QmlDesigner: Improve keyboard navigation on assets view

keyboard navigation now works when you focus the tab without
requiring to also click on the treeview itself.

Fixes: QDS-10397
Change-Id: I2cda08365c1a68c72121166d4fd50f1786f913bc
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>

share/qtcreator/qmldesigner/assetsLibraryQmlSources/Assets.qml

@@ -264,6 +264,7 @@ Item {
             contextMenu: contextMenu
             width: parent.width
             height: parent.height - assetsView.y
+            focus: true
         }
     }
 }

share/qtcreator/qmldesigner/assetsLibraryQmlSources/AssetsView.qml

@@ -348,22 +348,21 @@ TreeView {
         root.currentFilePath = filePath
     }
 
-    Keys.enabled: true
-
-    Keys.onUpPressed: {
-        if (!root.currentFilePath)
+    function moveSelection(amount)
+    {
+        if (!assetsModel.haveFiles || !amount)
             return
 
-        let index = assetsModel.indexForPath(root.currentFilePath)
+        let index = root.currentFilePath ? assetsModel.indexForPath(root.currentFilePath)
+                                         : root.__modelIndex(root.firstRow)
         let row = root.rowAtIndex(index)
         let nextRow = row
         let nextIndex = index
 
         do {
-            if (nextRow <= root.firstRow)
-                return // don't select hidden rows
-
-            nextRow--
+            nextRow = nextRow + amount
+            if ((amount < 0 && nextRow < root.firstRow) || (amount > 0 && nextRow > root.lastRow))
+                return
             nextIndex = root.__modelIndex(nextRow)
         } while (assetsModel.isDirectory(nextIndex))
 
@@ -371,26 +370,14 @@ TreeView {
         root.positionViewAtRow(nextRow, TableView.Contain)
     }
 
+    Keys.enabled: true
+
+    Keys.onUpPressed: {
+        moveSelection(-1)
+    }
+
     Keys.onDownPressed: {
-        if (!root.currentFilePath)
-            return
-
-        let index = assetsModel.indexForPath(root.currentFilePath)
-        let row = root.rowAtIndex(index)
-
-        let nextRow = row
-        let nextIndex = index
-
-        do {
-            if (nextRow >= root.lastRow)
-                return // don't select hidden rows
-
-            nextRow++
-            nextIndex = root.__modelIndex(nextRow)
-        } while (assetsModel.isDirectory(nextIndex))
-
-        root.__selectRow(nextRow)
-        root.positionViewAtRow(nextRow, TableView.Contain)
+        moveSelection(1)
     }
 
     ConfirmDeleteFilesDialog {

src/plugins/qmldesigner/components/assetslibrary/assetslibrarywidget.cpp

@@ -151,6 +151,8 @@ AssetsLibraryWidget::AssetsLibraryWidget(AsynchronousImageCache &asynchronousFon
 
     // init the first load of the QML UI elements
     reloadQmlSource();
+
+    setFocusProxy(m_assetsWidget->quickWidget());
 }
 
 void AssetsLibraryWidget::contextHelp(const Core::IContext::HelpCallback &callback) const