[dcoffin88]

Summary

Fixes email printing in Electron.

Changes

• Fixed both print buttons on electron apps.

Testing

• Fully tested in my dev and prod environments

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[maathimself]

Thanks, the cause is right: the desktop app's window-open handler denies the blank window printing opens, so Print silently did nothing there. The windowOpening change that allows only a named mailflow-print window from the app's own origin is the fix we want.

Could you split this PR?

1. This PR: just the fix, the named print window plus the windowOpening allowance and its tests. Please also give the print window its own webPreferences without the main preload: as it is, the hidden window holding the email HTML gets the full mailflowNative bridge. CSP and DOMPurify keep scripts out today, but it shouldn't be one layer away.
2. The print preview (page ranges, Save as PDF, selection only, the context-menu Print) as a feature: per CONTRIBUTING, please open an issue first so we can agree on it. Things it would need: "Print selection only" copies the reading pane's DOM after dark recoloring (Support inverted mail body (dark mode mail body) #228), so in dark themes it prints light text on white; the preview and its errors need translations; the context-menu Print shows for any selection or image in the window but prints the open message; a failed print:open leaves the hidden window alive, which can keep the app from quitting on Windows and Linux without a tray; and pdf.js loading from file:// inside app.asar needs checking in a packaged build.

Once the fix is split out I'll test it on the desktop builds and merge it.

[dcoffin88]

• Removed the feature.
• The print window now has its own web preferences with the main preload cleared.