Gecko:Printing API

Scope

Purpose of this document is to define a set of standards and API's to give web developers more control over printing output.

Example

window.startPrintJob(function (state) {
	var canvas = document.createElement("canvas");
	var ctx = canvas.getContext("2d");
	if (!state.isPreview) {
		canvas.width *= 5;
		canvas.height *= 5;
		ctx.scale(5, 5);
	}
	switch (state.currentPage) {
		case 1:
			ctx.drawText(0, 0, state.title);
			break;
		case 2:
		case 3:
			ctx.drawText(0, 0, "Page " + state.currentPage + " of " + state.totalPages);
			break;
		default:
			return Promise.reject(Error("Invalid page number"));
	}
	return Promise.resolve(canvas);
}, 3, "Printing Example")
.then(function () {
	console.log('Printing done');
}, function () {
	console.error('Printing failed');
});

IDL addition

interface PrintPageHandler {
	Promise getPageElement(PrintState state);
}

interface PrintState {
	readonly attribute double totalPages;
	readonly attribute DOMString title;
	readonly attribute double currentPage;
	readonly boolean isPreview: Boolean;
}

dictionary PrintOptions {
	double totalPages	= 1;
	DOMString title 	= "";
	...
};

interface Printing {
  Promise startPrintJob(PrintPageHandler handler,
  			optional (unrestricted double or PrintOptions) options);
};

Window implements Printing;

Bugs

• https://bugzilla.mozilla.org/show_bug.cgi?id=1209273
• https://bugzilla.mozilla.org/show_bug.cgi?id=132035