Showing content only to Tumblr blog owner/admin

Question

Is there a way to determine whether the current user is the admin of the blog? Something like

{Block:Owner}
    This is your blog. Click here to update the theme settings.
{/Block:Owner}

Even something via javascript/API would be helpful. I couldn't find anything in the theme documentation

Answer 1

I found a way, but it's not completely reliable and it depends on the language and possibly the OS.

The Tumblr controls bar's size varies in the 3 possible situations:

261x36 not logged in (this depends on the blog's name)

190x26 logged in, admin

179x26 logged in, but no admin

So we can sort of figure out if the user is logged in with this code:

//true: the current user is an admin
//false: the current user is not an admin
//'ask-later': the bar is not ready yet
//'dont-know': the bar is not there 
function isAdmin (tolerance) {
    // source: http://stackoverflow.com/a/27506229/288906

    //these values are expected for English blogs
    var EXPECTED_WIDTH = 190;
    var EXPECTED_HEIGHT = 26;

    tolerance = tolerance || 10;
    var controls = document.getElementById('tumblr_controls');
    if(!controls) {
        //the bar is not there
        return 'dont-know';
    }
    if(controls.width === '1') {
        //the bar is not ready, try later
        return 'ask-later';
    }
    var differenceW = Math.abs(controls.width - EXPECTED_WIDTH)
    var differenceH = Math.abs(controls.height - EXPECTED_HEIGHT);
    return differenceW + differenceH < tolerance;
}

With tolerance we can specify a range of values that can still be considered acceptable, so 195x28 can still work. This code doesn't work on password-protected blogs since they don't show that bar.

This could be improved further by making it async with promises, so you can avoid that "not yet ready" state.