Table Of Contents
Graphics compiler¶
Before rendering an InstructionGroup, we
compile the group in order to reduce the number of instructions executed
at rendering time.
Reducing the context instructions¶
Imagine that you have a scheme like this:
Color(1, 1, 1)
Rectangle(source='button.png', pos=(0, 0), size=(20, 20))
Color(1, 1, 1)
Rectangle(source='button.png', pos=(10, 10), size=(20, 20))
Color(1, 1, 1)
Rectangle(source='button.png', pos=(10, 20), size=(20, 20))
The real instructions seen by the graphics canvas would be:
Color: change 'color' context to 1, 1, 1
BindTexture: change 'texture0' to `button.png texture`
Rectangle: push vertices (x1, y1...) to vbo & draw
Color: change 'color' context to 1, 1, 1
BindTexture: change 'texture0' to `button.png texture`
Rectangle: push vertices (x1, y1...) to vbo & draw
Color: change 'color' context to 1, 1, 1
BindTexture: change 'texture0' to `button.png texture`
Rectangle: push vertices (x1, y1...) to vbo & draw
Only the first Color and
BindTexture are useful and really
change the context. We can reduce them to:
Color: change 'color' context to 1, 1, 1
BindTexture: change 'texture0' to `button.png texture`
Rectangle: push vertices (x1, y1...) to vbo & draw
Rectangle: push vertices (x1, y1...) to vbo & draw
Rectangle: push vertices (x1, y1...) to vbo & draw
This is what the compiler does in the first place, by flagging all the unused instruction with GI_IGNORE flag. As soon as a Color content changes, the whole InstructionGroup will be recompiled and a previously unused Color might be used for the next compilation.
Note to any Kivy contributor / internal developer:
- All context instructions are checked to see if they change anything in the cache.
- We must ensure that a context instruction is needed for our current Canvas.
- We must ensure that we don’t depend of any other canvas.
- We must reset our cache if one of our children is another instruction group because we don’t know whether it might do weird things or not.