RFC: Dark mode on fltk.org, and slightly modified colors

[Albrecht Schlosser]

Announcement:

I updated the CSS file of our FLTK server to introduce "Dark Mode" and to improve some contrasts, particularly in "Night Mode". This is currently experimental, but I'd like to keep it. See below for details.
https://www.fltk.org/

The FLTK server should now support "Dark Mode" automatically if your system/browser is set to "Dark Mode".

One reason to do this was GitHub Discussion #1476 which requests to improve some color constrasts.
https://github.com/fltk/fltk/discussions/1476
However, the images posted in this discussion are NOT exactly what we see now on fltk.org. Please try yourself.

I also tweaked the table background and link colors for better contrast. Note that this is still work in progress and may need further tweaks. I'm aware of this.

Anyway, I decided to update the web server with the new CSS file to let you test and comment on the new feature.

All users (not only FLTK devs) are invited to leave their comments here and to suggest improvements on the current status. This is not meant to start a discussion about a different (better) color theme which should be considered separately.

What I want to know now is if there are subtle issues I may have overlooked, and how good the "dark mode" is for users liking and using this.

You are also encouraged to test visibility and readability when applying a blue filter like Gnome's "Night Light" [1], and to help improve the colors if the contrast is insufficient. You should be aware though that applying "Night Light" will definitely decrease contrast, there's nothing we can do except choosing more contrast in "normal / daylight mode".

To clarify: there are now four different modes to view the FLTK website, i.e. all combinations of

- Light mode vs. dark mode
- Blue filter (aka Night Light) on / off

Please test and report your results, all feedback is welcome!


----------

[1] Gnome's "Night Light" mode is by default scheduled automatically if it is enabled. You can change this is Display Settings / Night Light / Schedule by setting this to "Manual Schedule". Then you can change it instantly by switching Night Light on/off, even when using a Wayland session.

[Greg Ercolano]

On 6/28/26 07:05, 'Albrecht Schlosser' via fltk.general wrote:

Announcement:

I updated the CSS file of our FLTK server to introduce "Dark Mode" and to improve some contrasts, particularly in "Night Mode". This is currently experimental, but I'd like to keep it. See below for details.
https://www.fltk.org/

    Looks fine to me..

The FLTK server should now support "Dark Mode" automatically if your system/browser is set to "Dark Mode".

    Ah, I've never messed with it; in Firefox I take it this is Edit -> Settings -> Dark Mode

    Seems readable in that mode too.

- Blue filter (aka Night Light) on / off

    Hmm, ya, I enabled that in Gnome and our page (e.g. "Bugs") is still very readable.

    (What a weird mode.. while I like warm incandescent lighting for room light, but I'm not liking it on my screen.. bleh! Subjective I'm sure, but anyway..)

Anyway, I decided to update the web server with the new CSS file to let you test and comment on the new feature.

    No problems here..
    I guess you're still in progress, but feel free to commit the new unstaged fltk-modernized.css
    (I haven't done any dev on the website since the caching newsgroup mods; no load issues since that mod that I'm aware)

[Albrecht Schlosser]

On 6/29/26 05:13 Greg Ercolano wrote:

On 6/28/26 07:05, 'Albrecht Schlosser' via fltk.general wrote:

Announcement:

I updated the CSS file of our FLTK server to introduce "Dark Mode" and to improve some contrasts, particularly in "Night Mode". This is currently experimental, but I'd like to keep it. See below for details.
https://www.fltk.org/

    Looks fine to me..

Thanks for testing!

- Blue filter (aka Night Light) on / off

    Hmm, ya, I enabled that in Gnome and our page (e.g. "Bugs") is still very readable.

    (What a weird mode.. while I like warm incandescent lighting for room light, but I'm not liking it on my screen.. bleh! Subjective I'm sure, but anyway..)

Recently there was a GitHub Issue (Discussion) that mentioned that the contrast was very bad in that mode - which I could confirm. It is now much better with the new setup.

The idea behind that mode is to reduce blue light in the evening because blue light is going to keep you awake, or something like that. The default setting in Gnome is to switch it on at 8pm in your timezone if it is enabled. This is known to work well for reading text, news, whatever, but obviously it can reduce contrast for other tasks. In Gnome it's also configurable to set the whitepoint (IIRC) to something in the range 1.700 K to 4.700 K (Kelvin) whereas the normal whitepoint would be 6.500 K (don't ask me for details).

Anyway, I decided to update the web server with the new CSS file to let you test and comment on the new feature.

    No problems here..

Good, thanks.

    I guess you're still in progress, but feel free to commit the new unstaged fltk-modernized.css

Done today.

    (I haven't done any dev on the website since the caching newsgroup mods; no load issues since that mod that I'm aware)

I'll send you a private mail regarding recent changes (minor issues), but please don't hold your breath, I'm still working on that stuff.

[duncan gibson]

There's certainly enhanced contrast using Firefox on MacOS in Dark mode but not everywhere, as shown in the screenshot.

Similar colours appear when using Safari.

Firefox on CentOS 7 in XFCE in Light mode at work doesn't show this anomaly.

[Greg Ercolano]

On 6/29/26 10:57, duncan gibson wrote:

There's certainly enhanced contrast using Firefox on MacOS in Dark mode but not everywhere, as shown in the screenshot.

    Good catch.

    That's probably my fault; when we changed everything around to google groups and such, I made that notice on the "Forums" page by just hand typing the HTML, without using FLTK's css class citations for styling, so it's not being affected by Albrecht's new .css file.

    I think I can make a simple tweak to fix that.

[Greg Ercolano]

    OK, fix for that applied; should look like this now in dark mode:

    Albrecht: leaving that change unstaged for now, in case there's a better way to make a centered 'site-news' styled table.

[Greg Ercolano]

There's certainly enhanced contrast using Firefox on MacOS in Dark mode but not everywhere, as shown in the screenshot.

    Good catch.
    That's probably my fault; when we changed everything around to google groups and such, I made that notice on the "Forums" page by just hand typing the HTML, without using FLTK's css class citations for styling, so it's not being affected by Albrecht's new .css file.
    I think I can make a simple tweak to fix that.

    OK, fix for that applied [snip]

    Found a few other "hand edited" tables; one in submitting new articles, another in the website admin pages.
    Fixing those now.

    Albrecht, I'll follow up in email as well, as I noticed the entire CMP's code examples have issues in dark mode, probably a small css tweak.

[Albrecht Schlosser]

On 6/29/26 21:33 Greg Ercolano wrote:

[Duncan:] There's certainly enhanced contrast using Firefox on MacOS in Dark mode but not everywhere, as shown in the screenshot.

Thanks, Duncan, for reviewing and reporting issues.

[Greg:] OK, fix for that applied

    Found a few other "hand edited" tables; one in submitting new articles, another in the website admin pages.
    Fixing those now.

    Albrecht, I'll follow up in email as well, as I noticed the entire CMP's code examples have issues in dark mode, probably a small css tweak.

Thanks to Greg for all his fixes. I merged Greg's and my own fixes yesterday, uploaded the changes, and current online status is IMHO fine except some small opportunities for fine tuning.
Known issues:

1. The colors of "links" vs. "visited links" are not well distinguishable. This is due to the new color theme and a compromise for all four "modes": normal and dark mode  x  day and night light.

2. The comment numbers in the old STR system are hardly readable in dark mode.

I'll look into these issues later, when time permits. If anybody finds other color/contrast issues, please report here. TIA.

[Albrecht Schlosser]

Progress report:

On 7/1/26 12:19 'Albrecht Schlosser' wrote:
> Known issues:
>
> 1. The colors of "links" vs. "visited links" are not well
> distinguishable. This is due to the new color theme and a compromise
> for all four "modes": normal and dark mode  x  day and night light.

Working on this now, but this will take some time. It's complex, given
all the constraints ...

> 2. The comment numbers in the old STR system are hardly readable in
> dark mode.

Fixed.

[Albrecht Schlosser]

On 7/1/26 15:14 'Albrecht Schlosser' via fltk.general wrote:

Known issues:

1. The colors of "links" vs. "visited links" are not well distinguishable. This is due to the new color theme and a compromise for all four "modes": normal and dark mode  x  day and night light.

Working on this now, but this will take some time. It's complex, given all the constraints ...

Done: I updated the FLTK website with the new CSS about one hour ago. Please test.

Note: Link colors are as follows:

    All link colors clear WCAG AA (contrast ratio 4.5:1) against the
    four possible background colors: `data0` and `data1` in both light
    and dark mode. Link colors were chosen such that
    - unvisited links are red (as before)
    - visited links are blue
    - hovered links are yellow in dark mode
    - hovered links are "dark orange" (brown?) in light mode
    
    The latter is a compromise due to having the contrast requirements.
    All modes stay at least readable in `Night Light`, i.e. when applying
    a blue filter, and have good properties for some kinds of color
    blindness.

That's it. It was a long struggle to get to this solution, I hope it's acceptable.

Known issue: Dillo doesn't support the "CSS Custom Properties" syntax `var(name)` for all colors, hence Dillo doesn't work well with this new CSS. This syntax (and its semantics) is known to work in all major browsers since April 2017, which is now more than 9 years ago. Other not working browsers are Internet Explorer and Opera Mini, see also
https://github.com/fltk/fltk/discussions/1476#discussioncomment-17537887

Anyway, I'm looking for a workaround, but I can't promise anything.