Text: expand certain characters during editing, but still treat as single chars?
Text: expand certain characters during editing, but still treat as single chars?
- Subject: Text: expand certain characters during editing, but still treat as single chars?
- From: Andrew Abernathy <email@hidden>
- Date: Fri, 11 Jul 2003 23:16:59 -0700
I wish to have a text view where certain individual characters in the text
storage get expanded to longer text for display/editing, but are stored and
manipulated (for the most part, anyway) as single characters.
I'm currently targeting 10.1, but if there is a good solution that requires
10.2 I would like to be aware of that as well.
For more detail on my exact situation, to give some context (and so people
can tell me if I'm barking up a completely wrong tree):
I have the situation where the user can insert a variable in a text view and
meaningful placeholder text will be displayed, highlighted to indicate that
it is a variable. While editing, I want the variable to be treated as a single
character - if the user backspaces over the end of the variable, it should
delete the entire variable; if they select into the variable text the entire
variable text should be selected; etc. At print time the placeholder text
is replaced with the "real" value of the variable (page number, print time,
etc).
My approach has been to store a variable as some placeholder text in the text
storage, so it looks meaningful to the user, with a custom attribute indicating
that it is a variable (and which variable it was), and to use a text delegate
to manage the special behavior. That worked mostly; I had to subclass the
text view to get nice text selection (the delegate method only gets called
at mouse up, so the user could select part-way through the variable placeholder
text, and the selection highlight wouldn't snap to engulf the entire variable
until mouse up).
But I'm left with one problem: you can't have multiple instances of the same
variable side-by-side. For instance, you can't insert the "page number" variable
twice in a row with no separating space. Well, you can, but there's now no
way to tell that they are intended to be two instances of the same variable
- since the attribute name is the same and the attribute value is the same,
the two ranges get unioned in the attributed string (normally a good thing)
and it now gets treated as a single variable instance.
I thought I could get around this by having my variable marker in the text
storage always be a single character, so if I get a text range marked with
the variable attribute, I simply repeat the variable by the length of the
effective range of the attribute. But I don't know how to go about handling
this in the text system during editing - I need the placeholder text to be
displayed for each character in the effective range, and I need to know the
boundaries between the placeholder text to manage the user selection, etc.
Thoughts?
-andrew
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