[Win32] Remove OS.IsAppThemed() — always true on Windows 10+

[HeikoKlare]

Summary

OS.IsAppThemed() always returns true on Windows 8 and later, see https://learn.microsoft.com/en-us/windows/win32/api/uxtheme/nf-uxtheme-isappthemed
Since SWT targets Windows 10+, every !OS.IsAppThemed() branch is unreachable dead code and every if (OS.IsAppThemed()) guard can be reduced to its body.

This removes all 70+ call sites across 21 widget files and cleans up the OS.java declarations that became unused as a result.

Changes to widget code

• Dead !OS.IsAppThemed() branches deleted — Classic theme fallbacks for DrawFrameControl/DFCS_* checkbox and arrow drawing, TBSTYLE_TRANSPARENT clearing, RTL text-clipping space-padding, ILC_MASK image list flag, XP marquee workaround in ProgressBar, separator workaround in CoolBar
• if (OS.IsAppThemed()) guards unwrapped — Explorer theme setup in Tree/Table createHandle, themed checkbox image lists, THEME_BACKGROUND handling in drawBackground/wmColorChild/WM_ERASEBKGND/WM_MOVE/wmNCPaint, setBoundsInPixels, widgetStyle bits, and more
• Ternary OS.IsAppThemed() ? x : y replaced with x — Group Y-offset adjustments, ToolBar TBSTYLE_TRANSPARENT style bit
• Stale //TEMPORARY CODE commented-out blocks removed — CoolBar.java and TabFolder.java
• Group.fixText(boolean enabled) — enabled parameter removed (became unused after the Classic-theme RTL space-padding workaround was deleted)

Changes to OS.java

Removed OS.IsAppThemed() itself (declaration + auto-generated os.c/os_stats.h), and the following declarations that became entirely unused:

Removed	Was used in
DrawFrameControl()	Non-themed checkbox/arrow drawing in Table, Tree, Button
DFCS_BUTTONCHECK/CHECKED/FLAT/INACTIVE/PUSHED/SCROLLDOWN/SCROLLLEFT/SCROLLRIGHT/SCROLLUP, DFC_BUTTON/SCROLL	Arguments to DrawFrameControl
ImageList_AddMasked()	Non-themed setCheckboxImageList() (replaced by ImageList_Add)
BS_BITMAP, BS_ICON	Non-themed RTL clipping workaround in Button.enableWidget()

Test plan

• Verify themed rendering of checkboxes in Table and Tree (checked, unchecked, mixed, disabled states)
• Verify arrow Button draws correctly via theme
• Verify ToolBar layout with SWT.RIGHT, SWT.FLAT, and mixed text+image items
• Verify Group size/trim/client-area calculations with RTL and FLIP_TEXT_DIRECTION styles
• Verify ExpandBar with and without custom foreground/background/font
• Run existing Win32 widget test suite

🤖 Generated with Claude Code

[github-actions]

Test Results (win32)

   30 files  ±0     30 suites  ±0   4m 19s ⏱️ -12s
4 698 tests ±0  4 623 ✅ ±0  75 💤 ±0  0 ❌ ±0 
1 228 runs  ±0  1 204 ✅ ±0  24 💤 ±0  0 ❌ ±0 

Results for commit 4d00ad4. ± Comparison against base commit 81da08f.

♻️ This comment has been updated with latest results.

[Copilot]

Pull request overview

This PR simplifies SWT’s Win32 widget code by removing all uses of OS.IsAppThemed() and associated classic/non-themed fallback paths, based on the Windows 10+ target where IsAppThemed() is effectively always true. It also cleans up the Win32 PI/native layer by deleting now-unused constants and JNI bindings.

Changes:

• Removed unreachable !OS.IsAppThemed() branches and unwrapped if (OS.IsAppThemed()) guards across Win32 widgets.
• Standardized themed rendering paths for controls (checkbox image lists, themed backgrounds, explorer theme setup, etc.).
• Removed OS.IsAppThemed() and related unused constants/native methods from OS.java, os.c, and os_stats.h.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Widget.java	Makes themed non-client border printing unconditional for client-edge controls.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/TreeColumn.java	Always applies themed header sizing and forces header invalidation on sort updates.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Tree.java	Removes theming guards; always applies explorer theme behaviors and themed checkbox rendering.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/ToolBar.java	Removes theme conditionals around layout/style workarounds and list-style toggling.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Text.java	Unwraps theme-background logic and cancel-icon themed drawing.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/TableColumn.java	Always applies themed header sizing in pack().
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Table.java	Removes theming guards for explorer theme setup and themed checkbox image list rendering.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/TabFolder.java	Removes stale commented “TEMPORARY CODE” block.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/ScrollBar.java	Makes scrollbar visibility workaround unconditional.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Scale.java	Simplifies themed/background control detection for repaint workaround.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/ProgressBar.java	Removes XP-only marquee workaround code.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/MenuItem.java	Makes the themed menu-image bitmap path unconditional.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Label.java	Unwraps theme-control redraw detection.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Group.java	Removes classic RTL workaround and simplifies text-direction adjustments.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/ExpandBar.java	Replaces OS.IsAppThemed() usage with a constant true (subject to custom colors/fonts).
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Decorations.java	Unwraps UpdateWindow() call previously gated by theme/hung checks.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/CoolBar.java	Removes classic-theme erase/background workarounds and temp blocks; simplifies theme background handling.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Control.java	Unwraps theme-background painting paths.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Composite.java	Makes canvas non-client hit-test workaround unconditional.
bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/widgets/Button.java	Removes classic RTL/text clipping workarounds and non-themed drawing fallbacks; always uses theme APIs.
bundles/org.eclipse.swt/Eclipse SWT PI/win32/org/eclipse/swt/internal/win32/OS.java	Deletes IsAppThemed() and now-unused constants/native declarations.
bundles/org.eclipse.swt/Eclipse SWT PI/win32/library/os.c	Removes JNI wrappers for deleted native calls.
bundles/org.eclipse.swt/Eclipse SWT PI/win32/library/os_stats.h	Removes stats enum entries for deleted native calls.