The intent of this use of glBitmap is to move the raster position without drawing anything. However, it may be required to use None instead of the empty bytes object for this. I couldn't quite verify this as I don't have an affected system. The final argument is the 'bitmap' argument. The use of a NULL bitmap together with nonzero xmove/ymove parameters is explicitly documented as a valid way to move the raster position (including to offscreen positions); doing it with a zero byte bitmap is apparently unsupported in some OpenGL implementation even if the width×height of the bitmap is 0 pixels. https://docs.gl/gl3/glBitmap specifically documents that negative width and height are errors, but doesn't document that a height or width of 0 is invalid. |
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