ch02-04-crate-render: initial documentation

Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>

src/ch02-04-crate-render.md

@@ -1,3 +1,46 @@
-# The Render Crate
+# Render Crates
 
-WIP: all about the OrbTK rendering services
+Rendering is a key component of the toolkit. Everybody is expecting state
+of the art presentation of implemented widgets. User interaction that will
+result in layout and entity changes inside the GUI should be updated as
+soon as possible. A comfortable users experience is mainly influenced by
+fast rendering tasks. New rendering of layouts should only take place, if
+constraint changes will need to do so. Entities and it attributes will
+only require new rendering, if a user interaction will change their state
+to be dirty.
+
+Lets summarize the main goals of `OrbTK` rendering infrastructure:
+
+* API encapsulated access to all renderer functions
+
+  This design decision is taken to keep freedom for further development of
+  OrbTK when it comes to support different renderer. We are able to support
+
+	* different versions of a given renderer
+	* support different renderer for different target platforms
+
+* 2D rendering fast and complete implementation of all rendering functions
+  used in the OrbTK toolkit.provided functions
+
+  * Pixmaps
+  * Canvas
+  * Path
+  * geometry primitives
+  * Blending modes
+  * Path filling
+  * Anti-aliased Path filling
+  * Path stroking
+  * Path hairline stroking
+  * Anti-aliased Path hairline stroking
+  * Stroke dashing
+  * Gradients (linear and radial)
+  * Pixmaps blending (image on image rendering)
+  * Patterns
+  * Fill rect
+  * Stroke rect
+  * Rectangular clipping
+  * Clipping
+  * Anti-aliased clipping
+  * Analytical anti-aliased Path filling
+  * Dithering
+  * Blending modes