Windows: Rnote window not recognized by Snap Layouts / DWM (multi-window multitasking broken)

[Nikita55612]

Description

When using Rnote on Windows 10/11, the application window is not properly recognized by the system’s window manager:

• Cannot use Snap Layouts (Win+←/→ or drag-to-edge).
• Does not appear in Alt+Tab switcher consistently.
• Fails to integrate with third-party window managers (e.g., PowerToys FancyZones).

This severely limits multitasking, as Rnote cannot share the screen with other apps.

Steps to Reproduce

1. Launch Rnote on Windows.
2. Attempt to snap it to half of the screen (Win + ← or drag to edge).
3. Observe: Window either ignores the command or maximizes instead.

Expected Behavior

Rnote should behave like a standard Windows application:

• Supports Snap Layouts.
• Appears in Alt+Tab.
• Works with FancyZones/other tiling tools.

Technical Context

• Likely related to GTK4 integration with Windows DWM.
• Other GTK4 apps (e.g., GNOME Apps on Windows) sometimes exhibit similar issues unless explicitly configured.

Proposed Solutions

1. Add WM_CLASS hints for better Windows integration.
2. Implement DWMWINDOWATTRIBUTE (e.g., DWMWA_WINDOW_CORNER_PREFERENCE) for modern Windows UI.
3. Document a workaround (e.g., registry tweaks or flags like --disable-gtk-shell).

Environment

• Rnote version: rnote-win-installer-0.12.0-x86_64.exe
• OS: Windows 11