Re: Another highlighting questi

[bill@cambridge.apple.com (Bill St. Clair)]

At  7:44 PM 5/4/94 -0600, Rodney Daughtrey wrote:
>Subject:   Another highlighting question
>Thanks again to Bill St. Clair for answering my first question.
>
>Now another: I'm trying to add highlighting/selection behavior to some views
>which inherit from ccl:view.  I've gotten the code to work when the highlighting
>color is black (using ccl:invert-rect, etc), but I'm having problems with other
>colors where you don't want to invert the (usually black) text.  I've written a
>simple mixin (see below) for the highlighting colors other than black that
>works, but it has the disadvantage of having to redraw the view each time the
>view is selected/deselected.  In the simple example below the redraw is hardly
>noticeable, but for more complex views it flickers.  What I'd really like is a
>version which, when a view is selected/deselected, draws/undraws the colored
>selection rectangle over the view without disturbing the foreground pixels of
>the text or graphics.  I've tried using the :pator pen pattern in conjunction w/
>ccl:paint-rect, etc, but could not get this to work.  Also, using dialog items
>and their colorable parts aren't applicable for our needs.
>
>The example below illustrates the behavior I'm after, minus the need to
>redisplay each time.  Does anyone have any suggestions/code that implements something
>like this?  Are there Macintosh traps that implement some/all of this for me?

MCL's inspector does what you want, and you've got source to look at.
Basically, you keep a highlight region and use #_InvertRgn along with
a magical low-memory global to use the highlight color. Here is the relevant
code from "ccl:library;inspector;inspector-window.lisp". I didn't include
source for highlight-selection as its details would obscure my point.
(Basically, it computes what the highlighted region should be,
stores it with (setf (highlight-region inspector-view) rgn), then calls
%invert-region).

----------------------------------------------------------------------------

(in-package :inspector)

(defun unhighlight-selection (inspector-view)
  (let ((rgn (highlight-region inspector-view)))
    (when (and (handlep rgn) (not (#_EmptyRgn :ptr rgn :boolean)))
      (with-focused-view inspector-view
        (%invert-region rgn)
        (#_SetEmptyRgn :ptr rgn)))))

; Invert a region using the highlight color (see Inside Mac V-62).
(defun %invert-region (rgn)
  (with-macptrs ((hiliteMode (%int-to-ptr #$HiliteMode)))
    (%put-byte hiliteMode
               (logand (lognot (ash 1 #$hiliteBit)) (%get-byte hiliteMode))))
  (#_InvertRgn :ptr rgn))