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Re: Working with pointers
- To: email@example.com (Jeffrey B Kane)
- Subject: Re: Working with pointers
- From: firstname.lastname@example.org (Bill St. Clair)
- Date: Fri, 13 Nov 1992 11:41:25 -0600
- Cc: info-mcl
>I've been playing around all morning, trying to get some resources to work properly.
>I need a pointer to an icon (for an icon-dialog-item) so I used the resource package
>to get a handle, but when I try to use the pointer, all sorts of problems occur.
>(with-open-resource-file (*my-rsrcs* "Application.rsrc")
> (defparameter *icon-hndl-1* (get-resource "ICON" "Telephone"))
> (defparameter *icon-hndl-2* (get-resource "ICON" "Honda")))
Here's your first problem. WITH-OPEN-RESOURCE closes the resource
file when it exits. This will deallocate (e.g. #_DisposeHandle) any
resources that belong to that file. If you want to close the
file and keep the resources, you'll have to call DETACH-RESOURCE on them:
(with-open-resource-file (*my-rsrcs* "Application.rsrc")
(detach-resource (setq *icon-hndl-1* (get-resource "ICON" "Telephone")))
(detach-resource (setq *icon-hndl-2* (get-resource "ICON" "Honda"))))
> I next try to get a pointer to use by:
> (#_MoveHHi *icon-hndl-1*)
> (#_HLock *icon-hndl-1*)
> (defparameter *my-icon-ptr* (%hget-ptr *icon-hndl-1*)))
Two problems here. First off, you should say (%get-ptr *icon-hndl-1*),
not (%hget-ptr *icon-hndl-1*), to get the pointer from a handle. %hget-ptr
does a double indirection, %get-ptr does a single indirection.
>I should now have a locked, dereferenced pointer, but when I use it to define
>and icon-dialog-item I get into trouble:
>(setf my-window (make-instance 'ccl::scrolling-window :color-p t))
>(add-subviews my-window (make-instance 'icon-dialog-item
> :icon *my-icon-ptr*
> :view-position #@(50 0)))
>Inspecting *my-icon-ptr* shows it to be:
> #<A Mac Handle, Unlocked, Size 40 #x263364>
>as it should be.
As you may have noticed, ICON-DIALOG-ITEM's VIEW-DRAW-CONTENTS method
calls PLOT-ICON to actually do the work. PLOT-ICON's documentation says:
;; a function for displaying icons. It can be passed a pointer or a number
;; if passed a pointer, it assumes this is a pointer to an icon record.
;; if passed a number, it assumes this is the resource id of an icon.
;; Draws to the current grafport, so call it inside WITH-FOCUSED-VIEW.
Unfortunately, this is not quite right. Instead of "an icon record" it should
say "an icon handle", which is what the #_PlotIcon & #_PlotCIcon traps expect.
Here's a working example:
; DEF-LOAD-POINTERS so that we can compile the file and SAVE-APPLICATION
; and the resources will be loaded when the application starts up.
; (Actually, if you want to save an application, you usually put the
; icons in the application's own resource fork so that the
; WITH-OPEN-RESOURCE-FILE and DETACH-RESOURCE are unnecessary [an
; application's resource fork is always open while it is running].)
(def-load-pointers initialize-icons ()
(with-open-resource-file (refnum "Application.rsrc")
(detach-resource (setq *icon-1* (get-resource "ICON" "Loudspeaker")))))
(setf my-window (make-instance 'window :color-p t))
(add-subviews my-window (make-instance 'icon-dialog-item
:view-position #@(50 0)))