HDPI not working for Eclipse RCP applications created with the pde plug-in template

[vogella]

Looks like the handling for Eclipse RCP application is incorrect either in Platform UI or in SWT, I don't know.

I create a new Eclipse RCP basedon the plug-in template and set my notebook monitor to:

My "big" screen has the following resolution:

If I start the application on my big screen, everything looks good, here is the IDE and the RCP app, side by side:

But the e4 part is not resized correct.

The dialog looks ok if I open it up on the laptop monitor but if I move it to the primary monitor is alse get scaled incorrectly.

hpdi.zip

[vogella]

I was using the 2026-03 as target platform:

  <location includeAllPlatforms="false" includeConfigurePhase="true" includeMode="planner" includeSource="true" type="InstallableUnit">
   <repository location="https://download.eclipse.org/releases/2026-03"/>
   <unit id="org.eclipse.equinox.sdk.feature.group"/>
   <unit id="org.eclipse.platform.feature.group"/>
  </location>

[laeubi]

Looks like the handling for Eclipse RCP application is incorrect either in Platform UI or in SWT

As far as I know runtime scaling must be explicitly enabled and you are using a RCP4 Application that likely has this disabled by default.

[vogella]

It scales parts of the application as you can see in the screenshot. I would expect either no scaling or all.

But how do we enable runtime scaling?

[HeikoKlare]

There is a preference to enable/disable monitor-specific scaling. To just force enablement via system property, you can specify -Dswt.autoScale.updateOnRuntime=true. Can you test what happens then?

The screenshots look to me as if no scaling happens at all. Title and menu bar are always scaled by the OS. The contents are scaled in a way depending on the DPI awareness of the process. In a runtime Eclipse application with default JVM settings this will be "Per Monitor V2" which, if monitor-specific scaling is not enabled, leads to the shell contents not being scaled (as with that DPI awareness the application is responsible for doing the scaling, which does not happen). Note that this has been the case for runtime Eclipse applications for a long time.
The EPP products include a manifest that change the DPI awareness of the product to "System", which makes the OS blurry-scale the whole shell for other monitors (the behavior we used to have before monitor-specific scaling was available). An option to emulate that is to add a Manifest to your JRE that sets the DPI awareness to "System". You can see the DPI awareness in the task manager:

What might be a bit confusing: with monitor-specific scaling enabled, the DPI awareness of the UI thread is changed to "Per Monitor V2" to make the application scale correctly, while the process DPI awareness may still be "System" (or anything else). This was done as the process DPI awareness is defined by manifest of the application or JRE and cannot be changed at runtime but depending on whether monitor-specific scaling is enabled or not, a different DPI awareness is required. So we modify the DPI awareness of the UI thread only to support both scenarios.