Detect pinch to zoom when 'user-scalable' is set to yes

Question

How can I detect the scale (or distance pinched) of the pinch to zoom when the meta name="viewport" is set to user-scalable=yes?

I've tested on Android but the pinch to zoom can't be detected if the meta name="viewport" is set to user-scalable=yes. If the meta name="viewport" is set to user-scalable=no then the pinch to zoom can be detected but then I'm not able to zoom in on the document.

Here are my tests on jsFiddle:

Hammer.js: http://jsfiddle.net/pE42S/

var pziW = "test";
var viewport_width = $(window).innerWidth();
var zoom = 0;

var hammer = new Hammer(document.getElementById("touchme"));

hammer.ontransformstart = function(ev) {
    console.log("ontransformstart");
    console.log(ev);
    //pziW = $(window).innerWidth() / 2 * ev.scale;
    zoom = ev.scale;
    var msg = "ontransformstart " + pziW + " scale " + zoom;
    log(msg);
};
hammer.ontransform = function(ev) {
    console.log("ontransform");
    console.log(ev);
    zoom -= ev.scale;
    viewport_width+=viewport_width*zoom;
    zoom = ev.scale;
    pziW=viewport_width;
    //pziW = $(window).innerWidth() / 2 * ev.scale;
    jqUpdateSize();
    var msg = "ontransform " + pziW + " scale " + zoom;
    log(msg);
};
hammer.ontransformend = function(ev) {
    console.log("ontransformend");
    console.log(ev);
    var msg = "ontransformend " + pziW + " scale " + zoom;
    log(msg);
};

TouchSwipe: http://jsfiddle.net/pE42S/1/

$(function() {      
    $("#touchme").swipe( {
        pinchStatus:function(event, phase, direction, distance , duration , fingerCount, pinchZoom) {
            console.log("pinchStatus");
            console.log(event);
            pziW=viewport_width - distance;
            $("#log").text(pziW);
            jqUpdateSize();
        },
        fingers:2,  
        pinchThreshold:0  
    });
});

Somebody has an answer?

Have you looked at the jQuery plugin Touchy? [touchyjs.org](http://touchyjs.org/) — Cholesterol, Jan 09 '14 at 21:25
images doesn't work in jsfiddle. I can't check how it works right now. You mean native zoom doesn't work or 'pinch' zoom ? — fearis, Apr 10 '14 at 00:49
I would refer to the answer to this StackOverflow question: http://stackoverflow.com/questions/11183174/simplest-way-to-detect-a-pinch. — óscar gutiérrez jr., May 16 '14 at 18:47
why this is not working for you : http://labs.rampinteractive.co.uk/touchSwipe/demos/Pinch_and_Swipe.html — flakerimi, May 28 '14 at 15:28

score 0 · Answer 1 · edited May 23 '17 at 12:10

0

One way to achieve this would be with a generic touchstart handler:

Wait until the user starts touching at least two points ( event.touches.length > 1)
Note the x & y start coordinates for both touches, attach touchend listeners
Wait until the touches end.
Remove touchend listeners & measure distance.

Even easier would be using gesture events and the event.scale property, see the great answers at Simplest way to detect a pinch for more details.

edited May 23 '17 at 12:10

Community

1
1

answered Jun 22 '14 at 10:43

Bruno

579
6
15

Hey, you have explained the logic very well. But I wonder why we didn't use it, wouldn't we get results if we use ScreenX / Y coordinates instead of PageX / Y? – BOZ Apr 03 '19 at 17:54

score 0 · Answer 2 · answered Jan 25 '19 at 09:44

0

Now you can use Visual Viewport API for this (not for all browsers). Just check window.visualViewport.scale > 1.

answered Jan 25 '19 at 09:44

Grigory

13
3

Detect pinch to zoom when 'user-scalable' is set to yes

2 Answers2