Issue 1726 batched defer window pos

[vogella]

No description provided.

[gemini-code-assist]

Summary of Changes

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This pull request focuses on enhancing the visual stability and performance of SWT applications on Windows by mitigating common flickering issues. It achieves this through the introduction of batched window positioning for composite children, leveraging the native DeferWindowPos API, and by implementing specific rendering optimizations for SashForm and Link widgets, resulting in a smoother and more responsive user interface.

Highlights

• Batched Window Positioning: Implemented a batched version of the Windows API DeferWindowPos for more efficient and flicker-free repositioning of multiple child windows within a Composite on Win32 platforms.
• SashForm Flicker Fix: Introduced platform-specific deferred layout calls (setLayoutDeferred) within SashForm on Win32 to prevent flickering during sash drag operations.
• Link Widget Flicker Fix: Addressed flickering in Link widgets on Win32 by overriding WM_ERASEBKGND to prevent background erasure, which is a known issue with the native SysLink control during resizing.
• New Link Widget Tests: Added comprehensive JUnit tests for the Link widget to verify its rendering stability, content integrity, and lack of flickering during rapid resizing and redrawing scenarios.

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[gemini-code-assist]

Code Review

This pull request introduces batched window positioning for Win32 platforms, which should improve performance and reduce flickering during layout operations. It also includes a specific fix for the Link widget on Windows to prevent flashing during resize, along with corresponding unit tests. The changes are well-implemented and address the stated issues effectively.