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/* 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/. */
/*
* Common thumbnailing routines used by various consumers, including
* PageThumbs and BackgroundPageThumbs.
*/
var EXPORTED_SYMBOLS = ["PageThumbUtils"];
const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
ChromeUtils.defineModuleGetter(
this,
"BrowserUtils",
);
var PageThumbUtils = {
// The default thumbnail size for images
THUMBNAIL_DEFAULT_SIZE: 448,
// The default background color for page thumbnails.
THUMBNAIL_BG_COLOR: "#fff",
// The namespace for thumbnail canvas elements.
HTML_NAMESPACE: "http://www.w3.org/1999/xhtml",
/**
* Creates a new canvas element in the context of aWindow.
*
* @param aWindow The document of this window will be used to
* create the canvas.
* @param aWidth (optional) width of the canvas to create
* @param aHeight (optional) height of the canvas to create
* @return The newly created canvas.
*/
createCanvas(aWindow, aWidth = 0, aHeight = 0) {
let doc = aWindow.document;
let canvas = doc.createElementNS(this.HTML_NAMESPACE, "canvas");
canvas.mozOpaque = true;
canvas.imageSmoothingEnabled = true;
let [thumbnailWidth, thumbnailHeight] = this.getThumbnailSize(aWindow);
canvas.width = aWidth ? aWidth : thumbnailWidth;
canvas.height = aHeight ? aHeight : thumbnailHeight;
return canvas;
},
/**
* Calculates a preferred initial thumbnail size based based on newtab.css
* sizes or a preference for other applications. The sizes should be the same
* as set for the tile sizes in newtab.
*
* @param aWindow (optional) aWindow that is used to calculate the scaling size.
* @return The calculated thumbnail size or a default if unable to calculate.
*/
getThumbnailSize(aWindow = null) {
if (!this._thumbnailWidth || !this._thumbnailHeight) {
let screenManager = Cc["@mozilla.org/gfx/screenmanager;1"].getService(
Ci.nsIScreenManager
);
let left = {},
top = {},
screenWidth = {},
screenHeight = {};
screenManager.primaryScreen.GetRectDisplayPix(
left,
top,
screenWidth,
screenHeight
);
/**
* The primary monitor default scale might be different than
* what is reported by the window on mixed-DPI systems.
* To get the best image quality, query both and take the highest one.
*/
let primaryScale = screenManager.primaryScreen.defaultCSSScaleFactor;
let windowScale = aWindow ? aWindow.devicePixelRatio : primaryScale;
let scale = Math.max(primaryScale, windowScale);
/** *
* THESE VALUES ARE DEFINED IN newtab.css and hard coded.
* If you change these values from the prefs,
* ALSO CHANGE THEM IN newtab.css
*/
let prefWidth = Services.prefs.getIntPref("toolkit.pageThumbs.minWidth");
let prefHeight = Services.prefs.getIntPref(
"toolkit.pageThumbs.minHeight"
);
let divisor = Services.prefs.getIntPref(
"toolkit.pageThumbs.screenSizeDivisor"
);
prefWidth *= scale;
prefHeight *= scale;
this._thumbnailWidth = Math.max(
Math.round(screenWidth.value / divisor),
prefWidth
);
this._thumbnailHeight = Math.max(
Math.round(screenHeight.value / divisor),
prefHeight
);
}
return [this._thumbnailWidth, this._thumbnailHeight];
},
/** *
* Given a browser window, return the size of the content
* minus the scroll bars.
*/
getContentSize(aWindow) {
let utils = aWindow.windowUtils;
let sbWidth = {};
let sbHeight = {};
try {
utils.getScrollbarSize(false, sbWidth, sbHeight);
} catch (e) {
// This might fail if the window does not have a presShell.
Cu.reportError("Unable to get scrollbar size in determineCropSize.");
sbWidth.value = sbHeight.value = 0;
}
// Even in RTL mode, scrollbars are always on the right.
// So there's no need to determine a left offset.
let width = aWindow.innerWidth - sbWidth.value;
let height = aWindow.innerHeight - sbHeight.value;
return [width, height];
},
/**
* Renders an image onto a new canvas of a given width and proportional
* height. Uses an image that exists in the window and is loaded, or falls
* back to loading the url into a new image element.
*/
async createImageThumbnailCanvas(
window,
url,
targetWidth = 448,
backgroundColor = this.THUMBNAIL_BG_COLOR
) {
// 224px is the width of cards in ActivityStream; capture thumbnails at 2x
const doc = (window || Services.appShell.hiddenDOMWindow).document;
let image = doc.querySelector("img");
if (!image) {
image = doc.createElementNS(this.HTML_NAMESPACE, "img");
await new Promise((resolve, reject) => {
image.onload = () => resolve();
image.onerror = () => reject(new Error("LOAD_FAILED"));
image.src = url;
});
}
// <img src="*.svg"> has width/height but not naturalWidth/naturalHeight
const imageWidth = image.naturalWidth || image.width;
const imageHeight = image.naturalHeight || image.height;
if (imageWidth === 0 || imageHeight === 0) {
throw new Error("IMAGE_ZERO_DIMENSION");
}
const width = Math.min(targetWidth, imageWidth);
const height = (imageHeight * width) / imageWidth;
// As we're setting the width and maintaining the aspect ratio, if an image
// is very tall we might get a very large thumbnail. Restricting the canvas
// size to {width}x{width} solves this problem. Here we choose to clip the
// image at the bottom rather than centre it vertically, based on an
// estimate that the focus of a tall image is most likely to be near the top
// (e.g., the face of a person).
const canvasHeight = Math.min(height, width);
const canvas = this.createCanvas(window, width, canvasHeight);
const context = canvas.getContext("2d");
context.fillStyle = backgroundColor;
context.fillRect(0, 0, width, canvasHeight);
context.drawImage(image, 0, 0, width, height);
return {
width,
height: canvasHeight,
imageData: canvas.toDataURL(),
};
},
/**
* Given a browser, this creates a snapshot of the content
* and returns a canvas with the resulting snapshot of the content
* at the thumbnail size. It has to do this through a two step process:
*
* 1) Render the content at the window size to a canvas that is 2x the thumbnail size
* 2) Downscale the canvas from (1) down to the thumbnail size
*
* This is because the thumbnail size is too small to render at directly,
* causing pages to believe the browser is a small resolution. Also,
* at that resolution, graphical artifacts / text become very jagged.
* It's actually better to the eye to have small blurry text than sharp
* jagged pixels to represent text.
*
* @params aBrowser - the browser to create a snapshot of.
* @params aDestCanvas destination canvas to draw the final
* snapshot to. Can be null.
* @param aArgs (optional) Additional named parameters:
* fullScale - request that a non-downscaled image be returned.
* @return Canvas with a scaled thumbnail of the window.
*/
async createSnapshotThumbnail(aBrowser, aDestCanvas, aArgs) {
const aWindow = aBrowser.contentWindow;
let backgroundColor = aArgs
? aArgs.backgroundColor
: PageThumbUtils.THUMBNAIL_BG_COLOR;
let fullScale = aArgs ? aArgs.fullScale : false;
let [contentWidth, contentHeight] = this.getContentSize(aWindow);
let [thumbnailWidth, thumbnailHeight] = aDestCanvas
? [aDestCanvas.width, aDestCanvas.height]
: this.getThumbnailSize(aWindow);
// If the caller wants a fullscale image, set the desired thumbnail dims
// to the dims of content and (if provided) size the incoming canvas to
// support our results.
if (fullScale) {
thumbnailWidth = contentWidth;
thumbnailHeight = contentHeight;
if (aDestCanvas) {
aDestCanvas.width = contentWidth;
aDestCanvas.height = contentHeight;
}
}
let intermediateWidth = thumbnailWidth * 2;
let intermediateHeight = thumbnailHeight * 2;
let skipDownscale = false;
// If the intermediate thumbnail is larger than content dims (hiDPI
// devices can experience this) or a full preview is requested render
// at the final thumbnail size.
if (
intermediateWidth >= contentWidth ||
intermediateHeight >= contentHeight ||
fullScale
) {
intermediateWidth = thumbnailWidth;
intermediateHeight = thumbnailHeight;
skipDownscale = true;
}
// Create an intermediate surface
let snapshotCanvas = this.createCanvas(
aWindow,
intermediateWidth,
intermediateHeight
);
// Step 1: capture the image at the intermediate dims. For thumbnails
// this is twice the thumbnail size, for fullScale images this is at
// content dims.
// Also by default, canvas does not draw the scrollbars, so no need to
// remove the scrollbar sizes.
let scale = Math.min(
Math.max(
intermediateWidth / contentWidth,
intermediateHeight / contentHeight
),
1
);
let snapshotCtx = snapshotCanvas.getContext("2d");
snapshotCtx.save();
snapshotCtx.scale(scale, scale);
const image = await aBrowser.drawSnapshot(
0,
0,
contentWidth,
contentHeight,
scale,
backgroundColor
);
snapshotCtx.drawImage(image, 0, 0, contentWidth, contentHeight);
snapshotCtx.restore();
// Part 2: Downscale from our intermediate dims to the final thumbnail
// dims and copy the result to aDestCanvas. If the caller didn't
// provide a target canvas, create a new canvas and return it.
let finalCanvas =
aDestCanvas ||
this.createCanvas(aWindow, thumbnailWidth, thumbnailHeight);
let finalCtx = finalCanvas.getContext("2d");
finalCtx.save();
if (!skipDownscale) {
finalCtx.scale(0.5, 0.5);
}
finalCtx.drawImage(snapshotCanvas, 0, 0);
finalCtx.restore();
return finalCanvas;
},
/**
* Determine a good thumbnail crop size and scale for a given content
* window.
*
* @param aWindow The content window.
* @param aCanvas The target canvas.
* @return An array containing width, height and scale.
*/
determineCropSize(aWindow, aCanvas) {
let utils = aWindow.windowUtils;
let sbWidth = {};
let sbHeight = {};
try {
utils.getScrollbarSize(false, sbWidth, sbHeight);
} catch (e) {
// This might fail if the window does not have a presShell.
Cu.reportError("Unable to get scrollbar size in determineCropSize.");
sbWidth.value = sbHeight.value = 0;
}
// Even in RTL mode, scrollbars are always on the right.
// So there's no need to determine a left offset.
let width = aWindow.innerWidth - sbWidth.value;
let height = aWindow.innerHeight - sbHeight.value;
let { width: thumbnailWidth, height: thumbnailHeight } = aCanvas;
let scale = Math.min(
Math.max(thumbnailWidth / width, thumbnailHeight / height),
1
);
let scaledWidth = width * scale;
let scaledHeight = height * scale;
if (scaledHeight > thumbnailHeight) {
height -= Math.floor(Math.abs(scaledHeight - thumbnailHeight) * scale);
}
if (scaledWidth > thumbnailWidth) {
width -= Math.floor(Math.abs(scaledWidth - thumbnailWidth) * scale);
}
return [width, height, scale];
},
shouldStoreContentThumbnail(aDocument, aDocShell) {
if (BrowserUtils.isFindbarVisible(aDocShell)) {
return false;
}
// FIXME Bug 720575 - Don't capture thumbnails for SVG or XML documents as
// that currently regresses Talos SVG tests.
if (ChromeUtils.getClassName(aDocument) === "XMLDocument") {
return false;
}
let webNav = aDocShell.QueryInterface(Ci.nsIWebNavigation);
// Don't take screenshots of about: pages.
if (webNav.currentURI.schemeIs("about")) {
return false;
}
// There's no point in taking screenshot of loading pages.
if (aDocShell.busyFlags != Ci.nsIDocShell.BUSY_FLAGS_NONE) {
return false;
}
let channel = aDocShell.currentDocumentChannel;
// No valid document channel. We shouldn't take a screenshot.
if (!channel) {
return false;
}
// Don't take screenshots of internally redirecting about: pages.
// This includes error pages.
let uri = channel.originalURI;
if (uri.schemeIs("about")) {
return false;
}
let httpChannel;
try {
httpChannel = channel.QueryInterface(Ci.nsIHttpChannel);
} catch (e) {
/* Not an HTTP channel. */
}
if (httpChannel) {
// Continue only if we have a 2xx status code.
try {
if (Math.floor(httpChannel.responseStatus / 100) != 2) {
return false;
}
} catch (e) {
// Can't get response information from the httpChannel
// because mResponseHead is not available.
return false;
}
// Cache-Control: no-store.
if (httpChannel.isNoStoreResponse()) {
return false;
}
// Don't capture HTTPS pages unless the user explicitly enabled it.
if (
uri.schemeIs("https") &&
!Services.prefs.getBoolPref("browser.cache.disk_cache_ssl")
) {
return false;
}
} // httpChannel
return true;
},
/**
* Given a channel, returns true if it should be considered an "error
* response", false otherwise.
*/
isChannelErrorResponse(channel) {
// No valid document channel sounds like an error to me!
if (!channel) {
return true;
}
if (!(channel instanceof Ci.nsIHttpChannel)) {
// it might be FTP etc, so assume it's ok.
return false;
}
try {
return !channel.requestSucceeded;
} catch (_) {
// not being able to determine success is surely failure!
return true;
}
},
};