Layout not respected when selecting blocks of vertical text

[Pikrass]

On zathura 0.5.8 from the Debian repo
Possibly related to #669

When selecting a block of vertical text, Zathura selects text from other parts of the page. It seems like it can't figure out the layout.

Here's a side-by-side comparison with Zathura on the left and Firefox's PDF viewer on the right. I tried to select only the top right paragraph. Firefox has no problem, but Zathura includes text from the bottom paragraph and from the diagrams.

[sun-dazer]

Hi, I am a beginner contributor and I would like to try to fix this issue.