StaticLayout inaccurate height for multi-line Arabic text

Question

I am trying to calculate the height needed by a text programmatically, so I am using StaticLayout.

I was experimenting with a Label (TextView) using its paint object, to make sure the height calculated is the same as TextView's height rendered by Android.

It works good for single-line text both in Arabic and English, and works for mutli-line text in English, but Arabic height is off, it is always shorter than what Android renders.

The top height ~80 is what the TextView's height is, while the latter ~75 is the calculated height needed.

Since that it works fine in English, I guess I might need to set some other property or something, but I cannot tell what.

Following is my code, it is in C# since I am using Xamarin, but it should be clear for Android developers.

Control is TextView.

        double getTextHeight(string str, double widthConstraint)
        {
            if (Control == null || String.IsNullOrWhiteSpace(str))
                return 0;

            var builder = StaticLayout.Builder.Obtain(str, 0, str.Length, Control.Paint, (int)widthConstraint);
            builder.SetAlignment(Control.Layout.GetAlignment());
            builder.SetIncludePad(true);
            builder.SetLineSpacing(Control.Layout.SpacingAdd, Control.Layout.SpacingMultiplier);
            builder.SetBreakStrategy(Control.BreakStrategy);
            builder.SetJustificationMode(Control.JustificationMode);
            builder.SetHyphenationFrequency(Control.HyphenationFrequency);

            var staticLayout = builder.Build();
            return staticLayout.Height;
        }

Answer 1

This is the code I was missing, it is working like charm :)

builder.SetUseLineSpacingFromFallbacks(true);