Rounded corners expose desktop background in fullscreen mode when bar opacity is 0

### Compositor

Niri

### Distribution

Arch Linux

### If Other, please specify

_No response_

### Select your Installation Method

Distro Packaging

### Was this your original Installation method?

Yes

### If no, specify

_No response_

### dms doctor -vC

Click to expand

## DMS Doctor Report

**System**
- [ok] Operating System: Arch Linux
- ID: arch, Version: rolling, Arch: amd64
- [ok] Architecture: amd64
- [ok] Display Server: Wayland
- WAYLAND_DISPLAY=wayland-1

**Versions**
- [ok] DMS CLI: dms v1.5.2
- /usr/bin/dms
- [ok] Quickshell: Quickshell 0.3.0 (revision 7d1c9a9c6721606b129829134d6f614f015621e2, distributed by AUR (package: quickshell-git))
- /usr/bin/qs
- [ok] DMS Shell: v1.5.2
- /usr/share/quickshell/dms

**Installation**
- [ok] DMS Configuration: Found
- /usr/share/quickshell/dms
- [ok] shell.qml: Present
- /usr/share/quickshell/dms/shell.qml
- [info] Install Type: System package
- /usr/share/quickshell/dms

**Compositor**
- [ok] niri: 26.04
- /usr/bin/niri
- [ok] labwc: 0.20.1
- /usr/bin/labwc
- [info] Active: niri
- [ok] Background Blur: Supported
- Compositor supports ext-background-effect-v1

**Quickshell Features**
- [ok] Polkit: Available
- Authentication prompts
- [ok] IdleMonitor: Available
- Idle detection
- [ok] IdleInhibitor: Available
- Prevent idle/sleep
- [ok] ShortcutInhibitor: Available
- Allow shortcut management (niri)
- [ok] BackgroundBlur: Available
- Background blur API support in Quickshell

**Optional Features**
- [ok] accountsservice: Available
- User accounts
- [ok] power-profiles-daemon: Available
- Power profile management
- [ok] logind: Available
- Session management
- [warn] cups-pk-helper: Not available (install cups-pk-helper)
- Printer management
- [info] I2C/DDC: No monitors detected
- External monitor brightness control
- [ok] qt6-imageformats: Installed (5 formats)
- Formats: WebP, TIFF, GIF, JP2, ICNS (/usr/lib/qt6/plugins/imageformats:/usr/lib64/qt6/plugins/imageformats)
- [ok] kimageformats: Installed (4 formats)
- Formats: AVIF, HEIF, JXL, EXR (/usr/lib/qt6/plugins/imageformats:/usr/lib64/qt6/plugins/imageformats)
- [ok] Terminal: ghostty, kitty
- [ok] Network: NetworkManager
- NetworkManager present. Using NM API.
- [ok] matugen: Installed
- Dynamic theming
- [ok] dgop: Installed
- System monitoring
- [ok] cava: Installed
- Audio visualizer
- [info] khal: Not installed
- Calendar events
- [info] danksearch: Not installed
- File search
- [info] dankcalendar: Not installed
- Calendar app
- [info] fprintd: Not installed
- Fingerprint auth

**Config Files**
- [ok] settings.json: Present
- /home/ashgrey/.config/DankMaterialShell/settings.json
- [info] clsettings.json: Not yet created
- /home/ashgrey/.config/DankMaterialShell/clsettings.json
- [ok] plugin_settings.json: Present
- /home/ashgrey/.config/DankMaterialShell/plugin_settings.json
- [ok] session.json: Present
- /home/ashgrey/.local/state/DankMaterialShell/session.json
- [info] dms-colors.json: Not yet created
- /home/ashgrey/.cache/DankMaterialShell/dms-colors.json

**Services**
- [ok] dms.service: enabled, active
- [ok] greetd: enabled

**Environment**
- [info] QT_QPA_PLATFORMTHEME: gtk3
- [info] QS_ICON_THEME: Not set
- [warn] XDG_MENU_PREFIX: Not set
- Dolphin file associations and 'Open with…' dialog may be empty. Set XDG_MENU_PREFIX=plasma- in your compositor's environment block.

**Fonts**
- [ok] Normal Font: Cascadia Mono
- Available
- [ok] Monospace Font: Cascadia Mono
- Available

---
**Summary:** 0 error(s), 2 warning(s), 33 ok

### Description

When an application enters fullscreen mode and move (dank bar will still show in ~1 second), the rounded corners of the Dank Bar occasionally expose a few transparent pixels. Instead of being completely covered by the bar background, those pixels show the desktop wallpaper underneath.

The artifacts only appear along the outer rounded corners and look like small triangular or irregular transparent fragments. They are visible against dark wallpapers and become much easier to notice while the application is fullscreen.

### Expected Behavior

The rounded corners should remain fully opaque, without exposing the desktop background

### Steps to Reproduce

1. Open any application (e.g. VSCodium).
2. Set the bar opacity (controls opacity of the bar background) to 0.
3. Maximize or fullscreen the application so that the Dank Bar is displayed over it at first ~1 second.
4. Look closely at the outer rounded corners of the Dank Bar, especially the left and right edges of the screen.
5. Observe that a few pixels near the rounded corners become transparent and reveal the desktop wallpaper underneath.
### Error Messages/Logs

_No response_

### Screenshots/Recordings

No source file or test is named. First reproduce the issue with VSCodium under niri, using bar opacity 0 while entering fullscreen, then trace the Dank Bar's rounded-corner rendering during its first-second transition. Done means the outer corners remain opaque without revealing the desktop wallpaper.

Written by the indexing model from the issue text.