fix: avoid hiding floating docks when the OBS app is not active.

This PR changes the behavior of floating docks on macOS to have them stay visible while the OBS app is not active.

The main change is to set the `NSWindow.hidesOnDeactivate` setting to false. This is enough to keep the docks visible.
The remaining changes are just making sure that this setting is consistent across all the different ways OBS creates docks.

In macOS, only one app can be "active" (aka "focused") at the time, and "floating panels" (OBS' docks in this case) disappear by default when their parent app is not active.

The issue is that disappearing floating panels defy many of the use cases that OBS is great for. For example:
- I'm doing game streaming on Twitch. I want to keep track of my chat.
- I have a floating panel displaying the "Twitch chat" dock on a side monitor.
- I click on my game, which becomes the active app. OBS is not the active app anymore, therefore the chat dock panel disappears.

This is a common issue between macOS users:
- https://obsproject.com/forum/threads/popped-out-docks-disappear-when-obs-is-not-in-focus.165011/
- https://obsproject.com/forum/threads/keep-dock-windows-visible-even-when-obs-is-not-in-focus.167324/

Author: TizianoCoroneo

frontend/docks/OBSDock.cpp

@@ -2,11 +2,26 @@
 
 #include <widgets/OBSBasic.hpp>
 
+#ifdef __APPLE__
+#include <utility/platform.hpp>
+#endif
+
 #include <QCheckBox>
 #include <QMessageBox>
+#include <QTimer>
 
 #include "moc_OBSDock.cpp"
 
+OBSDock::OBSDock(QWidget *parent) : QDockWidget(parent)
+{
+	InstallDockFloatingBehavior(this);
+}
+
+OBSDock::OBSDock(const QString &title, QWidget *parent) : QDockWidget(title, parent)
+{
+	InstallDockFloatingBehavior(this);
+}
+
 void OBSDock::closeEvent(QCloseEvent *event)
 {
 	auto msgBox = []() {
@@ -43,4 +58,24 @@ void OBSDock::closeEvent(QCloseEvent *event)
 void OBSDock::showEvent(QShowEvent *event)
 {
 	QDockWidget::showEvent(event);
+#ifdef __APPLE__
+	SetMacOSDockFloatingBehavior(this, isFloating());
+#endif
+}
+
+void InstallDockFloatingBehavior(QDockWidget *dock)
+{
+#ifdef __APPLE__
+	if (!dock)
+		return;
+
+	QObject::connect(dock, &QDockWidget::topLevelChanged, dock,
+			 [dock](bool) { SetMacOSDockFloatingBehavior(dock, dock->isFloating()); });
+
+	if (dock->isFloating()) {
+		QTimer::singleShot(0, dock, [dock]() { SetMacOSDockFloatingBehavior(dock, dock->isFloating()); });
+	}
+#else
+	Q_UNUSED(dock);
+#endif
 }

frontend/docks/OBSDock.hpp

@@ -10,9 +10,11 @@ class OBSDock : public QDockWidget {
 	Q_OBJECT
 
 public:
-	inline OBSDock(QWidget *parent = nullptr) : QDockWidget(parent) {}
-	inline OBSDock(const QString &title, QWidget *parent = nullptr) : QDockWidget(title, parent) {}
+	OBSDock(QWidget *parent = nullptr);
+	OBSDock(const QString &title, QWidget *parent = nullptr);
 
 	virtual void closeEvent(QCloseEvent *event);
 	virtual void showEvent(QShowEvent *event);
 };
+
+void InstallDockFloatingBehavior(QDockWidget *dock);

frontend/utility/platform-osx.mm

@@ -128,6 +128,24 @@ void SetAlwaysOnTop(QWidget *window, bool enable)
     window->show();
 }
 
+void SetMacOSDockFloatingBehavior(QWidget *window, bool floating)
+{
+    if (!window)
+        return;
+
+    NSView *view = (__bridge NSView *) reinterpret_cast<void *>(window->winId());
+    NSWindow *nsWindow = [view window];
+    if (!nsWindow)
+        return;
+
+    if (floating) {
+        nsWindow.level = NSFloatingWindowLevel;
+        nsWindow.hidesOnDeactivate = NO;
+    } else {
+        nsWindow.level = NSNormalWindowLevel;
+    }
+}
+
 bool SetDisplayAffinitySupported(void)
 {
     // Not implemented yet

frontend/utility/platform.hpp

@@ -101,6 +101,7 @@ void InstallNSApplicationSubclass();
 void InstallNSThreadLocks();
 void disableColorSpaceConversion(QWidget *window);
 void SetMacOSDarkMode(bool dark);
+void SetMacOSDockFloatingBehavior(QWidget *window, bool floating);
 
 MacPermissionStatus CheckPermissionWithPrompt(MacPermissionType type, bool prompt_for_permission);
 #define CheckPermission(x) CheckPermissionWithPrompt(x, false)

frontend/widgets/OBSBasic_Docks.cpp

@@ -19,6 +19,7 @@
 
 #include "OBSBasic.hpp"
 
+#include <docks/OBSDock.hpp>
 #include <qt-wrappers.hpp>
 
 void setupDockAction(QDockWidget *dock)
@@ -148,6 +149,7 @@ void OBSBasic::AddDockWidget(QDockWidget *dock, Qt::DockWidgetArea area, bool ex
 			QDockWidget::DockWidgetFloatable);
 
 	setupDockAction(dock);
+	InstallDockFloatingBehavior(dock);
 	dock->setFeatures(features);
 	addDockWidget(area, dock);
 
@@ -207,6 +209,8 @@ void OBSBasic::AddCustomDockWidget(QDockWidget *dock)
 	// Prevent the object name from being changed
 	connect(dock, &QObject::objectNameChanged, this, &OBSBasic::RepairCustomExtraDockName);
 
+	InstallDockFloatingBehavior(dock);
+
 	bool lock = ui->lockDocks->isChecked();
 	QDockWidget::DockWidgetFeatures features =
 		lock ? QDockWidget::NoDockWidgetFeatures