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fix(desktop): Install Linux theme icons named after the app id - #14471

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mwolson:fix/linux-app-id-theme-icons
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mwolson:fix/linux-app-id-theme-icons

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@mwolson

@mwolson mwolson commented Sep 30, 2026 •

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What Changed

Linux docks and bars that look the Wayland app id up in the icon theme now find
the T3 Code icon. T3 installs com.t3tools.t3code and com.t3tools.T3Code
icons into the user's hicolor theme when it registers its URL handler.

Follows up #10895 linux-wayland-desktop-icon, which fixed launcher grouping.

Why

When no visible desktop entry matches the window, some shells fall back to a
theme lookup of the app id, for example for an AppImage run without
integration. Current Noctalia's taskbar does this with the literal,
case-sensitive com.t3tools.T3Code, and other shells try the lowercase form.
The hidden handler entry already carries an absolute icon path since #8673
linux-mime-cache, so this only adds the two theme names. It does not use the
t3code name, which would hide the .deb and AUR system icon.

The copy runs with the URL-handler registration after the window is up, not
during pre-ready startup. Icons that already match are left alone. An existing
icon-theme.cache is refreshed after this launch changes an icon, or when it is
older than the installed icons, so a failed refresh is retried on a later
launch; none is created. The refresh times out after five seconds and
force-kills a helper that ignores SIGTERM.

UI Changes

No in-app UI changes. In shells that fall back to the icon theme, the taskbar
shows the T3 icon instead of a generic one.

The screenshots use Noctalia 5.2.0's taskbar on Sway 1.12, with T3 Code run
from its .deb payload without desktop integration, so only the hidden handler
entry exists. Before is the 0.0.45-nightly.20260930.2493 .deb; after is this
PR's .deb. On T3's first launch Noctalia picks up the new icon at its next
icon-theme check (it polls every 60 seconds), as the recording shows. Once the
icons exist, Noctalia includes their directory when it starts, so later
sessions do not wait for that check. T3 ran through Xwayland here because Electron's
native Wayland path crashed under GPU-less headless Sway; Noctalia sees the
same com.t3tools.T3Code id either way.

Noctalia taskbar before and after

Before: full screen.

Before, full screen

After: full screen.

After, full screen

Recording of the first launch, sped up 8x (MP4):

Recording: the taskbar icon switches from generic to T3

Checklist

  • This PR is small and focused
  • I explained what changed and why
  • I included before/after screenshots for any UI changes
  • I included a video for animation/interaction changes

@github-actions github-actions Bot added vouch:trusted PR author is trusted by repo permissions or the VOUCHED list. size:M 30-99 changed lines (additions + deletions). labels Sep 30, 2026
Comment thread apps/desktop/src/app/DesktopLinuxUrlHandler.ts
@macroscopeapp

macroscopeapp Bot commented Sep 30, 2026 •

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Approvability

Verdict: Approved at 6c76cb1

Macroscope's review found this PR approvable — This is a focused Linux desktop integration fix that installs app-ID theme icons and conditionally refreshes the existing icon cache without changing application workflows. The production path is isolated to packaged Linux startup registration, failures are contained, and the added behavior has targeted filesystem and process-lifecycle tests.

Notes:

  • Diff unchanged. Approvability was decided on eligibility alone.

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coderabbitai Bot commented Sep 30, 2026 •

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  • apps/desktop/src/app/DesktopLinuxUrlHandler.ts

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📝 Walkthrough

Walkthrough

Linux URL-handler registration now installs lowercase and original-case app-ID theme icons. It writes only changed icon files and conditionally refreshes an existing GTK icon cache. Installation and cache-refresh failures do not stop handler registration.

Changes

Linux theme icon registration

Layer / File(s) Summary
Icon installation and cache refresh
apps/desktop/src/app/DesktopLinuxUrlHandler.ts
Adds icon-name generation and installation for 256×256 theme icons. The installer writes changed targets and refreshes an existing cache when needed.
Registration integration and validation
apps/desktop/src/app/DesktopLinuxUrlHandler.ts, apps/desktop/src/app/DesktopLinuxUrlHandler.test.ts
Calls the installer during registration. Filesystem-backed tests cover icon updates, cache refresh outcomes, and continued desktop-database and MIME registration.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Registration as URL registration
  participant Installer as Theme icon installer
  participant Filesystem as hicolor icon directory
  participant CacheTool as gtk-update-icon-cache
  participant MimeTool as xdg-mime
  Registration->>Installer: Install theme icons
  Installer->>Filesystem: Read packaged icon and write changed targets
  Installer->>CacheTool: Refresh an existing cache when needed
  Registration->>MimeTool: Continue MIME registration
Loading

Suggested reviewers: limwa

Merge Risk: 🔵 Low · up to 6c76c

The change is mergeable with awareness of one remaining edge case: if cache refresh fails and the icon source disappears on a later launch, shells may continue showing a generic icon.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 6c76c

The change remains within the launching user's authority and preserves URL-handler registration after icon-installation failures. No introduced security vulnerability was established. Residual uncertainty concerns interrupted writes and coordination with other writers of the shared icon cache.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

  • inferred — The added operations run with the desktop process's existing authority against its selected user-theme location. Refresh touches the shared hicolor cache, so its effects can extend beyond the two app icons to other theme lookups using that cache; no new elevated execution path is shown.

Trust Boundaries and Controls

  • observed — The new process call uses a fixed executable and separate arguments rather than constructing a shell command. Directory selection remains an existing process-environment input, and installation is reached from startup registration rather than URL payload handling.

Resilience and Maintainability Implications

  • inferred — Best-effort handling contains icon-refresh failures without changing downstream URL-handler authority. Sequential writes can leave mixed icon versions after partial completion, and recovery is conditional; the inspected evidence does not establish atomic replacement or coordination with other theme writers.
🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 2 files. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (4 passed)
Check name Status Explanation
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
Title check ✅ Passed The title clearly and concisely describes the main change: installing Linux theme icons using the application ID.
Description check ✅ Passed The description is complete and relevant. It explains what changed, why the change is needed, implementation details, UI impact, screenshots, video evidence, and checklist completion.
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@mwolson
mwolson force-pushed the fix/linux-app-id-theme-icons branch from b7c55aa to 5836fd7 Compare September 30, 2026 18:26
Comment thread apps/desktop/src/app/DesktopLinuxUrlHandler.ts Outdated

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Caution

Some comments are outside the diff and can’t be posted inline due to GitHub limitations.

⚠️ Outside diff range comments (1)

🟡 Minor · Run the cache-age check when the icon source is absent. · DesktopLinuxUrlHandler.ts:225

apps/desktop/src/app/DesktopLinuxUrlHandler.ts:225
🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Run the cache-age check when the icon source is absent.

installThemeIcons returns before it checks existing icon files against icon-theme.cache. If an earlier refresh failed, a later packaged Linux registration with no available resource path will not retry the refresh. Keep icon writes conditional on the source, but always evaluate the cache timestamps.

Suggested fix
     const source = yield* assets.resolveResourcePath(`icons/${LINUX_THEME_ICON_SIZE}.png`);
-    if (Option.isNone(source)) return;
-    const icon = yield* fileSystem.readFile(source.value);
     const targets = linuxThemeIconNames(environment.linuxDesktopEntryName).map((name) =>
       environment.path.join(themeIconDir, `${name}.png`),
     );
     let changed = false;
-    for (const target of targets) {
-      const current = yield* fileSystem.readFile(target).pipe(Effect.option);
-      if (Option.isSome(current) && sameBytes(current.value, icon)) continue;
-      yield* fileSystem.makeDirectory(themeIconDir, { recursive: true });
-      yield* fileSystem.writeFile(target, icon);
-      changed = true;
+    if (Option.isSome(source)) {
+      const icon = yield* fileSystem.readFile(source.value);
+      for (const target of targets) {
+        const current = yield* fileSystem.readFile(target).pipe(Effect.option);
+        if (Option.isSome(current) && sameBytes(current.value, icon)) continue;
+        yield* fileSystem.makeDirectory(themeIconDir, { recursive: true });
+        yield* fileSystem.writeFile(target, icon);
+        changed = true;
+      }
     }
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Review comment at @apps/desktop/src/app/DesktopLinuxUrlHandler.ts at line 225:
Update installThemeIcons so a missing icon source skips only icon file reads and
writes, not the existing icon-theme.cache age check; keep cache timestamp
evaluation and refresh retry behavior reachable regardless of whether
assets.resolveResourcePath returns a source.

🤖 Prompt to fix review comments
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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
minimal, and validate.

Outside diff comments:
Review comments at @apps/desktop/src/app/DesktopLinuxUrlHandler.ts:
- Line 225: Update installThemeIcons so a missing icon source skips only icon
file reads and writes, not the existing icon-theme.cache age check; keep cache
timestamp evaluation and refresh retry behavior reachable regardless of whether
assets.resolveResourcePath returns a source.

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Reviewing files that changed from the base of the PR and between b7c55aa and 5836fd7.

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  • apps/desktop/src/app/DesktopLinuxUrlHandler.ts

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Some docks and bars look the Wayland app id up in the icon theme when no
visible desktop entry matches the window, for example an AppImage run
without integration. Current Noctalia's taskbar does this with the
literal, case-sensitive id.

When registering the URL handler, copy the packaged 256px icon into the
user hicolor theme as com.t3tools.t3code and com.t3tools.T3Code, skipping
icons that already match. Refresh icon-theme.cache only when one already
exists, and only after this launch changed an icon or when an installed
icon is newer than the cache, so a failed refresh is retried on a later
launch. The refresh times out after five seconds and force-kills the
helper if it ignores SIGTERM.
@mwolson
mwolson force-pushed the fix/linux-app-id-theme-icons branch from 5836fd7 to 6c76cb1 Compare September 30, 2026 18:36
macroscopeapp[bot]
macroscopeapp Bot previously approved these changes Sep 30, 2026
@mwolson

mwolson commented Sep 30, 2026

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Screenshots

Noctalia 5.2.0 taskbar on Sway 1.12, with T3 Code run from its .deb payload without desktop integration. Before is the 0.0.45-nightly.20260930.2493 .deb, after is this PR's .deb. On the first launch the icon switches at Noctalia's next 60-second icon-theme check. T3 ran through Xwayland because Electron's native Wayland path crashed under GPU-less headless Sway; Noctalia sees the same com.t3tools.T3Code id either way. Also inlined in the description.

Noctalia taskbar before and after

Before: full screen.

Before, full screen

After: full screen.

After, full screen

Recording of the first launch, sped up 8x (MP4):

Recording: the taskbar icon switches from generic to T3

@juliusmarminge juliusmarminge added the macroscope-review Opt PRs made by unvouched contributors in for Macroscope review. Vouched contributors auto-reviews label Oct 1, 2026 — with ChatGPT Codex Connector
@macroscopeapp
macroscopeapp Bot dismissed their stale review October 1, 2026 21:32

Dismissing prior approval to re-evaluate 6c76cb1

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