Re: [whatwg] window.print() when printing is not supported

[Markus Ernst]

Michael A. Puls II schrieb:
On Mon, 28 Dec 2009 14:39:06 -0500, Michael A. Puls II 
<shadow2...@gmail.com> wrote:

On Mon, 28 Dec 2009 12:08:48 -0500, Boris Zbarsky <bzbar...@mit.edu> 
wrote:

On 12/28/09 9:54 AM, Michael A. Puls II wrote:
As for window.print(), what if it returns false if printing is not
supported?

It might be better as |true| (crappy API issues aside), because 
otherwise if a page writes |if (window.print())| it'll get false in 
all existing browsers, no?

Ah, I see. Good point.

Since making print() return something isn't going to help with older UAs 
and returning true would feel backwards, instead of:

if (window.print()) {
    alert("Printing is not supported");
}

, we could do this:

if (typeof navigator.printingEnabled === "function" && 
!navigator.printingEnabled()) {
    alert("Printing is not supported");
} else {
    window.print();
}

It's more verbose though and I'm not sure any will like it. But, tossing 
it out there.


What about:

if (!window.print) {
    alert("Printing is not supported"); [1]
} else {
    window.print();
}

This is possible if - one of Ollis initial proposals - browsers which 
don't support window.print() do not have the print method at all. That 
is backwards compatible, as legacy Handheld, TV and whatever UAs, that 
may have a however-working print method, just behave the same way they 
always did.

[1] I'd actually prefer something like:
body.onload = function() {
    if (window.print) {
        // Code that creates the print button
        // and adds it to the appropriate parent element
    }
}