Shaders don't seem to apply to drawn text

[duysqubix]

When I'm drawing text in a window to which a fragment shader is set (e.g. like in the wavy shader example) it looks rather garbled

It looks like down there the whole atlas is drawn (abc...) although only fmt.Fprintln(basicTxt, "Hello, text!") was added to the basicTxt drawn.

And the black boxes could be the shader not knowing the output color.

I thought that both the image and the text was drawn to the canvas and therefore it should be treated as an entity and subject to the shader. This doesn't seem to be the case. Any help appreciated.

Original issue: faiface/pixel#260