#244 GLTriangle's fragment shader is used when rendered by the Canvas.

[dusk125]

Allows for custom fragment shaders to be used with canvas.MakeTriangles.

Usage:

shader := pixelgl.NewGLShader(shaderText)
...
tris := pixel.MakeTrianglesData(5)
// fill triangles...
shaderTris := pixelgl.NewGLTriangles(shader, tris)
win.Canvas().MakeTriangles(shaderTris).Draw()

[dusk125]

My use case for this feature is that in the Pixleui project, imgui returns a list of draw data; part of this draw data is a list of triangles. I need to draw these triangles using a specific fragment shader and I don't want to change the windows (canvas's) fragment shader since that will change it globally (and cause a shader rebuild every frame).

If this is not accepted, I can create my own canvas in pixelui with the fragment shader and just render that canvas ontop the window canvas, at the cost of some performance.

[delp]

I want to play around with this some more

[dusk125]

Fixed the conflict generated by my other PR.

[dusk125]

@delp here is a link to how I'm using the triangles in pixelui. Let me know if any explanation is needed.

[delp]

This PR will be better now that its been allowed to age like a fine wine :P