wallpaper: engine page commits like the others, Start changes at once

The page was the only settings page without the header's buttons, and
it switched the engine from a checkbox beside the interval. Both looked
like the engine had been started when it had not:

- The minutes field saved on editingFinished, which needs Enter or a
  focus change. Clicking the checkbox takes neither, so a typed 1 was
  left at 30 and the first change was half an hour away.
- Even at the right interval, the first change waited one full
  interval, so starting the engine did nothing visible.

The interval and the two sources are now a draft in WallEngine, updated
on every keystroke, and the header carries the state ("running, next
change at hh:mm", "stopped", "unsaved changes") with Reset, Stop and
Start, which reads Apply while running. Start commits the draft, sets
the homes and changes the wallpapers straight away; Apply commits and
restarts the timer. Hearts stay undrafted, written as clicked.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/desktop/modules/appearance/WallEngineModule.qml b/desktop/modules/appearance/WallEngineModule.qml
index e907695..5b8a39c 100644
--- a/desktop/modules/appearance/WallEngineModule.qml
+++ b/desktop/modules/appearance/WallEngineModule.qml
@@ -19,6 +19,7 @@ Module {
     // nf-fa-shuffle, present in Inconsolata Nerd Font.
     icon: "\uf074"
     settings: true
+    dirty: WallEngine.dirty
     group: "Appearance"
     keywords: ["wallpaper", "timer", "rotate", "rotation", "shuffle", "slideshow", "heart"]
 
@@ -30,6 +31,38 @@ Module {
     page: Component {
         Page {
             title: "Wallpaper engine"
+            // SaveBar's place, not SaveBar: the engine is started and stopped
+            // here as well as saved, and its state is what the header reports.
+            actions: Component {
+                Row {
+                    spacing: 8
+                    Text {
+                        anchors.verticalCenter: parent.verticalCenter
+                        text: WallEngine.dirty ? "unsaved changes"
+                            : WallEngine.on ? "running, next change at "
+                              + Qt.formatTime(new Date(WallEngine.nextAt), "hh:mm")
+                            : "stopped"
+                        color: WallEngine.dirty ? Theme.yellow : WallEngine.on ? Theme.green : Theme.overlay
+                        font { family: Theme.fontFamily; pixelSize: Theme.fontSize - 4 }
+                    }
+                    Button {
+                        visible: WallEngine.dirty
+                        text: "Reset"
+                        onClicked: WallEngine.reset()
+                    }
+                    Button {
+                        visible: WallEngine.on
+                        text: "Stop"
+                        enabled: !Wallpapers.applying
+                        onClicked: WallEngine.stop()
+                    }
+                    Button {
+                        text: WallEngine.on ? "Apply" : "Start"
+                        enabled: (!WallEngine.on || WallEngine.dirty) && !Wallpapers.applying
+                        onClicked: WallEngine.on ? WallEngine.apply() : WallEngine.start()
+                    }
+                }
+            }
             WallEngineTab { width: parent.width }
         }
     }