Merge pull request matplotlib#27599 from meeseeksmachine/auto-backport-of-pr-27594-on-v3.8.2-doc

Backport PR matplotlib#27594 on branch v3.8.2-doc (Cleanup viewlims example.)

Author: oscargus

galleries/examples/event_handling/viewlims.py

@@ -14,21 +14,15 @@
     You can copy and paste individual parts, or download the entire example
     using the link at the bottom of the page.
 """
+
+import functools
+
 import matplotlib.pyplot as plt
 import numpy as np
 
 from matplotlib.patches import Rectangle
 
 
-# We just subclass Rectangle so that it can be called with an Axes
-# instance, causing the rectangle to update its shape to match the
-# bounds of the Axes
-class UpdatingRect(Rectangle):
-    def __call__(self, ax):
-        self.set_bounds(*ax.viewLim.bounds)
-        ax.figure.canvas.draw_idle()
-
-
 # A class that will regenerate a fractal set as we zoom in, so that you
 # can actually see the increasing detail.  A box in the left panel will show
 # the area to which we are zoomed.
@@ -40,9 +34,9 @@ def __init__(self, h=500, w=500, niter=50, radius=2., power=2):
         self.radius = radius
         self.power = power
 
-    def compute_image(self, xstart, xend, ystart, yend):
-        self.x = np.linspace(xstart, xend, self.width)
-        self.y = np.linspace(ystart, yend, self.height).reshape(-1, 1)
+    def compute_image(self, xlim, ylim):
+        self.x = np.linspace(*xlim, self.width)
+        self.y = np.linspace(*ylim, self.height).reshape(-1, 1)
         c = self.x + 1.0j * self.y
         threshold_time = np.zeros((self.height, self.width))
         z = np.zeros(threshold_time.shape, dtype=complex)
@@ -56,38 +50,43 @@ def compute_image(self, xstart, xend, ystart, yend):
     def ax_update(self, ax):
         ax.set_autoscale_on(False)  # Otherwise, infinite loop
         # Get the number of points from the number of pixels in the window
-        self.width, self.height = \
-            np.round(ax.patch.get_window_extent().size).astype(int)
-        # Get the range for the new area
-        vl = ax.viewLim
-        extent = vl.x0, vl.x1, vl.y0, vl.y1
+        self.width, self.height = ax.patch.get_window_extent().size.round().astype(int)
         # Update the image object with our new data and extent
-        im = ax.images[-1]
-        im.set_data(self.compute_image(*extent))
-        im.set_extent(extent)
+        ax.images[-1].set(data=self.compute_image(ax.get_xlim(), ax.get_ylim()),
+                          extent=(*ax.get_xlim(), *ax.get_ylim()))
         ax.figure.canvas.draw_idle()
 
 
 md = MandelbrotDisplay()
-Z = md.compute_image(-2., 0.5, -1.25, 1.25)
-
-fig1, (ax1, ax2) = plt.subplots(1, 2)
-ax1.imshow(Z, origin='lower',
-           extent=(md.x.min(), md.x.max(), md.y.min(), md.y.max()))
-ax2.imshow(Z, origin='lower',
-           extent=(md.x.min(), md.x.max(), md.y.min(), md.y.max()))
-
-rect = UpdatingRect(
-    [0, 0], 0, 0, facecolor='none', edgecolor='black', linewidth=1.0)
-rect.set_bounds(*ax2.viewLim.bounds)
-ax1.add_patch(rect)
-
-# Connect for changing the view limits
-ax2.callbacks.connect('xlim_changed', rect)
-ax2.callbacks.connect('ylim_changed', rect)
-
-ax2.callbacks.connect('xlim_changed', md.ax_update)
-ax2.callbacks.connect('ylim_changed', md.ax_update)
-ax2.set_title("Zoom here")
+
+fig1, (ax_full, ax_zoom) = plt.subplots(1, 2)
+ax_zoom.imshow([[0]], origin="lower")  # Empty initial image.
+ax_zoom.set_title("Zoom here")
+
+rect = Rectangle(
+    [0, 0], 0, 0, facecolor="none", edgecolor="black", linewidth=1.0)
+ax_full.add_patch(rect)
+
+
+def update_rect(rect, ax):  # Let the rectangle track the bounds of the zoom axes.
+    xlo, xhi = ax.get_xlim()
+    ylo, yhi = ax.get_ylim()
+    rect.set_bounds((xlo, ylo, xhi - xlo, yhi - ylo))
+    ax.figure.canvas.draw_idle()
+
+
+# Connect for changing the view limits.
+ax_zoom.callbacks.connect("xlim_changed", functools.partial(update_rect, rect))
+ax_zoom.callbacks.connect("ylim_changed", functools.partial(update_rect, rect))
+
+ax_zoom.callbacks.connect("xlim_changed", md.ax_update)
+ax_zoom.callbacks.connect("ylim_changed", md.ax_update)
+
+# Initialize: trigger image computation by setting view limits; set colormap limits;
+# copy image to full view.
+ax_zoom.set(xlim=(-2, .5), ylim=(-1.25, 1.25))
+im = ax_zoom.images[0]
+ax_zoom.images[0].set(clim=(im.get_array().min(), im.get_array().max()))
+ax_full.imshow(im.get_array(), extent=im.get_extent(), origin="lower")
 
 plt.show()