Remove one indirection layer in ToolSetCursor.

Instead of having both _add_tool_cbk (the main callback that handles
addition of new tools) and _add_tool (which does the same but for
pre-existing tools), we can just always use _add_tool_cbk, sending
synthetic tool_added_events for the initialization step).

Also move _tool_trigger_cbk down, next to _set_cursor_cbk, with which it
is semantically associated.

Author: anntzer

lib/matplotlib/backend_tools.py

@@ -261,9 +261,9 @@ def __init__(self, *args, **kwargs):
         self._last_cursor = self._default_cursor
         self.toolmanager.toolmanager_connect('tool_added_event',
                                              self._add_tool_cbk)
-        # process current tools
-        for tool in self.toolmanager.tools.values():
-            self._add_tool(tool)
+        for tool in self.toolmanager.tools.values():  # process current tools
+            self._add_tool_cbk(mpl.backend_managers.ToolEvent(
+                'tool_added_event', self.toolmanager, tool))
 
     def set_figure(self, figure):
         if self._id_drag:
@@ -273,24 +273,15 @@ def set_figure(self, figure):
             self._id_drag = self.canvas.mpl_connect(
                 'motion_notify_event', self._set_cursor_cbk)
 
-    def _tool_trigger_cbk(self, event):
-        if event.tool.toggled:
-            self._current_tool = event.tool
-        else:
-            self._current_tool = None
-        self._set_cursor_cbk(event.canvasevent)
-
-    def _add_tool(self, tool):
-        """Set the cursor when the tool is triggered."""
-        if getattr(tool, 'cursor', None) is not None:
-            self.toolmanager.toolmanager_connect('tool_trigger_%s' % tool.name,
-                                                 self._tool_trigger_cbk)
-
     def _add_tool_cbk(self, event):
         """Process every newly added tool."""
-        if event.tool is self:
-            return
-        self._add_tool(event.tool)
+        if getattr(event.tool, 'cursor', None) is not None:
+            self.toolmanager.toolmanager_connect(
+                f'tool_trigger_{event.tool.name}', self._tool_trigger_cbk)
+
+    def _tool_trigger_cbk(self, event):
+        self._current_tool = event.tool if event.tool.toggled else None
+        self._set_cursor_cbk(event.canvasevent)
 
     def _set_cursor_cbk(self, event):
         if not event or not self.canvas: