WindowServer: Add IPC endpoint to get the color under cursor

This allows any client to ask the WindowServer to give it the color
of the screen bitmap under the cursor.

There's currently no way to get the screen bitmap *without* the
cursor already drawn on it, so for now we just take a pixel
beside the actual cursor position to avoid just getting the cursors
color.

Userland/Services/WindowServer/ClientConnection.cpp

@@ -1048,6 +1048,16 @@ Messages::WindowServer::GetScreenBitmapAroundCursorResponse ClientConnection::ge
     return { {} };
 }
 
+Messages::WindowServer::GetColorUnderCursorResponse ClientConnection::get_color_under_cursor()
+{
+    // FIXME: Add a mechanism to get screen bitmap without cursor, so we don't have to do this
+    //        manual translation to avoid sampling the color on the actual cursor itself.
+    auto cursor_location = ScreenInput::the().cursor_location().translated(-1, -1);
+    auto& screen_with_cursor = ScreenInput::the().cursor_location_screen();
+    auto color = Compositor::the().color_at_position({}, screen_with_cursor, cursor_location);
+    return color;
+}
+
 Messages::WindowServer::IsWindowModifiedResponse ClientConnection::is_window_modified(i32 window_id)
 {
     auto it = m_windows.find(window_id);

Userland/Services/WindowServer/ClientConnection.h

@@ -169,6 +169,7 @@ private:
     virtual void add_window_stealing_for_client(i32, i32) override;
     virtual void remove_window_stealing_for_client(i32, i32) override;
     virtual void remove_window_stealing(i32) override;
+    virtual Messages::WindowServer::GetColorUnderCursorResponse get_color_under_cursor() override;
 
     Window* window_from_id(i32 window_id);
 

Userland/Services/WindowServer/WindowServer.ipc

@@ -136,6 +136,7 @@ endpoint WindowServer
 
     get_screen_bitmap(Optional<Gfx::IntRect> rect, Optional<u32> screen_index) => (Gfx::ShareableBitmap bitmap)
     get_screen_bitmap_around_cursor(Gfx::IntSize size) => (Gfx::ShareableBitmap bitmap)
+    get_color_under_cursor() => (Gfx::Color color)
 
     pong() =|