Several wrong font sizes with "-Dswt.autoScale"

[hayos]

I am using the following settings in eclipse.ini:
-Dswt.enable.autoScale=true
-Dswt.autoScale=150
-Dswt.autoScale.method=nearest

If set to
-Dswt.autoScale=100
everything looks fine.

After updating from "Eclipse IDE for Enterprise Java and Web Developers (includes Incubating components)" 12-2024 (or maybe 9-2024) to Version: 2025-06 (4.36.0) Build id: 20250605-1316 a lot of font sizes are messed up.
Affected are (at least):

• 'Show Line Numbers' (if on obviously) the line numbers are unreadably large
• In 'About Eclipse' -> '?' (the Help button) the font size is quite large, until you hover the entries. The the display is messed up.

As said, this should be introduced recently. The current Spring Tools for Eclipse is not (yet) affected. (Version: 4.30.0.RELEASE Build Id: 202504180233 Revision: ee1fc74e10e11091fad0be134cc6ec1524ffcf93).

Please fix the regression an introduce some test setups for eclipse.ini for final UI testing which show such errors.

I am aware that this setting is not officially supported for end users. (See https://www.eclipse.org/lists/platform-swt-dev/msg07902.html".) But that does not mean that it is meant to be deliberately broken. In particular as DPI densities are getting much higher the last years and will in future.
(Thus in my opinion this feature should be officially documented for end users in one of the coming releases.)

[fedejeanne]

cc @akoch-yatta

[hayosc]

Meanwhile I have more insights.

The effect is related to Preferences -> Appearance -> Use Monitor-specific UI scaling. (I wasn't aware this exists when I opened this.)

The trigger of changed font sizes seems to be that the functionality was changed from experimental to normal functionality, and for this the default was changed to 'Use Monitor-specific UI scaling': "checked on". Maybe this is the only recent relevant code change. If I switch it off, everything works as before.

Since Monitor-specific UI scaling already does what I need, double the icon size on my 4K monitor, the '-Dswt.autoScale=xxx' is unnecessary for people like me with slightly impaired vision (aka: old eyes and old glasses). But: It still is a magnificent accessibility tool for the severely visually impaired. Please, do not drop this report, just put it to lower priority.

Beware

• The '-Dswt.autoScale=150' led to the wrong font size effect on a system with two 1920x1080 monitor, plus the 12'' laptop monitor.
• On my 4K monitor at home this setting has no side effect. But if set to '-Dswt.autoScale=300', the effect is also there on 4K resolution (32'').

[fedejeanne]

Thank you for the extra details, @hayosc ! It's good to know that disabling the monitor-specific UI scaling solves your issue.

Don't worry, the issue hasn't been dropped, in fact I pinned it in our internal (public) backlog yesterday and I was about to test the behavior in older Versions (so that I know what the "normal" was before introducing HiDPI support and activating it by default) when I read your comment.

Here it goes...

The behavior in 4.33 (before we even started working on the improved HiDPI support) was that increasing the zoom by setting the parameters -Dswt.enable.autoScale=true, -Dswt.autoScale=150 and -Dswt.autoScale.method=nearest let the fonts still use the zoom from the monitor they are in (just like they do in 4.36) but the font of the line number ruler (the line numbers) also use that zoom and they looked fine.

This is what we suspected and what was reported in vi-eclipse/Eclipse-Platform#336. Since now this is confirmed and it is a regression, I reported it in the official repository: eclipse-platform/eclipse.platform.swt#2311.

There is still the matter of the fonts having a different size/zoom than other UI elements. This is also a valid point but since the behavior in 4.33 was the same then improving this would be an enhancement (one that I would personally like to have) and not a bug. It remains pinned in our internal (public) board for now and it will have a lower priority.

I hope this helps!

[HeikoKlare]

The issue has been addressed with a bunch of recent PRs including:

• [win32] Introduce ZoomContext in Image eclipse.platform.swt#2404
• [Win32] Fix wrong line height in StyledText #2405 eclipse.platform.swt#2406
• [win32] Fix inconsistency when an Image with GC is drawn on a GC eclipse.platform.swt#2387
• Fix LineNumberRuler for fixed zoom #3158

Some final glitches may remain (even though we are not yet aware of them), because the combination of monitor-specific scaling and a fixed auto-scale zoom via manually setting -Dswt.autoScale=XXX is difficult and actually not very useful. We plan to work on better excluding that combination for the next release (2025-12), as we actually do not want to support a fixed auto-scale zoom together with monitor-specific scaling at all.