[Gimp-developer] IWarp as a tool

[Bill Skaggs]

On Fri, Feb 15, 2008 at 2:57 AM, Tor Lillqvist <tml at iki.fi> wrote:
> Unfortunately now that I have had time to think a bit harder, I
>  understand that there is a fundamental difference in how my
>  initial effort to implement a warp tool works compared to how
>  the IWarp filter does.

Do you really need to do it exactly the way the filter does it?
>From your description, I don't really understand why your
current approach is less valid, or even why it will produce a
significantly different result.  (The filter needs to do it that
way because it doesn't act on the image until the user has
finished working with the preview, but that logic doesn't
apply to your tool.)

>  Can a GimpWarpTool object know when some other tool or
>  filter is being used on the drawable, and thus the warping
>  data for that drawable should be discarded?

Yes, many tools face this problem, and the system is set up
so that tools are automatically halted if a drawable is dirtied
while a tool is active.  (More precisely, while tool_control
is active.)  Even tools themselves must take measures to
keep from being halted when they make changes to the
image:  they do this by calling gimp_tool_control_set_preserve()
before making a change.

  -- Bill