Stop recomposing the window hierarchy after every dang widget paint.

Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/cfd76ade73d

Widgets/Painter.cpp

@@ -21,8 +21,6 @@ Painter::Painter(Widget& widget)
 
 Painter::~Painter()
 {
-    if (m_window)
-        m_window->did_paint();
 }
 
 void Painter::fillRect(const Rect& rect, Color color)

Widgets/RootWidget.cpp

@@ -8,7 +8,8 @@
 
 RootWidget::RootWidget()
 {
-    m_backing = GraphicsBitmap::create_wrapper(FrameBufferSDL::the().size(), (byte*)FrameBufferSDL::the().scanline(0));
+    setWindowRelativeRect(FrameBufferSDL::the().rect());
+    m_backing = GraphicsBitmap::create_wrapper(size(), (byte*)FrameBufferSDL::the().scanline(0));
 }
 
 RootWidget::~RootWidget()

Widgets/Widget.cpp

@@ -19,16 +19,18 @@ Widget::~Widget()
 {
 }
 
-void Widget::setWindowRelativeRect(const Rect& rect)
+void Widget::setWindowRelativeRect(const Rect& rect, bool should_update)
 {
     // FIXME: Make some kind of event loop driven ResizeEvent?
     m_relativeRect = rect;
-    update();
+    if (should_update)
+        update();
 }
 
 void Widget::repaint(const Rect& rect)
 {
-    event(*make<PaintEvent>(rect));
+    if (auto* w = window())
+        w->repaint(rect);
 }
 
 void Widget::event(Event& event)
@@ -109,10 +111,13 @@ void Widget::mouseMoveEvent(MouseEvent&)
 
 void Widget::update()
 {
+    auto* w = window();
+    if (!w)
+        return;
     if (m_hasPendingPaintEvent)
         return;
     m_hasPendingPaintEvent = true;
-    EventLoop::main().postEvent(this, make<PaintEvent>(rect()));
+    EventLoop::main().postEvent(w, make<PaintEvent>(rect()));
 }
 
 Widget::HitTestResult Widget::hitTest(int x, int y)

Widgets/Widget.h

@@ -34,6 +34,7 @@ public:
     int height() const { return m_relativeRect.height(); }
 
     Rect rect() const { return { 0, 0, width(), height() }; }
+    Size size() const { return m_relativeRect.size(); }
 
     void update();
     void repaint(const Rect&);
@@ -50,7 +51,7 @@ public:
 
     virtual const char* class_name() const override { return "Widget"; }
 
-    void setWindowRelativeRect(const Rect&);
+    void setWindowRelativeRect(const Rect&, bool should_update = true);
 
     Color backgroundColor() const { return m_backgroundColor; }
     Color foregroundColor() const { return m_foregroundColor; }

Widgets/Window.cpp

@@ -1,6 +1,7 @@
 #include "Window.h"
 #include "WindowManager.h"
 #include "Event.h"
+#include "EventLoop.h"
 #include "Widget.h"
 
 Window::Window(Object* parent)
@@ -46,9 +47,14 @@ void Window::setRect(const Rect& rect)
     WindowManager::the().notifyRectChanged(*this, oldRect, m_rect);
 }
 
-void Window::repaint()
+void Window::repaint(const Rect& rect)
 {
-    event(*make<PaintEvent>());
+    event(*make<PaintEvent>(rect));
+}
+
+void Window::update(const Rect& rect)
+{
+    EventLoop::main().postEvent(this, make<PaintEvent>(rect));
 }
 
 void Window::event(Event& event)
@@ -80,9 +86,11 @@ void Window::event(Event& event)
         }
         if (m_mainWidget) {
             if (pe.rect().is_empty())
-                return m_mainWidget->event(*make<PaintEvent>(m_mainWidget->rect()));
+                m_mainWidget->event(*make<PaintEvent>(m_mainWidget->rect()));
             else
-                return m_mainWidget->event(event);
+                m_mainWidget->event(event);
+            WindowManager::the().did_paint(*this);
+            return;
         }
         return Object::event(event);
     }

Widgets/Window.h

@@ -40,7 +40,8 @@ public:
     bool isBeingDragged() const { return m_isBeingDragged; }
     void setIsBeingDragged(bool b) { m_isBeingDragged = b; }
 
-    void repaint();
+    void repaint(const Rect& = Rect());
+    void update(const Rect& = Rect());
 
     bool isActive() const;
 

Widgets/WindowManager.cpp

@@ -136,9 +136,10 @@ void WindowManager::repaint()
 void WindowManager::did_paint(Window& window)
 {
     auto& framebuffer = FrameBufferSDL::the();
-    if (m_windows_in_order.head() == &window) {
+    if (m_windows_in_order.tail() == &window) {
         ASSERT(window.backing());
         framebuffer.blit(window.position(), *window.backing());
+        printf("[WM] frontmost_only_compose_count: %u\n", ++m_frontmost_only_compose_count);
         return;
     }
 
@@ -167,7 +168,7 @@ void WindowManager::notifyTitleChanged(Window& window)
 void WindowManager::notifyRectChanged(Window& window, const Rect& oldRect, const Rect& newRect)
 {
     printf("[WM] Window %p rect changed (%d,%d %dx%d) -> (%d,%d %dx%d)\n", &window, oldRect.x(), oldRect.y(), oldRect.width(), oldRect.height(), newRect.x(), newRect.y(), newRect.width(), newRect.height());
-    repaintAfterMove(oldRect, newRect);
+    recompose();
 }
 
 void WindowManager::handleTitleBarMouseEvent(Window& window, MouseEvent& event)
@@ -190,28 +191,6 @@ void WindowManager::handleTitleBarMouseEvent(Window& window, MouseEvent& event)
 #endif
 }
 
-void WindowManager::repaintAfterMove(const Rect& oldRect, const Rect& newRect)
-{
-    printf("[WM] repaint: [%d,%d %dx%d] -> [%d,%d %dx%d]\n",
-            oldRect.x(),
-            oldRect.y(),
-            oldRect.width(),
-            oldRect.height(),
-            newRect.x(),
-            newRect.y(),
-            newRect.width(),
-            newRect.height());
-
-    m_rootWidget->repaint(oldRect);
-    m_rootWidget->repaint(newRect);
-    for (auto* window = m_windows_in_order.head(); window; window = window->next()) {
-        if (outerRectForWindow(*window).intersects(oldRect) || outerRectForWindow(*window).intersects(newRect)) {
-            paintWindowFrame(*window);
-            window->repaint();
-        }
-    }
-}
-
 void WindowManager::processMouseEvent(MouseEvent& event)
 {
     if (event.type() == Event::MouseUp) {
@@ -220,8 +199,7 @@ void WindowManager::processMouseEvent(MouseEvent& event)
             m_dragWindow->setIsBeingDragged(false);
             m_dragEndRect = outerRectForWindow(*m_dragWindow);
             m_dragWindow = nullptr;
-
-            repaintAfterMove(m_dragStartRect, m_dragEndRect);
+            recompose();
             return;
         }
     }
@@ -281,7 +259,8 @@ void WindowManager::recompose()
 {
     printf("[WM] recompose_count: %u\n", ++m_recompose_count);
     auto& framebuffer = FrameBufferSDL::the();
-    m_rootWidget->repaint(m_rootWidget->rect());
+    PaintEvent dummy_event(m_rootWidget->rect());
+    m_rootWidget->paintEvent(dummy_event);
     for (auto* window = m_windows_in_order.head(); window; window = window->next()) {
         if (!window->backing())
             continue;

Widgets/WindowManager.h

@@ -41,7 +41,6 @@ private:
     void processMouseEvent(MouseEvent&);
     void handleTitleBarMouseEvent(Window&, MouseEvent&);
     void handlePaintEvent(PaintEvent&);
-    void repaintAfterMove(const Rect& oldRect, const Rect& newRect);
     
     virtual void event(Event&) override;
 
@@ -68,4 +67,5 @@ private:
     Rect m_dragEndRect;
 
     unsigned m_recompose_count { 0 };
+    unsigned m_frontmost_only_compose_count { 0 };
 };