On 3 Jul 2010, at 21:17, Graham Cox wrote: > >> How is 'truncate last visible line' accomplished for wrapped text? >> >> I have a custom cell that I would like to have this behaviour in. Most of >> the system controls/cells support this but it's not clear how it's done for >> custom cells. I thought it would be a paragraph style attribute but I don't >> see anything there. > > > The simple solution seems to be to use [NSAttributedString > drawWithRect:options:] >
Not exactly the same issue, but this may help: recently I was working on an
NSTextView subclass that needed to have 'truncate last visible line' behaviour
(when not being edited). I got this working by iterating through the line
fragments until I found one that did not entirely fit within the view's
visibleRect, then replaced the whitespace character preceding that line with a
\n, essentially creating a new paragraph at that point - this was the only way
I could figure to get the truncation happening in the right place, but had the
benefit of causing the text system to re-layout. Obviously this needed
updating when the view was resized, and cleared out when the view became 1st
responder. The code looked like this:
// ivars
NSUInteger _tempTruncatingBreakIndex = UINT_MAX;
BOOL _textIsTruncated = NO;
- (void)reTruncateLastVisibleLine
{
NSUInteger length = [[self textStorage] length];
if ( (!self.truncatesLastVisibleLine) || (length == 0) )
{
return;
}
// remove previously inserted temporary line break
if (_tempTruncatingBreakIndex != UINT_MAX)
{
NSMutableAttributedString *str = [[[self textStorage]
mutableCopy] autorelease];
[str
deleteCharactersInRange:NSMakeRange(_tempTruncatingBreakIndex, 1)];
[[self textStorage] setAttributedString:str];
_tempTruncatingBreakIndex = UINT_MAX;
length = [[self textStorage] length];
}
// clear the old truncating style
NSMutableParagraphStyle *paraStyle = [[[[self textStorage]
attribute:NSParagraphStyleAttributeName atIndex:0 effectiveRange:NULL]
mutableCopy] autorelease];
if(paraStyle == nil)
{
paraStyle = [[[NSParagraphStyle defaultParagraphStyle]
mutableCopy] autorelease];
}
[paraStyle setLineBreakMode:NSLineBreakByWordWrapping];
[[self textStorage] addAttribute:NSParagraphStyleAttributeName
value:paraStyle range:NSMakeRange(0, length)];
_textIsTruncated = NO;
// walk through each line from the top and find the first one that is
not fully visible
NSUInteger lineIndex, glyphIndex, glyphCount = [[self layoutManager]
numberOfGlyphs], preccedingLineStartIndex = 0;
NSRange lineRange = MWZeroRange, styleRange;
for (lineIndex = 0, glyphIndex = 0; glyphIndex < glyphCount;
lineIndex++)
{
NSRect lineRect = [[self layoutManager]
lineFragmentUsedRectForGlyphAtIndex:glyphIndex effectiveRange:&lineRange];
if(!NSContainsRect([self visibleRect], lineRect))
{
_textIsTruncated = YES;
if(preccedingLineStartIndex == 0)
{
// there is only 1 line, so apply the
truncating para style to the whole string
styleRange = NSMakeRange(0, length);
}
else
{
// the text is clipped after the first line.
insert a temp line break at the begining of the last full line & apply the
truncating style from there
_tempTruncatingBreakIndex =
preccedingLineStartIndex;
[[self textStorage]
replaceCharactersInRange:NSMakeRange(_tempTruncatingBreakIndex, 0)
withString:@"\n"];
styleRange =
NSMakeRange(_tempTruncatingBreakIndex + 1, [[self textStorage] length] -
(_tempTruncatingBreakIndex + 1));
}
// apply the truncating style
[paraStyle
setLineBreakMode:NSLineBreakByTruncatingTail];
[[self textStorage]
addAttribute:NSParagraphStyleAttributeName value:paraStyle range:styleRange];
break;
}
glyphIndex = NSMaxRange(lineRange);
preccedingLineStartIndex = lineRange.location;
}
}
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