[Libreoffice-bugs] [Bug 135126] Paragraph or Character attributes applied to the U+0020 "Space" NPC change text layout (Harfbuzz)

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=135126

V Stuart Foote <vstuart.foote at utsa.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |103729, 71732
                 CC|                            |dr.khaled.hosny at gmail.com
            Summary|Changing font color changes |Paragraph or Character
                   |text layout (Harfbuzz)      |attributes applied to the
                   |                            |U+0020 "Space" NPC change
                   |                            |text layout (Harfbuzz)

--- Comment #10 from V Stuart Foote <vstuart.foote at utsa.edu> ---
Confirmed. Applying a paragraph attribute to a single space glyph (U+0020)
results in a change in its width on document canvas relative to the paragraph
style.  But so will applying a character style to the glyph.

That is, open the 'Formatting Styles' toolbar, and apply the 'Emphasis' or
'Strong' character style against the selected space.

So, it is not an issue of Direct Formatting over riding Paragraph style.

I am not certain, but believe it is an issue in the HarfBuzz handling of
unattributed space glyphs vs. rendering with an applied attribute.

A space glyph  with VCLs artificial Strike-through or Underline has to be
rendered to canvas, likewise our artificial Bold or Italic--that size/width has
to be calculated against the font metrics. That's obvious, less so are
attributes like the color of a space glyph or applying a background color for
the space.

Look closely and you'll see both colors get the same calculated width as the
Strike-through or the Underline attribute applied to the glyph.

So, behavior is actually pretty consistent--DF of the space glyph can be
removed with an Undo or <Ctrl>+M, while applied Character style (E, S, Q) can
be removed by applying the default Character style (A).

Applying Paragraph/Character attributes to other NPC in string would probably
behave same.

But, I suspect that this can only be improved with a solution to bug 103322 to
provide greater precision in composing the document canvas. And that this
ultimately is a duplicate of that issue.

@Khaled?


Referenced Bugs:

https://bugs.documentfoundation.org/show_bug.cgi?id=71732
[Bug 71732] [META] Bugs related to text rendering, typography and font features
in LO
https://bugs.documentfoundation.org/show_bug.cgi?id=103729
[Bug 103729] [META] HarfBuzz-based common text layout regressions
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