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Re: drawGlyphsForGlyphRange layout issue
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Re: drawGlyphsForGlyphRange layout issue


  • Subject: Re: drawGlyphsForGlyphRange layout issue
  • From: "email@hidden" <email@hidden>
  • Date: Mon, 24 Sep 2012 15:02:12 +0100



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: Aki Inoue <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>)

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