GUITable: Scale images with display density / row height

[grorp]

Fixes #3403, opened in 2015

5.8.1

this PR

Offtopic complaints

Something you can also see very well on these screenshots is that the mainmenu is way too small by default on Android, at least on my device. With proper scaling, the serverlist would be much more readable. This PR with gui_scaling = 1.3:

While you can set gui_scaling manually to get reasonable scaling (except for the scrollbars, which are too big now), you shouldn't have to do that. Minetest should use a reasonable fraction of the screen by default.

To do

This PR is a Ready for Review.

If you find a case where this PR makes an existing formspec look worse, please tell me. However, this isn't very likely to happen anymore with the latest commit. Zipgrep: https://web.archive.org/web/20240530091120/https://content.minetest.net/zipgrep/62090fd0-3f2e-4806-b04c-53cd5e8a20f1/

How to test

Look at the Devtest test formspec, "Table" tab. Verify that what you see matches what the code requests.

Look at the serverlist on a device with a high display density.

[grorp]

Unfortunately we can't scale images up to match the row height without accidentally affecting some formspecs. If a formspec uses blank.png (from textures/base/pack, 1x1 pixels) as a placeholder for "no image", that placeholder is scaled up to rowheight x rowheight, potentially increasing the column width.

Repixture awards formspec before

Repixture awards formspec after

To avoid this, I've changed this PR's approach to scale by display density instead. Row height is now only used to scale down images which are too tall.

[grorp]

This PR has undergone more transformation so that it is a pure bugfix now.

Example case on desktop:
Fantasy Commodity Markets
SharpNet Photo Realism 64px)

before

after

[SmallJoker]

Tested with math.randomseed(1337). Looks good.

[grorp]

Unfortunately I had to change the approach to display density scaling used in this PR again. With the previous approach, the icons were too big proportionally to the row height on my Android device:

previous screenshot

Because the row height is derived from the font size and the default font size is lower (14 instead of 16) on Android, the images were more affected by the higher display density than the row height was.

To fix this, I've made image scaling respect font size as well.

new screenshot