Bug 1736429 - Set up jswindowactors for screenshots and pass dimensions and scroll offsets from the child. r=mconley,sfoster

* Add jswindowactors for the Screenshots component, to facilitate communication between the UI (lives in the parent) and the content document.
* Fetch content document dimensions/offsets with e.g: `ScreenshotsUtils.fetchContentBounds(gBrowser.selectedBrowser)`.

Differential Revision: https://phabricator.services.mozilla.com/D129326

browser/actors/ScreenshotsComponentChild.jsm

@@ -0,0 +1,156 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+/* eslint-env mozilla/browser-window */
+
+"use strict";
+
+var EXPORTED_SYMBOLS = ["ScreenshotsComponentChild"];
+
+class ScreenshotsComponentChild extends JSWindowActorChild {
+  receiveMessage(message) {
+    switch (message.name) {
+      case "Screenshots:ShowOverlay":
+        return this.startScreenshotsOverlay();
+      case "Screenshots:HideOverlay":
+        return this.endScreenshotsOverlay();
+      case "Screenshots:getFullPageBounds":
+        return this.getFullPageBounds();
+      case "Screenshots:getVisibleBounds":
+        return this.getVisibleBounds();
+    }
+    return null;
+  }
+
+  /**
+   * Resolves when the document is ready to have an overlay injected into it.
+   *
+   * @returns {Promise}
+   * @resolves {Boolean} true when document is ready or rejects
+   */
+  documentIsReady() {
+    const document = this.document;
+    // Some pages take ages to finish loading - if at all.
+    // We want to respond to enable the screenshots UI as soon that is possible
+    function readyEnough() {
+      return (
+        document.readyState !== "uninitialized" && document.documentElement
+      );
+    }
+
+    if (readyEnough()) {
+      return Promise.resolve();
+    }
+    return new Promise((resolve, reject) => {
+      function onChange(event) {
+        if (event.type === "pagehide") {
+          document.removeEventListener("readystatechange", onChange);
+          this.contentWindow.removeEventListener("pagehide", onChange);
+          reject(new Error("document unloaded before it was ready"));
+        } else if (readyEnough()) {
+          document.removeEventListener("readystatechange", onChange);
+          this.contentWindow.removeEventListener("pagehide", onChange);
+          resolve();
+        }
+      }
+      document.addEventListener("readystatechange", onChange);
+      this.contentWindow.addEventListener("pagehide", onChange, { once: true });
+    });
+  }
+
+  /**
+   * Wait until the document is ready and then show the screenshots overlay
+   *
+   * @returns {Boolean} true when document is ready and the overlay is shown
+   * otherwise false
+   */
+  async startScreenshotsOverlay(details = {}) {
+    try {
+      await this.documentIsReady();
+    } catch (ex) {
+      console.warn(`ScreenshotsComponentChild: ${ex.message}`);
+      return false;
+    }
+    return true;
+  }
+
+  /**
+   * Remove the screenshots overlay.
+   *
+   * @returns {Boolean}
+   *   true when the overlay has been removed otherwise false
+   */
+  endScreenshotsOverlay() {
+    // this function will be implemented soon
+    return true;
+  }
+
+  /**
+   * Gets the full page bounds for a full page screenshot.
+   *
+   * @returns { object }
+   *   The device pixel ratio and a DOMRect of the scrollable content bounds.
+   *
+   *   devicePixelRatio (float):
+   *      The device pixel ratio of the screen
+   *
+   *   rect (object):
+   *      top (int):
+   *        The scroll top position for the content window.
+   *
+   *      left (int):
+   *        The scroll left position for the content window.
+   *
+   *      width (int):
+   *        The scroll width of the content window.
+   *
+   *      height (int):
+   *        The scroll height of the content window.
+   */
+  getFullPageBounds() {
+    let doc = this.document.documentElement;
+    let rect = new DOMRect(
+      doc.scrollTop,
+      doc.scrollLeft,
+      doc.scrollWidth,
+      doc.scrollHeight
+    );
+    let devicePixelRatio = this.document.ownerGlobal.devicePixelRatio;
+    return { devicePixelRatio, rect };
+  }
+
+  /**
+   * Gets the visible page bounds for a visible screenshot.
+   *
+   * @returns { object }
+   *   The device pixel ratio and a DOMRect of the current visible
+   *   content bounds.
+   *
+   *   devicePixelRatio (float):
+   *      The device pixel ratio of the screen
+   *
+   *   rect (object):
+   *      top (int):
+   *        The top position for the content window.
+   *
+   *      left (int):
+   *        The left position for the content window.
+   *
+   *      width (int):
+   *        The width of the content window.
+   *
+   *      height (int):
+   *        The height of the content window.
+   */
+  getVisibleBounds() {
+    let doc = this.document.documentElement;
+    let rect = new DOMRect(
+      doc.clientTop,
+      doc.clientLeft,
+      doc.clientWidth,
+      doc.clientHeight
+    );
+    let devicePixelRatio = this.document.ownerGlobal.devicePixelRatio;
+    return { devicePixelRatio, rect };
+  }
+}

browser/actors/moz.build

@@ -25,6 +25,9 @@ with Files("PageStyleChild.jsm"):
 with Files("PluginChild.jsm"):
     BUG_COMPONENT = ("Core", "Plug-ins")
 
+with Files("ScreenshotsComponentChild.jsm"):
+    BUG_COMPONENT = ("Firefox", "Screenshots")
+
 with Files("WebRTCChild.jsm"):
     BUG_COMPONENT = ("Firefox", "Site Permissions")
 
@@ -79,6 +82,7 @@ FINAL_TARGET_FILES.actors += [
     "RefreshBlockerParent.jsm",
     "RFPHelperChild.jsm",
     "RFPHelperParent.jsm",
+    "ScreenshotsComponentChild.jsm",
     "SearchSERPTelemetryChild.jsm",
     "SearchSERPTelemetryParent.jsm",
     "SwitchDocumentDirectionChild.jsm",

browser/components/BrowserGlue.jsm

@@ -645,6 +645,13 @@ let JSWINDOWACTORS = {
     enablePreference: "accessibility.blockautorefresh",
   },
 
+  ScreenshotsComponent: {
+    child: {
+      moduleURI: "resource:///actors/ScreenshotsComponentChild.jsm",
+    },
+    enablePreference: "screenshots.browser.component.enabled",
+  },
+
   SearchSERPTelemetry: {
     parent: {
       moduleURI: "resource:///actors/SearchSERPTelemetryParent.jsm",

browser/components/screenshots/ScreenshotsUtils.jsm

@@ -14,6 +14,14 @@ const PanelOffsetY = -8;
 
 var ScreenshotsUtils = {
   initialize() {
+    if (
+      !Services.prefs.getBoolPref(
+        "screenshots.browser.component.enabled",
+        false
+      )
+    ) {
+      return;
+    }
     Services.obs.addObserver(this, "menuitem-screenshot");
     Services.obs.addObserver(this, "screenshots-take-screenshot");
   },
@@ -23,6 +31,8 @@ var ScreenshotsUtils = {
 
     let currDialogBox = browser.tabDialogBox;
 
+    let zoom = subj.ZoomManager.getZoomForBrowser(browser);
+
     switch (topic) {
       case "menuitem-screenshot":
         // if dialog box exists then find the correct dialog box and close it
@@ -56,7 +66,7 @@ var ScreenshotsUtils = {
         // init UI as a tab dialog box
         let dialogBox = gBrowser.getTabDialogBox(browser);
 
-        return dialogBox.open(
+        let { dialog } = dialogBox.open(
           `chrome://browser/content/screenshots/screenshots.html?browsingContextId=${browser.browsingContext.id}`,
           {
             features: "resizable=no",
@@ -64,9 +74,15 @@ var ScreenshotsUtils = {
             allowDuplicateDialogs: false,
           }
         );
+        this.doScreenshot(browser, dialog, zoom, data);
     }
     return null;
   },
+  /**
+   * Notify screenshots when screenshot command is used.
+   * @param window The current window the screenshot command was used.
+   * @param type The type of screenshot taken. Used for telemetry.
+   */
   notify(window, type) {
     if (Services.prefs.getBoolPref("screenshots.browser.component.enabled")) {
       Services.obs.notifyObservers(
@@ -77,16 +93,40 @@ var ScreenshotsUtils = {
       Services.obs.notifyObservers(null, "menuitem-screenshot-extension", type);
     }
   },
+  /**
+   * Creates and returns a Screenshots actor.
+   * @param browser The current browser.
+   * @returns JSWindowActor The screenshot actor.
+   */
+  getActor(browser) {
+    let actor = browser.browsingContext.currentWindowGlobal.getActor(
+      "ScreenshotsComponent"
+    );
+    return actor;
+  },
+  /**
+   * If the buttons panel exists and the panel is open we will hipe the panel
+   * popup and hide the screenshot overlay.
+   * Otherwise create or display the buttons.
+   * @param browser The current browser.
+   */
   togglePreview(browser) {
     let buttonsPanel = browser.ownerDocument.querySelector(
       "#screenshotsPagePanel"
     );
     if (buttonsPanel && buttonsPanel.state !== "closed") {
       buttonsPanel.hidePopup();
-    } else {
+      let actor = this.getActor(browser);
-      this.createOrDisplayButtons(browser);
+      return actor.sendQuery("Screenshots:HideOverlay");
     }
+    return this.createOrDisplayButtons(browser);
   },
+  /**
+   * If the buttons panel does not exist then we will replace the buttons
+   * panel template with the buttons panel then open the buttons panel and
+   * show the screenshots overaly.
+   * @param browser The current browser.
+   */
   createOrDisplayButtons(browser) {
     let doc = browser.ownerDocument;
     let buttonsPanel = doc.querySelector("#screenshotsPagePanel");
@@ -98,5 +138,90 @@ var ScreenshotsUtils = {
     }
     let anchor = doc.querySelector("#navigator-toolbox");
     buttonsPanel.openPopup(anchor, PanelPosition, PanelOffsetX, PanelOffsetY);
+    let actor = this.getActor(browser);
+    return actor.sendQuery("Screenshots:ShowOverlay");
+  },
+  /**
+   * Gets the full page bounds from the screenshots child actor.
+   * @param browser The current browser.
+   * @returns { object }
+   *    Contains the full page bounds from the screenshots child actor.
+   */
+  fetchFullPageBounds(browser) {
+    let actor = this.getActor(browser);
+    return actor.sendQuery("Screenshots:getFullPageBounds");
+  },
+  /**
+   * Gets the visible bounds from the screenshots child actor.
+   * @param browser The current browser.
+   * @returns { object }
+   *    Contains the visible bounds from the screenshots child actor.
+   */
+  fetchVisibleBounds(browser) {
+    let actor = this.getActor(browser);
+    return actor.sendQuery("Screenshots:getVisibleBounds");
+  },
+  /**
+   * Add screenshot-ui to the dialog box and then take the screenshot
+   * @param browser The current browser.
+   * @param dialog The dialog box to show the screenshot preview.
+   * @param zoom The current zoom level.
+   * @param type The type of screenshot taken.
+   */
+  async doScreenshot(browser, dialog, zoom, type) {
+    await dialog._dialogReady;
+    let screenshotsUI = dialog._frame.contentDocument.createElement(
+      "screenshots-ui"
+    );
+    dialog._frame.contentDocument.body.appendChild(screenshotsUI);
+
+    let rect;
+    if (type === "full-page") {
+      ({ rect } = await this.fetchFullPageBounds(browser));
+    } else {
+      ({ rect } = await this.fetchVisibleBounds(browser));
+    }
+    return this.takeScreenshot(browser, dialog, rect, zoom);
+  },
+  /**
+   * Take the screenshot and add the image to the dialog box
+   * @param browser The current browser.
+   * @param dialog The dialog box to show the screenshot preview.
+   * @param rect DOMRect containing bounds of the screenshot.
+   * @param zoom The current zoom level.
+   */
+  async takeScreenshot(browser, dialog, rect, zoom) {
+    let browsingContext = BrowsingContext.get(browser.browsingContext.id);
+
+    let snapshot = await browsingContext.currentWindowGlobal.drawSnapshot(
+      rect,
+      zoom,
+      "rgb(255,255,255)"
+    );
+
+    let canvas = dialog._frame.contentDocument.createElementNS(
+      "http://www.w3.org/1999/xhtml",
+      "html:canvas"
+    );
+    let context = canvas.getContext("2d");
+
+    canvas.width = snapshot.width;
+    canvas.height = snapshot.height;
+
+    context.drawImage(snapshot, 0, 0);
+
+    canvas.toBlob(function(blob) {
+      let newImg = dialog._frame.contentDocument.createElement("img");
+      let url = URL.createObjectURL(blob);
+
+      newImg.id = "placeholder-image";
+
+      newImg.src = url;
+      dialog._frame.contentDocument
+        .getElementById("preview-image-div")
+        .appendChild(newImg);
+    });
+
+    snapshot.close();
   },
 };

browser/components/screenshots/content/screenshots.html

@@ -37,7 +37,5 @@
         </div>
       </div>
     </template>
-
-    <screenshots-ui></screenshots-ui>
   </body>
 </html>

browser/components/screenshots/content/screenshots.js

@@ -21,8 +21,6 @@ class ScreenshotsUI extends HTMLElement {
   }
   async connectedCallback() {
     this.initialize();
-
-    await this.takeVisibleScreenshot();
   }
 
   initialize() {