cocoa - 当水平调整包含的 NSTextView 大小时，如何阻止 NSScrollView 滚动到顶部？

Question

我有一个 NSTextView，我想显示水平滚动条。按照互联网上的一些线索，我的大部分功能都可以正常工作，除了垂直滚动条出现问题。

我所做的是找到最长线的宽度(以给定字体的像素为单位)，然后适当调整 NSTextContainer 和 NSTextView 的大小。这样水平滚动条代表宽度，向右滚动将滚动到最长文本行的末尾。

完成这项工作后，我注意到我的 NSScrollView 会在我键入时显示和隐藏垂直滚动条。我通过在调整大小之前将 autohidesScrollers 设置为“否”，然后在调整大小之后设置为"is"来“修复”了这个问题。然而，仍然存在另一个问题，当我键入时，垂直滚动条thumb跳到滚动条的顶部，然后在我键入时返回到正确的位置。我输入“a”，它跳到顶部，我再次按，它跳回到正确的位置。

有什么想法吗？

这里是一些示例代码:

- (CGFloat)longestLineOfText
{
    CGFloat longestLineOfText = 0.0;

    NSRange lineRange;

    NSString* theScriptText = [myTextView string];

    NSDictionary* attributesDict = [NSDictionary dictionaryWithObject:scriptFont forKey:NSFontAttributeName]; //scriptFont is a instance variable

    NSUInteger characterIndex = 0;
    NSUInteger stringLength = [theScriptText length];

    while (characterIndex < stringLength) {
        lineRange = [theScriptText lineRangeForRange:NSMakeRange(characterIndex, 0)];

        NSSize lineSize = [[theScriptText substringWithRange:lineRange] sizeWithAttributes:attributesDict];
        longestLineOfText = max(longestLineOfText, lineSize.width);

        characterIndex = NSMaxRange(lineRange);
    }

    return longestLineOfText;

}

// ----------------------------------------------------------------------------

- (void)updateMyTextViewWidth
{
    static CGFloat previousLongestLineOfText = 0.0;

    CGFloat currentLongestLineOfText = [self longestLineOfText];
    if (currentLongestLineOfText != previousLongestLineOfText) {
        BOOL shouldStopBlinkingScrollBar = (previousLongestLineOfText < currentLongestLineOfText);
        previousLongestLineOfText = currentLongestLineOfText;

        NSTextContainer* container = [myTextView textContainer];
        NSScrollView* scrollView = [myTextView enclosingScrollView];
        if (shouldStopBlinkingScrollBar) {
            [scrollView setAutohidesScrollers:NO];
        }

        CGFloat padding = [container lineFragmentPadding];

        NSSize size = [container containerSize];
        size.width = currentLongestLineOfText + padding * 2;
        [container setContainerSize:size];

        NSRect frame = [myTextView frame];
        frame.size.width = currentLongestLineOfText + padding * 2;
        [myTextView setFrame:frame];

        if (shouldStopBlinkingScrollBar) {
            [scrollView setAutohidesScrollers:YES];
        }
    }   
}

Answer 1

感谢罗斯·卡特的post上Cocoa-Dev list ，我解决了这个问题。

A.您必须设置 TextView 以支持水平滚动:

- (void)awakeFromNib {
    [myTextView setHorizontallyResizable:YES];
    NSSize tcSize = [[myTextView textContainer] containerSize];
    tcSize.width = FLT_MAX;
    [[myTextView textContainer] setContainerSize:tcSize];
    [[myTextView textContainer] setWidthTracksTextView:NO];
}

B.您必须在 TextView 的宽度发生变化时更新它，否则水平滚动条无法正确更新:

- (void)textDidChange:(NSNotification *)notification
{
    [self updateTextViewWidth];
}

- (CGFloat)longestLineOfText
{
    CGFloat longestLineOfText = 0.0;

    NSLayoutManager* layoutManager = [myTextView layoutManager];

    NSRange lineRange;
    NSUInteger glyphIndex = 0;
    NSUInteger glyphCount = [layoutManager numberOfGlyphs];
    while (glyphIndex < glyphCount) {

        NSRect lineRect = [layoutManager lineFragmentUsedRectForGlyphAtIndex:glyphIndex
                                                              effectiveRange:&lineRange
                                                     withoutAdditionalLayout:YES];

        longestLineOfText = max(longestLineOfText, lineRect.size.width);

        glyphIndex = NSMaxRange(lineRange);
    }

    return longestLineOfText;

}

// ----------------------------------------------------------------------------

- (void)updateTextViewWidth
{
    static CGFloat previousLongestLineOfText = 0.0;

    CGFloat currentLongestLineOfText = [self longestLineOfText];
    if (currentLongestLineOfText != previousLongestLineOfText) {
        previousLongestLineOfText = currentLongestLineOfText;

        NSTextContainer* container = [myTextView textContainer];
        CGFloat padding = [container lineFragmentPadding];

        NSRect frame = [myTextView frame];
        frame.size.width = currentLongestLineOfText + padding * 2;
        [myTextView setFrame:frame];
    }
}