High values of colspan take too much time

[chrisfrigo1]

Hi, can't seem to work out why specifically this html string is causing weasyprint to hang during conversion. i'm using the latest version 51. Any suggestions would be appreciated.

example-html.txt

[Tontyna]

It's because of colspan="65534"

[liZe]

It's because of colspan="65534"

Then I suppose it’s not struck, it’s just extremely slow 😄. There’s an optimization waiting to be found.

[chrisfrigo1]

thanks guys. appreciated.

[liZe]

There are horrible nested loops here:

WeasyPrint/weasyprint/layout/preferred.py

Lines 490 to 495 in 1b8ac91

	for span in range(1, grid_width):
	percentage_contributions = []
	for i in range(grid_width):
	percentage_contribution = intrinsic_percentages[i]
	for j in range(len(zipped_grid[i])):
	indexes = [k for k in range(i + 1) if grid[j][k]]

Here’s a fix that makes colspan=2000 take less than a second instead of 2 mins 30 on my computer. With the original 65534 value, it takes about 25 seconds. That’s not perfect, but I think it’s OK for such a dirty corner case 😄.