WindowServer: Support windows with alpha channels. And per-WSWindow opacity.

This patch also adds a Format concept to GraphicsBitmap. For now there are
only two formats: RGB32 and RGBA32. Windows with alpha channel have their
backing stores created in the RGBA32 format.

Use this to make Terminal windows semi-transparent for that comfy rice look.
There is one problem here, in that window compositing overdraw incurs
multiple passes of blending of the same pixels. This leads to a mismatch in
opacity which is obviously not good. I will work on this in a later patch.

The alpha blending is currently straight C++. It should be relatively easy
to optimize this using SSE instructions.

For now I'm just happy with the cute effect. :^)

1 files changed, 2 insertions, 2 deletions

diff --git a/LibGUI/GWidget.h b/LibGUI/GWidget.h
index 5b5cb957d5..f3211e6c6b 100644
--- a/LibGUI/GWidget.h
+++ b/LibGUI/GWidget.h
@@ -128,8 +128,8 @@ private:
     OwnPtr<GLayout> m_layout;
 
     Rect m_relative_rect;
-    Color m_background_color { 0xffffff };
-    Color m_foreground_color { 0x000000 };
+    Color m_background_color;
+    Color m_foreground_color;
     RetainPtr<Font> m_font;
 
     SizePolicy m_horizontal_size_policy { SizePolicy::Fill };