/*

     File: BetterWormView.m

 Abstract: This subclass of WormView and GoodWormView draws only the changed rectangle, rather than the whole view, on each frame.

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 */

#import "BetterWormView.h"

@implementation BetterWormView

- (BOOL)performAnimation {

    BOOL done;

    NSRect rect = NSZeroRect;

    GamePosition oldTargetPosition = targetPosition;

    NSUInteger i;

    // Compute a rect covering the worm's original position

    for (i = 0; i < wormLength; i++) {

        rect = NSUnionRect(rect, [self rectForPosition:wormPositions[i]]);

    }

    // Update game state

    done = [self updateState];

    // Union in the new head (since the worm has moved)

    rect = NSUnionRect(rect, [self rectForPosition:wormPositions[0]]);

    // If the target has changed locations, also include that in

    if (oldTargetPosition.x != targetPosition.x || oldTargetPosition.y != targetPosition.y) {

        rect = NSUnionRect(rect, [self rectForPosition:targetPosition]);

    }

    // Now, mark only the computed rect as needing redisplay

    [self setNeedsDisplayInRect:rect];

    return done;

}

/* BetterWormView overrides drawRect: to pay attention to the rect passed in, instead of drawing everything. This optimization goes hand-in-hand with the optimization in performAnimation above to compute the tight update rect. 

Note that because the tight update rect already contains the worm's body, it might seem unnecessary to do an intersection check in the code below for the worm's body --- after all, the update rect will always include the body, right? Usually yes, but there might be situations where that is not the case. For instance, if someone put the worm in a scrollView, or if something else caused the window to redraw and passed in a different rect.

*/

- (void)drawRect:(NSRect)rect {

    NSUInteger i;

    NSRect tRect;

    [backgroundColor set];

    NSRectFill(rect);   // Fill in only the update rect, not whole bounds

    for (i = 0; i < wormLength; i++) {

        NSRect wRect = [self rectForPosition:wormPositions[i]];

        if (NSIntersectsRect(wRect, rect)) {    // Draw this portion of the body only if in the update rect

            NSUInteger characterIndex = i % [wormString length];

            NSString *string = [wormString substringWithRange:NSMakeRange(characterIndex, 1)];

            [string drawInRect:wRect withAttributes: wormTextAttributes];

        }

    }

    tRect = [self rectForPosition:targetPosition];

    if (NSIntersectsRect(tRect, rect)) {    // Draw target only if in the update rect

        [[NSColor blackColor] set];

        [[NSBezierPath bezierPathWithOvalInRect:NSInsetRect(tRect, 2, 2)] fill];

    }

}

@end