWidget *parent)
 	setAcceptDrops(true);
 	setFrameShape(QFrame::NoFrame);
 
-	auto &settings = dpApp().settings();
+	DrawpileApp &app = dpApp();
+	connect(
+		&app, &DrawpileApp::tabletDriverChanged, this,
+		&CanvasView::resetTabletFilter, Qt::QueuedConnection);
+
+	desktop::settings::Settings &settings = app.settings();
 	settings.bindCanvasViewBackgroundColor(this, [this](QColor color) {
 		color.setAlpha(255);
 		setBackgroundBrush(color);
@@ -1024,6 +1029,8 @@ void CanvasView::enterEvent(compat::EnterEvent *event)
 		 oldfocus->inherits("QPlainTextEdit"))) {
 		setFocus(Qt::MouseFocusReason);
 	}
+
+	m_tabletFilter.reset();
 }
 
 void CanvasView::leaveEvent(QEvent *event)
@@ -1037,6 +1044,7 @@ void CanvasView::leaveEvent(QEvent *event)
 	m_scene->removeHover();
 	updateOutline();
 	resetCursor();
+	m_tabletFilter.reset();
 }
 
 void CanvasView::focusInEvent(QFocusEvent *event)
@@ -1211,6 +1219,11 @@ void CanvasView::startTabletEventTimer()
 	}
 }
 
+void CanvasView::resetTabletFilter()
+{
+	m_tabletFilter.reset();
+}
+
 void CanvasView::penPressEvent(
 	QEvent *event, long long timeMsec, const QPointF &pos, qreal pressure,
 	qreal xtilt, qreal ytilt, qreal rotation, Qt::MouseButton button,
@@ -2006,16 +2019,20 @@ bool CanvasView::viewportEvent(QEvent *event)
 		QTabletEvent *tabev = static_cast<QTabletEvent *>(event);
 		const auto tabPos = compat::tabPosF(*tabev);
 		Qt::KeyboardModifiers modifiers = getTabletModifiers(tabev);
+		bool ignore = m_tabletFilter.shouldIgnore(tabev);
 		DP_EVENT_LOG(
 			"tablet_press spontaneous=%d x=%f y=%f pressure=%f xtilt=%d "
 			"ytilt=%d rotation=%f buttons=0x%x modifiers=0x%x pendown=%d "
-			"touching=%d effectivemodifiers=0x%u",
-			tabev->spontaneous(), tabPos.x(), tabPos.y(), tabev->pressure(),
-			compat::cast_6<int>(tabev->xTilt()),
+			"touching=%d effectivemodifiers=0x%u ignore=%d",
+			int(tabev->spontaneous()), tabPos.x(), tabPos.y(),
+			tabev->pressure(), compat::cast_6<int>(tabev->xTilt()),
 			compat::cast_6<int>(tabev->yTilt()),
 			qDegreesToRadians(tabev->rotation()), unsigned(tabev->buttons()),
 			unsigned(tabev->modifiers()), m_pendown, m_touch->isTouching(),
-			unsigned(modifiers));
+			unsigned(modifiers), int(ignore));
+		if(ignore) {
+			return true;
+		}
 
 		Qt::MouseButton button;
 		bool eraserOverride;
@@ -2057,16 +2074,20 @@ bool CanvasView::viewportEvent(QEvent *event)
 		const auto tabPos = compat::tabPosF(*tabev);
 		Qt::KeyboardModifiers modifiers = getTabletModifiers(tabev);
 		Qt::MouseButtons buttons = tabev->buttons();
+		bool ignore = m_tabletFilter.shouldIgnore(tabev);
 		DP_EVENT_LOG(
 			"tablet_move spontaneous=%d x=%f y=%f pressure=%f xtilt=%d "
 			"ytilt=%d rotation=%f buttons=0x%x modifiers=0x%x pendown=%d "
-			"touching=%d effectivemodifiers=0x%u",
-			tabev->spontaneous(), tabPos.x(), tabPos.y(), tabev->pressure(),
-			compat::cast_6<int>(tabev->xTilt()),
+			"touching=%d effectivemodifiers=0x%u ignore=%d",
+			int(tabev->spontaneous()), tabPos.x(), tabPos.y(),
+			tabev->pressure(), compat::cast_6<int>(tabev->xTilt()),
 			compat::cast_6<int>(tabev->yTilt()),
 			qDegreesToRadians(tabev->rotation()), unsigned(buttons),
 			unsigned(tabev->modifiers()), m_pendown, m_touch->isTouching(),
-			unsigned(modifiers));
+			unsigned(modifiers), int(ignore));
+		if(ignore) {
+			return true;
+		}
 
 		if(!tabletinput::passPenEvents()) {
 			tabev->accept();
@@ -2091,12 +2112,17 @@ bool CanvasView::viewportEvent(QEvent *event)
 		QTabletEvent *tabev = static_cast<QTabletEvent *>(event);
 		const auto tabPos = compat::tabPosF(*tabev);
 		Qt::KeyboardModifiers modifiers = getTabletModifiers(tabev);
+		bool ignore = m_tabletFilter.shouldIgnore(tabev);
 		DP_EVENT_LOG(
 			"tablet_release spontaneous=%d x=%f y=%f buttons=0x%x pendown=%d "
-			"touching=%d effectivemodifiers=0x%u",
-			tabev->spontaneous(), tabPos.x(), tabPos.y(),
+			"touching=%d effectivemodifiers=0x%u ignore=%d",
+			int(tabev->spontaneous()), tabPos.x(), tabPos.y(),
 			unsigned(tabev->buttons()), m_pendown, m_touch->isTouching(),
-			unsigned(modifiers));
+			unsigned(modifiers), int(ignore));
+		if(ignore) {
+			return true;
+		}
+
 		updateCursorPos(tabPos.toPoint());
 		if(!tabletinput::passPenEvents()) {
 			tabev->accept();

src/desktop/scene/canvasview.h

@@ -2,6 +2,7 @@
 #ifndef DESKTOP_SCENE_CANVASVIEW
 #define DESKTOP_SCENE_CANVASVIEW
 #include "desktop/utils/qtguicompat.h"
+#include "desktop/utils/tabletfilter.h"
 #include "desktop/view/lock.h"
 #include "libclient/canvas/canvasshortcuts.h"
 #include "libclient/canvas/point.h"
@@ -274,6 +275,7 @@ private slots:
 	class SetDragParams;
 
 	void startTabletEventTimer();
+	void resetTabletFilter();
 
 	// unified mouse/stylus event handlers
 	void penPressEvent(
@@ -457,6 +459,7 @@ private slots:
 #ifdef Q_OS_LINUX
 	bool m_waylandWorkarounds;
 #endif
+	TabletFilter m_tabletFilter;
 };
 
 }

src/desktop/tabletinput.cpp

@@ -20,45 +20,12 @@ static Mode currentMode = Mode::Uninitialized;
 
 #ifdef Q_OS_WIN
 
-class SpontaneousTabletEventFilter final : public QObject {
-public:
-	explicit SpontaneousTabletEventFilter(QObject *parent)
-		: QObject{parent}
-	{
-	}
-
-protected:
-	bool eventFilter(QObject *watched, QEvent *event) override final
-	{
-		switch(event->type()) {
-		case QEvent::TabletEnterProximity:
-		case QEvent::TabletLeaveProximity:
-		case QEvent::TabletMove:
-		case QEvent::TabletPress:
-		case QEvent::TabletRelease:
-			// KisTablet uses QApplication::sendEvent, which means its events
-			// are never set to be spontaneous. We use that to filter out Qt's
-			// own tablet events, which in turn are always spontaneous.
-			if(event->spontaneous()) {
-				return false;
-			}
-			[[fallthrough]];
-		default:
-			return QObject::eventFilter(watched, event);
-		}
-	}
-};
-
 static KisTabletSupportWin8 *kisTabletSupportWin8;
-static SpontaneousTabletEventFilter *spontaneousTabletEventFilter;
+static bool shouldPassPenEvents = true;
 
 static void resetKisTablet(DrawpileApp &app)
 {
-	if(spontaneousTabletEventFilter) {
-		app.removeEventFilter(spontaneousTabletEventFilter);
-		delete spontaneousTabletEventFilter;
-		spontaneousTabletEventFilter = nullptr;
-	}
+	shouldPassPenEvents = true;
 	if(kisTabletSupportWin8) {
 		app.removeNativeEventFilter(kisTabletSupportWin8);
 		delete kisTabletSupportWin8;
@@ -67,17 +34,11 @@ static void resetKisTablet(DrawpileApp &app)
 	KisTabletSupportWin::quit();
 }
 
-static void installSpontaneousTabletEventFilter(DrawpileApp &app)
-{
-	spontaneousTabletEventFilter = new SpontaneousTabletEventFilter{&app};
-	app.installEventFilter(spontaneousTabletEventFilter);
-}
-
 static void enableKisTabletWinink(DrawpileApp &app)
 {
 	kisTabletSupportWin8 = new KisTabletSupportWin8;
 	if(kisTabletSupportWin8->init()) {
-		installSpontaneousTabletEventFilter(app);
+		shouldPassPenEvents = false;
 		app.installNativeEventFilter(kisTabletSupportWin8);
 		currentMode = Mode::KisTabletWinink;
 	} else {
@@ -87,10 +48,10 @@ static void enableKisTabletWinink(DrawpileApp &app)
 	}
 }
 
-static void enableKisTabletWintab(DrawpileApp &app, bool relativePenModeHack)
+static void enableKisTabletWintab(bool relativePenModeHack)
 {
 	if(KisTabletSupportWin::init()) {
-		installSpontaneousTabletEventFilter(app);
+		shouldPassPenEvents = false;
 		KisTabletSupportWin::enableRelativePenModeHack(relativePenModeHack);
 		if(relativePenModeHack) {
 			currentMode = Mode::KisTabletWintabRelativePenHack;
@@ -148,10 +109,10 @@ void init(DrawpileApp &app)
 			enableKisTabletWinink(app);
 			break;
 		case Mode::KisTabletWintab:
-			enableKisTabletWintab(app, false);
+			enableKisTabletWintab(false);
 			break;
 		case Mode::KisTabletWintabRelativePenHack:
-			enableKisTabletWintab(app, true);
+			enableKisTabletWintab(true);
 			break;
 #	if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
 		case Mode::Qt5:
@@ -171,6 +132,7 @@ void init(DrawpileApp &app)
 		case Mode::Uninitialized:
 			break;
 		}
+		emit app.tabletDriverChanged();
 	});
 #else
 	// Nothing to do on other platforms.
@@ -201,9 +163,7 @@ const char *current()
 #ifdef Q_OS_WIN
 bool passPenEvents()
 {
-	// The spontaneous event filter is installed if and only if a KisTablet
-	// input mode is currently active.
-	return !spontaneousTabletEventFilter;
+	return shouldPassPenEvents;
 }
 #endif
 

src/desktop/tabletinput.h

@@ -1,12 +1,17 @@
 // SPDX-License-Identifier: GPL-3.0-or-later
-#ifndef TABLETINPUT_H
-#define TABLETINPUT_H
-
+#ifndef DESTKOP_TABLETINPUT_H
+#define DESTKOP_TABLETINPUT_H
 #include <QMetaType>
 #include <QString>
 
 class DrawpileApp;
 
+#ifdef Q_OS_WIN
+#	define TABLETINPUT_CONSTEXPR_OR_INLINE inline
+#else
+#	define TABLETINPUT_CONSTEXPR_OR_INLINE constexpr
+#endif
+
 namespace tabletinput {
 Q_NAMESPACE
 
@@ -60,6 +65,11 @@ constexpr bool passPenEvents()
 }
 #endif
 
+TABLETINPUT_CONSTEXPR_OR_INLINE bool ignoreSpontaneous()
+{
+	return !passPenEvents();
+}
+
 }
 
 #endif

src/desktop/utils/tabletfilter.h

@@ -0,0 +1,39 @@
+#ifndef DESKTOP_UTILS_TABLETFILTER_H
+#define DESKTOP_UTILS_TABLETFILTER_H
+#include "desktop/tabletinput.h"
+#include <QTabletEvent>
+
+class TabletFilter {
+public:
+	TABLETINPUT_CONSTEXPR_OR_INLINE void reset()
+	{
+#ifdef Q_OS_WIN
+		m_ignoreSpontaneous = false;
+#endif
+	}
+
+	TABLETINPUT_CONSTEXPR_OR_INLINE bool shouldIgnore(const QTabletEvent *event)
+	{
+#ifdef Q_OS_WIN
+		bool spontaneous = event->spontaneous();
+		if(m_ignoreSpontaneous) {
+			return spontaneous;
+		} else {
+			if(!spontaneous && tabletinput::ignoreSpontaneous()) {
+				m_ignoreSpontaneous = true;
+			}
+			return false;
+		}
+#else
+		Q_UNUSED(event);
+		return false;
+#endif
+	}
+
+#ifdef Q_OS_WIN
+private:
+	bool m_ignoreSpontaneous = false;
+#endif
+};
+
+#endif