Bug 160345

Created attachment 193278 [details]
A problematic polygon

Attached is a (modified) single polygon extracted from the 3rd party external pdf referenced in tdf#113050;  I've cut it down to a single polygon and tweaked it a bit, so hopefully that's OK.

It's a single, 125 point, polygon with a tiled image fill with an especially tiny image; it's taking VclProcessor2D::RenderMaskPrimitive2DPixel about 1.6s to render that on my Linux box (Radeon 540 GPU, 4k display, X under xfce)
The original document has 3 of these polygons overlayed with a bunch of other smaller ones, so taking ~10 seconds to render the page (and then another 10 to render the thumbnail and by the time you're done ~50 seconds for it to settle after load).

I suspect this is the slow paths that 6b8c157a0b4f3 avoids in some case.

Maybe there's an opportunity to improve this for our case; it's got a complex boundary but because of the vast number of image repetitions, most of the images are entirely contained within the shape so probably don't need the clever processing of anything intersecting the boundary.