[ui] dispatch thumbnail creation signal from grid

meshroom/ui/qml/ImageGallery/ImageDelegate.qml

@@ -31,17 +31,13 @@ Item {
         property var metadata: metadataStr ? JSON.parse(viewpoint.get("metadata").value) : {}
     }
 
+    // update thumbnail location
+    // can be called from the GridView when a new thumbnail has been written on disk
+    function updateThumbnail() {
+        thumbnail.source = ThumbnailCache.thumbnail(root.source);
+    }
     onSourceChanged: {
-        thumbnail.source = ThumbnailCache.thumbnail(root.source)
+        updateThumbnail();
-    }
-
-    Connections {
-        target: ThumbnailCache
-        function onThumbnailCreated(imgSource) {
-            if (imgSource == root.source) {
-                thumbnail.source = ThumbnailCache.thumbnail(root.source)
-            }
-        }
     }
 
     MouseArea {

meshroom/ui/qml/ImageGallery/ImageGallery.qml

@@ -201,6 +201,19 @@ Panel {
                 }
             }
 
+            // Update grid item when corresponding thumbnail is computed
+            Connections {
+                target: ThumbnailCache
+                function onThumbnailCreated(imgSource) {
+                    for (let i = 0; i < grid.count; i++) {
+                        let item = grid.itemAtIndex(i);  // item is an ImageDelegate
+                        if (item && item.source == imgSource) {
+                            item.updateThumbnail();
+                        }
+                    }
+                }
+            }
+
             model: SortFilterDelegateModel {
                 id: sortedModel
                 model: m.viewpoints