Hit Testing Layout

[gerdus]

Hi

I am trying to do hit testing and selection rendering.
Basically I need bounding box per grapheme along with the associated start/end index in the source string.
The data seems to be present in internal classes TextBox/TextLine/GlyphLayout;

Is there some public method I have overlooked that can give me this information?

Thank you.

[gerdus]

I wrote some code to do this for a single line text.

        public void HitTest1()
        {
            FontCollection collection = new();
            collection.AddSystemFonts();

            var family = collection.Get("Segoe UI");
            var emojiFamily = collection.Get("Segoe UI Emoji");
            var runText = "The quick👩🏽‍🚒 brown fox jumps over the lazy dog";

            var runRTO = new RichTextOptions(family.CreateFont(72, FontStyle.Regular))
            {
                Origin = new PointF(10, 200),
                WrappingLength = -1,
                FallbackFontFamilies = new[] { emojiFamily },
                WordBreaking = WordBreaking.BreakWord
            };

            using (Image<Rgba32> image = new Image<Rgba32>(1200, 600))
            {
                Console.WriteLine($"runText:{runText} Len:{runText.Length}");

                image.Mutate(x => x.Fill(Color.White));
                image.Mutate(x => x.DrawText(runRTO, runText, Color.Black));

                var txtBounds = TextMeasurer.MeasureBounds(runText, runRTO);
                Console.WriteLine($"Bounds: {txtBounds}");

                int testpoint_x = 600;
                image.Mutate(x => x.DrawLine(Pens.Solid(Color.Green, 1), new PointF { X = testpoint_x, Y = runRTO.Origin.Y }, new PointF { X = testpoint_x, Y = runRTO.Origin.Y + txtBounds.Height }));

                var topY = runRTO.Origin.Y;
                var bottomY = runRTO.Origin.Y + txtBounds.Height;
                var offsetX = runRTO.Origin.X;

                SpanGraphemeEnumerator graphemeEnumerator = new(runText);
                int characterIndex = 0;
                while (graphemeEnumerator.MoveNext())
                {
                    Console.WriteLine($"{graphemeEnumerator.Current}");

                    var mBounds = TextMeasurer.MeasureAdvance(runText.Substring(0, characterIndex), runRTO);

                    if (mBounds.Width > (testpoint_x - offsetX))
                    {
                        Console.WriteLine($"FOUND");
                        break;
                    }

                    image.Mutate(x => x.DrawLine(Pens.Solid(Color.Teal, 2), new PointF { X = mBounds.Right + offsetX, Y = topY }, new PointF { X = mBounds.Right + offsetX, Y = bottomY }));

                    characterIndex += graphemeEnumerator.Current.Length;
                }

                var startBounds = TextMeasurer.MeasureAdvance(runText.Substring(0, characterIndex - 1), runRTO);
                var endBounds = TextMeasurer.MeasureAdvance(runText.Substring(0, characterIndex), runRTO);
                image.Mutate(x => x.DrawLine(Pens.Solid(Color.Orange, 2), new PointF { X = startBounds.Right + offsetX, Y = topY }, new PointF { X = startBounds.Right + offsetX, Y = bottomY }));
                image.Mutate(x => x.DrawLine(Pens.Solid(Color.DarkBlue, 2), new PointF { X = endBounds.Right + offsetX, Y = topY }, new PointF { X = endBounds.Right + offsetX, Y = bottomY }));

                image.Save(@"T:\hit_test_2.png");
            }


        }

screenshot:

[JimBobSquarePants]

Let me know which specific properties you require to be exposed and we can work together to get them done.

[gerdus]

I need the string index on the GlyphBounds returned by TextMeasurer.TryMeasureCharacterBounds.
Although I suppose the grapheme index would also work since I can use SpanGraphemeEnumerator to calculate the character index from the graphemeIndex.

It look like the internal GlyphLayout would need to carry this data since it is what TryGetCharacterBounds uses.

If this is OK, I can attempt it and submit a pull request when I get time.

[JimBobSquarePants]

Yeah, add the string and grapheme index to GlyphBounds, I'd also add them to GlyphRendererParameters also. Everything you'd touch is internal so should be non-breaking.

[gerdus]

Fixed by #396