Add the touch event handlers to the webagg and nbagg backends.

pelson · pelson · commit 58fb0d9fdb84 · 2020-10-31T00:19:28.000+01:00
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1976,6 +1976,21 @@ def enter_notify_event(self, guiEvent=None, xy=None):
         event = LocationEvent('figure_enter_event', self, x, y, guiEvent)
         self.callbacks.process('figure_enter_event', event)
 
+    def touch_start_event(self, touches, guiEvent=None):
+        # Placeholder implementation awaiting
+        # https://github.com/matplotlib/matplotlib/pull/8041.
+        pass
+
+    def touch_move_event(self, touches, guiEvent=None):
+        # Placeholder implementation awaiting
+        # https://github.com/matplotlib/matplotlib/pull/8041.
+        pass
+
+    def touch_end_event(self, touches, guiEvent=None):
+        # Placeholder implementation awaiting
+        # https://github.com/matplotlib/matplotlib/pull/8041.
+        pass
+
     def inaxes(self, xy):
         """
         Return the topmost visible `~.axes.Axes` containing the point *xy*.
diff --git a/lib/matplotlib/backends/backend_webagg_core.py b/lib/matplotlib/backends/backend_webagg_core.py
@@ -291,6 +291,18 @@ def _handle_key(self, event):
             self.key_release_event(key, guiEvent=guiEvent)
     handle_key_press = handle_key_release = _handle_key
 
+    def _handle_touch(self, event):
+        e_type = event['type']
+        guiEvent = event.get('guiEvent', None)
+        # TODO: Use event['touches'] to build up an appropriate backend event record.
+        if e_type == 'touch_start':
+            self.touch_start_event([], guiEvent=guiEvent)
+        elif e_type == 'touch_move':
+            self.touch_move_event([], guiEvent=guiEvent)
+        elif e_type == 'touch_end':
+            self.touch_end_event([], guiEvent=guiEvent)
+    handle_touch_start = handle_touch_move = handle_touch_end = _handle_touch
+
     def handle_toolbar_button(self, event):
         # TODO: Be more suspicious of the input
         getattr(self.toolbar, event['name'])()
diff --git a/lib/matplotlib/backends/web_backend/all_figures.html b/lib/matplotlib/backends/web_backend/all_figures.html
@@ -24,11 +24,13 @@
           main_div.appendChild(figure_div);
           var websocket_type = mpl.get_websocket_type();
           var websocket = new websocket_type("{{ ws_uri }}" + fig_id + "/ws");
-          var fig = new mpl.figure(fig_id, websocket, mpl_ondownload, figure_div);
-
-          fig.focus_on_mouseover = true;
-
-          fig.canvas.setAttribute("tabindex", fig_id);
+          var fig;
+          websocket.onopen = function ()
+          {
+            fig = new mpl.figure(fig_id, websocket, mpl_ondownload, figure_div);
+            fig.focus_on_mouseover = true;
+            fig.canvas.setAttribute("tabindex", fig_id);
+          }
         }
       };
 
diff --git a/lib/matplotlib/backends/web_backend/js/mpl.js b/lib/matplotlib/backends/web_backend/js/mpl.js
@@ -230,6 +230,12 @@ mpl.figure.prototype._init_canvas = function () {
         };
     }
 
+    function on_touch_event_closure(name) {
+        return function (event) {
+            return fig.touch_event(event, name);
+        };
+    }
+
     rubberband_canvas.addEventListener(
         'mousedown',
         on_mouse_event_closure('button_press')
@@ -242,12 +248,10 @@ mpl.figure.prototype._init_canvas = function () {
         'dblclick',
         on_mouse_event_closure('dblclick')
     );
-    // Throttle sequential mouse events to 1 every 20ms.
     rubberband_canvas.addEventListener(
         'mousemove',
         on_mouse_event_closure('motion_notify')
     );
-
     rubberband_canvas.addEventListener(
         'mouseenter',
         on_mouse_event_closure('figure_enter')
@@ -256,6 +260,18 @@ mpl.figure.prototype._init_canvas = function () {
         'mouseleave',
         on_mouse_event_closure('figure_leave')
     );
+    rubberband_canvas.addEventListener(
+        'touchmove',
+        on_touch_event_closure('touch_move')
+    );
+    rubberband_canvas.addEventListener(
+        'touchenter',
+        on_touch_event_closure('touch_start')
+    );
+    rubberband_canvas.addEventListener(
+        'touchleave',
+        on_touch_event_closure('touch_end')
+    );
 
     canvas_div.addEventListener('wheel', function (event) {
         if (event.deltaY < 0) {
@@ -628,6 +644,27 @@ mpl.figure.prototype.mouse_event = function (event, name) {
     return false;
 };
 
+mpl.figure.prototype.touch_event = function (event, name) {
+    var touches = [];
+    for (var i = 0; i < event.changedTouches.length; i++) {
+        var canvas_pos = mpl.findpos(event.changedTouches[i]);
+        var x = canvas_pos.x * this.ratio;
+        var y = canvas_pos.y * this.ratio;
+        touches.push({x: x, y: y});
+    }
+
+    this.send_message(name, {
+        touches: touches
+    });
+
+    // TODO: preventDefault will stop the event having any further impact
+    // in the user's browser. This effectively will stop things like
+    // pinch-to-zoom etc. Sometimes this is desirable, but certainly
+    // not always. For now, err on the side of caution.
+    // event.preventDefault();
+    return false;
+};
+
 mpl.figure.prototype._key_event_extra = function (_event, _name) {
     // Handle any extra behaviour associated with a key event
 };
diff --git a/lib/matplotlib/backends/web_backend/single_figure.html b/lib/matplotlib/backends/web_backend/single_figure.html
@@ -20,9 +20,13 @@
           var websocket_type = mpl.get_websocket_type();
           var websocket = new websocket_type(
               "{{ ws_uri }}" + {{ str(fig_id) }} + "/ws");
-          var fig = new mpl.figure(
+          var fig;
+          websocket.onopen = function ()
+          {
+            fig = new mpl.figure(
               {{ str(fig_id) }}, websocket, mpl_ondownload,
               document.getElementById("figure"));
+          }
         }
       );
     </script>
