I'm subclassing NSATSTypesetter to add custom line wrapping behavior which
indents wrapped lines relative to the starting line's indentation (like Xcode).
To do this, I'm overriding -
getLineFragmentRect:usedRect:remainingRect:forStartingGlyphAtIndex:... and for
wrapped lines am modifying the proposed rect's x origin to add indentation
before passing the parameters up to super to let it handle the rest of the
fragment generation.
Questions:
1) When I dump rich text into the text view, this method is called *twice* for
each starting glyph index, and the proposed rect for the second call is the
proposed rect I modify during the first call. For plain text it's only called
once for each line. Any explanations for what's going on?
2) Is simply modifying the proposed rect's origin the right approach?
a) Does the proposed rect ever include lineFragmentPadding
b) Is the proposed rect always a bazillion points wide?
Basically, I'm wondering if I need to add to the x value, or if I should simply
set it to the indentation I want.
proposedRect.origin.x += indent; Versus proposedRect.origin.x =
indent;
I've already noticed a problem with the former when pasting in rich text since
for a single line, getLineFragmentRect: is called with the normal proposedRect,
I add to it, then it gets calls again with the proposed I passed to super, and
I add to it again which of course is wrong (and also leads to some very strange
and broken layout). So it appears I must simply *set* the x value, but I don't
know if I need to take lineFragment padding and the width into account.
3) Is it always going to be safe to ask the layout manage
locationForGlyphAtIndex: for a glyph index < startingGlyphIndex or is there any
possibility of an infinite loop?
Here's a simple implementation I'm starting with:
- (void)getLineFragmentRect:(NSRectPointer)lineFragmentRect
usedRect:(NSRectPointer)lineFragmentUsedRect
remainingRect:(NSRectPointer)remainingRect
forStartingGlyphAtIndex:(NSUInteger)startingGlyphIndex
proposedRect:(NSRect)proposedRect lineSpacing:(CGFloat)lineSpacing
paragraphSpacingBefore:(CGFloat)paragraphSpacingBefore
paragraphSpacingAfter:(CGFloat)paragraphSpacingAfter
{
NSString * string = self.layoutManager.textStorage.string;
NSUInteger stringLength = string.length;
NSUInteger characterIndex = [self.layoutManager
characterIndexForGlyphAtIndex:startingGlyphIndex];
NSRange lineRange = [string
lineRangeForRange:NSMakeRange(characterIndex, 0)];
// Find the line range for the line of text this glyph is a part of
characterIndex = [self.layoutManager
characterIndexForGlyphAtIndex:startingGlyphIndex];
lineRange = [string lineRangeForRange:NSMakeRange(characterIndex, 0)];
// If the startingGlyphIndex's character is *after* the beginning of
the line
// of text it's on, then the lineFragmentRect being asked for must be
part
// of a wrapped line - which we want to indent.
if (characterIndex > lineRange.location) {
NSCharacterSet * cs = [NSCharacterSet whitespaceCharacterSet];
CGFloat indentation = 0.0;
// Find the indentation of the first non-whitespace
// character in the line.
for (NSUInteger i = 0; lineRange.location + i < stringLength;
i++) {
unichar c = [string characterAtIndex:lineRange.location
+ i];
if (![cs characterIsMember:c]) {
NSUInteger glyphIndex = [self.layoutManager
glyphIndexForCharacterAtIndex:lineRange.location + i];
indentation = [self.layoutManager
locationForGlyphAtIndex:glyphIndex].x;
break;
}
}
// NOTE: Do we need to do anything special for
lineFragmentPadding *here*?
// ...
// Increase the indentation from the first line
indentation += 28; // 4 spaces width (to be calculated for real
later)
// Modify the proposed rect to create that indentation
CGFloat maxX = NSMaxX(proposedRect);
proposedRect.origin.x = indentation;
proposedRect.size.width = maxX - indentation;
}
[super getLineFragmentRect:lineFragmentRect
usedRect:lineFragmentUsedRect remainingRect:remainingRect
forStartingGlyphAtIndex:startingGlyphIndex proposedRect:proposedRect
lineSpacing:lineSpacing paragraphSpacingBefore:paragraphSpacingBefore
paragraphSpacingAfter:paragraphSpacingAfter];
}
--
Seth Willits
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