在可可中绘图，xy值错误

Question

我试图在NSScrollView内的NSView中绘制一堆矩形。代码工作得很好，但它似乎像计算机正在绘制错误的点。

当我使用NSLog()登录当前x和y值是正确的，但是当我看到我的看法，有图纸坐标之前添加额外的空间。

这是代码：

// 
// CoverFlowView.m 
// iWatch 
// 
// Created by ief2 on 03/11/10. 
// 
// 

#import "CoverFlowView.h" 

#pragma mark Defaults 
#define COVER_HEIGHT2WIDTH(a) ((float)a/1.4) 
#define COVER_HEIGHT (200.0) 
#define COVER_WIDTH (COVER_HEIGHT2WIDTH(COVER_HEIGHT)) 
#define COVER_SPACE_MIN (20.0) 

#pragma mark Private Methods 
@interface CoverFlowView (PrivateMethods) 
- (CGFloat)coverSpaceForMoviesPerLine:(NSUInteger *)n; 
- (void)frameDidChange; 
- (void)updateFrame; 
@end 

NSColor *RandomColor() { 
    float red = (float)(rand() % 255)/254.0; 
    float green = (float)(rand() % 255)/254.0; 
    float blue = (float)(rand() % 255)/254.0; 

    NSColor *theColor = [[NSColor colorWithDeviceRed:red 
               green:green 
               blue:blue 
               alpha:1.0] retain]; 
    return [theColor autorelease]; 
} 

#pragma mark Implementation 
@implementation CoverFlowView 
#pragma mark Init and Dealloc 
- (void)awakeFromNib { 
    srand(time(NULL)); 
    NSMutableArray *colors = [[NSMutableArray alloc] initWithCapacity:100]; 
    register int i; 
    for(i = 0; i < 100; i++) { 
     [colors addObject:RandomColor()]; 
    } 
    self.movies = colors; 
    [colors autorelease]; 

    [[NSNotificationCenter defaultCenter] addObserver:self 
              selector:@selector(frameDidChange) 
               name:NSViewFrameDidChangeNotification 
               object:self]; 

} 

- (id)initWithFrame:(NSRect)frame movies:(NSArray *)movs { 

    self = [super initWithFrame:frame]; 
    if(self != nil) { 
     self.movies = movs; 

     // FIXME: Debug color array to movie 
     NSMutableArray *colors = [[NSMutableArray alloc] initWithCapacity:100]; 
     register int i; 
     srand((unsigned int)time(NULL)); 
     for(i = 0; i < 100; i++) { 
      [colors addObject:RandomColor()]; 
     } 
    } 
    return self; 
} 

- (void)dealloc { 
    [_movies release]; 

    [super dealloc]; 
} 

#pragma mark Drawing 
- (void)drawRect:(NSRect)dirtyRect { 
    [[NSColor blackColor] setFill]; 
    NSRectFill(dirtyRect); 

    NSUInteger moviesPerLine = 0; 
    CGFloat coverSpace = 0; 

    // Get the values 
    coverSpace = [self coverSpaceForMoviesPerLine:&moviesPerLine]; 



    // if it's less than 1, break the drawing 
    if(moviesPerLine < 1) { 
     return; 
    } 

    // get the rows not to draw 
    // p = top left point's y 
    // h = movie cover height ->\ 
    // s = space between  -->The movies height and it's space above it 
    // 
    //   p 
    // f(x) = ------- 
    //   h + s 
    double rows = ((dirtyRect.origin.y)/(COVER_HEIGHT + coverSpace)); 


    // get the first movie that has to be drawn 
    // could be half-draw 
    // 
    // (NSUInteger)rows * moviesPerLine 
    NSUInteger index = (NSUInteger)rows * moviesPerLine; 
    if(!(index < [self.movies count])) 
     return; 


    // variable declaration 
    CGFloat curY; 
    CGFloat curX; 

    // start drawing until the line after max 
    // start the loop 
    do { 
     NSUInteger rowIndex; 
     // get the y for the movie 
     // x = movie index (start from 1) 
     // m = movies per row 
     // h = movie height 
     // s = movie space 
     // 
     //   [x - (x % m)] 
     // f(x) = (|-----------|) * (h + s) + s 
     //   [  m  ] 
     // BUT: if rows == 2, rows -= 1 
     rowIndex = ((index + 1) - ((index + 1) % moviesPerLine))/moviesPerLine; 
     ((index + 1) % moviesPerLine == 0) ? (rowIndex -= 1) : (rowIndex = rowIndex); 
     curY = rowIndex * (COVER_HEIGHT + coverSpace) + coverSpace; 


     // get the x fot the movie 
     // x = movie index (start from 1) 
     // m = movies per line 
     // w = movie width 
     // s = cover space 
     // 
     //    
     // f(x) = ((x - (x - (x % m))) - 1) * (w + s) + s 
     // BUT: if row == 0, row = m 
     // 
     rowIndex = (index+1) - (((index+1) - ((index + 1) % moviesPerLine))); 
     (rowIndex == 0) ? (rowIndex = moviesPerLine) : (rowIndex = rowIndex); 
     curX = (rowIndex - 1) * (COVER_WIDTH + coverSpace) + coverSpace; 
     NSLog(@"%s index: %3u || x: %5.0f || y: %5.0f", __FUNCTION__, index, curX, curY); 

     // Start the drawing 
     NSRect bezierPathRect = NSMakeRect(curX + coverSpace, curY, COVER_WIDTH, COVER_HEIGHT); 
     NSBezierPath *path = [NSBezierPath bezierPathWithRect:bezierPathRect]; 
     [path setLineWidth:2.0]; 
     [[NSColor whiteColor] setStroke]; 
     [(NSColor *)[self.movies objectAtIndex:index] setFill]; 
     [path fill]; 
     [path stroke]; 

     // add up values 
     index++; 
     if(!(index < [self.movies count])) 
      return; 

    } while(curY - (COVER_HEIGHT + coverSpace) < dirtyRect.origin.y + dirtyRect.size.height); 
} 

- (BOOL)isFlipped { 
    return YES; 
} 

#pragma mark Private Methods 
- (void)frameDidChange { 

} 

- (CGFloat)coverSpaceForMoviesPerLine:(NSUInteger *)n { 
    // x = number of covers 
    // w = view width 
    // m = cover width 
    // y = the space 
    // 
    //  w - (mx) 
    // f(x) = -------- 
    //   x + 1 

    CGFloat m = COVER_WIDTH; 
    CGFloat w = [self bounds].size.width; 

    register NSUInteger x = 1; 
    CGFloat space; 
    while(1) { 
     space = ((w-(m*x))/(x + 1.0)); 
     if(space < COVER_SPACE_MIN) { 
      x--; 
      space = ((w - (m*x))/(x + 1.0)); 
      break; 
     } 
     x++; 
    } 

    if(n) *n = x; 
    return space; 
} 

#pragma mark Properties 
@synthesize movies=_movies; 
- (void)setMovies:(NSArray *)ar { 

    if(ar != _movies) { 
     [_movies release]; 
     _movies = [ar retain]; 

     // Update frame size 
     NSUInteger m; 
     CGFloat space = [self coverSpaceForMoviesPerLine:&m]; 
     NSUInteger lines = [ar count]/m; 
     CGFloat height = (COVER_HEIGHT + space) * ((CGFloat)lines) + space; 
     CGFloat width = [self frame].size.width; 
     NSRect frame = [self frame]; 
     frame.size = NSMakeSize(width, height); 
     [self setFrame:frame]; 
     [self setNeedsDisplay:YES]; 
    } 
} 
@end 

，在这里你可以找到运行的应用程序的屏幕截图：

如果有人能告诉我什么，我做错了，我会真的很感激它！

谢谢 ief2

编辑：请不要介意错了冠军，我犯过错误给文件命名:-)

Answer 1

在我看来，你计算的X坐标错误办法。您在行的开头处有两倍的间距，并且在行的末尾没有空格。所以，如果你curX减去一个距离你得到正确的结果：

curX = (rowIndex - 1) * (COVER_WIDTH + coverSpace); 

而且你的代码复杂得多，它需要的。例如，您不需要在coverSpaceForMoviesPerLine:中执行循环，并且可以简化（并且同时更高效）drawRect:中的循环。