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waitForExplicitFinish();
var pageSource =
'<html><body>' +
'<img id="testImg" src="' + TESTROOT + 'big.png">' +
'</body></html>';
var oldDiscardingPref, oldTab, newTab;
var prefBranch = Cc["@mozilla.org/preferences-service;1"]
.getService(Ci.nsIPrefService)
.getBranch('image.mem.');
var gWaitingForDiscard = false;
var gScriptedObserver;
var gClonedRequest;
function ImageObserver(decodeCallback, discardCallback) {
this.decodeComplete = function onDecodeComplete(aRequest) {
decodeCallback();
}
this.discard = function onDiscard(request)
{
if (!gWaitingForDiscard) {
return;
}
this.synchronous = false;
discardCallback();
}
this.synchronous = true;
}
function currentRequest() {
let img = gBrowser.getBrowserForTab(newTab).contentWindow
.document.getElementById('testImg');
img.QueryInterface(Ci.nsIImageLoadingContent);
return img.getRequest(Ci.nsIImageLoadingContent.CURRENT_REQUEST);
}
function isImgDecoded() {
let request = currentRequest();
return request.imageStatus & Ci.imgIRequest.STATUS_DECODE_COMPLETE ? true : false;
}
// Ensure that the image is decoded by drawing it to a canvas.
function forceDecodeImg() {
let doc = gBrowser.getBrowserForTab(newTab).contentWindow.document;
let img = doc.getElementById('testImg');
let canvas = doc.createElement('canvas');
let ctx = canvas.getContext('2d');
ctx.drawImage(img, 0, 0);
}
function runAfterAsyncEvents(aCallback) {
function handlePostMessage(aEvent) {
if (aEvent.data == 'next') {
window.removeEventListener('message', handlePostMessage, false);
aCallback();
}
}
window.addEventListener('message', handlePostMessage, false);
// We'll receive the 'message' event after everything else that's currently in
// the event queue (which is a stronger guarantee than setTimeout, because
// setTimeout events may be coalesced). This lets us ensure that we run
// aCallback *after* any asynchronous events are delivered.
window.postMessage('next', '*');
}
function test() {
// Enable the discarding pref.
oldDiscardingPref = prefBranch.getBoolPref('discardable');
prefBranch.setBoolPref('discardable', true);
// Create and focus a new tab.
oldTab = gBrowser.selectedTab;
newTab = gBrowser.addTab('data:text/html,' + pageSource);
gBrowser.selectedTab = newTab;
// Run step2 after the tab loads.
gBrowser.getBrowserForTab(newTab)
.addEventListener("pageshow", step2);
}
function step2() {
// Create the image observer.
var observer =
new ImageObserver(() => runAfterAsyncEvents(step3), // DECODE_COMPLETE
() => runAfterAsyncEvents(step5)); // DISCARD
gScriptedObserver = Cc["@mozilla.org/image/tools;1"]
.getService(Ci.imgITools)
.createScriptedObserver(observer);
// Clone the current imgIRequest with our new observer.
var request = currentRequest();
gClonedRequest = request.clone(gScriptedObserver);
// Check that the image is decoded.
forceDecodeImg();
// The DECODE_COMPLETE notification is delivered asynchronously. ImageObserver will
// eventually call step3.
}
function step3() {
ok(isImgDecoded(), 'Image should initially be decoded.');
// Focus the old tab, then fire a memory-pressure notification. This should
// cause the decoded image in the new tab to be discarded.
gBrowser.selectedTab = oldTab;
// Allow time to process the tab change.
runAfterAsyncEvents(step4);
}
function step4() {
gWaitingForDiscard = true;
var os = Cc["@mozilla.org/observer-service;1"]
.getService(Ci.nsIObserverService);
os.notifyObservers(null, 'memory-pressure', 'heap-minimize');
// The DISCARD notification is delivered asynchronously. ImageObserver will
// eventually call step5. (Or else, sadly, the test will time out.)
}
function step5() {
ok(true, 'Image should be discarded.');
// And we're done.
gBrowser.removeTab(newTab);
prefBranch.setBoolPref('discardable', oldDiscardingPref);
gClonedRequest.cancelAndForgetObserver(0);
finish();
}
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