wallpaper engine: count down to the next change

The header gave the clock time of the next change, which left the sum to
the reader. It now counts down, from a one second timer that lives on the
page, so nothing ticks while the page is closed. The engine still keeps
only nextAt.

The function is remaining(), not left(): left is Item's anchor line, so
the call threw a TypeError and the status text went blank, which a clean
hot reload does not show until the page is opened.

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

1 files changed, 22 insertions, 2 deletions

diff --git a/desktop/modules/appearance/WallEngineModule.qml b/desktop/modules/appearance/WallEngineModule.qml
index 5b8a39c..9eb191c 100644
--- a/desktop/modules/appearance/WallEngineModule.qml
+++ b/desktop/modules/appearance/WallEngineModule.qml
@@ -37,10 +37,30 @@ Module {
                 Row {
                     spacing: 8
                     Text {
+                        id: status
+                        // Only ticks while the page is open: the engine
+                        // itself keeps nextAt, not a count.
+                        property double now: Date.now()
+                        Timer {
+                            interval: 1000
+                            repeat: true
+                            running: WallEngine.on
+                            triggeredOnStart: true
+                            onTriggered: status.now = Date.now()
+                        }
+                        // Floored, as now can be up to a second old: a
+                        // restarted timer reads the full interval, not one
+                        // second over it. Not named left: that is Item's
+                        // anchor line, which a function cannot shadow.
+                        function remaining() {
+                            const s = Math.max(0, Math.floor((WallEngine.nextAt - now) / 1000));
+                            const two = n => (n < 10 ? "0" : "") + n;
+                            const h = Math.floor(s / 3600);
+                            return (h > 0 ? h + ":" : "") + two(Math.floor(s / 60) % 60) + ":" + two(s % 60);
+                        }
                         anchors.verticalCenter: parent.verticalCenter
                         text: WallEngine.dirty ? "unsaved changes"
-                            : WallEngine.on ? "running, next change at "
-                              + Qt.formatTime(new Date(WallEngine.nextAt), "hh:mm")
+                            : WallEngine.on ? "running, next change in " + remaining()
                             : "stopped"
                         color: WallEngine.dirty ? Theme.yellow : WallEngine.on ? Theme.green : Theme.overlay
                         font { family: Theme.fontFamily; pixelSize: Theme.fontSize - 4 }