why don't I get mouse events with brush tool?

[Tiemo Hollmann TB]

Hello,

some days ago Björnke taught me that it’s not a bug but a feature that I
can’t pick the mousecolor while having the brush tool activated.

Now I am experiencing, that I also don’t get even a mouseDown or mouseUp
with the brush tool. The dictionary doesn’t says anything about this
behavior. What I want to do is:

The user can paint with the brush tool on an image. To supply the user an
undo with several states, I wanted to make a backup of the image each time
at mouseDown, so that the user can roll back every newly painted state.

I tried to choose the brush tool with mouseEnter and make the backup with
mouseDown (I don’t get the mouseDown event).

I tried to make the backup with mouseDown and choose brush tool afterwards
(works only once until the brush tool is choosen in the first mouseDown)

I tried to switch back to the browse tool with every mouseUp to make the
backup with next mouseDown (I don’t get the mouseUp event, when having
selected the brush tool)

Probably I am again too narrow minded and looking into the wrong direction,
can anybody point me into another direction, how I can realize my undo
function?

Thanks

Tiemo