ENH : Nbagg blit

lib/matplotlib/backends/backend_webagg_core.py

@@ -138,7 +138,7 @@ def _handle_key(key):
 
 
 class FigureCanvasWebAggCore(backend_agg.FigureCanvasAgg):
-    supports_blit = False
+    supports_blit = True
 
     def __init__(self, *args, **kwargs):
         backend_agg.FigureCanvasAgg.__init__(self, *args, **kwargs)
@@ -180,9 +180,22 @@ def draw(self):
             # Swap the frames
             self.manager.refresh_all()
 
+    def blit(self, bbox=None):
+        """
+        Blit the region in bbox
+        """
+        self._png_is_old = True
+        self.manager.refresh_all()
+
     def draw_idle(self):
         self.send_event("draw")
 
+    def copy_from_bbox(self, bbox):
+        # make sure both renderers exist
+        self.get_renderer()
+        renderer = self._last_renderer
+        return renderer.copy_from_bbox(bbox)
+
     def set_image_mode(self, mode):
         """
         Set the image mode for any subsequent images which will be sent
@@ -241,6 +254,13 @@ def get_diff_image(self):
             # Swap the renderer frames
             self._renderer, self._last_renderer = (
                 self._last_renderer, renderer)
+
+            # update the cached renders of the Figure and Axes so that
+            # draw_artist() methods work as expected.
+            self.figure._cachedRenderer = self._renderer
+            for ax in self.figure.axes:
+                ax._cachedRenderer = self._renderer
+
             self._force_full = False
             self._png_is_old = False
         return self._png_buffer.getvalue()

lib/matplotlib/backends/web_backend/nbagg_uat.ipynb

@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:a1ac68aba163c75eab3d1fc91aa4d9a8ca66b09159619563827a19967d96814b"
+  "signature": "sha256:b18e2b0bb3d6c7d68852e1691d2a961bb7c0dd6b254113a763473bbe83dd4f0e"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -439,6 +439,48 @@
      "language": "python",
      "metadata": {},
      "outputs": []
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "### UAT 17 - Blitting\n",
+      "\n",
+      "Clicking on the figure should plot a green horizontal line moving up the axes.\n",
+      "\n"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "import matplotlib.pyplot as plt\n",
+      "\n",
+      "prev_artist = None\n",
+      "cur_y = 0.1\n",
+      "\n",
+      "def onclick_handle(event):\n",
+      "    \"\"\"Should draw elevating green line on each mouse click\"\"\"\n",
+      "    global ax, bg, prev_artist, cur_y\n",
+      "    ax.figure.canvas.restore_region(bg)\n",
+      "    if prev_artist:\n",
+      "        prev_artist.remove()\n",
+      "    cur_y += 0.1\n",
+      "    prev_artist = ax.plot([0, 1], [cur_y, cur_y], 'g')[0]\n",
+      "    ax.draw_artist(prev_artist)\n",
+      "    ax.figure.canvas.blit(ax.bbox)\n",
+      "    print(\"Drew line\")\n",
+      "\n",
+      "fig, ax = plt.subplots()\n",
+      "ax.plot([0, 1], [0, 1], 'r')\n",
+      "plt.show()\n",
+      "ax.figure.canvas.draw()\n",
+      "bg = ax.figure.canvas.copy_from_bbox(ax.bbox)\n",
+      "ax.figure.canvas.mpl_connect('button_press_event', onclick_handle)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": []
     }
    ],
    "metadata": {}