WindowServer: Don't lookup configuration values in compose()

The compose() function is supposed to be fast since it can execute
60 times per second. Let's not do obviously avoidable things like
configuration value lookups in there. :^)

Services/WindowServer/Compositor.cpp

@@ -112,11 +112,20 @@ void Compositor::init_bitmaps()
     invalidate_screen();
 }
 
+void Compositor::did_construct_window_manager(Badge<WindowManager>)
+{
+    auto& wm = WindowManager::the();
+    m_wallpaper_mode = mode_to_enum(wm.config()->read_entry("Background", "Mode", "simple"));
+    m_custom_background_color = Color::from_string(wm.config()->read_entry("Background", "Color", ""));
+
+    invalidate_screen();
+    invalidate_occlusions();
+    compose();
+}
+
 void Compositor::compose()
 {
     auto& wm = WindowManager::the();
-    if (m_wallpaper_mode == WallpaperMode::Unchecked)
-        m_wallpaper_mode = mode_to_enum(wm.config()->read_entry("Background", "Mode", "simple"));
     auto& ws = Screen::the();
 
     {
@@ -185,10 +194,8 @@ void Compositor::compose()
     });
 
     Color background_color = wm.palette().desktop_background();
-    String background_color_entry = wm.config()->read_entry("Background", "Color", "");
+    if (m_custom_background_color.has_value())
-    if (!background_color_entry.is_empty()) {
+        background_color = m_custom_background_color.value();
-        background_color = Color::from_string(background_color_entry).value_or(background_color);
-    }
 
 #ifdef COMPOSE_DEBUG
     dbg() << "COMPOSE: invalidated: window:" << m_invalidated_window << " cursor:" << m_invalidated_cursor << " any: " << m_invalidated_any;
@@ -600,6 +607,12 @@ void Compositor::start_compose_async_timer()
 
 bool Compositor::set_background_color(const String& background_color)
 {
+    auto color = Color::from_string(background_color);
+    if (!color.has_value())
+        return false;
+
+    m_custom_background_color = color;
+
     auto& wm = WindowManager::the();
     wm.config()->write_entry("Background", "Color", background_color);
     bool ret_val = wm.config()->sync();

Services/WindowServer/Compositor.h

@@ -29,14 +29,15 @@
 #include <AK/OwnPtr.h>
 #include <AK/RefPtr.h>
 #include <LibCore/Object.h>
+#include <LibGfx/Color.h>
 #include <LibGfx/DisjointRectSet.h>
-#include <LibGfx/Forward.h>
 
 namespace WindowServer {
 
 class ClientConnection;
 class Cursor;
 class Window;
+class WindowManager;
 
 enum class WallpaperMode {
     Simple,
@@ -73,6 +74,8 @@ public:
 
     void invalidate_occlusions() { m_occlusions_dirty = true; }
 
+    void did_construct_window_manager(Badge<WindowManager>);
+
 private:
     Compositor();
     void init_bitmaps();
@@ -125,6 +128,8 @@ private:
 
     RefPtr<Core::Timer> m_display_link_notify_timer;
     size_t m_display_link_count { 0 };
+
+    Optional<Gfx::Color> m_custom_background_color;
 };
 
 }

Services/WindowServer/WindowManager.cpp

@@ -74,9 +74,7 @@ WindowManager::WindowManager(const Gfx::PaletteImpl& palette)
 
     reload_config(false);
 
-    Compositor::the().invalidate_screen();
+    Compositor::the().did_construct_window_manager({});
-    Compositor::the().invalidate_occlusions();
-    Compositor::the().compose();
 }
 
 WindowManager::~WindowManager()