[Libreoffice-bugs] [Bug 139296] scrolling document canvas down & up can cause a line of text to "tear" with loss of registration, it clears when the line moves out of view far enough or view passes to a new page

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=139296

--- Comment #41 from spokanemagneto at gmail.com ---
(In reply to Telesto from comment #40)
> (In reply to spokanemagneto from comment #39)
> It's likely in 4.3 too, have seen it happen on macOS. However never got a
> hold on it.. but looks like GDI isn't affected.. so needs testing on
> Linux/macOS.
> 
> I speculate it can not be seen in 4.4.7.2 with OpenGL enabled because some
> weird timer madness.. Timer logic changed with 4.4.7.2 - 5.1 branch. Causing
> the issue to be more prominent.. but lingering around earlier on.
> 
> It appears mouse clicks are triggering a (full?) layout refresh or something
> like that at some point.. With different offset of few pixels or even
> rounding?? Where the backend holding a different image of the page
> (shifting) compared to the 'paint buffer'. And clicking around triggers a
> paint buffer invalidation/ repaint) Where the difference shows up and
> incrementally resolved as screen refreshes in parts.. Leaving sometimes
> artifacts. 
> 
> But well that's my invented story of someone who has actually no knowledge
> the matter.



Well, it sounds plausible to me, but I'm an electronic technician by vocation
and only a software programmer by avocation. I have more reading to do on
OpenGL as initially I came away with the notion that it was primarily used for
heavy graphics usage, which I would not think would affect a word processor, so
I put that aside for the time being, but maybe I should look into downloading
OpenGL.

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