[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 #21 from spokanemagneto at gmail.com ---
Well, you were right. It turns out that did NOT fix the problem...but it is a
bug nonetheless. I spent another ten hours yesterday on this and found that it
goes a little further than I thought (the weird margins settings). I uncovered
some seemingly related issues. 

It appears that the reason for the weird margin settings, in particular those
in the Normal (0.75") page format is that ALL the templates are set to A4
instead of Letter for those of us in the USA (why we are still living in the
dark ages with regards to measurement standards is beyond me). I tried
resetting the Language of..., Formats, and Default Languages for Documents
settings from Default - English (USA) to simply English (USA), but that did not
help. 

To address that issue, I ended up simply making a couple new templates,
including a new default generic document template to use in the meantime, but
they still exhibited the text tearing issue.  

So, in thinking about how everything seems to be geared toward evenly divisible
cm units and thus perhaps causing the rounding errors when converting to
inches, which was the suggested root cause of this text tearing issue, I
decided to switch everything over to the standard points units (margins, tabs,
line spacing, etc.) since that is what printers use. 

One template I created had a font size of 10, single line space, and 54-pt.
(i.e., 3/4") side margins. If I switched from single space to a line space of
1.15 things improved, but it was still occasionally bad. I did some reading and
found an author who suggested using the "magic number", which is to say making
your measurements evenly divisible by your line spacing (or half the line
spacing) number. Earlier, I was doing that, but with the font size--not the
line spacing, which never occurred to me.

He indicated that the default for LibreOffice is 12/14 (font 12, line spacing
14). He also recommended that if at all possible when setting the paragraph
formats to use Fixed Line Spacing because it's a fixed size and not calculated
(it also has the benefit of being register true without having to select that
option as you otherwise would have to). 

With all that in mind, I kept the font size of 10, but changed to fixed line
spacing to 14 (12 did not work, but 14 is evenly divisible by most of the other
settings), and 54-pt. side margins. The default generic document template I
created has font 12, fixed line spacing of 14, and margins of 72-pt (i.e., 1").
I spent an hour this morning trying to get either one of those templates to
show any signs of text tearing, but I have not noticed any, but again, I know
Murphy's Law is lurking nearby waiting to make a fool of me again, thinking I
found it. 

So, the question is, even though the text tearing is still an issue, this is a
legitimate bug in and of itself, so should this be posted elsewhere?

Finally, I have a question. As a programmer hobbyist, if rounding is part of
the issue (along with incorrect USA settings), then why not ditch the float
data type and opt for a long long instead (providing you're using C++)?

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