Text is shifted between computers

[wbrenna]

The text gets shifted between different computers; I suspect a small bug due to the screen resolution. Also, sometimes written strokes differ in location with respect to text.

[andreasb242]

How much? Can you add a screenshot?

Which background? PDF or Xournal background?

[wbrenna]

It's usually just a small amount. In the slide below there is a Mathtex equation as well as two Text instances. This effect is amplified by having a long instance of Text.

[wbrenna]

I think this is likely similar to bug that exists in Xournal. Fortunately, Denis has it explained:
https://sourceforge.net/p/xournal/discussion/554377/thread/bfb88bd9/?limit=25#57eb
https://sourceforge.net/p/xournal/bugs/111/

Unfortunately he is not convinced it can be readily fixed. Evidently it's due to rounding problems in libgnomecanvas for Xournal. I checked the obvious thing for us - Xournalpp uses doubles for XojFont sizes, so it must be something deeper for us.

Attached is an example of the problem in the original Xournal, with the Xournal document and the PDF shown together. That said, Xournalpp does not exhibit the same behaviour. On Xournal, zooming in makes the rounding negligible, and eventually results in something that is faithful to the PDF export. On Xournalpp, zooming does not make a difference. This gives me a some hope that it can be fixed in Xournalpp.

[wbrenna]

I think the text shifting might be due to the use of absolute Pango font sizing in TextView.cpp. A sizing relative to DPI might prevent that problem; I'm testing it now.

The text shift in PDF looks to be caused by something else. For all I know this could be due to some font-rounding problem in poppler - it seems correct to use "true" in TextOutputDev instantiation in XojPopplerPage. But I might test some changes here too.

[wbrenna]

I believe I've fixed this in commit eb9d526. However, it crashes on some of my computers and I'm not sure why. I will leave it in unless I get complaints (in glib_new it works fine - I'm assuming because it might be a thread race condition for the settings file that was fixed by all the thread improvements in recent glib versions). Use the preferences file to match the DPI on all of your computers and this should make the spacing behave.

[wbrenna]

I think I fixed the crash with a better static int for the DPI (it's only reloaded on restart of Xournalpp).