dispose should clear activeInstance

[codepunkt]

If it doesn't (current state), the last instance is always leaked even after disposed and removed.

[asturur]

You mean something like this?

    /**
     * Clears a canvas element and removes all event listeners
     * @return {fabric.Canvas} thisArg
     * @chainable
     */
    dispose: function () {
      this.clear();
      this.interactive && this.removeListeners();
      if (fabric.Canvas.activeInstance === this) {
        fabric.Canvas.activeInstance = null;
      }
      return this;
    },

[codepunkt]

Exactly.

[asturur]

i do not really know the use of tha activeInstance property. track the canvas variable and clean it? and in case of multiple canvases?

[kangax]

I agree that we should be clearing it

[asturur]

this is a fast pr.

[asturur]

proposed this in a PR in dispose method:

+      var klass = fabric[fabric.util.string.capitalize(this.type)];
+      if (klass.activeInstance === this) {
+        klass.activeInstance = null;
+      }

[kangax]

@gonsfx out of curiosity, how are you using activeInstance and would you be OK if we removed it entirely (as it seems to belong on an application level)?

[codepunkt]

@kangax I'm not using it at all, just found out that it can lead to leaks.

[asturur]

on #2708 we are deleting it.