Memory leaks - nullifying DOM elements with event handlers attached is not sufficient

[Jemt]

Fit.UI relies on the browser's Garbage Collector to reclaim memory - we do that by nullifying all variables within a control. But to my surprise this does not guarantee that the browser cleans up event handlers registered on DOM elements. Chrome reports these handlers as detached:

Clicking the highlighted link takes us to:

Fit.UI/Controls/Input/Input.js

Line 111 in 55e08fe

input.onchange = function() // OnKeyUp does not catch changes by mouse (e.g. paste or moving selected text)

Other event handlers within Fit.Controls.Input has also been marked as the cause of retained references.

We need to find all event handlers and make sure they are removed when Dispose() is called.
It works - it has been tested with the following event handlers in the Input control: input.onkeyup, input.onchange, and "paste" on me.GetDomElement().

Search for (regex): [a-zA-Z0-9].on.+ =
Search for: Fit.Events.AddHandler(
Search for: addEventListener(
Search for: attachEvent(

Perform not only these searches in Fit.UI but also all projects built on Fit.UI.
With every single match we must ensure registered event handlers are removed when a component is disposed.

Also see #155 and #172

[FlowIT-JIT]

These lines keep a reference to controls even when disposed, which should be avoided, even though they are internally destroyed. Consider using a string reference instead such as me.GetId().

Fit.UI/Controls/ContextMenu/ContextMenu.js

Line 654 in 1fb4682

Fit._internal.ContextMenu.Current = me;

Fit.UI/Controls/Input/Input.js

Line 2770 in 1fb4682

emojiPanel._associatedFitUiControl = me;

Fit.UI/Controls/Input/Input.js

Line 3162 in 1fb4682

Fit._internal.Controls.Input.ActiveEditorForDialog = me; // Editor instance is needed when OnHide event is fired for dialog on global CKEditor instance