pinch to zoom gesture is broken - due to Skew changes

[mobidev111]

The pinch to zoom gesture is broken in current master.

Root cause: canvas_gestures.mixin.js has not been updated to changes introduced with the Skew changes

The Skew changes in #2482 introduced a new parameter "dim" to the _setObjectScale() method: cda0611#diff-9dc132ed9a0787568f773999ba577e2bR637

canvas_gestures.mixin.js has not been updated to reflect this change: https://github.com/kangax/fabric.js/blob/4a6001e3561de546c24b6f8cc4b61db990c43367/src/mixins/canvas_gestures.mixin.js#L140

     this._setObjectScale(new fabric.Point(t.scaleX * s * dim.x, t.scaleY * s * dim.y),
        t, lockScalingX, lockScalingY, null, target.get('lockScalingFlip'));

The lacking parameter causes an exception during calculation.

Just adding the missing parameter unfortunately does not resolve the gesture issue - please investigate.

[asturur]

When you add parameter, do you have still calculation error?
I have no gesture device, so i cannot test properly.

starting on https://github.com/kangax/fabric.js/blob/4a6001e3561de546c24b6f8cc4b61db990c43367/src/mixins/canvas_gestures.mixin.js#L136

If you have time to spare:

var constraintPosition = target.translateToOriginPoint(target.getCenterPoint(), t.originX, t.originY),
-        dim = target._getNonTransformedDimensions();
+        dim = target._getTransformedDimensions();

-      this._setObjectScale(new fabric.Point(t.scaleX * s * dim.x, t.scaleY * s * dim.y),
-        t, lockScalingX, lockScalingY, null, target.get('lockScalingFlip'));
+      this._setObjectScale(new fabric.Point(dim.x * s, dim.y * s),
+        t, lockScalingX, lockScalingY, null, target.get('lockScalingFlip'), dim);

and if you want to try it on a skewed object to see if it feels ok.

[kangax]

ping @mobidev111

[kangax]

Actually I see @mobidev111 said that "Just adding the missing parameter unfortunately does not resolve the gesture issue" so we'll need to check more

[mobidev111]

@asturur regarding touch devices:

a) cheap hardware - the easiest way would be e.g. a cheap android tablet with current android version.
This enables you to do nice remote debugging - you inspect the DOM of the device from your development machine:
https://developer.chrome.com/devtools/docs/remote-debugging

b) simulate multi-touch - you can simulate touch devices in the Chrome browser.
https://developer.chrome.com/devtools/docs/device-mode#touch-emulation
https://frontify.com/blog/how-to-emulate-touch-events-in-chrome/