Fix Windows multi-monitor window restore via WINDOWPLACEMENT - #8331
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Persisting logical pos/size breaks on mixed-DPI setups and loses the true restore rect when maximized or Aero-snapped. Capture Win32 WINDOWPLACEMENT, apply it twice with SW_HIDE before the first paint (so WM_DPICHANGED settles), create with position only using GetDpiForMonitor (never with_inner_size), cloak until after the first present, and defer geometry persist until reveal settles. When not max/min, prefer the visible GetWindowRect (screen→workspace) if width/height differs from rcNormalPosition (wxWidgets snap rule), so Aero Snap size is remembered without DPI jitter creep. Non-Windows paths stay on winit with a plain set_visible; only Windows links windows-sys / DWM cloak.
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Preview is being built... Preview will be available at https://egui-pr-preview.github.io/pr/8331-fix/windows-windowplacement-restore View snapshot changes at kitdiff |
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Summary
Persisting logical window position/size is not enough on Windows. On mixed-DPI and multi-monitor setups, winit-based restore can land on the wrong monitor, grow across restarts, fail to restore maximized state correctly (especially on a secondary display), forget Aero Snap size, and flash an empty frame on first show.
This change saves and restores the native Win32
WINDOWPLACEMENTblob. On create we apply only the restored position, scaled withGetDpiForMonitorfor the target rect, and intentionally skipwith_inner_sizeso create DPI and placement DPI cannot compound. Placement is applied twice while the window is still hidden (SW_HIDE) soWM_DPICHANGEDcan settle before the first paint. Maximized restore additionally sizes to the monitor work area before show.First show is DWM-cloaked, then revealed around the first present (glow uncloaks in the same frame; wgpu needs one extra redraw), and window-geometry persistence is deferred until after that reveal so mid-restore geometry is never written back. When a restored placement is present, centering and the old clamp/size paths are skipped so they cannot fight Win32 restore.
Aero Snap is handled explicitly:
GetWindowPlacementkeeps the pre-snap restore rect inrcNormalPosition, so when the window is not min/max and the visible size differs, we store the visibleGetWindowRectconverted screen→workspace (wxWidgets-style size compare with tolerance) instead.Non-Windows keeps the existing winit path with a plain
set_visibleon first show.windows-sysis linked on Windows only.