Fix macOS dock tile losing app icon and melt appearing in Dock during export

[Copilot]

Setting a custom NSView as NSDockTile.contentView replaces the system's default rendering, causing the app icon to disappear — leaving only the progress bar on a blank tile. Additionally, when melt runs inside Shotcut.app/Contents/MacOS/ and initializes Qt's Cocoa platform (e.g. for Qt-based MLT filters), Qt registers it as a foreground application, causing a new icon to appear in the Dock during export.

Changes

• src/macos.mm: In dockProgressBar(), add an NSImageView backed by NSApp.applicationIconImage as the base layer of the custom contentView before adding the NSProgressIndicator on top, so the app icon remains visible while progress is shown.

• src/jobs/meltjob.cpp: On macOS, set QT_QPA_PLATFORM=offscreen in melt's process environment so it uses Qt's offscreen backend instead of the Cocoa platform, preventing NSApplication registration and keeping melt invisible to the Dock. This is skipped when GPU processing mode is enabled (Settings.playerGPU()), since OpenGL requires the Cocoa platform. Note: libqoffscreen.dylib must be included in the macOS app bundle.

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[ddennedy]

@copilot when doing an export on macOS, a new app icon appears for the background terminal program. How to fix that?

[Copilot]

@copilot when doing an export on macOS, a new app icon appears for the background terminal program. How to fix that?

Fixed in commit a041908. When melt runs inside Shotcut.app/Contents/MacOS/ and initializes Qt's Cocoa platform (e.g., for Qt-based MLT filters), Qt calls TransformProcessType to register the process as a foreground application, which gives it a Dock icon. The fix sets QT_QPA_PLATFORM=offscreen in melt's environment on macOS so it uses the offscreen Qt platform instead of Cocoa — this prevents NSApplication registration and keeps melt as a background process with no Dock icon. Note: libqoffscreen.dylib needs to be included in the macOS app bundle for this to take effect.

[ddennedy]

@copilot The export fails on OpenGL when using GPU processing mode. Do not use the offscreen method when GPU processing mode

[Copilot]

@copilot The export fails on OpenGL when using GPU processing mode. Do not use the offscreen method when GPU processing mode

Fixed in commit e6c713a. QT_QPA_PLATFORM=offscreen is now only set when GPU processing mode is disabled — when Settings.playerGPU() is true, the Cocoa platform is used as before so OpenGL remains available.