Windows Store Apps: measure many pixels a TextBlock width will be? - xaml

Question

Is there a way to measure many pixels will a TextBlock width will occupy?
let's say I have a string with length of 10 characters.
and I have a text block (without an assigned width value), I'll set the string to the Text property of that textblock.
Is there a way to measure the actual width of the textblock before adding it to the layout?

Answer 1

Until any control is added to the VisualTree, it has a Width and Height of zero.
You have two options, the first is this:
var newTextBlock = new TextBlock() { Opacity = 0.001, Text = "Test" };
RoutedEventHandler handler = null;
handler = (s, e) =>
{
newTextBlock.Loaded -= handler;
Panel.Children.Remove(newTextBlock);
};
newTextBlock.Loaded += handler;
Panel.Children.Add(newTextBlock);
And in the handler make all the operations you need, because now you have ActualWidth and ActualHeight.
The other one is using Win2D, you can do the following:
var test = new CanvasTextFormat() { WordWrapping = CanvasWordWrapping.WholeWord };
session.DrawText(largeloremipsum, new Rect(0, 0, 480, 0), Colors.Black, test);
var size = new CanvasTextLayout(canvasControl, text, test, 480, float.MaxValue);
But this is a more complex way, you can define the TextFormat for the Size, Font, etc.

Answer 2

Well, the only way I got is to create a new -in memory- text block- then assign it the same text, style and attributes as my target TextBlock, I assumed that my text block has a fixed height, to calculate it's desired width to fit the text, I made the following function:
private double CalculateDesiredWidth(string text, TextBlock targetText)
{
int MIN_TEXT_WIDTH=200;
//create a new text block to calculate how much space will the string occupy
TextBlock txt = new TextBlock();
txt.Text = text;
txt.FontSize = 16;
txt.Margin = targetText.Margin;
Size desiredSize = new Size(0, targetText.ActualHeight);
Rect desiredRect = new Rect(new Point(0, 0), desiredSize);
//measure the desired size
txt.Measure(desiredSize);
txt.Arrange(desiredRect);
//if the desired width is small, use the minimum default width
if (txt.ActualWidth <= MIN_TEXT_WIDTH)
return MIN_TEXT_WIDTH;
//calculate the desired area
double desiredArea = txt.ActualWidth * txt.ActualHeight;
//calculate the the width required to fit the desired area to my text box
double width = desiredArea / (targetText.Height - txt.Margin.Top - txt.Margin.Bottom);
return width;
}