Fix VST plugin window crash on macOS when closing

[CubikingChill]

Problem

MuseScore crashes when closing VST plugin windows (e.g., ARIA player) on macOS. The crash occurs with a segmentation fault during the window close sequence.

Platform: macOS only

Root Cause

The crash is caused by calling IPlugView::removed() during the closeEvent() on macOS. When the window closes, macOS's Cocoa framework may already be deallocating the NSView as part of its own cleanup sequence. Calling removed() at this point attempts to interact with partially or fully deallocated NSView objects, resulting in a crash.

This is a platform-specific issue:

• macOS (NSView): The native view may already be in the process of deallocation when closeEvent() is triggered, making removed() unsafe
• Windows (HWND): Window handles remain valid throughout the close event
• Linux (X11): X11 window IDs remain valid throughout the close event

Solution

Skip calling IPlugView::removed() on macOS using #ifndef Q_OS_MAC. The NSView cleanup is handled automatically by the Cocoa framework during window destruction, so the explicit removed() call is unnecessary and harmful on macOS.

On Windows and Linux, removed() continues to be called to ensure proper plugin cleanup.

Changes

Modified two files:

1. src/framework/vst/widgets/vstviewdialog_qwidget.cpp - QWidget-based VST dialog
2. src/framework/vst/qml/Muse/Vst/vstview.cpp - QML-based VST view

Both deinit() methods now conditionally skip m_view->removed() on macOS.

Testing

• Verify VST plugins (especially ARIA) can be opened and closed without crashing on macOS
• Verify VST plugins continue to work correctly on Windows and Linux
• Verify no memory leaks or resource issues on any platform

Resolves: #32742

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)

[Jojo-Schmitz]

Seems needed for 4.7 too, right??

[RomanPudashkin]

Seems needed for 4.7 too, right??

We need to test it first. I'll port it myself later

[CubikingChill]

2026-04-06.16-47-04.mp4

Tested on MacOS Sequoia in a x86 VM, using latest nightly and latest version of ARIA player