🚚 Move uForOpening to standard uniforms

docs/changelog.md

@@ -4,6 +4,10 @@
 
 **Release Date:** TBD
 
+#### Enhancements
+
+* The standard uniforms of all shaders have been updated: The window size is now passed as a `vec2` and there is a new `bool uForOpening` which is set to `true` if a window-open animation is ongoing, to `false` otherwise.
+
 #### Bug Fixes
 
 * **Fixed a major memory leak**. Now, shaders are not re-created anymore whenever a window is opened or closed. Instead, previously created shaders are re-used as often as possible. This requires that all settings are set as uniform values (previously they were injected into the shader source) which in turn requires that `Shell.GLSLEffect` is used instead of `Clutter.ShaderEffect`. This change also requires that all shaders now work with straight instead of premultiplied alpha. Anyways, a lot needed to be refactored for this fix and I hope that it did not bring too many visual changes.