macOS: make conversation and main header draggable

stylesheets/_global.scss

@@ -21,8 +21,10 @@ body {
   // It'd be great if we could use the `:fullscreen` selector here, but that does not seem
   //   to work with Electron, at least on macOS.
   --title-bar-drag-area-height: 0px; // Needs to have a unit to work with `calc()`.
+  --draggable-app-region: initial;
   &.os-macos:not(.full-screen) {
     --title-bar-drag-area-height: 28px;
+    --draggable-app-region: drag;
   }
 }
 

stylesheets/_modules.scss

@@ -4217,6 +4217,8 @@ button.module-conversation-details__action-button {
 // Module: Main Header
 
 .module-main-header {
+  -webkit-app-region: var(--draggable-app-region);
+
   height: calc(#{$header-height} + var(--title-bar-drag-area-height));
   width: 100%;
 
@@ -4236,11 +4238,16 @@ button.module-conversation-details__action-button {
     }
   }
 
+  &__avatar {
+    -webkit-app-region: no-drag;
+  }
+
   &__search {
     flex-grow: 1;
     position: relative;
     display: flex;
     flex-direction: row;
+    -webkit-app-region: no-drag;
 
     &__input {
       flex-grow: 1;
@@ -4388,6 +4395,7 @@ button.module-conversation-details__action-button {
 
     width: 24px;
     height: 24px;
+    -webkit-app-region: no-drag;
 
     @include light-theme {
       @include color-svg($icon, $color-gray-90);

stylesheets/components/ConversationHeader.scss

@@ -8,11 +8,11 @@
     --button-spacing: 16px;
   }
 
+  -webkit-app-region: var(--draggable-app-region);
   padding-top: var(--title-bar-drag-area-height);
   display: flex;
   flex-direction: row;
   align-items: center;
-
   height: calc(#{$header-height} + var(--title-bar-drag-area-height));
 
   @include light-theme {
@@ -78,6 +78,7 @@
     &--clickable {
       @include button-reset;
       border-radius: 4px;
+      -webkit-app-region: no-drag;
 
       // These are clobbered by button-reset:
       margin-left: 4px;
@@ -171,6 +172,7 @@
   &__button {
     $icon-size: 32px;
 
+    -webkit-app-region: no-drag;
     @include button-reset;
     align-items: stretch;
     border-radius: 4px;

ts/background.ts

@@ -4,6 +4,8 @@
 import { DataMessageClass } from './textsecure.d';
 import { MessageAttributesType } from './model-types.d';
 import { WhatIsThis } from './window.d';
+import { getTitleBarVisibility, TitleBarVisibility } from './types/Settings';
+import { isWindowDragElement } from './util/isWindowDragElement';
 import { assert } from './util/assert';
 
 export async function startApp(): Promise<void> {
@@ -78,16 +80,14 @@ export async function startApp(): Promise<void> {
     },
   });
 
-  window.addEventListener('dblclick', (event: Event) => {
-    const target = event.target as HTMLElement;
-    const isDoubleClickOnTitleBar = Boolean(
-      target.classList.contains('module-title-bar-drag-area') ||
-        target.closest('module-title-bar-drag-area')
-    );
-    if (isDoubleClickOnTitleBar) {
-      window.titleBarDoubleClick();
-    }
-  });
+  if (getTitleBarVisibility() === TitleBarVisibility.Hidden) {
+    window.addEventListener('dblclick', (event: Event) => {
+      const target = event.target as HTMLElement;
+      if (isWindowDragElement(target)) {
+        window.titleBarDoubleClick();
+      }
+    });
+  }
 
   // Globally disable drag and drop
   document.body.addEventListener(

ts/components/MainHeader.tsx

@@ -367,6 +367,7 @@ export class MainHeader extends React.Component<PropsType, StateType> {
             {({ ref }) => (
               <Avatar
                 avatarPath={avatarPath}
+                className="module-main-header__avatar"
                 color={color}
                 conversationType="direct"
                 i18n={i18n}

ts/test-electron/util/isWindowDragElement_test.ts

@@ -0,0 +1,74 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { isWindowDragElement } from '../../util/isWindowDragElement';
+
+describe('isWindowDragElement', () => {
+  const crel = (tagName: string, appRegion?: string): Element => {
+    const result = document.createElement(tagName);
+    if (appRegion) {
+      result.style.cssText = `-webkit-app-region: ${appRegion}`;
+    }
+    return result;
+  };
+
+  let sandboxEl: HTMLElement;
+
+  beforeEach(() => {
+    sandboxEl = document.createElement('div');
+    document.body.appendChild(sandboxEl);
+  });
+
+  afterEach(() => {
+    sandboxEl.remove();
+  });
+
+  it('returns false for elements with no -webkit-app-region property in the heirarchy', () => {
+    const root = crel('div');
+    const outer = crel('span');
+    const inner = crel('div');
+    root.appendChild(outer);
+    outer.appendChild(inner);
+    sandboxEl.appendChild(root);
+
+    assert.isFalse(isWindowDragElement(root));
+    assert.isFalse(isWindowDragElement(outer));
+    assert.isFalse(isWindowDragElement(inner));
+  });
+
+  it('returns false for elements with -webkit-app-region: drag on a sub-element', () => {
+    const parent = crel('div');
+    const child = crel('div', 'drag');
+    parent.appendChild(child);
+    sandboxEl.appendChild(parent);
+
+    assert.isFalse(isWindowDragElement(parent));
+  });
+
+  it('returns false if any element up the chain is found to be -webkit-app-region: no-drag', () => {
+    const root = crel('div', 'drag');
+    const outer = crel('div', 'no-drag');
+    const inner = crel('div');
+    root.appendChild(outer);
+    outer.appendChild(inner);
+    sandboxEl.appendChild(root);
+
+    assert.isFalse(isWindowDragElement(outer));
+    assert.isFalse(isWindowDragElement(inner));
+  });
+
+  it('returns true if any element up the chain is found to be -webkit-app-region: drag', () => {
+    const root = crel('div', 'drag');
+    const outer = crel('div');
+    const inner = crel('div');
+    root.appendChild(outer);
+    outer.appendChild(inner);
+    sandboxEl.appendChild(root);
+
+    assert.isTrue(isWindowDragElement(root));
+    assert.isTrue(isWindowDragElement(outer));
+    assert.isTrue(isWindowDragElement(inner));
+  });
+});

ts/util/isWindowDragElement.ts

@@ -0,0 +1,21 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export function isWindowDragElement(el: Readonly<Element>): boolean {
+  let currentEl: Element | null = el;
+  do {
+    const appRegion = getComputedStyle(currentEl).getPropertyValue(
+      '-webkit-app-region'
+    );
+    switch (appRegion) {
+      case 'no-drag':
+        return false;
+      case 'drag':
+        return true;
+      default:
+        currentEl = currentEl.parentElement;
+        break;
+    }
+  } while (currentEl);
+  return false;
+}