Use desktopName from package.json for StartupWMClass in Linux desktop entries

[Copilot]

Electron derives app_id from desktopName in package.json, but electron-builder was hardcoding StartupWMClass to productName. This mismatch prevents desktop environments from associating windows with their .desktop entry (wrong icons, missing taskbar integration, etc.).

For example, Signal Desktop has desktopName: "signal.desktop", productName: "Signal", and executableName: "signal-desktop" — three different values where StartupWMClass and app_id must agree.

Changes

• options/metadata.ts — Add desktopName to the Metadata interface
• LinuxTargetHelper.ts — Read desktopName from package.json, strip .desktop suffix, and use as StartupWMClass. Falls back to productName when unset (backward compatible)
• Test + snapshot — Validates that desktopName: "signal.desktop" produces StartupWMClass=signal

// package.json
{
  "name": "signal-desktop",
  "productName": "Signal",
  "desktopName": "signal.desktop"
}

# Before: StartupWMClass=Signal
# After:  StartupWMClass=signal

Original prompt

---

This section details on the original issue you should resolve

<issue_title>desktopName is ignored when generating desktop entry</issue_title>
<issue_description>Discovered while investigating signalapp/Signal-Desktop#6239.

Electron sets the app_id of the app based on the desktopName entry in package.json when provided, see here.

According to electron/electron#34855 (comment) both WM_CLASS and app_id should be the same as the desktop entry filename, however, electron-builder sets the WM_CLASS to productName and the filename is based on executableName.

electron-builder/packages/app-builder-lib/src/targets/LinuxTargetHelper.ts

Line 141 in 7dbc6c7

StartupWMClass: appInfo.productName,

electron-builder/packages/app-builder-lib/src/targets/FpmTarget.ts

Line 248 in 7dbc6c7

args.push(`${desktopFilePath}=/usr/share/applications/${packager.executableName}.desktop`)

In case of Signal Desktop this means that the desktop filename is signal-desktop.desktop, the WM_CLASS is Signal while app_id is signal. This causes issues with desktop environments being unable to associate the correct icon with the app signalapp/Signal-Desktop#6122.</issue_description>

Comments on the Issue (you are @copilot in this section)

@mmaietta Is this a new change in electron? I didn't know of there being a `desktopName` field in `package.json`

Looking to start a conversation here. What's the expected resolution? It sounds like that StartupWMClass might need to default to appInfo.desktopName or something similar (once we pull desktopName from the package.json), then have a fallback to appInfo.productName?

Would that resolve this or do we also need to change the .desktop filename as well? I didn't notice anything implying the latter.</comment_new>

• Fixes desktopName is ignored when generating desktop entry #9103

---

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[mmaietta]

@copilot rebase this PR

[Copilot]

@copilot rebase this PR

I'm unable to rebase this PR because rebasing requires force pushing, which I don't have the ability to do. Could you rebase it manually, or alternatively, I can recreate the changes on top of the latest base branch if you'd prefer.