Timing issue of Button.Enabled property

einhugur

If I assign value to Button.Enabled property and then read it back right away after it then it will not read back the new state.

btnDecrypt.Enabled = mSelectedFile <> Nothing And tbName.Text.Length > 1

Var fm As MenuItem = Self.MenuBar.FindItemByTag("decrypt")

If fm <> Nothing Then
  fm.Enabled = btnDecrypt.Enabled     # Here we will not be reading the new state of the btnDecrypt.Enabled
End If

So in the code above then it will take 2 rounds to get the menu enabled. (which by that time might be wrong state)

The code bellow works since it does not read back the btnDecrypt.Enabled property.

btnDecrypt.Enabled = mSelectedFile <> Nothing And tbName.Text.Length > 1

Var fm As MenuItem = Self.MenuBar.FindItemByTag("decrypt")

If fm <> Nothing Then
  fm.Enabled = mSelectedFile <> Nothing And tbName.Text.Length > 1
End If

rgb

einhugur

Hi,
Confirmed,
Made simple example for Garry

bugbutton.objo

2kB

Garry

Yes, this is a bug. Reading Enabled immediately after assigning it should return the new value.

I’ve traced the cause: the assignment queues an update to the control, but the following read can happen before that update is applied. That explains both the menu behaviour and the title showing the previous state in the example project.

I’ve logged the bug. Thanks for the report and the sample project.

For now, your workaround is valid. You can also calculate the condition once, store it in a Boolean, and assign that value to both the button and menu item.

Garry

This has been fixed in the next release.