Method CalcTextSizeA

ImGUI GLFW Tutorial/imgui/imgui_draw.cpp:3400–3492

}

ImVec2 ImFont::CalcTextSizeA(float size, float max_width, float wrap_width, const char* text_begin, const char* text_end, const char** remaining) const
{
    if (!text_end)
        text_end = text_begin + strlen(text_begin); // FIXME-OPT: Need to avoid this.

    const float line_height = size;
    const float scale = size / FontSize;

    ImVec2 text_size = ImVec2(0, 0);
    float line_width = 0.0f;

    const bool word_wrap_enabled = (wrap_width > 0.0f);
    const char* word_wrap_eol = NULL;

    const char* s = text_begin;
    while (s < text_end)
    {
        if (word_wrap_enabled)
        {
            // Calculate how far we can render. Requires two passes on the string data but keeps the code simple and not intrusive for what's essentially an uncommon feature.
            if (!word_wrap_eol)
            {
                word_wrap_eol = CalcWordWrapPositionA(scale, s, text_end, wrap_width - line_width);
                if (word_wrap_eol == s) // Wrap_width is too small to fit anything. Force displaying 1 character to minimize the height discontinuity.
                    word_wrap_eol++;    // +1 may not be a character start point in UTF-8 but it's ok because we use s >= word_wrap_eol below
            }

            if (s >= word_wrap_eol)
            {
                if (text_size.x < line_width)
                    text_size.x = line_width;
                text_size.y += line_height;
                line_width = 0.0f;
                word_wrap_eol = NULL;

                // Wrapping skips upcoming blanks
                while (s < text_end)
                {
                    const char c = *s;
                    if (ImCharIsBlankA(c)) { s++; } else if (c == '\n') { s++; break; } else { break; }
                }
                continue;
            }
        }

        // Decode and advance source
        const char* prev_s = s;
        unsigned int c = (unsigned int)*s;
        if (c < 0x80)
        {
            s += 1;
        }
        else
        {
            s += ImTextCharFromUtf8(&c, s, text_end);
            if (c == 0) // Malformed UTF-8?
                break;
        }