Bug #12474

GUI icons get smaller (instead of larger) when GUI is scaled up for high dpi screens

Added by Vincent Fregeac over 1 year ago. Updated over 1 year ago.

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git master branch
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Darktable GUI is barely readable as is on modern screens with high dpi, so it has to be scaled up to become usable. However, since Darktable do not follow the desktop preferences for font size, icon size etc. as it should, the only option is to use the GUI scale factor (Text scaling factors in Linux Mint for example) to be able to read Darktable's GUI. The problem is not only the non-text items in Darktable GUI do not scale up but some icons (modules category icons in Darkroom, Active/Presets/Reset/Instances icons in modules in both Lightable and Darkroom) get in fact smaller smaller when the desktop GUI is scaled up.

To reproduce the problem:
- Set the Text Scaling Factor to 1.0 in Linux Mint (Preferences|Fonts|Font settings panel)
- Increase the Text Scaling Factor by .1
- Every 0.1 increase, the Darkroom module category icons decrease
- The Active/Presets/Reset/Instances icons seem to shrink every 0.2 or so
- For whatever reason, icons then start growing in size after scaling 3.0 or more (which is way to big anyway for current screen dpi).
- When we switch between Lightable and Darkroom, the Active/Presets etc. icons sometime come back to their original size but the module category don't.

Included are screen captures for 1.0; 1.1; 1.2 and 1.5


#1 Updated by Aurélien PIERRE over 1 year ago

You should probably use the screen DPI to do that, in the resolution setup. The text scaling factor, in Gnome and forks, is an accessibility feature, I don't know how it's coded, but it does not look like it was intended do be beautiful. It's more a magnifier than a scaling.

#2 Updated by Vincent Fregeac over 1 year ago

The problem is, at least in Linux Mint, there is no DPI setting. The test scalling factor has become the display setting to scale up the UI for high DPI screens (it's not part of accessibility, or not anymore). And, yes, it is not intended to make anything more beautiful, just easier to see and/or read when the screen dpi is too high for 1:1 scaling.

On the other hand, I think it would be logical if the icons on the module title bar (or whathever it's called) is directly linked to the size of the font on the same title bar. DT seems to handle font scaling well (not tested on MacOS, but various Linux distros as well as Win10) so it should simplify HiDPI scaling on all OSes and distros. At least, linking the icon size to the font size would make two separate problems a single problem, simplifying debugging when HiDPI problems occur, as long as DT can easily get the actual font size from Cairo. Make sense?

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