[Date Prev][Date Next][Thread Prev][Thread Next][Thread Index]

Re: [XaraXtreme-dev] Feather slider problem

Phil Martin wrote:
The trouble is caused by wxWidgets trying to be helpful and back-compatible - any message it doesn't understand gets turned into a SLIDER_UPDATED but it adds no extra information to distinguish between these "fake" events and real SLIDER_UPDATED events.

Of course, we supplied the patch to make sliders send THUMB_RELEASE events so it's probably only us who use them and worry about the details of message order surrounding them. So this new patch shouldn't adversely affect anyone else.

Actually I think what wxWidgets is doing is right. It's sending the
back compatibility message, and we are trying to hang off a combination
of the scroll messages and the back compatibility update message, which
is wrong.

I have now fixed the slider message order by ONLY hanging off the
wxEVT_SCROLL messages. I think this fixes the symptom - could you
check, Phil? Essentially I am relying on the fact that
wxEVT_SCROLL_CHANGED is always last (and is generated on thumb
release too), and I am translating any of the mechanisms of
change (including keyboard shortcuts) into a /prior/ update

However, I remain concerned that we are only fixing the symptom
here. What seems to upset feathering is the following
message sequence being sent to it:
1. DIM_SLIDER_SET (from the end of a drag)
2. DIM_SLIDER_UPDATE (spurious)
3. Change of selection before another DIM_SLIDER_SET
4. (possibly) another DIM_SLIDER_UPDATE

Now this can in theory happen ANYWAY if someone manages to
change the selection between the deferred messages being

Isn't the /real/ fix here that a selection change should cancel
any "real-time" feather that hasn't yet made it into the undo
record? Or failing cancelling it, apply it?

Whilst I /think/ it's working now, it seems to be pretty brittle.