研究4

在尋找WKWebView的畫面更新方法過程中發現- (void)_updateVisibleContentRects只有- (void)_addUpdateVisibleContentRectPreCommitHandler這有使用到，於是再往上追蹤到- (void)_scheduleVisibleContentRectUpdateAfterScrollInView:(UIScrollView *)scrollView就有很多地方再使用了，來分類一下出現的地方。

WKWebView畫面大小改變：

- (void)setFrame:(CGRect)frame
{
    CGRect oldFrame = self.frame;
    [super setFrame:frame];

    if (!CGSizeEqualToSize(oldFrame.size, frame.size))
        [self _frameOrBoundsChanged];
}

- (void)setBounds:(CGRect)bounds
{
    CGRect oldBounds = self.bounds;
    [super setBounds:bounds];
    [_customContentFixedOverlayView setFrame:self.bounds];

    if (!CGSizeEqualToSize(oldBounds.size, bounds.size))
        [self _frameOrBoundsChanged];
}

- (void)layoutSubviews
{
    [super layoutSubviews];
    [self _frameOrBoundsChanged];
}

最初就提及的地方。

WKScrollView滾動或縮放：

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    if (![self usesStandardContentView])
        [_customContentView scrollViewDidScroll:(UIScrollView *)scrollView];

    [self _scheduleVisibleContentRectUpdateAfterScrollInView:scrollView];

    if (WebKit::RemoteLayerTreeScrollingPerformanceData* scrollPerfData = _page->scrollingPerformanceData())
        scrollPerfData->didScroll([self visibleRectInViewCoordinates]);
}

- (void)scrollViewDidZoom:(UIScrollView *)scrollView
{
    [self _updateScrollViewBackground];
    [self _scheduleVisibleContentRectUpdateAfterScrollInView:scrollView];
}

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(CGFloat)scale
{
    ASSERT(scrollView == _scrollView);
    [self _scheduleVisibleContentRectUpdateAfterScrollInView:scrollView];
    [_contentView didZoomToScale:scale];
}