Cleanup interactive pan/zoom.

anntzer · anntzer · commit 395789c1e086 · 2020-10-30T13:59:35.000+01:00
Store all the relevant state in a single dict (`_pan_info`), similar
to the one used for zoom (`_zoom_info`), instead of scattering it
in two attributes (`_button_pressed`/`_xypress`).  Slightly reorder
logic in `press_pan` to match the order in `press_zoom`; likewise sync
`release_pan` with `release_zoom`.

We don't need to store the axes index (as was done in `_xypress`).

In `release_zoom`, move the less-than-5px check out of the loop, as it
only needs to be done once.
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -2871,7 +2871,6 @@ def __init__(self, canvas):
         self.canvas = canvas
         canvas.toolbar = self
         self._nav_stack = cbook.Stack()
-        self._xypress = None  # location and axis info at the time of the press
         # This cursor will be set after the initial draw.
         self._lastCursor = cursors.POINTER
 
@@ -2889,10 +2888,9 @@ def __init__(self, canvas):
             'button_release_event', self._zoom_pan_handler)
         self._id_drag = self.canvas.mpl_connect(
             'motion_notify_event', self.mouse_move)
+        self._pan_info = None
         self._zoom_info = None
 
-        self._button_pressed = None  # determined by button pressed at start
-
         self.mode = _Mode.NONE  # a mode string for the status bar
         self.set_history_buttons()
 
@@ -3076,24 +3074,20 @@ def pan(self, *args):
 
     def press_pan(self, event):
         """Callback for mouse button press in pan/zoom mode."""
-        if event.button in [1, 3]:
-            self._button_pressed = event.button
-        else:
-            self._button_pressed = None
+        if event.button not in [1, 3] or event.x is None or event.y is None:
+            return
+        axes = [a for a in self.canvas.figure.get_axes()
+                if a.in_axes(event) and a.get_navigate() and a.can_zoom()]
+        if not axes:
             return
         if self._nav_stack() is None:
-            # set the home button to this view
-            self.push_current()
-        x, y = event.x, event.y
-        self._xypress = []
-        for i, a in enumerate(self.canvas.figure.get_axes()):
-            if (x is not None and y is not None and a.in_axes(event) and
-                    a.get_navigate() and a.can_pan()):
-                a.start_pan(x, y, event.button)
-                self._xypress.append((a, i))
-                self.canvas.mpl_disconnect(self._id_drag)
-                self._id_drag = self.canvas.mpl_connect(
-                    'motion_notify_event', self.drag_pan)
+            self.push_current()  # set the home button to this view
+        for ax in axes:
+            ax.start_pan(event.x, event.y, event.button)
+        self.canvas.mpl_disconnect(self._id_drag)
+        id_drag = self.canvas.mpl_connect("motion_notify_event", self.drag_pan)
+        self._pan_info = {
+            "button": event.button, "axes": axes, "cid": id_drag}
         press = cbook._deprecate_method_override(
             __class__.press, self, since="3.3", message="Calling an "
             "overridden press() at pan start is deprecated since %(since)s "
@@ -3103,34 +3097,30 @@ def press_pan(self, event):
 
     def drag_pan(self, event):
         """Callback for dragging in pan/zoom mode."""
-        for a, ind in self._xypress:
-            #safer to use the recorded button at the press than current button:
-            #multiple button can get pressed during motion...
-            a.drag_pan(self._button_pressed, event.key, event.x, event.y)
+        for ax in self._pan_info["axes"]:
+            # Using the recorded button at the press is safer than the current
+            # button, as multiple buttons can get pressed during motion.
+            ax.drag_pan(self._pan_info["button"], event.key, event.x, event.y)
         self.canvas.draw_idle()
 
     def release_pan(self, event):
         """Callback for mouse button release in pan/zoom mode."""
-
-        if self._button_pressed is None:
+        if self._pan_info is None:
             return
-        self.canvas.mpl_disconnect(self._id_drag)
+        self.canvas.mpl_disconnect(self._pan_info["cid"])
         self._id_drag = self.canvas.mpl_connect(
             'motion_notify_event', self.mouse_move)
-        for a, ind in self._xypress:
-            a.end_pan()
-        if not self._xypress:
-            return
-        self._xypress = []
-        self._button_pressed = None
+        for ax in self._pan_info["axes"]:
+            ax.end_pan()
+        self._draw()
+        self._pan_info = None
         self.push_current()
         release = cbook._deprecate_method_override(
             __class__.press, self, since="3.3", message="Calling an "
             "overridden release() at pan stop is deprecated since %(since)s "
             "and will be removed %(removal)s; override release_pan() instead.")
         if release is not None:
             release(event)
-        self._draw()
 
     def zoom(self, *args):
         """Toggle zoom to rect mode."""
@@ -3146,9 +3136,7 @@ def zoom(self, *args):
 
     def press_zoom(self, event):
         """Callback for mouse button press in zoom to rect mode."""
-        if event.button not in [1, 3]:
-            return
-        if event.x is None or event.y is None:
+        if event.button not in [1, 3] or event.x is None or event.y is None:
             return
         axes = [a for a in self.canvas.figure.get_axes()
                 if a.in_axes(event) and a.get_navigate() and a.can_zoom()]
@@ -3194,35 +3182,31 @@ def release_zoom(self, event):
         self.remove_rubberband()
 
         start_x, start_y = self._zoom_info["start_xy"]
+        # Ignore single clicks: 5 pixels is a threshold that allows the user to
+        # "cancel" a zoom action by zooming by less than 5 pixels.
+        if ((abs(event.x - start_x) < 5 and event.key != "y")
+                or (abs(event.y - start_y) < 5 and event.key != "x")):
+            self._draw()
+            self._zoom_info = None
+            release = cbook._deprecate_method_override(
+                __class__.press, self, since="3.3", message="Calling an "
+                "overridden release() at zoom stop is deprecated since "
+                "%(since)s and will be removed %(removal)s; override "
+                "release_zoom() instead.")
+            if release is not None:
+                release(event)
+            return
 
         for i, ax in enumerate(self._zoom_info["axes"]):
-            x, y = event.x, event.y
-            # ignore singular clicks - 5 pixels is a threshold
-            # allows the user to "cancel" a zoom action
-            # by zooming by less than 5 pixels
-            if ((abs(x - start_x) < 5 and event.key != "y") or
-                    (abs(y - start_y) < 5 and event.key != "x")):
-                self._xypress = None
-                release = cbook._deprecate_method_override(
-                    __class__.press, self, since="3.3", message="Calling an "
-                    "overridden release() at zoom stop is deprecated since "
-                    "%(since)s and will be removed %(removal)s; override "
-                    "release_zoom() instead.")
-                if release is not None:
-                    release(event)
-                self._draw()
-                return
-
             # Detect whether this axes is twinned with an earlier axes in the
             # list of zoomed axes, to avoid double zooming.
             twinx = any(ax.get_shared_x_axes().joined(ax, prev)
                         for prev in self._zoom_info["axes"][:i])
             twiny = any(ax.get_shared_y_axes().joined(ax, prev)
                         for prev in self._zoom_info["axes"][:i])
-
             ax._set_view_from_bbox(
-                (start_x, start_y, x, y), self._zoom_info["direction"],
-                event.key, twinx, twiny)
+                (start_x, start_y, event.x, event.y),
+                self._zoom_info["direction"], event.key, twinx, twiny)
 
         self._draw()
         self._zoom_info = None
