cocoa - 使用 NSGlyph 和内存分配

Question

在经常跟踪换行符的方法中，对于 NSTextView visibleRect，我正在为 NSGlyph 分配内存> 使用 NSLayoutManager getGlyphs:range:。

我应该/可以找出这应该有多少内存，因为我有范围的引用(不影响布局)，而且，应该进行什么样的清理——使用ARC运行？

代码(在主队列上运行):

    NSLayoutManager *lm = [self.textView layoutManager];
    NSTextContainer *tc = [self.textView textContainer];
    NSRect vRect = [self.textView visibleRect];
    NSRange visibleRange = [lm glyphRangeForBoundingRectWithoutAdditionalLayout:vRect inTextContainer:tc];
    NSUInteger vRangeLoc = visibleRange.location;
    NSUInteger numberOfLines;
    NSUInteger index;
    NSGlyph glyphArray[5000]; // <--- memory assigned here
    NSUInteger numberOfGlyphs = [lm getGlyphs:glyphArray range:visibleRange];
    NSRange lineRange;
    NSMutableIndexSet *idxset = [NSMutableIndexSet indexSet];
    for (numberOfLines = 0, index = 0; index < numberOfGlyphs; numberOfLines++) {
        (void)[lm lineFragmentRectForGlyphAtIndex:index effectiveRange:&lineRange withoutAdditionalLayout:YES];
        [idxset addIndex:lineRange.location + vRangeLoc];
        index = NSMaxRange(lineRange);
    }
    self.currentLinesIndexSet = idxset;

Answer 1

使用 NSGlyph glyphs[5000] 表示法，您可以在堆栈上分配内存。但它只需要保存 visibleRange.length + 1 字形，而不是 5000 个字形:

glyphArray

On output, the displayable glyphs from glyphRange, null-terminated. Does not include in the result any NSNullGlyph or other glyphs that are not shown. The memory passed in should be large enough for at least glyphRange.length+1 elements.

而且因为它在堆栈上，所以您不必担心释放内存——因为从未分配过内存；当离开函数时它会自动释放——即使没有 ARC

如果你这样写，它应该可以工作:

NSLayoutManager *lm = ...
NSRange glyphRange = ...
NSGlyph glyphArray[glyphRange.length + 1];
NSUInteger numberOfGlyphs = [lm getGlyphs:glyphArray range:glyphRange];
// do something with your glyphs