gecko-dev/image/test/mochitest/imgutils.js

/* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
// Helper file for shared image functionality
//
// Note that this is use by tests elsewhere in the source tree. When in doubt,
// check mxr before removing or changing functionality.

// Helper function to clear both the content and chrome image caches
function clearAllImageCaches() {
  var tools = SpecialPowers.Cc["@mozilla.org/image/tools;1"].getService(
    SpecialPowers.Ci.imgITools
  );
  var imageCache = tools.getImgCacheForDocument(window.document);
  imageCache.clearCache(true); // true=chrome
  imageCache.clearCache(false); // false=content
}

// Helper function to clear the image cache of content images
function clearImageCache() {
  var tools = SpecialPowers.Cc["@mozilla.org/image/tools;1"].getService(
    SpecialPowers.Ci.imgITools
  );
  var imageCache = tools.getImgCacheForDocument(window.document);
  imageCache.clearCache(false); // true=chrome, false=content
}

// Helper function to determine if the frame is decoded for a given image id
function isFrameDecoded(id) {
  return !!(
    getImageStatus(id) & SpecialPowers.Ci.imgIRequest.STATUS_FRAME_COMPLETE
  );
}

// Helper function to determine if the image is loaded for a given image id
function isImageLoaded(id) {
  return !!(
    getImageStatus(id) & SpecialPowers.Ci.imgIRequest.STATUS_LOAD_COMPLETE
  );
}

// Helper function to get the status flags of an image
function getImageStatus(id) {
  // Get the image
  var img = SpecialPowers.wrap(document.getElementById(id));

  // Get the request
  var request = img.getRequest(
    SpecialPowers.Ci.nsIImageLoadingContent.CURRENT_REQUEST
  );

  // Return the status
  return request.imageStatus;
}

// Forces a synchronous decode of an image by drawing it to a canvas. Only
// really meaningful if the image is fully loaded first
function forceDecode(id) {
  // Get the image
  var img = document.getElementById(id);

  // Make a new canvas
  var canvas = document.createElement("canvas");

  // Draw the image to the canvas. This forces a synchronous decode
  var ctx = canvas.getContext("2d");
  ctx.drawImage(img, 0, 0);
}

// Functions to facilitate getting/setting various image-related prefs
//
// If you change a pref in a mochitest, Don't forget to reset it to its
// original value!
//
// Null indicates no pref set

const DISCARD_ENABLED_PREF = {
  name: "discardable",
  branch: "image.mem.",
  type: "bool",
};
const DECODEONDRAW_ENABLED_PREF = {
  name: "decodeondraw",
  branch: "image.mem.",
  type: "bool",
};
const DISCARD_TIMEOUT_PREF = {
  name: "min_discard_timeout_ms",
  branch: "image.mem.",
  type: "int",
};

function setImagePref(pref, val) {
  var prefService = SpecialPowers.Services.prefs;
  var branch = prefService.getBranch(pref.branch);
  if (val != null) {
    switch (pref.type) {
      case "bool":
        branch.setBoolPref(pref.name, val);
        break;
      case "int":
        branch.setIntPref(pref.name, val);
        break;
      default:
        throw new Error("Unknown pref type");
    }
  } else if (branch.prefHasUserValue(pref.name)) {
    branch.clearUserPref(pref.name);
  }
}

function getImagePref(pref) {
  var prefService = SpecialPowers.Services.prefs;
  var branch = prefService.getBranch(pref.branch);
  if (branch.prefHasUserValue(pref.name)) {
    switch (pref.type) {
      case "bool":
        return branch.getBoolPref(pref.name);
      case "int":
        return branch.getIntPref(pref.name);
      default:
        throw new Error("Unknown pref type");
    }
  } else {
    return null;
  }
}

// JS implementation of imgIScriptedNotificationObserver with stubs for all of its methods.
function ImageDecoderObserverStub() {
  this.sizeAvailable = function sizeAvailable(aRequest) {};
  this.frameComplete = function frameComplete(aRequest) {};
  this.decodeComplete = function decodeComplete(aRequest) {};
  this.loadComplete = function loadComplete(aRequest) {};
  this.frameUpdate = function frameUpdate(aRequest) {};
  this.discard = function discard(aRequest) {};
  this.isAnimated = function isAnimated(aRequest) {};
  this.hasTransparency = function hasTransparency(aRequest) {};
}