When to use fyne.Do

[nagylzs]

I just checked the 2.6 alpha, and fyne.Container no longer has a lock. How does this work then? What code must go into fyne.Do, and what code can be used outside of fyne.Do?

Documetation from the current 2.6 alpha

// Do is used to execute a specified function in the main Fyne runtime context without waiting.
// This is required when a background process wishes to adjust graphical elements of a running app.
// Developers should use this only from within goroutines they have created and when the result does not have to
// be waited for.

Some examples for code that is called from goroutine:

• Do I need to set the color of a canvas.Rectangle inside fyne.Do , before it has been returned by Objects()? and after it has been returned by Objects() at least once?
• Do I need to call Refresh() in fyne.Do ? I'm not sure if it counts as "adjusting an element" or not? (Probably it is not altering its state?)
• If I change a CanvasObject from a fyne.Do call, and I change it again from another fyne.Do call, then is it guaranteed that they will be executed in the same order?

Thanks

[dweymouth]

You should use fyne.Do or fyne.DoAndWait whenever you are invoking any Fyne APIs other than ones specifically marked as excluded (currently only data binding) from a goroutine that your code created. This includes calling Refresh() as well as setting properties on widgets, CanvasObjects, etc.

All callbacks from Fyne to your own code are now guaranteed to occur on the "app goroutine" - ie main - so it is never needed to use fyne.Do[AndWait] in your Fyne event handlers/ callbacks.

All functions passed to fyne.Do[AndWait] are executed sequentially in the order received.

[nagylzs]

Thank you!

[nagylzs]

@dweymouth can you please confirm that WidgetRenderer methods will be called from the "app goroutine", and there is no need to use fyne.Do and DoWait inside methods that are within renderer methods (Layout, Refresh, MinSize etc.)?

[Jacalz]

Nothing will be called from a goroutine unless you create one yourself. I.e. no need to use fyne.Do[AndWait] in any sort of callback.