Line numbers in editors do not scroll properly on displays with different scaling settings

[lmcbrien-ncs]

• [✓] I verified I can reproduce this issue against latest Integration Build of Eclipse SDK

After updating to Eclipse 2025-06, the line number bar in editors no longer updates properly on my secondary monitor, which has a different scaling setting from my primary monitor.

Screen.Recording.2025-06-12.at.16.24.38.mov

Bug is observed on a Macbook Pro M3 with a retina display (which requires 2x pixel scaling to be usable) and a 2560x1440 monitor running at native resolution. I don't have another system to hand to test with.

I see in the 2025-06 release notes that there is a new Windows-only feature for monitor-specific UI scaling. I have confirmed that the new setting is not visible in Preferences -> General -> Appearance on my Mac OS system.

Steps to reproduce

From a fresh installation and clean workspace:

• Initial display configuration: primary monitor with 2x display scaling enabled, secondary monitor at native resolution.
• Open Eclipse.
• Open or create a text file (e.g. a Java class) that is long enough to require scrolling.
• Move the Eclipse window to the secondary monitor.
• Scroll up and down. The main editor pane works normally but the left bar with line numbers, breakpoints, etc is frozen.
• Move the Eclipse window to the primary monitor.
• Scroll up and down. Normal behaviour is observed.
• Change the primary monitor settings to native resolution.
• Move the window between displays and try scrolling. Normal behaviour is observed.
• Re-enable display scaling on the primary monitor.
• Buggy behaviour returns.

Tested under this environment:

• OS & version:
  • Mac OS Sequoia 15.5 (aarch64)
• Eclipse IDE/Platform version (as shown in Help > About):
  • First observed after updating to Version: 2025-06 (4.36.0), Build id: 20250605-1316
  • Reproduced on latest integration build Version: 2025-09 (4.37), Build id: I20250611-1800
• Display:
  • Primary monitor: MacBook M3 Pro (16-inch, Nov 2023) running at default 2x scaling (1728x1117, native resolution 3456x2234)
  • Secondary monitor: Samsung LS27A600NWUXXU running at native resolution (2560x1440)

Community

• [✓] I understand reporting an issue to this OSS project does not mandate anyone to fix it. Other contributors may consider the issue, or not, at their own convenience. The most efficient way to get it fixed is that I fix it myself and contribute it back as a good quality patch to the project.

[HeikoKlare]

I can reproduce the issue. It seems like it was introduced with this PR:

• [MacOS] Fix getBounds for Image based on ImageGcDrawer eclipse.platform.swt#1883

When reverting that commit, the ruler works fine again. But actually I am a bit confused that the PR was merged 3 months ago and no one seems to have experienced the issue on MacOS so far, so I wonder if I miss something that makes the issue not occur for everyone or if some other change affected the behavior (as well).

[HeikoKlare]

The issue also occurs in the "opposite direction": if you start Eclipse on a 100% monitor and move the window to a 200% monitor, the line number ruler does not work there. In general, the ruler will only work on monitors that have the same zoom as the monitor on which the application was started.

In consequence there is this (unsatisfying) workaround:

Workaround

When an Eclipse application window is moved to another monitor with a different zoom than the monitor it was started on, such that the line number ruler stops working properly, one can restart the application on the "target" monitor. In consquence, the ruler will work on that monitor (and on any monitor with the same zoom) but not on monitors having a different zoom.

A potential fix is proposed here:

• [macOS] Initialize image data from ImageGcDrawer only at device zoom eclipse.platform.swt#2236

[lmcbrien-ncs]

Retested using integration build 20250621-1800 - seems to be working fine, thanks.

[jjjgenoese]

Another workaround:
1 .Open a terminal window and move it to target monitor.
2. start Eclipse.app from command line on target monitor.
For example
open -n ~/eclipse/jee-2025-06/Eclipse.app --args -data $ws -showlocation

$ws is for particular workspace.