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// screenshot.js: system screenshot module
//
// This system module takes a screenshot of the currently running app
// or homescreen and stores it with DeviceStorage when the user
// presses the home and sleep buttons at the same time. It communicates
// with gecko code running in b2g/chrome/content/shell.js using a private
// event-based API. It is the gecko code that creates the screenshot.
//
// This script must be used with the defer attribute.
//
//
(function() {
window.addEventListener('home+sleep', takeScreenshot);
// Assume that the maximum screenshot size is 4 bytes per pixel
// plus a bit extra. In practice, with compression, our PNG files will be
// much smaller than this.
var MAX_SCREENSHOT_SIZE = window.innerWidth * window.innerHeight * 4 + 4096;
function takeScreenshot() {
// Give feedback that the screenshot request was received
navigator.vibrate(100);
// We don't need device storage here, but check to see that
// it is available before sending the screenshot request to chrome.
// If device storage is available, the callback will be called.
// Otherwise, an error message notification will be displayed.
getDeviceStorage(function() {
// Let chrome know we'd like a screenshot.
// This is a completely non-standard undocumented API
// for communicating with our chrome code.
var screenshotProps = {
detail: {
type: 'take-screenshot'
}
};
window.dispatchEvent(new CustomEvent('mozContentEvent', screenshotProps));
});
}
// Display a screenshot success or failure notification.
// Localize the first argument, and localize the third if the second is null
function notify(titleid, body, bodyid) {
var title = navigator.mozL10n.get(titleid) || titleid;
body = body || navigator.mozL10n.get(bodyid);
navigator.mozNotification.createNotification(title, body).show();
}
// Get a DeviceStorage object and pass it to the callback.
// Or, if device storage is not available, display a notification.
function getDeviceStorage(callback) {
var storage = navigator.getDeviceStorage('pictures');
var availreq = storage.available();
availreq.onsuccess = function() {
var state = availreq.result;
if (state === 'unavailable') {
notify('screenshotFailed', null, 'screenshotNoSDCard');
}
else if (state === 'shared') {
notify('screenshotFailed', null, 'screenshotSDCardInUse');
}
else if (state === 'available') {
var freereq = storage.freeSpace();
freereq.onsuccess = function() {
if (freereq.result < MAX_SCREENSHOT_SIZE) {
notify('screenshotFailed', null, 'screenshotSDCardLow');
}
else {
callback(storage);
}
};
freereq.onerror = function() {
notify('screenshotFailed', freereq.error && freereq.error.name);
};
}
}
availreq.onerror = function() {
notify('screenshotFailed', availreq.error && availreq.error.name);
}
}
// Handle the event we get from chrome with the screenshot
window.addEventListener('mozChromeEvent', function ss_onMozChromeEvent(e) {
try {
if (e.detail.type === 'take-screenshot-success') {
getDeviceStorage(function(storage) {
var filename = 'screenshots/' +
new Date().toISOString().slice(0, -5).replace(/[:T]/g, '-') +
'.png';
var saveRequest = storage.addNamed(e.detail.file, filename);
saveRequest.onsuccess = function ss_onsuccess() {
// Vibrate again when the screenshot is saved
navigator.vibrate(100);
// Display filename in a notification
notify('screenshotSaved', filename);
};
saveRequest.onerror = function ss_onerror() {
notify('screenshotFailed', saveRequest.error.name);
};
});
}
else if (e.detail.type === 'take-screenshot-error') {
notify('screenshotFailed', e.detail.error);
}
}
catch (e) {
console.log('exception in screenshot handler', e);
notify('screenshotFailed', e.toString());
}
});
}());
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