/// <summary>
/// Called once per batch of updates by the <see cref="UIManagerModule"/>
/// if the text node is dirty.
/// </summary>
public override void OnBeforeLayout()
{
if (_isVirtual)
{
return;
}
_inline = DispatcherHelpers.CallOnDispatcher(() => ReactTextShadowNodeInlineVisitor.Apply(this)).Result;
MarkUpdated();
}
private static MeasureOutput MeasureText(CSSNode node, float width, CSSMeasureMode widthMode, float height, CSSMeasureMode heightMode)
{
// This is not a terribly efficient way of projecting the height of
// the text elements. It requires that we have access to the
// dispatcher in order to do measurement, which, for obvious
// reasons, can cause perceived performance issues as it will block
// the UI thread from handling other work.
//
// TODO: determine another way to measure text elements.
var task = DispatcherHelpers.CallOnDispatcher(() =>
{
var textBlock = new TextBlock
{
TextWrapping = TextWrapping.Wrap,
TextAlignment = TextAlignment.DetectFromContent,
TextTrimming = TextTrimming.CharacterEllipsis,
};
var textNode = (ReactTextShadowNode)node;
textBlock.CharacterSpacing = textNode._letterSpacing;
textBlock.LineHeight = textNode._lineHeight;
textBlock.MaxLines = textNode._numberOfLines;
textBlock.TextAlignment = textNode._textAlignment;
textBlock.Inlines.Add(ReactTextShadowNodeInlineVisitor.Apply(node));
try
{
var normalizedWidth = CSSConstants.IsUndefined(width) ? double.PositiveInfinity : width;
var normalizedHeight = CSSConstants.IsUndefined(height) ? double.PositiveInfinity : height;
textBlock.Measure(new Size(normalizedWidth, normalizedHeight));
return(new MeasureOutput(
(float)Math.Ceiling(textBlock.DesiredSize.Width),
(float)Math.Ceiling(textBlock.DesiredSize.Height)));
}
finally
{
textBlock.Inlines.Clear();
}
});
return(task.Result);
}
