Function ImFontAtlasBuildUpdateLinesTexData

src/imgui/imgui_draw.cpp:3510–3572

}

static void ImFontAtlasBuildUpdateLinesTexData(ImFontAtlas* atlas)
{
    if (atlas->Flags & ImFontAtlasFlags_NoBakedLines)
        return;

    // Pack and store identifier so we can refresh UV coordinates on texture resize.
    ImTextureData* tex = atlas->TexData;
    ImFontAtlasBuilder* builder = atlas->Builder;

    ImFontAtlasRect r;
    bool add_and_draw = atlas->GetCustomRect(builder->PackIdLinesTexData, &r) == false;
    if (add_and_draw)
    {
        ImVec2i pack_size = ImVec2i(IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 2, IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1);
        builder->PackIdLinesTexData = atlas->AddCustomRect(pack_size.x, pack_size.y, &r);
        IM_ASSERT(builder->PackIdLinesTexData != ImFontAtlasRectId_Invalid);
    }

    // Register texture region for thick lines
    // The +2 here is to give space for the end caps, whilst height +1 is to accommodate the fact we have a zero-width row
    // This generates a triangular shape in the texture, with the various line widths stacked on top of each other to allow interpolation between them
    for (int n = 0; n < IM_DRAWLIST_TEX_LINES_WIDTH_MAX + 1; n++) // +1 because of the zero-width row
    {
        // Each line consists of at least two empty pixels at the ends, with a line of solid pixels in the middle
        const int y = n;
        const int line_width = n;
        const int pad_left = (r.w - line_width) / 2;
        const int pad_right = r.w - (pad_left + line_width);
        IM_ASSERT(pad_left + line_width + pad_right == r.w && y < r.h); // Make sure we're inside the texture bounds before we start writing pixels

        // Write each slice
        if (add_and_draw && tex->Format == ImTextureFormat_Alpha8)
        {
            ImU8* write_ptr = (ImU8*)tex->GetPixelsAt(r.x, r.y + y);
            for (int i = 0; i < pad_left; i++)
                *(write_ptr + i) = 0x00;

            for (int i = 0; i < line_width; i++)
                *(write_ptr + pad_left + i) = 0xFF;

            for (int i = 0; i < pad_right; i++)
                *(write_ptr + pad_left + line_width + i) = 0x00;
        }
        else if (add_and_draw && tex->Format == ImTextureFormat_RGBA32)
        {
            ImU32* write_ptr = (ImU32*)(void*)tex->GetPixelsAt(r.x, r.y + y);
            for (int i = 0; i < pad_left; i++)
                *(write_ptr + i) = IM_COL32(255, 255, 255, 0);

            for (int i = 0; i < line_width; i++)
                *(write_ptr + pad_left + i) = IM_COL32_WHITE;

            for (int i = 0; i < pad_right; i++)
                *(write_ptr + pad_left + line_width + i) = IM_COL32(255, 255, 255, 0);
        }

        // Refresh UV coordinates
        ImVec2 uv0 = ImVec2((float)(r.x + pad_left - 1), (float)(r.y + y)) * atlas->TexUvScale;