UI: Disable QT's implicit colourspace conversion on macOS

Fixes issues as described in https://bugreports.qt.io/browse/QTBUG-47660
and halves CPU usage of OBS' UI by about 40-50%.

UI/platform-osx.mm

@@ -144,6 +144,13 @@ bool IsAlwaysOnTop(QWidget *window)
 	return (window->windowFlags() & Qt::WindowStaysOnTopHint) != 0;
 }
 
+void disableColorSpaceConversion(QWidget *window)
+{
+	NSView *view =
+		(__bridge NSView *)reinterpret_cast<void *>(window->winId());
+	view.window.colorSpace = NSColorSpace.sRGBColorSpace;
+}
+
 void SetAlwaysOnTop(QWidget *window, bool enable)
 {
 	Qt::WindowFlags flags = window->windowFlags();

UI/platform.hpp

@@ -67,4 +67,5 @@ QString GetMonitorName(const QString &id);
 void EnableOSXVSync(bool enable);
 void EnableOSXDockIcon(bool enable);
 void InstallNSApplicationSubclass();
+void disableColorSpaceConversion(QWidget *window);
 #endif

UI/window-basic-main.cpp

@@ -1867,6 +1867,10 @@ void OBSBasic::OBSInit()
 	SystemTray(true);
 #endif
 
+#ifdef __APPLE__
+	disableColorSpaceConversion(this);
+#endif
+
 	bool has_last_version = config_has_user_value(App()->GlobalConfig(),
 						      "General", "LastVersion");
 	bool first_run =