Query on Monitor-Specific UI Rescaling from SWT point of view introduced in 4.34

[deepika-u]

I see that there is a monitor specific UI scaling feature that was introduced in Eclipse 4.34(from platform UI - eclipse-platform/eclipse.platform.ui#2461). I wanted to take a look at the core implementation behind this feature(specific to SWT) for a requirement for one of my clients, but I haven’t been able to locate the original pull request where it was implemented. Although I could find the umbrella bug(#1961) related to HiDPI support, the actual PR containing the core changes isn’t obvious. Will you be able to redirect me to that particular PR which has the core implementation behind this feature.

[HeikoKlare]

The implementation of that feature consists of hundreds of PRs. It was incrementally implemented and integrated with the use of a feature toggle.
The best source of information is probably the recently added feature documentation.

[deepika-u]

Thanks alot, in case if i have specific query on this i shall get back to you.

[deepika-u]

@HeikoKlare
Thanks for your quick answer. We went though the doc indetail.
From the doc you have shared, what we understand is HiDPi support is implemented in 2 phases:

1. The first one being focused on rendering a sharp UI only on primary screen. This change targeted only on the primary monitor when starting up which is the HiDPi support itself.

2. The second phase is Monitor specific UI scaling which is extended support on the first one that handles runtime DPI changes not just in primary monitor but across different monitors automatically when switched between monitors.

From the bug report, it appears that basic HiDPI support (feature 1) was already implemented in Eclipse 4.4 at least partially (https://bugs.eclipse.org/bugs/show_bug.cgi?id=474252). so in that way 4.31 already includes this initial HiDPI support. What is missing in 4.31 is the second feature which is exactly our customer requirement.

Will you be able to direct us to a minimal set of prs(with which we can create a patch on 4.31 or a minimal version of eclipse upgrade) where this basic feature would work with a multi-monitor setup?

[HeikoKlare]

Will you be able to direct us to a minimal set of prs(with which we can create a patch on 4.31 or a minimal version of eclipse upgrade) where this basic feature would work with a multi-monitor setup?

There is no dedicated set of PRs that you can use, as it's a bunch of rework, refactoring and extensions, which, as explained above, led to hundreds of PRs implementing that feature guarded by a feature toggle.
For using the feature, my recommendation would be to use an as up-to-date state of SWT as possible for the best experience. With 4.36 the state was already quite decent, which is why it was enabled by default (https://eclipse.dev/eclipse/markdown/?f=news/4.36/platform.md). Still many fixes and improvements have been made afterwards, such that if you need to update anyway, you should consider directly moving to 4.38 or even 4.39.

[deepika-u]

Thanks alot for your inputs.

[elsazac]

@HeikoKlare

I have a 4.31 eclipse version (another product built on 4.31) with me and i am facing a problem of reduced font size when dragging eclipse from a low resolution screen to a high resolution screen. Setting the option Override high DPI scaling -> system in eclipse.exe file retains the system behaviour as it overrides the swt behaviour. I tried to update the .ini file with -Dswt.autoScale=auto option but it didn't work. Does anyone know any similar workaround to add to .ini file so that it autoscale according to the monitor? Any suggestions would be of great help.

[HeikoKlare]

Eclipse 4.31 and the SWT version shipped with it does not support any scaling that adapts to the monitor. The first state of the monitor-specific scaling feature that you may consider usable was the one set as default with the 4.36 release: https://eclipse.dev/eclipse/markdown/?f=news/4.36/platform.md

So if you need such a functionality you should at least update to the 4.36 release, even better to the most recent one.

[elsazac]

Agree on that. I was asking because I got to test the same with earlier versions like 4.15 and below that as well. Those were able to adapt to the second screen even after dropping without need for any particular settings specifically. there is no change on the font size for those versions.

[merks]

Note that are are WIndow-native settings on the executables (eclipse(c).exe and/or java(w).exe) that can have a significant impact on the behavior, i.e., whether the application should to the scaling or the operating system.

[HeikoKlare]

The UI did never really adapt to other screens. What used to happen is that the UI was rendered for the primary monitor zoom at startup and the adaptation to the zoom of other monitors happened via some bitmap scaling performed by Windows (leading to blurry scaling results). That stayed the same for many years until the 4.36 release of Eclipse. To work that way, the process has to be run with DPI awareness "System". That's what the Equinox native launcher defaulted to, so that kind of scaling should happen automatically if you don't do any changes to the Equinox native launcher, don't configure the .exe of your product with different DPI settings and the like.

The only scenario I can imagine where a reduced font size happen when moving to a higher-zoom monitor is when the application is not executed with DPI awareness "System" but either the "unaware" mode (so that no scaling happens at all) or any kind of application-side mode (such as "PerMonitor" and "PerMonitorV2"). You can see the DPI awareness that your process runs with also in the task manager: