[Openmcl-devel] easygui design: view size and position

Rich Sutton rich at richsutton.com
Sat Jun 7 22:33:13 UTC 2008


this is a question about the design of easygui.  i am trying to  
understand it a bit better so that can build on it effectively.

an easygui view is a CLOS object with instance variables for the size  
and position of (i believe) the view's frame.  here is the definition:

(defclass view (easy-cocoa-object)
      ((position :initarg :position :reader view-position)
       (size :initarg :size :reader view-size)
       (frame-inited-p :initform nil)))

a fourth instance variable (inherited from easy-cocoa-object) is a  
reference to the actual cocoa object for the view (the NSView).  and  
this leads to my question about the size and position instance  
variables, because the cocoa NSView also contains size and position  
information about the view's frame.  the question is: What is the  
intended relationship between the size and position variables stored  
in the CLOS object and those stored in the cocoa object?  i can  
imagine several possibilities:

1.  they are meant always to be the same, and the code should try to  
maintain the match whenever either changes.

2.  the CLOS variables are a convenience for initializing the frame of  
a view.  we try to initialize the cocoa view from them, but we don't  
rely on any relationship between them after that.

3.  we need to keep both sets of frame information distinct to handle  
some cases that are not apparent to me right now.

to me, naively, it would seem best to store the frame information only  
once, in the cocoa NSView, and to provide accessor functions for  
conveniently reading and writing it.  then the information would be  
only in one place and could not get out of synch.

please let me know if you have any insight into this.

rich



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