high contrast accessibility application guidelines?

[Michael Weghorn]

[Adding the accessibility mailing list, somebody on that list might have 
more insights]

On 10/10/2022 22.02, Caolán McNamara wrote:
> Is there a set of guidelines as to the intent of high contrast within
> documents?

Not sure I grasp the context of this question (s. below), but from a 
quick search: WCAG has a criterion 1.4.3 about contrast for (primarily 
web) documents:
https://www.w3.org/WAI/WCAG21/quickref/?tags=contrast#contrast-minimum

The "Understanding Success Criterion 1.4.3: Contrast (Minimum)" page has 
some more details on the intent, etc.:
https://www.w3.org/WAI/WCAG21/Understanding/contrast-minimum.html

> As far as I can see in impress/draw/shapes we ignore/force-highcontrast
> text color, line color and fill colors, and there's a certain logic to
> that. And in general in documents we use a high contrast text selection
> mode. >
> On the other hand in writer we do show the real text color and fill
> color in the normal document content, but do the opposite for shapes
> and for the content of frames. If we use the insert, table UI, then we
> have forced colors in the preview of what the table will look like, but
> the final inserted table then doesn't have forced colors.

Is that with any explicit high-contrast settings either in the desktop 
environment or OS (like a specific theme) or LibreOffice explicitly applied?

In a quick test of mine *without* having taken any explicit settings, it 
behaved like this for me (LO master as of 
221d76260096b9e6b4c4479b1b89c95af8b05774, gtk3 with Adwaita theme and 
kf5 with Breeze theme):

Impress:

1) With the font color in character settings set to "Automatic" (the 
default), font color seems to be chosen automatically to provide 
contrast to the slide background ("Slide properties" -> "Background" -> 
"Color"), e.g. changing slide background from white to black makes the 
text be shown in white.

2) Character highlighting color doesn't seem to be taken into account, 
though. (Setting black highlighting color for text in a new presentation 
results in black text on black background.)

3) If any explicit color is set in the character settings, that one is 
used, regardless of the background, nothing is forced then (i.e. if 
slide background is set to black and font color is explicitly set to 
black, text is unreadable).

Other than Impress, in Writer, "Automatic" text color seems to take into 
account the character highlighting color and page background. (Changing 
the character highlighting color or page background to black results in 
white text, and character background takes precedence over page 
background, which seems reasonable.) Explicitly setting font color to 
black in addition results in black text on black on black background, 
nothing is automatically adapted.

In a quick test on Windows 10 (with an older LO master as of  commit 
349e3af0c5dd5ed495ed61aab526f63c16f0e215), enabling "Use high contrast" 
in the Windows settings results in unreadable text in Impress in a new 
presentation (both, font and background use the same dark color).
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