/*

     File: MouseOverTextView.m 

 Abstract: Subclass of NSTextView that tracks the mouse and 

 highlights characters, words and rows. 

  Version: 1.2 

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 */

#import "MouseOverTextView.h"

/*

 This application demonstrates interrogating the layout manager for information about

 text layout, and the use of temporary attributes to color text.  Specifically, we 

 provide rollover coloring of text--one color for the line, another for the word, 

 and a third for the character under the mouse.  A subclass of NSTextView is used,

 but solely for the purpose of obtaining mouse events.  The interesting portion of 

 the code involves the conversion of mouse coordinates to a particular glyph and

 character index, then determining the corresponding line and word, and finally 

 using temporary attributes for coloring.

 */

@implementation MouseOverTextView

- (void)awakeFromNib {

    [[self window] setAcceptsMouseMovedEvents:YES];

}

- (void)mouseMoved:(NSEvent *)theEvent {

    NSLayoutManager *layoutManager = [self layoutManager];

    NSTextContainer *textContainer = [self textContainer];

    NSUInteger glyphIndex, charIndex, textLength = [[self textStorage] length];

    NSPoint point = [self convertPoint:[theEvent locationInWindow] fromView:nil];

    NSRange lineGlyphRange, lineCharRange, wordCharRange, textCharRange = NSMakeRange(0, textLength);

    NSRect glyphRect;

    // Remove any existing coloring.

    [layoutManager removeTemporaryAttribute:NSBackgroundColorAttributeName forCharacterRange:textCharRange];

    // Convert view coordinates to container coordinates

    point.x -= [self textContainerOrigin].x;

    point.y -= [self textContainerOrigin].y;

    // Convert those coordinates to the nearest glyph index

    glyphIndex = [layoutManager glyphIndexForPoint:point inTextContainer:textContainer];

    // Check to see whether the mouse actually lies over the glyph it is nearest to

    glyphRect = [layoutManager boundingRectForGlyphRange:NSMakeRange(glyphIndex, 1) inTextContainer:textContainer];

    if (NSPointInRect(point, glyphRect)) {

        // Convert the glyph index to a character index

        charIndex = [layoutManager characterIndexForGlyphAtIndex:glyphIndex];

        // Determine the range of glyphs, and of characters, in the corresponding line

        (void)[layoutManager lineFragmentRectForGlyphAtIndex:glyphIndex effectiveRange:&lineGlyphRange];        

        lineCharRange = [layoutManager characterRangeForGlyphRange:lineGlyphRange actualGlyphRange:NULL];

        // Determine the word containing that character

        wordCharRange = NSIntersectionRange(lineCharRange, [self selectionRangeForProposedRange:NSMakeRange(charIndex, 0) granularity:NSSelectByWord]);

        // Color the characters using temporary attributes

        [layoutManager addTemporaryAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[NSColor cyanColor], NSBackgroundColorAttributeName, nil] forCharacterRange:lineCharRange];

        [layoutManager addTemporaryAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[NSColor yellowColor], NSBackgroundColorAttributeName, nil] forCharacterRange:wordCharRange];

        [layoutManager addTemporaryAttributes:[NSDictionary dictionaryWithObjectsAndKeys:[NSColor magentaColor], NSBackgroundColorAttributeName, nil] forCharacterRange:NSMakeRange(charIndex, 1)];

    }

}

@end