drawing with fill or stroke=None produces black fill/stroke

[zpincus]

Is it a bug or a feature that using draw_shape() with fill=None or stroke=None will produce an image with a black fill or stroke? I had assumed that passing None would result in no fill or stroke. Simple example follows:

import celiagg
import freeimage
import numpy

state = celiagg.GraphicsState()
fill = celiagg.SolidPaint(1,1,1)
#stroke = celiagg.SolidPaint(0,0,0,0) # this produces the desired no-stroke outcome.
stroke = None
transform = celiagg.Transform()

image = numpy.zeros((100, 100), dtype=numpy.uint8)
image += 255
canvas = celiagg.CanvasG8(image)
path = celiagg.Path()
path.rect(25, 25, 50, 50)
canvas.draw_shape(path, transform, state, fill=fill, stroke=stroke)
freeimage.write(image, 'test.png')

[jwiggins]

Thanks for the report! It's a good question whether this is a bug or a feature. It's certainly confusing, so I would lean towards bug. Looking at the C++ code clarified things a bit for me.

Basically, passing None is not the way to achieve the result you want. Rather, you should set state.drawing_mode = celiagg.DrawingMode.DrawFill or state.drawing_mode = celiagg.DrawingMode.DrawStroke. It just so happens that DrawingMode.DrawFillStroke is the default, and passing None for fill or stroke results in celiagg.SolidPaint(0,0,0) being passed through to the underlying C++ code.

Do you think a descriptive exception would help here if the drawing mode is "incompatible" with the given stroke/fill paint?

[zpincus]

Alternately, perhaps the default could be celiagg.SolidPaint(0,0,0) instead of None? That might clarify thing. (An addition to the docstring mentioning the use of DrawingMode to disable fill / stroke would also be helpful.)

Or is there a reason that None is necessary instead of a specific paint default?

[jwiggins]

I've updated the documentation. The docstrings now reflect better what is happening internally.

[zpincus]

Looks very clear now! Thanks :)