Function ImFontAtlasPackAddRect

src/imgui/imgui_draw.cpp:4309–4354

Important: Calling this may recreate a new texture and therefore change atlas->TexData FIXME-NEWFONTS: Expose other glyph padding settings for custom alteration (e.g. drop shadows). See #7962

// Important: Calling this may recreate a new texture and therefore change atlas->TexData
// FIXME-NEWFONTS: Expose other glyph padding settings for custom alteration (e.g. drop shadows). See #7962
ImFontAtlasRectId ImFontAtlasPackAddRect(ImFontAtlas* atlas, int w, int h, ImFontAtlasRectEntry* overwrite_entry)
{
    IM_ASSERT(w > 0 && w <= 0xFFFF);
    IM_ASSERT(h > 0 && h <= 0xFFFF);

    ImFontAtlasBuilder* builder = (ImFontAtlasBuilder*)atlas->Builder;
    const int pack_padding = atlas->TexGlyphPadding;
    builder->MaxRectSize.x = ImMax(builder->MaxRectSize.x, w);
    builder->MaxRectSize.y = ImMax(builder->MaxRectSize.y, h);

    // Pack
    ImTextureRect r = { 0, 0, (unsigned short)w, (unsigned short)h };
    for (int attempts_remaining = 3; attempts_remaining >= 0; attempts_remaining--)
    {
        // Try packing
        stbrp_rect pack_r = {};
        pack_r.w = w + pack_padding;
        pack_r.h = h + pack_padding;
        stbrp_pack_rects((stbrp_context*)(void*)&builder->PackContext, &pack_r, 1);
        r.x = (unsigned short)pack_r.x;
        r.y = (unsigned short)pack_r.y;
        if (pack_r.was_packed)
            break;

        // If we ran out of attempts, return fallback
        if (attempts_remaining == 0 || builder->LockDisableResize)
        {
            IMGUI_DEBUG_LOG_FONT("[font] Failed packing %dx%d rectangle. Returning fallback.\n", w, h);
            return ImFontAtlasRectId_Invalid;
        }

        // Resize or repack atlas! (this should be a rare event)
        ImFontAtlasTextureMakeSpace(atlas);
    }

    builder->MaxRectBounds.x = ImMax(builder->MaxRectBounds.x, r.x + r.w + pack_padding);
    builder->MaxRectBounds.y = ImMax(builder->MaxRectBounds.y, r.y + r.h + pack_padding);
    builder->RectsPackedCount++;
    builder->RectsPackedSurface += (w + pack_padding) * (h + pack_padding);

    builder->Rects.push_back(r);
    if (overwrite_entry != NULL)
        return ImFontAtlasPackReuseRectEntry(atlas, overwrite_entry); // Write into an existing entry instead of adding one (used during repack)
    else
        return ImFontAtlasPackAllocRectEntry(atlas, builder->Rects.Size - 1);
}

// Generally for non-user facing functions: assert on invalid ID.
ImTextureRect* ImFontAtlasPackGetRect(ImFontAtlas* atlas, ImFontAtlasRectId id)