[Win32] FontMetrics.getAverageCharacterWidth should return unrounded value

[wahlbrink]

At moment FontMetrics.getAverageCharacterWidth always returns rounded integer values. This leads to poor estimates of text columns (when using scaling) with issues like here: eclipse-platform/eclipse.platform.ui#2836

Expected behavior
FontMetrics.getAverageCharacterWidth should return unrounded values.

Environment:

1. Select the platform(s) on which the behavior is seen:

• • All OS
• • Windows
• • Linux
• • macOS

Eclipse Version tested: 2025-06 (4.36), I20250528-1830

[HeikoKlare]

I can confirm this issue and I can confirm that from first experiments that improving FontMetrics.getAverageCharacterWidth would resolve the issue with wrong print margins being displayed (and maybe more).

It's important to note that issues should only occur when a monitor zoom != 100% is used: the problem with the implementation is that the conversion from pixel to point usually leads to fractional results which are unnecessarily rounded here.

@wahlbrink thank you for reporting! Since you mentioned "issues like ...", do you know about further user-experienced issues caused by this?

[wahlbrink]

do you know about further user-experienced issues caused by this?

Similar issue (computation in the other direction):
We try to estimate the width (in chars) of the console
https://gitlab.eclipse.org/eclipse/statet/statet/-/blob/main/r/org.eclipse.statet.r.console.ui/src/org/eclipse/statet/internal/r/console/ui/actions/AdjustWidthHandler.java#L149

[HeikoKlare]

Do you plan to propose a PR?