[cells-devel] Cello: 'find-view-under: Semantics ?

[Kenneth Tilton]

Frank Goenninger wrote:
> Hi again -
> 
> thanks again for the fast response on my last request - hoping for  
> another fast one here ;-)
> 
> So, Cello (the original one) has this function:
> 
> (defun find-ix-under (self os-pos &key (test #'true))
>    (when (and (not (typep self 'tool-tip)) ;; <g>
>            (visible self)
>            (not (collapsed self)))
>      (trc nil "find-ix-under" self os-pos (screen-box self))
>      (let ((inself (point-in-box os-pos (screen-box self))))
>        (or (when (or inself (not (clipped self)))
>              (trc nil "inside self sbox" self os-pos (screen-box self))
>              (dolistreversed (k (or (render-order self)(kids  
> self))) ;; overlap goes to last kid displayed
>                (unless (typep k 'window)
>                  (trc nil "fixunder kid!!!!!!!!" k)
>                  (bwhen (ix (find-ix-under k os-pos :test test))
>                    (return-from find-ix-under ix)))))
> 
>            (when (and inself
>                       (funcall test self)
>                       (not (ix-click-transparent self)))
>              (trc nil self os-pos (screen-box self))
>              self)))))
> 
> which is used as follows:
> 
> (defmd mouse-view-tracker ()
>    (mouse-view :initarg :mouse-view :accessor mouse-view
>      :initform (c? (let ((pos (mouse-pos .og.)))
>                      (trc nil "mouseview sees pos" .w. pos)
>                      (when pos
>                        (eko (nil "ix-togl mouseview >" self)
>                          (without-c-dependency
>                              (find-ix-under self pos)))))))
>    (:documentation "Mixin to have mouse view tracked in a subtree of  
> the window, mostly so other GUI layout can depend on
> the sub-tree layout without creating a cyclic dependency, as would  
> happen iof the whole window were watched."))
> 
> (defmd ix-togl (mouse-view-tracker #+not focuser ogl-lit-scene control  
> ogl-shared-resource-tender togl ix-view)
> ...
> 
> So, the togl widget is a sub-class of mouse-view-tracker. I understand  
> this as "show me the control that is currently being pointed at by the  
> mouse".
> 
> Only thing is: When looking at the code for 'find-ix-under I can't see  
> how this could possibly work? May I ask for a walk-through of find-ix- 
> under ?

haha, no! Please walk me thru what you do not understand. The disabled 
debug statements give you some hints: first I recursively check kids, if 
that comes up empty I check myself to see if I am under the mouse and 
want to be the result.

hth, kt

ps. Yes, it works. :) k