Let userland retain the window backing store while drawing into it.

To start painting, call:
gui$get_window_backing_store()

Then finish up with:
gui$release_window_backing_store()

Process will retain the underlying GraphicsBitmap behind the scenes.
This fixes racing between the WindowServer and GUI clients.

This patch also adds a WSWindowLocker that is exactly what it sounds like.

LibGUI/GWidget.cpp

@@ -18,12 +18,13 @@ GWidget::~GWidget()
 {
 }
 
-void GWidget::set_relative_rect(const Rect& rect, bool should_update)
+void GWidget::set_relative_rect(const Rect& rect)
 {
+    if (rect == m_relative_rect)
+        return;
     // FIXME: Make some kind of event loop driven ResizeEvent?
     m_relative_rect = rect;
-    if (should_update)
-        update();
+    update();
 }
 
 void GWidget::repaint(const Rect& rect)
@@ -147,10 +148,3 @@ void GWidget::set_font(RetainPtr<Font>&& font)
     else
         m_font = move(font);
 }
-
-GraphicsBitmap* GWidget::backing()
-{
-    if (auto* w = window())
-        return w->backing();
-    return nullptr;
-}

LibGUI/GWidget.h

@@ -51,7 +51,7 @@ public:
 
     virtual const char* class_name() const override { return "GWidget"; }
 
-    void set_relative_rect(const Rect&, bool should_update = true);
+    void set_relative_rect(const Rect&);
 
     Color background_color() const { return m_background_color; }
     Color foreground_color() const { return m_foreground_color; }
@@ -84,8 +84,6 @@ public:
     const Font& font() const { return *m_font; }
     void set_font(RetainPtr<Font>&&);
 
-    GraphicsBitmap* backing();
-
 private:
     GWindow* m_window { nullptr };
 

LibGUI/GWindow.cpp

@@ -39,14 +39,6 @@ GWindow::GWindow(GObject* parent)
         exit(1);
     }
 
-    GUI_WindowBackingStoreInfo backing;
-    int rc = gui_get_window_backing_store(m_window_id, &backing);
-    if (rc < 0) {
-        perror("gui_get_window_backing_store");
-        exit(1);
-    }
-    m_backing = GraphicsBitmap::create_wrapper(backing.size, backing.pixels);
-
     windows().set(m_window_id, this);
 }
 
@@ -58,34 +50,16 @@ void GWindow::set_title(String&& title)
 {
     dbgprintf("GWindow::set_title \"%s\"\n", title.characters());
     GUI_WindowParameters params;
-    int rc = gui_get_window_parameters(m_window_id, &params);
+    int rc = gui_set_window_title(m_window_id, title.characters(), title.length());
     ASSERT(rc == 0);
-    strcpy(params.title, title.characters());;
-    rc = gui_set_window_parameters(m_window_id, &params);
-    ASSERT(rc == 0);
-    m_title = move(title);
 }
 
-void GWindow::set_rect(const Rect& rect)
+void GWindow::set_rect(const Rect& a_rect)
 {
-    // FIXME: This is a hack to fudge the race with WSWindowManager trying to display @ old rect.
-    sleep(10);
-
-    dbgprintf("GWindow::set_rect %d,%d %dx%d\n", m_rect.x(), m_rect.y(), m_rect.width(), m_rect.height());
-    GUI_WindowParameters params;
-    int rc = gui_get_window_parameters(m_window_id, &params);
+    dbgprintf("GWindow::set_rect! %d,%d %dx%d\n", a_rect.x(), a_rect.y(), a_rect.width(), a_rect.height());
+    GUI_Rect rect = a_rect;
+    int rc = gui_set_window_rect(m_window_id, &rect);
     ASSERT(rc == 0);
-    params.rect = rect;
-    rc = gui_set_window_parameters(m_window_id, &params);
-    ASSERT(rc == 0);
-    m_rect = rect;
-    GUI_WindowBackingStoreInfo backing;
-    rc = gui_get_window_backing_store(m_window_id, &backing);
-    if (rc < 0) {
-        perror("gui_get_window_backing_store");
-        exit(1);
-    }
-    m_backing = GraphicsBitmap::create_wrapper(backing.size, backing.pixels);
 }
 
 void GWindow::event(GEvent& event)

LibGUI/GWindow.h

@@ -16,20 +16,17 @@ public:
 
     int window_id() const { return m_window_id; }
 
-    String title() const { return m_title; }
     void set_title(String&&);
 
-    int x() const { return m_rect.x(); }
-    int y() const { return m_rect.y(); }
-    int width() const { return m_rect.width(); }
-    int height() const { return m_rect.height(); }
+    int x() const { return rect().x(); }
+    int y() const { return rect().y(); }
+    int width() const { return rect().width(); }
+    int height() const { return rect().height(); }
 
-    const Rect& rect() const { return m_rect; }
+    Rect rect() const;
     void set_rect(const Rect&);
-    void set_rect_without_repaint(const Rect& rect) { m_rect = rect; }
 
-    Point position() const { return m_rect.location(); }
-    void set_position_without_repaint(const Point& position) { set_rect_without_repaint({ position.x(), position.y(), width(), height() }); }
+    Point position() const { return rect().location(); }
 
     virtual void event(GEvent&) override;
 
@@ -41,16 +38,11 @@ public:
     const GWidget* main_widget() const { return m_main_widget; }
     void set_main_widget(GWidget*);
 
-    GraphicsBitmap* backing() { return m_backing.ptr(); }
-
     void show();
 
     void update();
 
 private:
-    String m_title;
-    Rect m_rect;
-
     RetainPtr<GraphicsBitmap> m_backing;
     int m_window_id { -1 };
     GWidget* m_main_widget { nullptr };