[ui] Controls: add SearchBar component + better keyboard focus handling

* use it in MetadataListView and GraphEditor 'add Node' menu
* GraphEditor: forward MenuItem key events to searchBar to be able to continue editing the filter even if it lost active focus

meshroom/ui/qml/Controls/SearchBar.qml

@@ -0,0 +1,41 @@
+import QtQuick 2.9
+import QtQuick.Controls 2.3
+import QtQuick.Layouts 1.3
+import MaterialIcons 2.2
+
+
+/**
+ * Basic SearchBar component with an appropriate icon and a TextField.
+ */
+FocusScope {
+    property alias textField: field
+    property alias text: field.text
+
+    implicitHeight: childrenRect.height
+    Keys.forwardTo: [field]
+
+    function forceActiveFocus() {
+        field.forceActiveFocus()
+    }
+
+    function clear() {
+        field.clear()
+    }
+
+    RowLayout {
+        width: parent.width
+
+        MaterialLabel {
+            text: MaterialIcons.search
+        }
+
+        TextField {
+            id: field
+            focus: true
+            Layout.fillWidth: true
+            selectByMouse: true
+        }
+    }
+}
+
+

meshroom/ui/qml/Controls/qmldir

@@ -4,3 +4,4 @@ FloatingPane 1.0 FloatingPane.qml
 Group 1.0 Group.qml
 MessageDialog 1.0 MessageDialog.qml
 Panel 1.0 Panel.qml
+SearchBar 1.0 SearchBar.qml