WindowServer: Add initial support for rendering on multiple screens

This allows WindowServer to use multiple framebuffer devices and
compose the desktop with any arbitrary layout. Currently, it is assumed
that it is configured contiguous and non-overlapping, but this should
eventually be enforced.

To make rendering efficient, each window now also tracks on which
screens it needs to be rendered. This way we don't have to iterate all
the windows for each screen but instead use the same rendering loop and
then only render to the screen (or screens) that the window actually
uses.

1 files changed, 35 insertions, 12 deletions

diff --git a/Userland/Services/WindowServer/WindowFrame.h b/Userland/Services/WindowServer/WindowFrame.h
index dba13751c2..ee7f3f55a5 100644
--- a/Userland/Services/WindowServer/WindowFrame.h
+++ b/Userland/Services/WindowServer/WindowFrame.h
@@ -20,21 +20,46 @@ class Button;
 class Menu;
 class MouseEvent;
 class Window;
+class Screen;
 
 class WindowFrame {
 public:
+    class RenderedCache {
+        friend class WindowFrame;
+
+    public:
+        void paint(WindowFrame&, Gfx::Painter&, const Gfx::IntRect&);
+        void render(WindowFrame&, Screen&);
+        Optional<HitTestResult> hit_test(WindowFrame&, Gfx::IntPoint const&, Gfx::IntPoint const&);
+
+    private:
+        RefPtr<Gfx::Bitmap> m_top_bottom;
+        RefPtr<Gfx::Bitmap> m_left_right;
+        int m_bottom_y { 0 }; // y-offset in m_top_bottom for the bottom half
+        int m_right_x { 0 };  // x-offset in m_left_right for the right half
+        bool m_shadow_dirty { true };
+        bool m_dirty { true };
+    };
+    friend class RenderedCache;
+
     static void reload_config();
 
     explicit WindowFrame(Window&);
     ~WindowFrame();
 
+    void window_was_constructed(Badge<Window>);
+
+    Window& window() { return m_window; }
+    const Window& window() const { return m_window; }
+
     Gfx::IntRect rect() const;
     Gfx::IntRect render_rect() const;
     Gfx::DisjointRectSet opaque_render_rects() const;
     Gfx::DisjointRectSet transparent_render_rects() const;
-    void paint(Gfx::Painter&, const Gfx::IntRect&);
-    void render(Gfx::Painter&);
-    void render_to_cache();
+
+    void paint(Screen&, Gfx::Painter&, const Gfx::IntRect&);
+    void render(Screen&, Gfx::Painter&);
+    RenderedCache* render_to_cache(Screen&);
 
     void handle_mouse_event(MouseEvent const&);
     void handle_titlebar_mouse_event(MouseEvent const&);
@@ -78,13 +103,16 @@ public:
 
     void set_dirty(bool re_render_shadow = false)
     {
-        m_dirty = true;
-        m_shadow_dirty |= re_render_shadow;
+        for (auto& it : m_rendered_cache) {
+            auto& cached = *it.value;
+            cached.m_dirty = true;
+            cached.m_shadow_dirty |= re_render_shadow;
+        }
     }
 
     void theme_changed();
 
-    Optional<HitTestResult> hit_test(Gfx::IntPoint const&) const;
+    Optional<HitTestResult> hit_test(Gfx::IntPoint const&);
 
     void open_menubar_menu(Menu&);
 
@@ -109,17 +137,12 @@ private:
     Button* m_maximize_button { nullptr };
     Button* m_minimize_button { nullptr };
 
-    RefPtr<Gfx::Bitmap> m_top_bottom;
-    RefPtr<Gfx::Bitmap> m_left_right;
-    int m_bottom_y { 0 }; // y-offset in m_top_bottom for the bottom half
-    int m_right_x { 0 };  // x-offset in m_left_right for the right half
+    HashMap<int, NonnullOwnPtr<RenderedCache>> m_rendered_cache;
 
     RefPtr<Core::Timer> m_flash_timer;
     size_t m_flash_counter { 0 };
     float m_opacity { 1 };
     bool m_has_alpha_channel { false };
-    bool m_shadow_dirty { false };
-    bool m_dirty { false };
 };
 
 }