how to make a 2d fullscreen (screen-reading) glow shader (for vector graphics) ?

[system]

	Attention	Topic was automatically imported from the old Question2Answer platform.
	Asked By	zoltan
	Old Version	Published before Godot 3 was released.

I think something similar as in the “2d shaders for sprites” demo, but for full screen. (First draw the polygons, then apply the shader for the entire screen.)