GUI: Mouse Hide and Lock Keyboard Shortcut

This should address the second point of #4502.

A few notes:
1. it changes the current behaviour of the 'Fullscreen cursor'.  Currently it defaults to be captive.  This changes it so that it defaults to NOT being captive, but can be made captive with the CTRL+L key combination.
2. There are situations when in windowed mode it's possible to escape the captivity (it's like a minigame if you will).  This requires the mouse movement to exceed the bounds of the window in a single event scan.  It will just show up as a temporary visibility of the cursor when outside of the window bounds.  It's not too difficult to 'fix', but might not be a likely enough scenario to warrant either.
3. There currently isn't an ability to change what this keyboard combo maps to, but it's inline with a collection of other similar keyboard mappings.  I think adding such a more generic keyboard mapping system (not for just keypad items, but system items.. e.g. so that Emulator stop could be mapped to something other than CTRL+S etc) is a bit out-of-scope of this particular PR.

rpcs3/Input/basic_mouse_handler.cpp

@@ -89,11 +89,23 @@ void basic_mouse_handler::MouseScroll(QWheelEvent* event)
 	MouseHandlerBase::Scroll(event->angleDelta().y());
 }
 
+bool basic_mouse_handler::get_mouse_lock_state()
+{
+	if (m_target)
+	{
+		auto mouse_locked = m_target->property("mouse_locked");
+		if (mouse_locked.isValid())
+			return mouse_locked.toBool();
+		return false;
+	}
+	return false;
+}
+
 void basic_mouse_handler::MouseMove(QMouseEvent* event)
 {
 	if (is_time_for_update())
 	{
-		if (m_target && m_target->visibility() == QWindow::Visibility::FullScreen && m_target->isActive())
+		if (m_target && m_target->isActive() && get_mouse_lock_state())
 		{
 			// get the screen dimensions
 			const QSize screen = m_target->size();

rpcs3/Input/basic_mouse_handler.h

@@ -24,4 +24,5 @@ public:
 	bool eventFilter(QObject* obj, QEvent* ev) override;
 private:
 	QWindow* m_target = nullptr;
+	bool get_mouse_lock_state();
 };

rpcs3/Input/keyboard_pad_handler.cpp

@@ -313,6 +313,18 @@ void keyboard_pad_handler::mouseReleaseEvent(QMouseEvent* event)
 	event->ignore();
 }
 
+bool keyboard_pad_handler::get_mouse_lock_state()
+{
+	if (m_target)
+	{
+		auto mouse_locked = m_target->property("mouse_locked");
+		if (mouse_locked.isValid())
+			return mouse_locked.toBool();
+		return false;
+	}
+	return false;
+}
+
 void keyboard_pad_handler::mouseMoveEvent(QMouseEvent* event)
 {
 	static int movement_x = 0;
@@ -320,7 +332,7 @@ void keyboard_pad_handler::mouseMoveEvent(QMouseEvent* event)
 	static int last_pos_x = 0;
 	static int last_pos_y = 0;
 
-	if (m_target && m_target->visibility() == QWindow::Visibility::FullScreen && m_target->isActive())
+	if (m_target && m_target->isActive() && get_mouse_lock_state())
 	{
 		// get the screen dimensions
 		const QSize screen = m_target->size();

rpcs3/Input/keyboard_pad_handler.h

@@ -101,6 +101,8 @@ protected:
 
 private:
 	QWindow* m_target = nullptr;
+	bool get_mouse_lock_state();
+
 	std::vector<std::shared_ptr<Pad>> bindings;
 
 	// Button Movements

rpcs3/rpcs3qt/gs_frame.cpp

@@ -76,6 +76,11 @@ gs_frame::gs_frame(const QRect& geometry, const QIcon& appIcon, const std::share
 	connect(&m_mousehide_timer, &QTimer::timeout, this, &gs_frame::MouseHideTimeout);
 	m_mousehide_timer.setSingleShot(true);
 
+	// We default the mouse lock to being off
+	m_mouse_hide_and_lock = false;
+	// and we 'publish' this to the property values of this window
+	setProperty("mouse_locked", m_mouse_hide_and_lock);
+
 #ifdef _WIN32
 	m_tb_button = new QWinTaskbarButton();
 	m_tb_progress = m_tb_button->progress();
@@ -135,6 +140,11 @@ void gs_frame::keyPressEvent(QKeyEvent *keyEvent)
 			screenshot.success("Made forced mark %d in log", ++count);
 			return;
 		}
+		else if (keyEvent->modifiers() == Qt::ControlModifier)
+		{
+			toggle_mouselock();
+			return;
+		}
 		break;
 	case Qt::Key_Return:
 		if (keyEvent->modifiers() == Qt::AltModifier)
@@ -209,6 +219,17 @@ void gs_frame::toggle_fullscreen()
 	});
 }
 
+void gs_frame::toggle_mouselock()
+{
+	// first we toggle the value
+	m_mouse_hide_and_lock = !m_mouse_hide_and_lock;
+
+	// and then we publish it to the window properties
+	setProperty("mouse_locked", m_mouse_hide_and_lock);
+
+	HandleCursor(this->visibility());
+}
+
 void gs_frame::close()
 {
 	Emu.Stop();
@@ -465,14 +486,18 @@ void gs_frame::mouseDoubleClickEvent(QMouseEvent* ev)
 
 void gs_frame::HandleCursor(QWindow::Visibility visibility)
 {
-	if (visibility == QWindow::Visibility::FullScreen && !m_show_mouse_in_fullscreen)
+	if (m_mouse_hide_and_lock || (visibility == QWindow::Visibility::FullScreen && !m_show_mouse_in_fullscreen))
 	{
 		setCursor(Qt::BlankCursor);
 		m_mousehide_timer.stop();
 	}
 	else
 	{
-		setCursor(Qt::ArrowCursor);
+		if (!m_mouse_hide_and_lock)
+		{
+			setCursor(Qt::ArrowCursor);
+		}
+
 		if (m_hide_mouse_after_idletime)
 		{
 			m_mousehide_timer.start(m_hide_mouse_idletime);

rpcs3/rpcs3qt/gs_frame.h

@@ -36,6 +36,7 @@ private:
 	QString m_window_title;
 	bool m_disable_mouse = false;
 	bool m_disable_kb_hotkeys = false;
+	bool m_mouse_hide_and_lock = false;
 	bool m_show_mouse_in_fullscreen = false;
 	bool m_hide_mouse_after_idletime = false;
 	u32 m_hide_mouse_idletime = 2000; // ms
@@ -77,6 +78,9 @@ protected:
 
 	bool event(QEvent* ev) override;
 
+private:
+	void toggle_mouselock();
+
 private Q_SLOTS:
 	void HandleCursor(QWindow::Visibility visibility);
 	void MouseHideTimeout();