Printing: Listen for status updates in Printer settings

Receive local printers from the 'local-printers-updated' and parse their
printer status to update the Saved printers section when the
"local-printer-observing flag" is enabled.

Bug: b:300136694
Change-Id: Id7426b1162ca92b4de4ed47d6ab4c0ef90f6c0a1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4977749
Reviewed-by: Ashley Prasad <ashleydp@google.com>
Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Commit-Queue: Gavin Williams <gavinwill@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1217196}

chrome/browser/resources/ash/settings/os_printing_page/cups_saved_printers.ts

@@ -18,6 +18,7 @@ import './cups_printers_entry.js';
 
 import {WebUiListenerMixin} from 'chrome://resources/cr_elements/web_ui_listener_mixin.js';
 import {assert} from 'chrome://resources/js/assert.js';
+import {addWebUiListener, WebUiListener} from 'chrome://resources/js/cr.js';
 import {loadTimeData} from 'chrome://resources/js/load_time_data.js';
 import {PolymerElement} from 'chrome://resources/polymer/v3_0/polymer/polymer_bundled.min.js';
 
@@ -197,6 +198,17 @@ export class SettingsCupsSavedPrintersElement extends
         readOnly: true,
         reflectToAttribute: true,
       },
+
+      /**
+       * True when the "local-printer-observing" feature flag is enabled.
+       */
+      isLocalPrinterObservingEnabled_: {
+        type: Boolean,
+        value: () => {
+          return loadTimeData.getBoolean('isLocalPrinterObservingEnabled');
+        },
+        readOnly: true,
+      },
     };
   }
 
@@ -224,7 +236,9 @@ export class SettingsCupsSavedPrintersElement extends
   private pageStartTime_: number;
   private timeoutIds_: number[];
   private onFocusListener_: () => void;
+  private localPrintersUpdatedListener_: WebUiListener;
   private isPrinterSettingsPrinterStatusEnabled_: boolean;
+  private isLocalPrinterObservingEnabled_: boolean;
 
   constructor() {
     super();
@@ -237,6 +251,15 @@ export class SettingsCupsSavedPrintersElement extends
     this.visiblePrinterCounter_ = MIN_VISIBLE_PRINTERS;
 
     this.onFocusListener_ = () => this.resetPrinterStatusQueryTimers();
+
+    // Listen for updates of local printers from the 'local-printers-updated'
+    // event to consume their updated printer statuses.
+    if (this.isLocalPrinterObservingEnabled_) {
+      addWebUiListener(
+          'local-printers-updated',
+          (printers: CupsPrinterInfo[]) => printers.forEach(
+              printer => this.onPrinterStatusReceived_(printer.printerStatus)));
+    }
   }
 
   override ready(): void {
@@ -248,7 +271,11 @@ export class SettingsCupsSavedPrintersElement extends
           this.onOpenActionMenu_(event);
         });
 
-    if (this.isPrinterSettingsPrinterStatusEnabled_) {
+    // When `isLocalPrinterObservingEnabled_` is enabled printer statuses get
+    // pushed from the backend so printer statuses don't need to be
+    // individually requested.
+    if (this.isPrinterSettingsPrinterStatusEnabled_ &&
+        !this.isLocalPrinterObservingEnabled_) {
       this.startPrinterStatusQueryTimer_(/*forErrorStatePrinters=*/ true);
       this.startPrinterStatusQueryTimer_(/*forErrorStatePrinters=*/ false);
     }
@@ -469,9 +496,10 @@ export class SettingsCupsSavedPrintersElement extends
    * For each printer status received, add it to the printer status cache then
    * notify its respective printer entry to update its status.
    */
-  private onPrinterStatusReceived_(printerStatus: PrinterStatus): void {
+  private onPrinterStatusReceived_(printerStatus: PrinterStatus|
+                                   undefined): void {
     assert(this.isPrinterSettingsPrinterStatusEnabled_);
-    if (!printerStatus) {
+    if (!printerStatus?.printerId) {
       return;
     }
 
@@ -576,6 +604,10 @@ export class SettingsCupsSavedPrintersElement extends
   getPrinterStatusReasonCacheForTesting(): Map<string, PrinterStatusReason> {
     return this.printerStatusReasonCache_;
   }
+
+  getTimeoutIdsForTesting(): number[] {
+    return this.timeoutIds_;
+  }
 }
 
 declare global {

chrome/browser/ui/webui/ash/settings/pages/printing/printing_section.cc

@@ -333,6 +333,9 @@ void PrintingSection::AddLoadTimeData(content::WebUIDataSource* html_source) {
                           features::IsPrinterSettingsPrinterStatusEnabled());
   html_source->AddBoolean("isPrintPreviewDiscoveredPrintersEnabled",
                           features::IsPrintPreviewDiscoveredPrintersEnabled());
+  html_source->AddBoolean(
+      "isLocalPrinterObservingEnabled",
+      base::FeatureList::IsEnabled(::features::kLocalPrinterObserving));
 }
 
 void PrintingSection::AddHandlers(content::WebUI* web_ui) {

chrome/test/data/webui/settings/chromeos/os_printing_page/cups_printer_landing_page_test.ts

@@ -647,6 +647,73 @@ suite('CupsSavedPrintersTests', () => {
     assertFalse(printerStatusReasonCache.has('id2'));
   });
 
+  // Verify the printer statuses received from the 'local-printers-updated'
+  // event are added to the printer status cache.
+  test('LocalPrintersUpdatedPrinterStatusCache', async () => {
+    loadTimeData.overrideValues({
+      isLocalPrinterObservingEnabled: true,
+    });
+    createCupsPrinterPage([]);
+    await flushTasks();
+    const element =
+        page.shadowRoot!.querySelector('settings-cups-saved-printers');
+    assertTrue(!!element);
+    savedPrintersElement = element;
+
+    const id1 = 'id1';
+    const printer1 = createCupsPrinterInfo('test1', '1', id1);
+    printer1.printerStatus = {
+      printerId: id1,
+      statusReasons: [
+        {
+          reason: PrinterStatusReason.PRINTER_UNREACHABLE,
+          severity: PrinterStatusSeverity.ERROR,
+        },
+      ],
+      timestamp: 0,
+    };
+    const id2 = 'id2';
+    const printer2 = createCupsPrinterInfo('test2', '2', id2);
+    printer2.printerStatus = {
+      printerId: id2,
+      statusReasons: [
+        {
+          reason: PrinterStatusReason.LOW_ON_INK,
+          severity: PrinterStatusSeverity.ERROR,
+        },
+      ],
+      timestamp: 0,
+    };
+    // Printer3 has an undefined printer status so it shouldn't be added to the
+    // cache.
+    const id3 = 'id3';
+    const printer3 = createCupsPrinterInfo('test3', '3', id3);
+    printer3.printerStatus = {
+      printerId: '',
+      statusReasons: [],
+      timestamp: 0,
+    };
+
+    // The printer status cache should initialize empty.
+    const printerStatusReasonCache =
+        savedPrintersElement.getPrinterStatusReasonCacheForTesting();
+    assertFalse(printerStatusReasonCache.has(id1));
+    assertFalse(printerStatusReasonCache.has(id2));
+    assertFalse(printerStatusReasonCache.has(id3));
+
+    // Trigger the observer and expect the printer statuses to be extracted then
+    // added to the cache.
+    webUIListenerCallback('local-printers-updated', [printer1, printer2]);
+    await flushTasks();
+    assertTrue(printerStatusReasonCache.has(id1));
+    assertTrue(printerStatusReasonCache.has(id2));
+    assertFalse(printerStatusReasonCache.has(id3));
+
+    // This verifies that no printer status query timers are scheduled when the
+    // "local-printer-observing" flag is enabled.
+    assertEquals(0, savedPrintersElement.getTimeoutIdsForTesting().length);
+  });
+
   test('ShowMoreButtonIsInitiallyHiddenAndANewPrinterIsAdded', async () => {
     createCupsPrinterPage([
       createCupsPrinterInfo('google', '4', 'id4'),