ui: Allow text selection of clickable elements and their contents (#5770)

* ui: Allow text selection of clickable elements and their contents

This commit disables a click on mousedown be removing the `href`
attribute and moving it to a `data-href` attribute. On mouseup it will
only move it back if there is no selection. This means that an anchor
will only be followed on click _if_ there is no selection.

This fixes the fact that whenever you select some copy within a
clickable element it immediately throws you into the linked page when
you release your mouse.

Further notes:

We use the `isCollapsed` property here which 'seems' to be classed as
'experimental' in one place where I researched it:

https://developer.mozilla.org/en-US/docs/Web/API/Selection/isCollapsed

Although in others it makes no mention of this 'experimental' e.g:

- https://webplatform.github.io/docs/dom/Selection/isCollapsed/
- https://w3c.github.io/selection-api/#dom-selection-iscollapsed

I may have gone a little overboard in feature detection for this, but I
conscious of that fact that if `isCollapsed` doesn't exist at some point
in the future (something that seems unlikely). The code here will have
no effect on the UI. But I'd specifically like a second pair of eyes on
that.

* ui: Don't break right click, detects a secondary click on mousedown

* ui: Put anchor selection capability behind an ENV var

ui-v2/app/instance-initializers/selection.js

@@ -0,0 +1,62 @@
+import env from 'consul-ui/env';
+
+const SECONDARY_BUTTON = 2;
+const isSelecting = function(win = window) {
+  const selection = win.getSelection();
+  let selecting = false;
+  try {
+    selecting = 'isCollapsed' in selection && !selection.isCollapsed;
+  } catch (e) {
+    // passthrough
+  }
+  return selecting;
+};
+export default {
+  name: 'selection',
+  initialize(container) {
+    if (env('CONSUL_UI_DISABLE_ANCHOR_SELECTION')) {
+      return;
+    }
+    const dom = container.lookup('service:dom');
+    const findAnchor = function(el) {
+      return el.tagName === 'A' ? el : dom.closest('a', el);
+    };
+    const mousedown = function(e) {
+      const $a = findAnchor(e.target);
+      if ($a) {
+        if (typeof e.button !== 'undefined' && e.button === SECONDARY_BUTTON) {
+          const dataHref = $a.dataset.href;
+          if (dataHref) {
+            $a.setAttribute('href', dataHref);
+          }
+          return;
+        }
+        const href = $a.getAttribute('href');
+        if (href) {
+          $a.dataset.href = href;
+          $a.removeAttribute('href');
+        }
+      }
+    };
+    const mouseup = function(e) {
+      const $a = findAnchor(e.target);
+      if ($a) {
+        const href = $a.dataset.href;
+        if (!isSelecting() && href) {
+          $a.setAttribute('href', href);
+        }
+      }
+    };
+
+    document.body.addEventListener('mousedown', mousedown);
+    document.body.addEventListener('mouseup', mouseup);
+
+    container.reopen({
+      willDestroy: function() {
+        document.body.removeEventListener('mousedown', mousedown);
+        document.body.removeEventListener('mouseup', mouseup);
+        return this._super(...arguments);
+      },
+    });
+  },
+};

ui-v2/app/utils/dom/click-first-anchor.js

@@ -1,9 +1,15 @@
-const clickEvent = function() {
-  return new MouseEvent('click', {
-    bubbles: true,
-    cancelable: true,
-    view: window,
-  });
+const clickEvent = function($el) {
+  ['mousedown', 'mouseup', 'click']
+    .map(function(type) {
+      return new MouseEvent(type, {
+        bubbles: true,
+        cancelable: true,
+        view: window,
+      });
+    })
+    .forEach(function(event) {
+      $el.dispatchEvent(event);
+    });
 };
 export default function(closest, click = clickEvent) {
   // TODO: Decide whether we should use `e` for ease
@@ -24,7 +30,7 @@ export default function(closest, click = clickEvent) {
     // closest should probably be relaced with a finder function
     const $a = closest('tr', e.target).querySelector('a');
     if ($a) {
-      $a.dispatchEvent(click());
+      click($a);
     }
   };
 }

ui-v2/config/environment.js

@@ -29,7 +29,10 @@ module.exports = function(environment) {
   };
   // TODO: These should probably go onto APP
   ENV = Object.assign({}, ENV, {
+    // TODO: Let people alter this, as with anchor selection
     CONSUL_UI_DISABLE_REALTIME: false,
+    CONSUL_UI_DISABLE_ANCHOR_SELECTION:
+      typeof process.env.CONSUL_UI_DISABLE_ANCHOR_SELECTION !== 'undefined',
     CONSUL_GIT_SHA: (function() {
       if (process.env.CONSUL_GIT_SHA) {
         return process.env.CONSUL_GIT_SHA;

ui-v2/tests/unit/utils/dom/click-first-anchor-test.js

@@ -39,16 +39,16 @@ test("it does nothing if an anchor isn't found", function(assert) {
   });
   assert.equal(actual, expected);
 });
-test('it dispatches the result of `click` if an anchor is found', function(assert) {
-  assert.expect(1);
-  const expected = 'click';
+test('it dispatches the result of `mouseup`, `mousedown`, `click` if an anchor is found', function(assert) {
+  assert.expect(3);
+  const expected = ['mousedown', 'mouseup', 'click'];
   const closest = function() {
     return {
       querySelector: function() {
         return {
           dispatchEvent: function(ev) {
             const actual = ev.type;
-            assert.equal(actual, expected);
+            assert.equal(actual, expected.shift());
           },
         };
       },