[DevTools] Add more descriptive UI for state transitions.

This CL incorporates some of the changes discussed in the latest UX meeting:
- Reorder the columns and toolbar buttons
- Display the metadata in a manner to a similar to the Network panel
- Add instructions for the inital landing page and other UI states

Bug: 942174
Change-Id: I7bd451377b241ec70d49c6d0b443522b43e5bcfe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1578554
Commit-Queue: Rayan Kanso <rayankans@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653543}

third_party/blink/renderer/devtools/front_end/resources/ApplicationPanelSidebar.js

@@ -694,7 +694,7 @@ Resources.BackgroundServiceTreeElement = class extends Resources.BaseStorageTree
    * @param {!Protocol.BackgroundService.ServiceName} serviceName
    */
   constructor(storagePanel, serviceName) {
-    super(storagePanel, Resources.BackgroundServiceTreeElement._getUIString(serviceName), false);
+    super(storagePanel, Resources.BackgroundServiceView.getUIString(serviceName), false);
 
     /** @const {!Protocol.BackgroundService.ServiceName} */
     this._serviceName = serviceName;
@@ -712,21 +712,6 @@ Resources.BackgroundServiceTreeElement = class extends Resources.BaseStorageTree
     this.setLeadingIcons([backgroundServiceIcon]);
   }
 
-  /**
-   * @param {string} serviceName The name of the background service.
-   * @return {string} The UI String to display.
-   */
-  static _getUIString(serviceName) {
-    switch (serviceName) {
-      case Protocol.BackgroundService.ServiceName.BackgroundFetch:
-        return Common.UIString('Background Fetch');
-      case Protocol.BackgroundService.ServiceName.BackgroundSync:
-        return Common.UIString('Background Sync');
-      default:
-        return '';
-    }
-  }
-
   /**
    * @param {?Resources.BackgroundServiceModel} model
    */

third_party/blink/renderer/devtools/front_end/resources/BackgroundServiceView.js

@@ -3,6 +3,21 @@
 // found in the LICENSE file.
 
 Resources.BackgroundServiceView = class extends UI.VBox {
+  /**
+   * @param {string} serviceName The name of the background service.
+   * @return {string} The UI String to display.
+   */
+  static getUIString(serviceName) {
+    switch (serviceName) {
+      case Protocol.BackgroundService.ServiceName.BackgroundFetch:
+        return ls`Background Fetch`;
+      case Protocol.BackgroundService.ServiceName.BackgroundSync:
+        return ls`Background Sync`;
+      default:
+        return '';
+    }
+  }
+
   /**
    * @param {!Protocol.BackgroundService.ServiceName} serviceName
    * @param {!Resources.BackgroundServiceModel} model
@@ -57,6 +72,9 @@ Resources.BackgroundServiceView = class extends UI.VBox {
     /** @const {!UI.VBox} */
     this._previewPanel = new UI.VBox();
 
+    /** @type {?Resources.BackgroundServiceView.EventDataNode} */
+    this._selectedEventNode = null;
+
     /** @type {?UI.Widget} */
     this._preview = null;
 
@@ -82,16 +100,16 @@ Resources.BackgroundServiceView = class extends UI.VBox {
 
     this._toolbar.appendSeparator();
 
-    this._originCheckbox =
-        new UI.ToolbarCheckbox(ls`Show events from other domains`, undefined, () => this._refreshView());
-    this._toolbar.appendToolbarItem(this._originCheckbox);
-
-    this._toolbar.appendSeparator();
-
     this._saveButton = new UI.ToolbarButton(ls`Save events`, 'largeicon-download');
     this._saveButton.addEventListener(UI.ToolbarButton.Events.Click, () => this._saveToFile());
     this._saveButton.setEnabled(false);
     this._toolbar.appendToolbarItem(this._saveButton);
+
+    this._toolbar.appendSeparator();
+
+    this._originCheckbox =
+        new UI.ToolbarCheckbox(ls`Show events from other domains`, undefined, () => this._refreshView());
+    this._toolbar.appendToolbarItem(this._originCheckbox);
   }
 
   /**
@@ -108,9 +126,10 @@ Resources.BackgroundServiceView = class extends UI.VBox {
    * Clears the grid and panel.
    */
   _clearView() {
+    this._selectedEventNode = null;
     this._dataGrid.rootNode().removeChildren();
-    this._showPreview(null);
     this._saveButton.setEnabled(false);
+    this._showPreview(null);
   }
 
   /**
@@ -135,7 +154,12 @@ Resources.BackgroundServiceView = class extends UI.VBox {
     const state = /** @type {!Resources.BackgroundServiceModel.RecordingState} */ (event.data);
     if (state.serviceName !== this._serviceName)
       return;
+
+    if (state.isRecording === this._recordButton.toggled())
+      return;
+
     this._recordButton.setToggled(state.isRecording);
+    this._showPreview(this._selectedEventNode);
   }
 
   /**
@@ -163,8 +187,10 @@ Resources.BackgroundServiceView = class extends UI.VBox {
     const dataNode = new Resources.BackgroundServiceView.EventDataNode(data, serviceEvent.eventMetadata);
     this._dataGrid.rootNode().appendChild(dataNode);
 
-    // There's at least one event. So we can allow saving the events.
+    if (this._dataGrid.rootNode().children.length === 1) {
       this._saveButton.setEnabled(true);
+      this._showPreview(this._selectedEventNode);
+    }
   }
 
   /**
@@ -174,9 +200,9 @@ Resources.BackgroundServiceView = class extends UI.VBox {
     const columns = /** @type {!Array<!DataGrid.DataGrid.ColumnDescriptor>} */ ([
       {id: 'id', title: ls`#`, weight: 1},
       {id: 'timestamp', title: ls`Timestamp`, weight: 8},
+      {id: 'eventName', title: ls`Event`, weight: 10},
       {id: 'origin', title: ls`Origin`, weight: 10},
       {id: 'swSource', title: ls`SW Source`, weight: 4},
-      {id: 'eventName', title: ls`Event`, weight: 10},
       {id: 'instanceId', title: ls`Instance ID`, weight: 10},
     ]);
     const dataGrid = new DataGrid.DataGrid(columns);
@@ -238,13 +264,36 @@ Resources.BackgroundServiceView = class extends UI.VBox {
    * @param {?Resources.BackgroundServiceView.EventDataNode} dataNode
    */
   _showPreview(dataNode) {
+    if (this._selectedEventNode && this._selectedEventNode === dataNode)
+      return;
+
+    this._selectedEventNode = dataNode;
+
     if (this._preview)
       this._preview.detach();
 
-    if (dataNode)
-      this._preview = dataNode.createPreview();
-    else
-      this._preview = new UI.EmptyWidget(ls`Select a value to preview`);
+    if (this._selectedEventNode) {
+      this._preview = this._selectedEventNode.createPreview();
+    } else if (this._dataGrid.rootNode().children.length) {
+      // Inform users that grid entries are clickable.
+      this._preview = new UI.EmptyWidget(ls`Select an entry to view metadata`);
+    } else if (this._recordButton.toggled()) {
+      // Inform users that we are recording/waiting for events.
+      this._preview = new UI.EmptyWidget(
+          ls`Recording ${Resources.BackgroundServiceView.getUIString(this._serviceName)} activity...`);
+    } else {
+      this._preview = new UI.VBox();
+      this._preview.contentElement.classList.add('background-service-landing-page');
+      const centered = this._preview.contentElement.createChild('div');
+
+      const landingRecordButton =
+          new UI.ToolbarToggle(ls`Toggle Record`, 'largeicon-start-recording', 'largeicon-stop-recording');
+      landingRecordButton.addEventListener(UI.ToolbarButton.Events.Click, () => this._toggleRecording());
+
+      // TODO(rayankans): Add a keyboard shortcut.
+      centered.createChild('p').appendChild(UI.formatLocalized(
+          'Click the record button %s to start recording.', [UI.createInlineButton(landingRecordButton)]));
+    }
 
     this._preview.show(this._previewPanel.contentElement);
   }
@@ -291,12 +340,25 @@ Resources.BackgroundServiceView.EventDataNode = class extends DataGrid.DataGridN
   }
 
   /**
-   * @return {!UI.SearchableView}
+   * @return {!UI.VBox}
    */
   createPreview() {
-    const metadata = {};
-    for (const entry of this._eventMetadata)
-      metadata[entry.key] = entry.value;
-    return SourceFrame.JSONView.createViewSync(metadata);
+    const preview = new UI.VBox();
+    preview.element.classList.add('background-service-metadata');
+
+    for (const entry of this._eventMetadata) {
+      const div = createElementWithClass('div', 'background-service-metadata-entry');
+      div.createChild('div', 'background-service-metadata-name').textContent = entry.key + ': ';
+      div.createChild('div', 'background-service-metadata-value source-code').textContent = entry.value;
+      preview.element.appendChild(div);
+    }
+
+    if (!preview.element.children.length) {
+      const div = createElementWithClass('div', 'background-service-metadata-entry');
+      div.createChild('div', 'background-service-metadata-name').textContent = ls`No metadata for this event`;
+      preview.element.appendChild(div);
+    }
+
+    return preview;
   }
 };

third_party/blink/renderer/devtools/front_end/resources/backgroundServiceView.css

@@ -7,3 +7,44 @@
     flex: auto;
     border: none;
 }
+
+.background-service-landing-page {
+    justify-content: center;
+    align-items: center;
+    font-size: 13px;
+    color: #777;
+}
+
+.background-service-landing-page > div {
+    max-width: 450px;
+    margin: 10px;
+}
+
+.background-service-landing-page > div > p {
+    flex: none;
+    white-space: pre-line;
+}
+
+.background-service-metadata {
+    padding-left: 5px;
+    padding-top: 10px;
+}
+
+.background-service-metadata-entry {
+    padding-left: 10px;
+    padding-bottom: 5px;
+}
+
+.background-service-metadata-name {
+    color: rgb(33%, 33%, 33%);
+    display: inline-block;
+    margin-right: 0.25em;
+    font-weight: bold;
+}
+
+.background-service-metadata-value {
+    display: inline;
+    margin-right: 1em;
+    white-space: pre-wrap;
+    word-break: break-all;
+}
\ No newline at end of file