Hi Andrew,

This is one I bumped heads with a while back.

I tried things along the line you suggested and tied
myself in knots.

So I started with what I knew worked. Handles on
polygons and looked at what they used.

The #on:send: message is the best way I have found to
add behavior to morphs.

define a method in your inheritance chain (e.g.)

Morph>>initializeMyMove

self on: #mouseMove send: #moveThisWay to: self
   ; on: #mouseUp   send: #stopThat    to: self .

Then make methods 
  #moveThisWay and 
  #stopThat in your specific subclass to do what you
want.


Then make a sample of your morph and send it the
initializeMyMove message.

where circle understands what you mean by #moveThisWay
and #stopThat.

I found by experimenting that circle would not listen
to mouse move unless it was also listening to #mouseUp
or #mouseDown.

I also found I absolutely didn't need to write my own
low level stuff for the morphs.


-----
To stop the rectangle from moving you need to make it
"resist being picked up" from the red halo or tell it
to #beSticky programatically.

I also agree that if you can get away with using a
pasteup morph instead of the rectange thats a win. A
tip of the hat to Andreas who said it first.

-----

There are also tricks for making the gui feel
smoother. For my application I update my morphs
position from the 
delta of the mouse move

desiredPosition := oldPosition + mouseMoveEnd -
mouseMoveStart + tug.

Where tug was a vector based on the signs of the
coordinates of (mousePosition - oldPosition).

finally you apply constraints to desiredPosition (e.g.
constrain to be within the owners bounds and what
results is the newPosition to which you move your
morph.

On mouse up I wanted to insure my morph wound up on a
grid intersection. So the final behavior was
essentially snap to grid.

Again for ideas look at the behavior of handles.


HTH, 

Yours in service, --Jerome Peace








__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com