[Win32] Fix font metrics being scaled by GC transform for fallback fonts

[HeikoKlare]

Summary

Fixes #2978

When a font that does not exist on the platform is set on a GC and a Transform is active, GDI+ calls Font::GetLogFontW with the transformed Graphics to derive a fallback GDI font handle. This causes the lfHeight in the resulting LOGFONT to be scaled by the transform, so GetTextMetrics on the DC returns inflated (transform-scaled) metrics.

The fix temporarily saves and restores the GDI+ transform around the Font::GetLogFontW call so the LOGFONT always reflects device-pixel metrics, independent of any user-applied transform.

A regression test is added that verifies font metrics are consistent across all four combinations of transform-set/cleared and font-set/kept that the original issue demonstrated.

How to Test

The snippet from #2978 may be used for testing. That snippet reflects what is also done by the test added with this PR.

[github-actions]

Test Results

  182 files  +   31    182 suites  +31   26m 27s ⏱️ + 6m 32s
4 730 tests +    1  4 707 ✅ +    1   23 💤 ± 0  0 ❌ ±0 
6 854 runs  +1 131  6 691 ✅ +1 090  163 💤 +41  0 ❌ ±0 

Results for commit 27aecd6. ± Comparison against base commit 9ab3898.

[HeikoKlare]

@ptziegler I am not sure how severe #2978 still is for you, but this may be a solution to that issue

[ptziegler]

@HeikoKlare I think we agreed that this problem primarily happens when using a non-existent font, right? The reason I originally reported this was due to the GEF Logic editor, but otherwise I've never seen it in practice. Especially when the "fix" is to use a valid font instead. 😅

[HeikoKlare]

Yes, this problem should only happen when using a non-existent font (because the height calculation is wrong in exactly that case).
I remember that you reported the issue because of the numbers in the Logic editor, and I also agree that it should not happen that often in practice, as you should usually use/switch to a font that exists (on every OS you support) for proper UI results. I was just not sure if you may had faced that issue anywhere else as well 🙂