bug#67533: SVG images confound position pixel measurements

[JD Smith]

On Dec 1, 2023, at 2:08 AM, Eli Zaretskii <eliz@gnu.org> wrote:

Thanks, but I need recipes I could reproduce on my system, and
reproduce relatively easily.  

Please find a stand-alone reproduction code which can separately test both text-property and overlay inline SVGs at this gist.  See the header for instructions.  

You should get many reported errors in which the size above is larger than expected, but as you narrow your frame and re-run the check, you’ll eventually find some images reporting 0 height above.  Interestingly, for the same frame width, overlays produce some of the same but overall fewer errors than text-properties, using precisely the same images for ‘display.

The report also reveals that the posn-x-y of the mis-reporting images is usually wrong, which is at least partially responsible for incorrect pixel position measurements.  

The one bug in my original org file I haven’t been able to reproduce is random text characters (usually on a line with a bad image) misreporting pixel measurements.  But I could certainly imagine how in more complex files this could get out of sync. 

BTW, I haven’t tested it, but I do not think this misbehavior is specific to SVG images.