2 files changed, 40 insertions, 4 deletions

diff --git a/desktop/modules/appearance/WallpaperSpread.qml b/desktop/modules/appearance/WallpaperSpread.qml
index d1c383d..2f1dd03 100644
--- a/desktop/modules/appearance/WallpaperSpread.qml
+++ b/desktop/modules/appearance/WallpaperSpread.qml
@@ -73,7 +73,17 @@ Scope {
             // would pop in late over a half-drawn screen.
             readonly property bool ready: running && oldImg.status === Image.Ready
                 && newImg.status === Image.Ready
-            onReadyChanged: if (ready) anim.restart()
+            onReadyChanged: if (ready) {
+                anim.restart();
+                drawn.restart();
+            }
+            // A few frames for the cover to reach the screen, then wallp may
+            // swap swaybg underneath it.
+            Timer {
+                id: drawn
+                interval: 50
+                onTriggered: Wallpapers.covered()
+            }
 
             // -m fill is a centred crop, which is what PreserveAspectCrop does.
             Image {
diff --git a/desktop/modules/appearance/Wallpapers.qml b/desktop/modules/appearance/Wallpapers.qml
index 5507476..4d06a2e 100644
--- a/desktop/modules/appearance/Wallpapers.qml
+++ b/desktop/modules/appearance/Wallpapers.qml
@@ -244,17 +244,43 @@ Singleton {
         if (applying || (h === "" && v === "")) return false;
         applying = true;
         root.kind = kind;
-        if (h !== "" && currentH !== "" && h !== currentH) swapping("H", currentH, h);
-        if (v !== "" && currentV !== "" && v !== currentV) swapping("V", currentV, v);
+        let covers = 0;
+        if (h !== "" && currentH !== "" && h !== currentH) { covers++; swapping("H", currentH, h); }
+        if (v !== "" && currentV !== "" && v !== currentV) { covers++; swapping("V", currentV, v); }
         const args = [];
         if (h !== "") args.push(`H=${JSON.stringify(h)}`);
         if (v !== "") args.push(`V=${JSON.stringify(v)}`);
         const env = kind === "tick" ? "UDT_ROTATION=1 " : "";
         applyProc.command = ["sh", "-c", `${env}wallp --set ${args.join(" ")} >/dev/null 2>&1`];
-        applyProc.running = true;
+        uncovered = covers;
+        if (covers === 0) applyProc.running = true;
+        else coverWait.restart();
         return true;
     }
 
+    // Covers still to come up before wallp may swap swaybg under them. The
+    // cover decodes its pictures asynchronously, and starting wallp with
+    // swapping showed the new picture through the still empty cover for a
+    // moment, then the old one over it, then the burn. WallpaperSpread
+    // calls covered() once it is drawing; a cover that never comes (a
+    // screen missing, a picture that fails to load) is waited out.
+    property int uncovered: 0
+    function covered() {
+        if (uncovered === 0) return;
+        if (--uncovered === 0) {
+            coverWait.stop();
+            applyProc.running = true;
+        }
+    }
+    Timer {
+        id: coverWait
+        interval: 1500
+        onTriggered: if (root.uncovered > 0) {
+            root.uncovered = 0;
+            applyProc.running = true;
+        }
+    }
+
     Process {
         id: applyProc
         stderr: StdioCollector { id: applyErr }