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Re: drawGlyphsForGlyphRange layout issue
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Re: drawGlyphsForGlyphRange layout issue


  • Subject: Re: drawGlyphsForGlyphRange layout issue
  • From: Aki Inoue <email@hidden>
  • Date: Mon, 24 Sep 2012 11:19:18 -0700

To be compatible with NSLayoutManager, you should use -drawWithRect:options:attributes: here instead of using CT.

Your source of trouble is using -drawAtPoint: which uses NSStringDrawingUsesLineFragmentOrigin option (layout glyphs from the top instead of the glyph origin).

Aki

On 2012/09/24, at 7:02, email@hidden wrote:

>
>
>
> On 24 Sep 2012, at 12:49, email@hidden wrote:
>
>>
>> On 23 Sep 2012, at 17:33, Kyle Sluder <email@hidden> wrote:
>>>
>>> Attributes are specified on a character, rather than glyph, basis. So if
>>> you need to draw your characters with a separate color, you should
>>> probably override
>>> -showCGGlyphs:positions:count:font:matrix:attributes:inContext: to push
>>> and pop the foreground color you want before calling super. Should be a
>>> really simple override, because the context is already set up for you.
>>>
>>>
>> It turns out that customising NSGlyphGenerator is not necessary as the subclass merely calls its delegate, which is the layout manager.
>> So an override on NSLayoutManager of  - insertGlyphs:length:forStartingGlyphAtIndex:characterIndex: is appropriate.
>> I cache my substitute glyphs and swap them in as required (a secondary layout manager generates the substitute glyphs).
>>
>> However there are issues.
>>
>> Colourisation in - showCGGlyphs:positions:count:font:matrix:attributes:inContext:
>> will necessitate colouring by glyph value. So if a period is used to highlight a space then all periods in the text get highlighted regardless.
>>
>> Secondly, swapping out the tab glyph for another seems to break the tab functionality in the NSTextView.
>>
>> Also, new line and carriage return glyph substitution doesn't seem to work. The substitute glyph is not drawn.
>> Perhaps its omitted as part of the fragment processing.
>>
>> I imagine that  the second issue is related to the type setter, though that's just a guess.
>>
>
> I took another look at NSLayoutManager  - drawGlyphsForGlyphRange:atPoint: and decided to try dropping down to CoreText.
> NSString -drawAtPoint:withAttributes: seemed to be the source of trouble and was very inefficient.
>
> I created and cached a CTLineRef for each of my substitute characters thus:
>
>    attrString = [[NSAttributedString alloc] initWithString:newLineCharacter attributes:defAttributes];
>    textLine = CFMakeCollectable(CTLineCreateWithAttributedString((CFAttributedStringRef)attrString));
>    [lineRefs addObject:(id)textLine];
>
> I then used CTLineDraw to draw the required line on demand.
> The vertical alignment of the extra glyphs seems fine with this approach.
>
> - (void)drawGlyphsForGlyphRange:(NSRange)glyphRange atPoint:(NSPoint)containerOrigin
> {
>    if (showInvisibleCharacters ) {
>
> 		NSPoint pointToDrawAt;
> 		NSRect glyphFragment;
> 		NSString *completeString = [[self textStorage] string];
> 		NSInteger lengthToRedraw = NSMaxRange(glyphRange);
>
>        void *gcContext = [[NSGraphicsContext currentContext] graphicsPort];
>
>        // if our context is flipped then we need to flip our drawn text too
>        CGAffineTransform t = {1.0, 0.0, 0.0, -1.0, 0.0, 0.0};
>        if (![[NSGraphicsContext currentContext] isFlipped]) {
>            t = CGAffineTransformIdentity;
>        }
>        CGContextSetTextMatrix (gcContext, t);
>
>        // we may not have any glyphs generated at this stage
> 		for (NSInteger idx = glyphRange.location; idx < lengthToRedraw; idx++) {
> 			unichar characterToCheck = [completeString characterAtIndex:idx];
>            NSUInteger lineRefIndex = 0;
>
> 			if (characterToCheck == '\t') {
>                lineRefIndex = 0;
>            } else if (characterToCheck == ' ') {
>                lineRefIndex = 1;
> 			} else if (characterToCheck == '\n' || characterToCheck == '\r') {
>                lineRefIndex = 2;
> 			} else {
>                continue;
>            }
>
>            pointToDrawAt = [self locationForGlyphAtIndex:idx];
>            glyphFragment = [self lineFragmentRectForGlyphAtIndex:idx effectiveRange:NULL];
>            pointToDrawAt.x += glyphFragment.origin.x;
>            pointToDrawAt.y += glyphFragment.origin.y;
>
>            // get our text line object
>            CTLineRef line = (CTLineRef)[lineRefs objectAtIndex:lineRefIndex];
>
>            CGContextSetTextPosition(gcContext, pointToDrawAt.x, pointToDrawAt.y);
>            CTLineDraw(line, gcContext);
> 		}
>    }
>
>    // the following causes glyph generation to occur if required
>    [super drawGlyphsForGlyphRange:glyphRange atPoint:containerOrigin];
> }
>
>
> Regards
>
> Jonathan Mitchell
> Mugginsoft LLP
>
>
>
>
>
>
>
>
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  • Follow-Ups:
    • Re: drawGlyphsForGlyphRange layout issue
      • From: "email@hidden" <email@hidden>
References: 
 >drawGlyphsForGlyphRange layout issue (From: "email@hidden" <email@hidden>)
 >Re: drawGlyphsForGlyphRange layout issue (From: Graham Cox <email@hidden>)
 >Re: drawGlyphsForGlyphRange layout issue (From: "email@hidden" <email@hidden>)
 >Re: drawGlyphsForGlyphRange layout issue (From: Kyle Sluder <email@hidden>)
 >Re: drawGlyphsForGlyphRange layout issue (From: "email@hidden" <email@hidden>)
 >Re: drawGlyphsForGlyphRange layout issue (From: "email@hidden" <email@hidden>)

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