Add gSlapper video wallpaper plugin (#152)

* feat: add gSlapper wallpaper plugin

* docs: clarify gSlapper installation and testing

* docs: state Noctalia v5 requirement

* docs: use generated plugin thumbnail

* fix: keep gSlapper videos playing by default

gslapper/README.md

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+# gSlapper Wallpaper
+
+Choose images and video wallpapers from one picker. Apply one file to every
+detected output or select a different file for each connector.
+
+> Requires Noctalia v5 and plugin API 19. Noctalia v4 uses a different QML
+> plugin format and will not list or load this source.
+
+Video playback uses [gSlapper](https://github.com/Nomadcxx/gSlapper) instead of
+mpvpaper. gSlapper uses GStreamer rather than libmpv; its README documents lower
+CPU, memory, and GPU use than mpvpaper. Tests cover Niri, Hyprland, and Sway.
+
+## Plugin
+
+| Field | Value |
+| --- | --- |
+| ID | `nomadcxx/gslapper` |
+| Entries | Bar widget: `wallpaper`; panel: `picker`; service: `service` |
+
+## Requirements
+
+- `find` indexes the wallpaper roots
+- [gSlapper](https://github.com/Nomadcxx/gSlapper) 1.5.2 or newer provides the
+  `gslapper` command and renders video wallpapers
+- `gst-launch-1.0` creates image and video previews
+- `pkill` cleans up a plugin-owned process if its socket stops responding
+- `socat` sends gSlapper IPC commands
+
+Arch Linux provides `gst-launch-1.0` in `gstreamer`. Debian and Ubuntu provide
+it in `gstreamer1.0-tools`. Preview generation can fail without blocking image
+selection or video playback.
+
+## Install
+
+Add the canonical repository as a custom plugin source:
+
+1. Open **Settings → Plugins → Sources**.
+2. Choose **Add custom repository**.
+3. Enter `https://github.com/Nomadcxx/noctalia-gslapper`.
+4. Open **Settings → Plugins → Install** and select **gSlapper Wallpaper**.
+
+Or install it from a shell:
+
+```sh
+noctalia msg plugins source add gslapper git https://github.com/Nomadcxx/noctalia-gslapper
+noctalia msg plugins enable nomadcxx/gslapper
+```
+
+Choose this source or the Noctalia community source. If you add both, Noctalia
+uses the copy from the last user source. Remove the other source with:
+
+```sh
+noctalia msg plugins source remove <source-name>
+```
+
+## Usage
+
+In Noctalia Settings, open your existing bar, choose a widget section, select
+Add Widget, then add **gSlapper Wallpaper**. You can remove Noctalia's
+Wallpaper widget if you want one wallpaper button.
+
+Left-click the gSlapper widget to open the picker. Select **All outputs** or a
+connector such as `eDP-1` or `DP-1`, then choose an image or video. The All
+view can pause assigned videos or restore every output.
+
+Toggle the picker from a shell:
+
+```sh
+noctalia msg panel-toggle nomadcxx/gslapper:picker
+```
+
+The service indexes your image and video roots when Noctalia starts. It creates
+224 by 126 JPEG previews in the plugin data directory. The picker shows 24
+media files per page in a four-column grid and lists child folders in a
+separate selector.
+
+## Settings
+
+| Setting | Default | Description |
+| --- | --- | --- |
+| Video directory | `~/Videos/Wallpapers` | Root for video wallpapers. Noctalia's wallpaper directory supplies images. |
+| Video scale | `fill` | Uses gSlapper's fill, stretch, original, or panscan scaling mode. |
+| When hidden | `none` | Keeps playing unless you select Auto Pause or Auto Stop. |
+| Loop videos | On | Restarts video playback at the end. |
+| FPS cap | `30` | Caps video wallpaper playback at 30, 60, or 100 FPS. |
+| Fade between videos | Off | Enables gSlapper's fade transition. |
+| Fade duration | `0.5` seconds | Sets the transition duration when you enable fading. |
+| Additional GStreamer options | Empty | Appends options to gSlapper's GStreamer option list. |
+| Widget glyph | `wallpaper-selector` | Changes the icon shown in the bar. |
+
+The service restarts active video wallpapers after you change a playback
+setting.
+
+## Self-check
+
+Run the built-in model and trust-boundary checks with:
+
+```sh
+noctalia msg plugin nomadcxx/gslapper:service all self-test
+```
+
+## Notes
+
+- The plugin starts one `gslapper` process and one Unix socket under
+  `$XDG_RUNTIME_DIR/noctalia-gslapper/` for each output with a video.
+- The plugin stores assignments, its self-check report, its media index, and
+  cached preview JPEGs in Noctalia's plugin data directory. It makes no network
+  requests.
+- The picker skips filenames that do not use UTF-8.
+- Static images use Noctalia's wallpaper renderer. For video assignments, the
+  plugin disables Noctalia's wallpaper surface on that output while gSlapper
+  owns it, then restores the native surface when you select **Restore**.
+- Use **Restore all** before disabling or reloading the plugin. This stops its
+  processes, removes its sockets, and re-enables Noctalia's wallpaper surfaces.
+- The current plugin API does not report static wallpaper changes made outside
+  this plugin, so its saved image assignment can become stale.
+- Assignments follow connector names, not monitor serial numbers. Review them
+  after GPU, dock, or cabling changes that rename outputs.

gslapper/plugin.toml

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+id = "nomadcxx/gslapper"
+name = "gSlapper Wallpaper"
+version = "0.1.1"
+plugin_api = 19
+author = "Nomadcxx"
+license = "MIT"
+dependencies = ["find", "gslapper", "gst-launch-1.0", "pkill", "socat"]
+tags = ["bar", "panel", "service", "video", "wallpaper"]
+icon = "wallpaper-selector"
+description = "Choose an image or video wallpaper for each output."
+
+[[setting]]
+key = "video_directory"
+type = "folder"
+label_key = "settings.video_directory.label"
+description_key = "settings.video_directory.description"
+default = "~/Videos/Wallpapers"
+
+[[setting]]
+key = "scale"
+type = "select"
+label_key = "settings.scale.label"
+description_key = "settings.scale.description"
+default = "fill"
+options = [
+  { value = "fill", label_key = "settings.scale.options.fill" },
+  { value = "stretch", label_key = "settings.scale.options.stretch" },
+  { value = "original", label_key = "settings.scale.options.original" },
+  { value = "panscan", label_key = "settings.scale.options.panscan" },
+]
+
+[[setting]]
+key = "hidden_behavior"
+type = "select"
+label_key = "settings.hidden_behavior.label"
+description_key = "settings.hidden_behavior.description"
+default = "none"
+options = [
+  { value = "none", label_key = "settings.hidden_behavior.options.none" },
+  { value = "auto-pause", label_key = "settings.hidden_behavior.options.auto_pause" },
+  { value = "auto-stop", label_key = "settings.hidden_behavior.options.auto_stop" },
+]
+
+[[setting]]
+key = "loop"
+type = "bool"
+label_key = "settings.loop.label"
+description_key = "settings.loop.description"
+default = true
+
+[[setting]]
+key = "fps_cap"
+type = "select"
+label_key = "settings.fps_cap.label"
+description_key = "settings.fps_cap.description"
+default = "30"
+options = [
+  { value = "30", label_key = "settings.fps_cap.options.fps_30" },
+  { value = "60", label_key = "settings.fps_cap.options.fps_60" },
+  { value = "100", label_key = "settings.fps_cap.options.fps_100" },
+]
+
+[[setting]]
+key = "fade"
+type = "bool"
+label_key = "settings.fade.label"
+description_key = "settings.fade.description"
+default = false
+
+[[setting]]
+key = "fade_duration"
+type = "double"
+label_key = "settings.fade_duration.label"
+description_key = "settings.fade_duration.description"
+default = 0.5
+min = 0.1
+max = 5.0
+step = 0.1
+visible_when = { key = "fade", values = ["true"] }
+
+[[setting]]
+key = "gst_options"
+type = "string"
+label_key = "settings.gst_options.label"
+description_key = "settings.gst_options.description"
+default = ""
+advanced = true
+
+[[setting]]
+key = "glyph"
+type = "glyph"
+label_key = "settings.glyph.label"
+description_key = "settings.glyph.description"
+default = "wallpaper-selector"
+
+[[service]]
+id = "service"
+entry = "service.luau"
+
+[[panel]]
+id = "picker"
+entry = "panel.luau"
+width = 980
+height = 1100
+placement = "attached"
+position = "auto"
+keyboard_focus = "exclusive"
+
+[[widget]]
+id = "wallpaper"
+entry = "widget.luau"

gslapper/translations/en.json

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+{
+  "panel": {
+    "title": "Wallpaper",
+    "media_count": "{count} items",
+    "thumbnail_unavailable": "Video preview unavailable",
+    "settings": "Settings",
+    "close": "Close",
+    "search": "Search wallpapers",
+    "all_outputs": "All outputs",
+    "filter_all": "All",
+    "filter_images": "Images",
+    "filter_videos": "Videos",
+    "folders": "Folders",
+    "up": "Up",
+    "checking_dependencies": "Checking video support…",
+    "scanning": "Indexing wallpaper library…",
+    "preparing_library": "Preparing wallpaper library…",
+    "generating_previews": "Generating previews · {count} / {total}",
+    "video_unavailable": "Video wallpapers are unavailable",
+    "video_badge": "VIDEO",
+    "partial_badge": "{count} / {total}",
+    "mixed_summary": "{outputs} outputs · {videos} video · {images} image",
+    "pause_videos": "Pause videos",
+    "resume_videos": "Resume videos",
+    "restore_all": "Restore all",
+    "pause": "Pause",
+    "resume": "Resume",
+    "restore": "Restore",
+    "status_static": "Static",
+    "status_starting": "Starting",
+    "status_playing": "Playing",
+    "status_paused": "Paused",
+    "status_error": "Error",
+    "applying": "Applying wallpaper…",
+    "navigation_blocked": "The selected directory is outside its wallpaper root.",
+    "directory_unreadable": "Directory unavailable",
+    "directory_empty": "No supported wallpapers in this directory",
+    "no_search_results": "No wallpapers match your search",
+    "page": "{page} / {pages}"
+  },
+  "widget": {
+    "tooltip": "Choose wallpaper"
+  },
+  "service": {
+    "self_test_passed": "Self-test passed.",
+    "self_test_failed": "Self-test failed."
+  },
+  "settings": {
+    "video_directory": {
+      "label": "Video directory",
+      "description": "Directory containing video wallpapers."
+    },
+    "scale": {
+      "label": "Video scale",
+      "description": "How videos fit the output.",
+      "options": {
+        "fill": "Fill",
+        "stretch": "Stretch",
+        "original": "Original",
+        "panscan": "Panscan"
+      }
+    },
+    "hidden_behavior": {
+      "label": "When hidden",
+      "description": "Playback control when the wallpaper is hidden.",
+      "options": {
+        "none": "None",
+        "auto_pause": "Auto Pause",
+        "auto_stop": "Auto Stop"
+      }
+    },
+    "loop": {
+      "label": "Loop videos",
+      "description": "Restart a video when it reaches the end."
+    },
+    "fps_cap": {
+      "label": "FPS cap",
+      "description": "Maximum video wallpaper frame rate.",
+      "options": {
+        "fps_30": "30",
+        "fps_60": "60",
+        "fps_100": "100"
+      }
+    },
+    "fade": {
+      "label": "Fade between videos",
+      "description": "Use a fade when changing media."
+    },
+    "fade_duration": {
+      "label": "Fade duration",
+      "description": "Fade duration in seconds."
+    },
+    "gst_options": {
+      "label": "Additional GStreamer options",
+      "description": "Extra options passed to gSlapper's GStreamer pipeline."
+    },
+    "glyph": {
+      "label": "Widget glyph",
+      "description": "Glyph shown in the bar."
+    }
+  }
+}

gslapper/widget.luau

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+--!nonstrict
+
+local PANEL_ID = "nomadcxx/gslapper:picker"
+
+local function render()
+  barWidget.setGlyph(noctalia.getConfig("glyph") or "wallpaper-selector")
+  barWidget.setTooltip(noctalia.tr("widget.tooltip"))
+end
+
+function onClick()
+  noctalia.togglePanel(PANEL_ID)
+end
+
+function onConfigChanged()
+  render()
+end
+
+render()