protected override Size MeasureOverride(Size size)
{
// Size used to compare with the previous one. We don't want to use this one for the calculation.
var ceiledNewSize = new CGSize(Math.Ceiling(size.Width), Math.Ceiling(size.Height));
var hasSameDesiredSize =
!_measureInvalidated &&
_previousAvailableSize != null &&
_previousDesiredSize.Width == ceiledNewSize.Width &&
_previousDesiredSize.Height == ceiledNewSize.Height;
var isSingleLineNarrower =
!_measureInvalidated &&
_previousAvailableSize != null &&
_previousDesiredSize.Width <= ceiledNewSize.Width &&
_previousDesiredSize.Height == ceiledNewSize.Height;
if (hasSameDesiredSize || isSingleLineNarrower)
{
return(_previousDesiredSize);
}
else
{
_previousAvailableSize = size;
_measureInvalidated = false;
UpdateTypography();
var padding = Padding;
// available size considering padding
size = size.Subtract(padding);
var result = LayoutTypography(size);
if (result.Height == 0) // this can happen when Text is null or empty
{
// This measures the height correctly, even if the Text is null or empty
// This matches Windows where empty TextBlocks still have a height (especially useful when measuring ListView items with no DataContext)
var font = UIFontHelper.TryGetFont((float)FontSize, FontWeight, FontStyle, FontFamily);
result = (Text ?? NSString.Empty).StringSize(font, size);
}
result = result.Add(padding);
return(_previousDesiredSize = new CGSize(Math.Ceiling(result.Width), Math.Ceiling(result.Height)));
}
}
protected override Size MeasureOverride(Size size)
{
// `size` is used to compare with the previous one `_previousDesiredSize`
// We need to apply `Math.Ceiling` to compare them correctly
var isSameOrNarrower =
!_measureInvalidated &&
_previousAvailableSize != null &&
_previousDesiredSize.Width <= Math.Ceiling(size.Width) &&
_previousDesiredSize.Height == Math.Ceiling(size.Height);
if (isSameOrNarrower)
{
return(_previousDesiredSize);
}
else
{
_previousAvailableSize = size;
_measureInvalidated = false;
UpdateTypography();
var padding = Padding;
// available size considering padding
size = size.Subtract(padding);
var result = LayoutTypography(size);
if (result.Height == 0) // this can happen when Text is null or empty
{
// This measures the height correctly, even if the Text is null or empty
// This matches Windows where empty TextBlocks still have a height (especially useful when measuring ListView items with no DataContext)
var font = UIFontHelper.TryGetFont((float)FontSize, FontWeight, FontStyle, FontFamily);
#pragma warning disable BI1234 // error BI1234: 'UIStringDrawing.StringSize(string, UIFont, CGSize)' is obsolete: 'Starting with ios7.0 use NSString.GetBoundingRect (CGSize, NSStringDrawingOptions, UIStringAttributes, NSStringDrawingContext) instead.'
result = (Text ?? NSString.Empty).StringSize(font, size);
#pragma warning restore BI1234
}
result = result.Add(padding);
return(_previousDesiredSize = new Size(Math.Ceiling(result.Width), Math.Ceiling(result.Height)));
}
}
private UIStringAttributes GetAttributes()
{
var attributes = new UIStringAttributes();
var font = UIFontHelper.TryGetFont((float)FontSize, FontWeight, FontStyle, FontFamily);
attributes.Font = font;
attributes.ForegroundColor = (Foreground as SolidColorBrush)?.ColorWithOpacity;
if (TextDecorations != TextDecorations.None)
{
attributes.UnderlineStyle = (TextDecorations & TextDecorations.Underline) == TextDecorations.Underline
? NSUnderlineStyle.Single
: NSUnderlineStyle.None;
attributes.StrikethroughStyle = (TextDecorations & TextDecorations.Strikethrough) == TextDecorations.Strikethrough
? NSUnderlineStyle.Single
: NSUnderlineStyle.None;
}
var paragraphStyle = new NSMutableParagraphStyle()
{
MinimumLineHeight = (nfloat)LineHeight,
Alignment = TextAlignment.ToNativeTextAlignment(),
LineBreakMode = GetLineBreakMode(),
};
// For unknown reasons, the LineBreakMode must be set to WordWrap
// when applied to a NSTextStorage for text to wrap.
if (UseLayoutManager)
{
paragraphStyle.LineBreakMode = UILineBreakMode.WordWrap;
}
if (LineStackingStrategy != LineStackingStrategy.MaxHeight)
{
paragraphStyle.MaximumLineHeight = (nfloat)LineHeight;
}
attributes.ParagraphStyle = paragraphStyle;
if (LineHeight != 0 && font != null)
{
// iOS puts text at the bottom of the line box, whereas Windows puts it at the top.
// Empirically this offset gives similar positioning to Windows.
// Note: Descender is typically a negative value.
var verticalOffset = LineHeight - font.LineHeight + font.Descender;
// Because we're trying to move the text up (toward the top of the line box),
// we only set BaselineOffset to a positive value.
// A negative value indicates that the the text is already bottom-aligned.
attributes.BaselineOffset = Math.Max(0, (float)verticalOffset);
}
if (CharacterSpacing != 0)
{
//CharacterSpacing is in 1/1000 of an em, iOS KerningAdjustment is in points. 1 em = 12 points
attributes.KerningAdjustment = (CharacterSpacing / 1000f) * 12;
}
return(attributes);
}