[ui] Viewer3D: fix wrong keyboard modifier state

Keyboard Actions are never deactivated when focus is lost, leading to picking being enabled on a single click when Control was pressed in the 3D viewer and focus was lost to another Item.
* keep track of focus loss inside the DefaultCameraController
* use it to disable picking while Keyboard has not been pressed back in the 3D viewer
* do the same for 'moving' state with Alt modifier

meshroom/ui/qml/Viewer3D/DefaultCameraController.qml

@@ -12,8 +12,9 @@ Entity {
     property real translateSpeed: 75.0
     property real tiltSpeed: 500.0
     property real panSpeed: 500.0
-    property bool moving: pressed || actionAlt.active
+    property bool moving: pressed || (actionAlt.active && keyboardHandler._pressed)
-    readonly property alias controlPressed: actionControl.active
+    property alias focus: keyboardHandler.focus
+    readonly property bool pickingActive: actionControl.active && keyboardHandler._pressed
 
     readonly property alias pressed: mouseHandler._pressed
     signal mousePressed(var mouse)
@@ -40,6 +41,20 @@ Entity {
         }
     }
 
+    KeyboardHandler {
+        id: keyboardHandler
+        sourceDevice: keyboardSourceDevice
+        property bool _pressed
+
+        // When focus is lost while pressing a key, the corresponding action
+        // stays active, even when it's released.
+        // Handle this issue manually by keeping an additional _pressed state
+        // which is cleared when focus changes (used for 'pickingActive' property).
+        onFocusChanged: if(!focus) _pressed = false
+        onPressed: _pressed = true
+        onReleased: _pressed = false
+    }
+
     LogicalDevice {
         id: cameraControlDevice
         actions: [

meshroom/ui/qml/Viewer3D/Viewer3D.qml

@@ -193,6 +193,7 @@ FocusScope {
             DefaultCameraController {
                 id: cameraController
                 camera: mainCamera
+                focus: scene3D.activeFocus
                 onMousePressed: {
                     scene3D.forceActiveFocus()
                     if(mouse.button == Qt.LeftButton)
@@ -273,7 +274,7 @@ FocusScope {
                     id: picker
                     // Triangle picking is expensive
                     // Only activate it when a double click may happen or when the 'Control' key is pressed
-                    enabled: cameraController.controlPressed || doubleClickTimer.running
+                    enabled: cameraController.pickingActive || doubleClickTimer.running
                     hoverEnabled: false
                     onPressed: {
                         if(pick.button == Qt.LeftButton)