[Win32] Simplify and fix Region class

[HeikoKlare]

Summary

This change cleans up the win32 Region.java implementation by removing duplication, fixing a formatting bug, and applying idiomatic Java patterns throughout.

Bug fix

• toString() produced malformed output: The method opened a { but never closed it, producing strings like Region {handle(zoom:100) instead of Region {handle(zoom:100)}. This made debugging harder and was inconsistent with the disposed-region case which does close its braces.

Simplifications

• getRegionHandle(int): Replaced the manual containsKey / put / get triple with Map.computeIfAbsent, which is the idiomatic Java way to lazily populate a map and avoids two redundant lookups.

• getBounds(): A block lambda containing only a single return was converted to an expression lambda.

• isEmpty(): The RECT object was allocated before the lambda, even though it is only needed inside it. Moved it inside the lambda to keep allocation and use co-located and to avoid capturing a mutable object across a closure boundary unnecessarily.

Eliminated code duplication

• OperationWithRectangle: The three methods addInPixels, subtractInPixels, and intersectInPixels were virtually identical — each created a rect region, called CombineRgn with a different mode constant, then deleted the region. These were replaced by a single combineWithRectInPixels(handle, x, y, w, h, mode) helper, reducing ~15 lines to ~5.

• OperationWithArray: The same pattern applied to addInPixels and subtractInPixels, collapsed into combineWithPolyInPixels(handle, pointArray, mode).

• OperationWithRegion: Three block lambdas each containing a single return OS.CombineRgn(...) call were converted to expression lambdas, removing the syntactic noise.

Access modifiers

• Removed redundant public from the constructors of OperationWithArray and OperationWithPoint. Both classes are declared private static, so public on their constructors has no semantic effect and is misleading.

Test plan

• Existing Region-related JUnit tests pass without modification
• Verify toString() output now includes the closing } for non-disposed regions
• Smoke-test region operations (add, subtract, intersect, translate) on Windows

[github-actions]

Test Results (win32)

   28 files  ±0     28 suites  ±0   4m 27s ⏱️ -9s
4 666 tests ±0  4 593 ✅ ±0  73 💤 ±0  0 ❌ ±0 
1 200 runs  ±0  1 176 ✅ ±0  24 💤 ±0  0 ❌ ±0 

Results for commit 7ce8659. ± Comparison against base commit 188aed6.

[vogella]

I did not check in the code (sorry)but would that cleanup also make sense for Linux ans Mac Implementation or why is this "only" done for windows?

[HeikoKlare]

The Resource implementations (Region, Transform, Image etc.) are significantly different between Windows and macOS/Linux (due to Windows requiring handles for multiple zooms for proper multi-monitor scaling support, which is non-existent in the limited HiDPI support of macOS and Linux). So, a cleanup may be performed on the Linux and macOS implementations as well, but the result would be significantly different. I chose to apply this to the Windows implementations (first) as those have been recently revised (for monitor-specific scaling).