Tooltip's need revised for GC

[dlamkins]

There is an issue with Tooltips that prevents them from being properly collected. Some initial investigation is discussed here:
https://discord.com/channels/531175899588984842/599270434642460753/1208556624902492250

[ynzenu]

The problem is indeed the _allTooltips property on the Tooltip class. The solution could be as simple as removing the tooltip from the collection when it's disposed.

This is the solution I came up with for the Mystic Crafting module:

public class DisposableTooltip : Tooltip
   {
       public DisposableTooltip(ITooltipView tooltipView) : base(tooltipView) { }

       private void RemoveFromCollection()
       {
           var type = typeof(Tooltip);
           var field = type.GetField("_allTooltips", BindingFlags.NonPublic | BindingFlags.Static);

           if (field == null)
               return;

           var tooltips = (ControlCollection<Tooltip>)field.GetValue(null);

           if (tooltips == null)
               return;

           tooltips.Remove(this);
       }

       protected override void DisposeControl()
       {
           RemoveFromCollection();

           base.DisposeControl();
       }
   }

[ynzenu]

@dlamkins I'm happy to help with this issue, but I'm not entirely sure how to solve the problem below.

Firstly, there are 3 issues I've found

• Tooltip cannot be collected by GC because of static reference
• Tooltip is not disposed
• Menu is not disposed

Menu and Tooltip are not disposed, because they are not called in the Dispose method of Control.cs. They are also not children of a container (parent = null).

Is it safe to dispose the Tooltip and Menu when a control is disposed? The same Tooltip object could be assigned to multiple controls. For example:

var tooltip = new Tooltip()
var imageControl = new Image();
var labelControl = new Label();

imageControl.Tooltip = tooltip;
labelControl.Tooltip = tooltip;

imageControl.Dispose() //Tooltip should not be disposed because it's used multiple times?

The Tooltip.DisposeControl function also executes CurrentView?.DoUnload() while the view might be used elsewhere. I'm not sure what would be a good solution in this case.

Let me know what you think, but if the above is not an issue, then I can implement the following solution:

• Remove tooltip static reference when disposed.
• Dispose Tooltip and Menu when Control is disposed.

[ynzenu]

Something else to note, is that tooltips are seemingly disposed when using the BasicTooltipView thanks an event initialized during build:

protected override void Build(Container buildPanel) {
        _tooltipLabel.Parent = buildPanel;

        buildPanel.Hidden += (sender, args) => buildPanel.Dispose();
}

I think we should change this as well.