Qt: Set QStyleHints colorScheme property properly

common/CocoaTools.h

@@ -15,10 +15,6 @@ namespace CocoaTools
 	void DestroyMetalLayer(WindowInfo* wi);
 	std::optional<float> GetViewRefreshRate(const WindowInfo& wi);
 
-	/// Add a handler to be run when macOS changes between dark and light themes
-	void AddThemeChangeHandler(void* ctx, void(handler)(void* ctx));
-	/// Remove a handler previously added using AddThemeChangeHandler with the given context
-	void RemoveThemeChangeHandler(void* ctx);
 	/// Mark an NSMenu as the help menu
 	void MarkHelpMenu(void* menu);
 	/// Returns the bundle path.
@@ -44,6 +40,6 @@ namespace CocoaTools
 	void RunCocoaEventLoop(bool wait_forever = false);
 	/// Posts an event to the main telling `RunCocoaEventLoop(true)` to exit
 	void StopMainThreadEventLoop();
-}
+} // namespace CocoaTools
 
 #endif // __APPLE__

common/CocoaTools.mm

@@ -85,63 +85,7 @@
 	return ret;
 }
 
-// MARK: - Theme Change Handlers
-
-@interface PCSX2KVOHelper : NSObject
-
-- (void)addCallback:(void*)ctx run:(void(*)(void*))callback;
-- (void)removeCallback:(void*)ctx;
-
-@end
-
-@implementation PCSX2KVOHelper
-{
-	std::vector<std::pair<void*, void(*)(void*)>> _callbacks;
-}
-
-- (void)addCallback:(void*)ctx run:(void(*)(void*))callback
-{
-	_callbacks.push_back(std::make_pair(ctx, callback));
-}
-
-- (void)removeCallback:(void*)ctx
-{
-	auto new_end = std::remove_if(_callbacks.begin(), _callbacks.end(), [ctx](const auto& entry){
-		return ctx == entry.first;
-	});
-	_callbacks.erase(new_end, _callbacks.end());
-}
-
-- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context
-{
-	for (const auto& callback : _callbacks)
-		callback.second(callback.first);
-}
-
-@end
-
-static PCSX2KVOHelper* s_themeChangeHandler;
-
-void CocoaTools::AddThemeChangeHandler(void* ctx, void(handler)(void* ctx))
-{
-	assert([NSThread isMainThread]);
-	if (!s_themeChangeHandler)
-	{
-		s_themeChangeHandler = [[PCSX2KVOHelper alloc] init];
-		NSApplication* app = [NSApplication sharedApplication];
-		[app addObserver:s_themeChangeHandler
-		      forKeyPath:@"effectiveAppearance"
-		         options:0
-		         context:nil];
-	}
-	[s_themeChangeHandler addCallback:ctx run:handler];
-}
-
-void CocoaTools::RemoveThemeChangeHandler(void* ctx)
-{
-	assert([NSThread isMainThread]);
-	[s_themeChangeHandler removeCallback:ctx];
-}
+// MARK: - Help menu
 
 void CocoaTools::MarkHelpMenu(void* menu)
 {

pcsx2-qt/Debugger/DisassemblyView.cpp

@@ -939,7 +939,7 @@ inline QString DisassemblyView::DisassemblyStringFromAddress(u32 address, QFont
 QColor DisassemblyView::GetAddressFunctionColor(u32 address)
 {
 	std::array<QColor, 6> colors;
-	if (QtUtils::IsLightTheme(palette()))
+	if (!QtHost::IsDarkApplicationTheme())
 	{
 		colors = {
 			QColor::fromRgba(0xFFFA3434),

pcsx2-qt/Debugger/Docking/DropIndicators.cpp

@@ -3,6 +3,7 @@
 
 #include "DropIndicators.h"
 
+#include "QtHost.h"
 #include "QtUtils.h"
 #include "Debugger/Docking/DockViews.h"
 
@@ -21,7 +22,7 @@ static std::pair<QColor, QColor> pickNiceColours(const QPalette& palette, bool h
 	QColor fill = palette.highlight().color();
 	QColor outline = palette.highlight().color();
 
-	if (QtUtils::IsLightTheme(palette))
+	if (!QtHost::IsDarkApplicationTheme())
 	{
 		fill = fill.darker(200);
 		outline = outline.darker(200);
@@ -197,7 +198,7 @@ static const constexpr int INDICATOR_MARGIN = 10;
 static bool isWayland()
 {
 	return KDDockWidgets::Core::Platform::instance()->displayType() ==
-		   KDDockWidgets::Core::Platform::DisplayType::Wayland;
+	       KDDockWidgets::Core::Platform::DisplayType::Wayland;
 }
 
 static QWidget* parentForIndicatorWindow(KDDockWidgets::Core::ClassicDropIndicatorOverlay* classic_indicators)

pcsx2-qt/MainWindow.cpp

@@ -138,21 +138,11 @@ MainWindow::~MainWindow()
 #ifdef _WIN32
 	unregisterForDeviceNotifications();
 #endif
-#ifdef __APPLE__
-	CocoaTools::RemoveThemeChangeHandler(this);
-#endif
 }
 
 void MainWindow::initialize()
 {
 #ifdef __APPLE__
-	CocoaTools::AddThemeChangeHandler(this, [](void* ctx) {
-		// This handler is called *before* the style change has propagated far enough for Qt to see it
-		// Use RunOnUIThread to delay until it has
-		QtHost::RunOnUIThread([ctx = static_cast<MainWindow*>(ctx)] {
-			ctx->updateTheme(); // Qt won't notice the style change without us touching the palette in some way
-		});
-	});
 	// The cocoa backing isn't initialized yet, delay this until stuff is set up with a `RunOnUIThread` call
 	QtHost::RunOnUIThread([this] {
 		CocoaTools::MarkHelpMenu(m_ui.menuHelp->toNSMenu());

pcsx2-qt/QtUtils.cpp

@@ -90,7 +90,9 @@ namespace QtUtils
 
 		const int min_column_width = header->minimumSectionSize();
 		const int scrollbar_width = ((view->verticalScrollBar() && view->verticalScrollBar()->isVisible()) ||
-			view->verticalScrollBarPolicy() == Qt::ScrollBarAlwaysOn) ? view->verticalScrollBar()->width() : 0;
+										view->verticalScrollBarPolicy() == Qt::ScrollBarAlwaysOn) ?
+		                                view->verticalScrollBar()->width() :
+		                                0;
 		int num_flex_items = 0;
 		int total_width = 0;
 		int column_index = 0;
@@ -346,11 +348,6 @@ namespace QtUtils
 		return csv;
 	}
 
-	bool IsLightTheme(const QPalette& palette)
-	{
-		return palette.text().color().lightnessF() < 0.5;
-	}
-
 	bool IsCompositorManagerRunning()
 	{
 		if (qEnvironmentVariableIsSet("PCSX2_NO_COMPOSITING"))

pcsx2-qt/QtUtils.h

@@ -96,9 +96,7 @@ namespace QtUtils
 	/// Converts an abstract item model to a CSV string.
 	QString AbstractItemModelToCSV(QAbstractItemModel* model, int role = Qt::DisplayRole, bool useQuotes = false);
 
-	// Heuristic to check if the current theme is a light or dark theme.
-	bool IsLightTheme(const QPalette& palette);
-
+	/// Checks if we can use transparency effects e.g. for dock drop indicators.
 	bool IsCompositorManagerRunning();
 
 	/// Sets the scalable icon to a given label (svg icons, or icons with multiple size pixmaps)

pcsx2-qt/Themes.cpp

@@ -11,19 +11,27 @@
 #include <QtCore/QFile>
 #include <QtGui/QPalette>
 #include <QtGui/QPixmapCache>
+#include <QtGui/QStyleHints>
 #include <QtWidgets/QApplication>
 #include <QtWidgets/QStyle>
 #include <QtWidgets/QStyleFactory>
 
 namespace QtHost
 {
 	static void SetStyleFromSettings();
+	static void SetColorScheme(Qt::ColorScheme color_scheme);
 } // namespace QtHost
 
 static QString s_unthemed_style_name;
 static QPalette s_unthemed_palette;
 static bool s_unthemed_style_name_set;
 
+// This is different than the result of qApp->styleHints()->colorScheme() since
+// if we set that to Qt::ColorScheme::Unknown it would return what the Qt
+// platform code thinks is the correct color scheme instead (it can still return
+// Qt::ColorScheme::Unknown if it doesn't know).
+static Qt::ColorScheme s_color_scheme = Qt::ColorScheme::Unknown;
+
 const char* QtHost::GetDefaultThemeName()
 {
 #ifdef __APPLE__
@@ -54,8 +62,18 @@ void QtHost::UpdateApplicationTheme()
 
 bool QtHost::IsDarkApplicationTheme()
 {
+	// If the current theme uses a fixed color scheme just return that.
+	if (s_color_scheme != Qt::ColorScheme::Unknown)
+		return s_color_scheme == Qt::ColorScheme::Dark;
+
+	// Otherwise, fallback to using the palette heuristic. We don't bother
+	// asking the Qt platform code because it sometimes returns the wrong
+	// result. In particular, if the Windows Classic (windowsvista) theme is
+	// applied, and dark mode is enabled in the OS, it will return
+	// Qt::ColorScheme::Dark even though it's a light theme. We also can't treat
+	// it as a fixed color theme because of high contrast mode.
 	QPalette palette = qApp->palette();
-	return (palette.windowText().color().value() > palette.window().color().value());
+	return palette.windowText().color().value() > palette.window().color().value();
 }
 
 void QtHost::SetIconThemeFromStyle()
@@ -73,13 +91,18 @@ void QtHost::SetStyleFromSettings()
 		qApp->setStyle(QStyleFactory::create("Fusion"));
 		qApp->setPalette(s_unthemed_palette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Unknown);
 	}
 #ifdef _WIN32
 	else if (theme == "windowsvista")
 	{
 		qApp->setStyle(QStyleFactory::create("windowsvista"));
 		qApp->setPalette(s_unthemed_palette);
 		qApp->setStyleSheet(QString());
+
+		// We can't set this to Qt::ColorScheme::Light because that breaks high
+		// contrast themes on Windows.
+		SetColorScheme(Qt::ColorScheme::Unknown);
 	}
 #endif
 	else if (theme == "darkfusion")
@@ -116,6 +139,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(darkPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "darkfusionblue")
 	{
@@ -151,6 +175,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(darkBluePalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "GreyMatter")
 	{
@@ -187,6 +212,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(greyMatterPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "UntouchedLagoon")
 	{
@@ -222,6 +248,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(untouchedLagoonPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Light);
 	}
 	else if (theme == "BabyPastel")
 	{
@@ -259,6 +286,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(babyPastelPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Light);
 	}
 	else if (theme == "PizzaBrown")
 	{
@@ -296,6 +324,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(pizzaPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Light);
 	}
 	else if (theme == "PCSX2Blue")
 	{
@@ -331,6 +360,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(pcsx2BluePalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Light);
 	}
 	else if (theme == "ScarletDevilRed")
 	{
@@ -364,6 +394,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(scarletDevilPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "VioletAngelPurple")
 	{
@@ -397,6 +428,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(violetAngelPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "CobaltSky")
 	{
@@ -434,6 +466,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(cobaltSkyPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "AMOLED")
 	{
@@ -470,6 +503,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(AMOLEDPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "Ruby")
 	{
@@ -503,6 +537,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(rubyPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "Sapphire")
 	{
@@ -536,6 +571,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(sapphirePalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "Emerald")
 	{
@@ -569,6 +605,7 @@ void QtHost::SetStyleFromSettings()
 
 		qApp->setPalette(emeraldPalette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Dark);
 	}
 	else if (theme == "Custom")
 	{
@@ -587,11 +624,20 @@ void QtHost::SetStyleFromSettings()
 		{
 			qApp->setStyle(QStyleFactory::create("Fusion"));
 		}
+
+		SetColorScheme(Qt::ColorScheme::Unknown);
 	}
 	else
 	{
 		qApp->setStyle(s_unthemed_style_name);
 		qApp->setPalette(s_unthemed_palette);
 		qApp->setStyleSheet(QString());
+		SetColorScheme(Qt::ColorScheme::Unknown);
 	}
 }
+
+static void QtHost::SetColorScheme(Qt::ColorScheme color_scheme)
+{
+	s_color_scheme = color_scheme;
+	qApp->styleHints()->setColorScheme(color_scheme);
+}