Fix #983. Bypass panel multi-select when only shift and tool utilizes…

… shift.

nion/swift/DisplayCanvasItem.py

@@ -87,6 +87,14 @@ def create_lattice(self, u_pos: Geometry.FloatSize) -> Graphics.LatticeGraphic:
 
 
 class DisplayCanvasItem(CanvasItem.CanvasItemComposition):
+    """Allow display canvas items (tools) to bypass multi-select.
+
+    In cases where only_shift is used in the tool, the tool should bypass multi-select and the result will be as if
+    the user clicked in the target display panel without modifiers. For instance, if the user shift-clicks using the
+    crop tool to restrict the crop to a square shape, the crop tool should bypass multi-select and the result will be
+    as if the user clicked in the target display panel without modifiers, selecting the target panel.
+    """
+    bypass_multi_select = False
 
     @property
     def key_contexts(self) -> typing.Sequence[str]:

nion/swift/DisplayPanel.py

@@ -1846,7 +1846,11 @@ def drop(mime_data: UserInterface.MimeData, region: str, x: int, y: int) -> str:
             return "ignore"
 
         def adjust_secondary_focus(modifiers: UserInterface.KeyboardModifiers) -> None:
-            if modifiers.only_shift:
+            display_canvas_item = self.display_canvas_item
+            if display_canvas_item and display_canvas_item.bypass_multi_select:
+                display_canvas_item.bypass_multi_select = False
+                self.__document_controller.selected_display_panel = self
+            elif modifiers.only_shift:
                 self.__document_controller.add_secondary_display_panel(self)
             elif modifiers.only_control:
                 self.__document_controller.toggle_secondary_display_panel(self)

nion/swift/ImageCanvasItem.py

@@ -663,6 +663,10 @@ async def _reactor_loop(self, r: Stream.ValueChangeStreamReactorInterface[MouseP
         pos = widget_mapping.map_point_widget_to_image_norm(mouse_pos)
         start_drag_pos = mouse_pos
 
+        # bypass multi-select if this tool is started with only the shift key selected. see notes where
+        # bypass_multi_select is defined.
+        image_canvas_item.bypass_multi_select = modifiers.only_shift
+
         with delegate.create_create_graphic_task(self.graphic_type, pos) as create_create_graphic_task:
             # create the graphic and assign a drag part
             graphic = getattr(create_create_graphic_task, "_graphic")