Method HitTestText

Source/Engine/Render2D/Font.cpp:332–406

}

int32 Font::HitTestText(const StringView& text, const Float2& location, const TextLayoutOptions& layout)
{
    // Check if there is no need to do anything
    if (text.Length() <= 0)
        return 0;

    // Process text
    Array<FontLineCache, InlinedAllocation<8>> lines;
    ProcessText(text, lines, layout);
    ASSERT(lines.HasItems());
    float scale = layout.Scale / FontManager::FontScale;
    float baseLinesDistance = static_cast<float>(_height) * layout.BaseLinesGapScale * scale;

    // Offset position to match lines origin space
    Float2 testPoint = location - layout.Bounds.Location;

    // Get line which may intersect with the position (it's possible because lines have fixed height)
    int32 lineIndex = Math::Clamp(Math::FloorToInt((testPoint.Y - lines.First().Location.Y) / baseLinesDistance), 0, lines.Count() - 1);
    const FontLineCache& line = lines[lineIndex];
    float x = line.Location.X;

    // Check all characters in the line to find hit point
    FontCharacterEntry previous;
    FontCharacterEntry entry;
    int32 smallestIndex = INVALID_INDEX;
    float dst, smallestDst = MAX_float;
    for (int32 currentIndex = line.FirstCharIndex; currentIndex <= line.LastCharIndex; currentIndex++)
    {
        // Cache current character
        const Char currentChar = text[currentIndex];
        GetCharacter(currentChar, entry);
        const bool isWhitespace = StringUtils::IsWhitespace(currentChar);

        // Apply kerning
        if (!isWhitespace && previous.IsValid)
        {
            x += entry.Font->GetKerning(previous.Character, entry.Character);
        }
        previous = entry;

        // Test
        dst = Math::Abs(testPoint.X - x);
        if (dst < smallestDst)
        {
            // Found closer character
            smallestIndex = currentIndex;
            smallestDst = dst;
        }
        else if (dst > smallestDst)
        {
            // Current char is worse so return the best result
            return smallestIndex;
        }

        // Move
        x += entry.AdvanceX * scale;
    }