Align message context menu to right and vertically where space available

res/css/structures/_ContextualMenu.scss

@@ -39,7 +39,11 @@ limitations under the License.
     z-index: 5001;
 }
 
-.mx_ContextualMenu.mx_ContextualMenu_right {
+.mx_ContextualMenu_right {
+    right: 0;
+}
+
+.mx_ContextualMenu.mx_ContextualMenu_withChevron_right {
     right: 8px;
 }
 
@@ -66,7 +70,11 @@ limitations under the License.
     right: 1px;
 }
 
-.mx_ContextualMenu.mx_ContextualMenu_left {
+.mx_ContextualMenu_left {
+    left: 0;
+}
+
+.mx_ContextualMenu.mx_ContextualMenu_withChevron_left {
     left: 8px;
 }
 
@@ -93,7 +101,11 @@ limitations under the License.
     left: 1px;
 }
 
-.mx_ContextualMenu.mx_ContextualMenu_top {
+.mx_ContextualMenu_top {
+    top: 0;
+}
+
+.mx_ContextualMenu.mx_ContextualMenu_withChevron_top {
     top: 8px;
 }
 
@@ -120,7 +132,11 @@ limitations under the License.
     top: 1px;
 }
 
-.mx_ContextualMenu.mx_ContextualMenu_bottom {
+.mx_ContextualMenu_bottom {
+    bottom: 0;
+}
+
+.mx_ContextualMenu.mx_ContextualMenu_withChevron_bottom {
     bottom: 8px;
 }
 

src/components/structures/ContextualMenu.js

@@ -183,11 +183,14 @@ export default class ContextualMenu extends React.Component {
 
         const menuClasses = classNames({
             'mx_ContextualMenu': true,
-            'mx_ContextualMenu_noChevron': chevronFace === 'none',
-            'mx_ContextualMenu_left': chevronFace === 'left',
-            'mx_ContextualMenu_right': chevronFace === 'right',
-            'mx_ContextualMenu_top': chevronFace === 'top',
-            'mx_ContextualMenu_bottom': chevronFace === 'bottom',
+            'mx_ContextualMenu_left': !hasChevron && position.left,
+            'mx_ContextualMenu_right': !hasChevron && position.right,
+            'mx_ContextualMenu_top': !hasChevron && position.top,
+            'mx_ContextualMenu_bottom': !hasChevron && position.bottom,
+            'mx_ContextualMenu_withChevron_left': chevronFace === 'left',
+            'mx_ContextualMenu_withChevron_right': chevronFace === 'right',
+            'mx_ContextualMenu_withChevron_top': chevronFace === 'top',
+            'mx_ContextualMenu_withChevron_bottom': chevronFace === 'bottom',
         });
 
         const menuStyle = {};

src/components/views/messages/MessageActionBar.js

@@ -69,10 +69,6 @@ export default class MessageActionBar extends React.PureComponent {
         const MessageContextMenu = sdk.getComponent('context_menus.MessageContextMenu');
         const buttonRect = ev.target.getBoundingClientRect();
 
-        // The window X and Y offsets are to adjust position when zoomed in to page
-        const x = buttonRect.right + window.pageXOffset;
-        const y = (buttonRect.top + (buttonRect.height / 2) + window.pageYOffset) - 19;
-
         const { getTile, getReplyThread } = this.props;
         const tile = getTile && getTile();
         const replyThread = getReplyThread && getReplyThread();
@@ -82,19 +78,33 @@ export default class MessageActionBar extends React.PureComponent {
             e2eInfoCallback = () => this.onCryptoClicked();
         }
 
-        createMenu(MessageContextMenu, {
-            chevronOffset: 10,
+        const menuOptions = {
             mxEvent: this.props.mxEvent,
-            left: x,
-            top: y,
+            chevronFace: "none",
             permalinkCreator: this.props.permalinkCreator,
             eventTileOps: tile && tile.getEventTileOps ? tile.getEventTileOps() : undefined,
             collapseReplyThread: replyThread && replyThread.canCollapse() ? replyThread.collapse : undefined,
             e2eInfoCallback: e2eInfoCallback,
             onFinished: () => {
                 this.onFocusChange(false);
             },
-        });
+        };
+
+        // The window X and Y offsets are to adjust position when zoomed in to page
+        const buttonRight = buttonRect.right + window.pageXOffset;
+        const buttonBottom = buttonRect.bottom + window.pageYOffset;
+        const buttonTop = buttonRect.top + window.pageYOffset;
+        // Align the right edge of the menu to the right edge of the button
+        menuOptions.right = window.innerWidth - buttonRight;
+        // Align the menu vertically on whichever side of the button has more
+        // space available.
+        if (buttonBottom < window.innerHeight / 2) {
+            menuOptions.top = buttonBottom;
+        } else {
+            menuOptions.bottom = window.innerHeight - buttonTop;
+        }
+
+        createMenu(MessageContextMenu, menuOptions);
 
         this.onFocusChange(true);
     }