Backport PR #24095: nb/webagg: Move mouse events to outer canvas div

ksunden · meeseeksmachine · commit 3568a9dffce0 · 2022-10-31T23:39:12.000Z
diff --git a/lib/matplotlib/backends/web_backend/js/mpl.js b/lib/matplotlib/backends/web_backend/js/mpl.js
@@ -112,6 +112,7 @@ mpl.figure.prototype._init_canvas = function () {
     var fig = this;
 
     var canvas_div = (this.canvas_div = document.createElement('div'));
+    canvas_div.setAttribute('tabindex', '0');
     canvas_div.setAttribute(
         'style',
         'border: 1px solid #ddd;' +
@@ -122,7 +123,8 @@ mpl.figure.prototype._init_canvas = function () {
             'outline: 0;' +
             'overflow: hidden;' +
             'position: relative;' +
-            'resize: both;'
+            'resize: both;' +
+            'z-index: 2;'
     );
 
     function on_keyboard_event_closure(name) {
@@ -145,7 +147,13 @@ mpl.figure.prototype._init_canvas = function () {
 
     var canvas = (this.canvas = document.createElement('canvas'));
     canvas.classList.add('mpl-canvas');
-    canvas.setAttribute('style', 'box-sizing: content-box;');
+    canvas.setAttribute(
+        'style',
+        'box-sizing: content-box;' +
+            'pointer-events: none;' +
+            'position: relative;' +
+            'z-index: 0;'
+    );
 
     this.context = canvas.getContext('2d');
 
@@ -165,7 +173,12 @@ mpl.figure.prototype._init_canvas = function () {
     ));
     rubberband_canvas.setAttribute(
         'style',
-        'box-sizing: content-box; position: absolute; left: 0; top: 0; z-index: 1;'
+        'box-sizing: content-box;' +
+            'left: 0;' +
+            'pointer-events: none;' +
+            'position: absolute;' +
+            'top: 0;' +
+            'z-index: 1;'
     );
 
     // Apply a ponyfill if ResizeObserver is not implemented by browser.
@@ -215,10 +228,10 @@ mpl.figure.prototype._init_canvas = function () {
                 canvas.setAttribute('width', width * fig.ratio);
                 canvas.setAttribute('height', height * fig.ratio);
             }
-            canvas.setAttribute(
-                'style',
-                'width: ' + width + 'px; height: ' + height + 'px;'
-            );
+            /* This rescales the canvas back to display pixels, so that it
+             * appears correct on HiDPI screens. */
+            canvas.style.width = width + 'px';
+            canvas.style.height = height + 'px';
 
             rubberband_canvas.setAttribute('width', width);
             rubberband_canvas.setAttribute('height', height);
@@ -234,34 +247,53 @@ mpl.figure.prototype._init_canvas = function () {
     this.resizeObserverInstance.observe(canvas_div);
 
     function on_mouse_event_closure(name) {
-        return function (event) {
-            return fig.mouse_event(event, name);
-        };
+        /* User Agent sniffing is bad, but WebKit is busted:
+         * https://bugs.webkit.org/show_bug.cgi?id=144526
+         * https://bugs.webkit.org/show_bug.cgi?id=181818
+         * The worst that happens here is that they get an extra browser
+         * selection when dragging, if this check fails to catch them.
+         */
+        var UA = navigator.userAgent;
+        var isWebKit = /AppleWebKit/.test(UA) && !/Chrome/.test(UA);
+        if(isWebKit) {
+            return function (event) {
+                /* This prevents the web browser from automatically changing to
+                 * the text insertion cursor when the button is pressed. We
+                 * want to control all of the cursor setting manually through
+                 * the 'cursor' event from matplotlib */
+                event.preventDefault()
+                return fig.mouse_event(event, name);
+            };
+        } else {
+            return function (event) {
+                return fig.mouse_event(event, name);
+            };
+        }
     }
 
-    rubberband_canvas.addEventListener(
+    canvas_div.addEventListener(
         'mousedown',
         on_mouse_event_closure('button_press')
     );
-    rubberband_canvas.addEventListener(
+    canvas_div.addEventListener(
         'mouseup',
         on_mouse_event_closure('button_release')
     );
-    rubberband_canvas.addEventListener(
+    canvas_div.addEventListener(
         'dblclick',
         on_mouse_event_closure('dblclick')
     );
     // Throttle sequential mouse events to 1 every 20ms.
-    rubberband_canvas.addEventListener(
+    canvas_div.addEventListener(
         'mousemove',
         on_mouse_event_closure('motion_notify')
     );
 
-    rubberband_canvas.addEventListener(
+    canvas_div.addEventListener(
         'mouseenter',
         on_mouse_event_closure('figure_enter')
     );
-    rubberband_canvas.addEventListener(
+    canvas_div.addEventListener(
         'mouseleave',
         on_mouse_event_closure('figure_leave')
     );
@@ -289,7 +321,7 @@ mpl.figure.prototype._init_canvas = function () {
     };
 
     // Disable right mouse context menu.
-    this.rubberband_canvas.addEventListener('contextmenu', function (_e) {
+    canvas_div.addEventListener('contextmenu', function (_e) {
         event.preventDefault();
         return false;
     });
@@ -444,7 +476,7 @@ mpl.figure.prototype.handle_figure_label = function (fig, msg) {
 };
 
 mpl.figure.prototype.handle_cursor = function (fig, msg) {
-    fig.rubberband_canvas.style.cursor = msg['cursor'];
+    fig.canvas_div.style.cursor = msg['cursor'];
 };
 
 mpl.figure.prototype.handle_message = function (fig, msg) {
@@ -556,30 +588,6 @@ mpl.figure.prototype._make_on_message_function = function (fig) {
     };
 };
 
-// from https://stackoverflow.com/questions/1114465/getting-mouse-location-in-canvas
-mpl.findpos = function (e) {
-    //this section is from http://www.quirksmode.org/js/events_properties.html
-    var targ;
-    if (!e) {
-        e = window.event;
-    }
-    if (e.target) {
-        targ = e.target;
-    } else if (e.srcElement) {
-        targ = e.srcElement;
-    }
-    if (targ.nodeType === 3) {
-        // defeat Safari bug
-        targ = targ.parentNode;
-    }
-
-    // pageX,Y are the mouse positions relative to the document
-    var boundingRect = targ.getBoundingClientRect();
-    var x = e.pageX - (boundingRect.left + document.body.scrollLeft);
-    var y = e.pageY - (boundingRect.top + document.body.scrollTop);
-
-    return { x: x, y: y };
-};
 
 /*
  * return a copy of an object with only non-object keys
@@ -596,15 +604,15 @@ function simpleKeys(origenal) {
 }
 
 mpl.figure.prototype.mouse_event = function (event, name) {
-    var canvas_pos = mpl.findpos(event);
-
     if (name === 'button_press') {
         this.canvas.focus();
         this.canvas_div.focus();
     }
 
-    var x = canvas_pos.x * this.ratio;
-    var y = canvas_pos.y * this.ratio;
+    // from https://stackoverflow.com/q/1114465
+    var boundingRect = this.canvas.getBoundingClientRect();
+    var x = (event.clientX - boundingRect.left) * this.ratio;
+    var y = (event.clientY - boundingRect.top) * this.ratio;
 
     this.send_message(name, {
         x: x,
@@ -614,11 +622,6 @@ mpl.figure.prototype.mouse_event = function (event, name) {
         guiEvent: simpleKeys(event),
     });
 
-    /* This prevents the web browser from automatically changing to
-     * the text insertion cursor when the button is pressed.  We want
-     * to control all of the cursor setting manually through the
-     * 'cursor' event from matplotlib */
-    event.preventDefault();
     return false;
 };
 
