Bug 1854298 - Implement PrintingEnabled policy r=emilio,mkaply,Gijs,fluent-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D188792

browser/base/content/browser.js

@@ -586,6 +586,16 @@ XPCOMUtils.defineLazyPreferenceGetter(
   }
 );
 
+XPCOMUtils.defineLazyPreferenceGetter(
+  this,
+  "gPrintEnabled",
+  "print.enabled",
+  false,
+  (aPref, aOldVal, aNewVal) => {
+    updatePrintCommands(aNewVal);
+  }
+);
+
 XPCOMUtils.defineLazyPreferenceGetter(
   this,
   "gScreenshotsComponentEnabled",
@@ -847,6 +857,19 @@ function UpdateBackForwardCommands(aWebNavigation) {
   }
 }
 
+function updatePrintCommands(enabled) {
+  var printCommand = document.getElementById("cmd_print");
+  var printPreviewCommand = document.getElementById("cmd_printPreviewToggle");
+
+  if (enabled) {
+    printCommand.removeAttribute("disabled");
+    printPreviewCommand.removeAttribute("disabled");
+  } else {
+    printCommand.setAttribute("disabled", "true");
+    printPreviewCommand.setAttribute("disabled", "true");
+  }
+}
+
 /**
  * Click-and-Hold implementation for the Back and Forward buttons
  * XXXmano: should this live in toolbarbutton.js?
@@ -1643,6 +1666,8 @@ var gBrowserInit = {
 
     updateFxaToolbarMenu(gFxaToolbarEnabled, true);
 
+    updatePrintCommands(gPrintEnabled);
+
     gUnifiedExtensions.init();
 
     // Setting the focus will cause a style flush, it's preferable to call anything

browser/components/enterprisepolicies/Policies.sys.mjs

@@ -1877,6 +1877,12 @@ export var Policies = {
     },
   },
 
+  PrintingEnabled: {
+    onBeforeUIStartup(manager, param) {
+      setAndLockPref("print.enabled", param);
+    },
+  },
+
   PromptForDownloadLocation: {
     onBeforeAddons(manager, param) {
       setAndLockPref("browser.download.useDownloadDir", !param);

browser/components/enterprisepolicies/schemas/policies-schema.json

@@ -1145,6 +1145,10 @@
       "type": "boolean"
     },
 
+    "PrintingEnabled": {
+      "type": "boolean"
+    },
+
     "PromptForDownloadLocation": {
       "type": "boolean"
     },

browser/locales/en-US/browser/policies/policies-descriptions.ftl

@@ -155,6 +155,8 @@ policy-ManualAppUpdateOnly = Allow manual updates only and do not notify the use
 
 policy-PrimaryPassword = Require or prevent using a Primary Password.
 
+policy-PrintingEnabled = Enable or disable printing.
+
 policy-NetworkPrediction = Enable or disable network prediction (DNS prefetching).
 
 policy-NewTabPage = Enable or disable the New Tab page.

dom/base/nsGlobalWindowOuter.cpp

@@ -4960,6 +4960,11 @@ void nsGlobalWindowOuter::PrintOuter(ErrorResult& aError) {
     return;
   }
 
+  // Printing is disabled, silently return.
+  if (!StaticPrefs::print_enabled()) {
+    return;
+  }
+
   // If we're loading, queue the print for later. This is a special-case that
   // only applies to the window.print() call, for compat with other engines and
   // pre-existing behavior.

modules/libpref/init/StaticPrefList.yaml

@@ -12813,6 +12813,12 @@
   value: true
   mirror: always
 
+# Disabling this will no-op window.print()
+- name: print.enabled
+  type: RelaxedAtomicBool
+  value: true
+  mirror: always
+
 #---------------------------------------------------------------------------
 # Prefs starting with "privacy."
 #---------------------------------------------------------------------------

toolkit/components/printing/tests/browser.toml

@@ -46,6 +46,8 @@ support-files = ["file_link_modulepreload.html"]
 
 ["browser_print_context_menu.js"]
 
+["browser_print_disabled.js"]
+
 ["browser_print_copies.js"]
 
 ["browser_print_duplex.js"]

toolkit/components/printing/tests/browser_print_disabled.js

@@ -0,0 +1,43 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+add_setup(async function setup() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["print.enabled", false]],
+  });
+});
+
+add_task(async function test_print_commands_disabled() {
+  let printCommand = document.getElementById(`cmd_print`);
+  let printPreview = document.getElementById(`cmd_printPreviewToggle`);
+
+  is(
+    printCommand.getAttribute("disabled"),
+    "true",
+    "print command is disabled when print.enabled=false"
+  );
+  is(
+    printPreview.getAttribute("disabled"),
+    "true",
+    "print preview command is disabled when print.enabled=false"
+  );
+});
+
+add_task(async function test_window_print_disabled() {
+  await BrowserTestUtils.withNewTab("https://example.org/", async browser => {
+    await SpecialPowers.spawn(browser, [], function () {
+      content.window.print();
+    });
+
+    // When the print dialog is open, the main thread of our tab is blocked, so
+    // the failure mode of this test is a timeout caused by the print dialog never
+    // closing.
+
+    Assert.ok(
+      true,
+      "window.print doesn't do anything when print.enabled=false"
+    );
+  });
+});