VPN-7529: Missing window decorations on GNOME+Wayland

[encrypt94]

Description

GNOME / Mutter does not support server-side window decorations https://gitlab.gnome.org/GNOME/mutter/-/issues/217 so after the introduction of qtwayland plugin we lost them.

Lacking of window decoration is a common issue for qt applications on GNOME, this causes a problem in the light theme: the window blends into the white background due to the absence of shadows (also the window looks ugly)

This PR introduces the QWaylandAdwaitaDecorationPlugin to provide Adwaita-style window decorations (rounded corners, nice title bar coherent with system theme). It also includes a patch to draw shiny shadows, which is not yet supported by the plugin itself (even in the Qt dev branch).

MozillaVPN client vs gnome calculator

active windows

non active windows

Reference

Jira Issue

Checklist

• My code follows the style guidelines for this project
• I have not added any packages that contain high risk or unknown licenses (GPL, LGPL, MPL, etc. consult with DevOps if in question)
• I have performed a self review of my own code
• I have commented my code PARTICULARLY in hard to understand areas
• I have added thorough tests where needed

[strseb]

Neat! Did you write it yourself? If so, are you planning to upstream that?
If not, can we add an error when compiling the Qt with it's Planned Fix version, so we can revisit this?

[encrypt94]

Yep, wrote it myself! i'll try to upstream it!

[strseb]

Wow, nice!

[firefoxci-taskcluster]

Uh oh! Looks like an error!

Client ID static/taskcluster/github does not have sufficient scopes and is missing the following scopes:

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This request requires the client to satisfy the following scope expression:

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---

• method: rerunTask
• errorCode: InsufficientScopes
• statusCode: 403
• time: 2026-04-21T12:46:45.037Z

[oskirby]

I think this looks good.

[firefoxci-taskcluster]

Uh oh! Looks like an error!

Client ID static/taskcluster/github does not have sufficient scopes and is missing the following scopes:

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    "queue:rerun-task-in-project:none",
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This request requires the client to satisfy the following scope expression:

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---

• method: rerunTask
• errorCode: InsufficientScopes
• statusCode: 403
• time: 2026-04-22T12:25:51.159Z