https://bugs.documentfoundation.org/show_bug.cgi?id=157153

--- Comment #12 from Adam Fontenot <[email protected]> ---
(In reply to anixxsus from comment #11)
> Somewhat paradoxically they used the term "subpixel font rendering" to mean
> something different (an close to opposite) of what this term usually means.
> This is the post that announces this controversial change using this
> confusing terminology:
> https://adamfontenot.com/post/libreoffice_7.
> 4_has_a_new_approach_to_text_rendering

Hi, I wrote the linked blog post. For clarification I'm not affiliated with TDF
nor did I write the code for this change. I was simply enthusiastic about it
and couldn't find any discussion elsewhere.

I'm a little confused about your complaint regarding terminology. To clarify,
"sub-pixel rendering" usually refers to sub-pixel anti-aliasing, which you are
calling "subpixel font smoothing". [1] This is unrelated to the change in 7.4,
which involves subpixel font *positioning*. This is when anti-aliasing
capabilities (whether RGB or grayscale) are used to align glyphs more precisely
with their true location as specified by the font metrics, rather than locking
them to a single position relative to the screen pixels.

But I don't want to bicker about terminology, since it's not relevant to this
report.

> But it makes the fonts more blurry.

It's possible that enabling sub-pixel positioning could make some fonts
slightly more blurry, but I don't believe this is expected to be true in the
general case. The extremely heavy hinting that Tahoma uses could be the source
of some issues.

> Plus, they disabled the subpixel font
> smoothing, that is using subpixels to increase horizontal resolution thrice
> (which is standard terminology).

This indicates to me that the issue you are facing was probably not an
intentional change in 7.4 and may not be related to the sub-pixel positioning
change at all. That's because my platform (which doesn't use Skia) continues to
display sub-pixel anti-aliasing (this is actually visible in the blog post's
screenshots).

I wonder if your issue could be caused by a change in anti-aliasing behavior at
small rendering sizes. You might check Options -> LibreOffice -> View, and
decrease the value for the minimum screen font anti-aliasing (the default seems
to be 8 pixels). Do you see sub-pixel anti-aliasing when you change your zoom
level to 100% or 150%? Just a guess.

> In the post linked above it is evident that the new rendering overall looks
> much worse, but some issues with letter fusing as in "rn" are indeed solved.

I strongly disagree, of course. :-)


[1] I believe Microsoft uses the language of "smoothing" when describing their
ClearType feature, which may have led to this confusion. Most experts writing
in this space (as well as Wikipedia) call it sub-pixel rendering or sub-pixel
anti-aliasing. Personally, I don't like using the "rendering" term (and mention
this in the blog post) precisely because it's irritatingly ambiguous.

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