r2 – Lightweight 2D Renderer

Modern immediate-mode 2D renderer with font atlas, Unicode support, rounded shapes, shadows, multi-color gradients, clipping and thread-safe font updates.

Features

• Immediate-mode API
• High-quality font rendering (subpixel, glow, oversampling)
• Dynamic glyph loading
• Unicode + emoji support via font stacking
• Rects, rounded rects, lines, convex polygons, images
• Multi-color gradients & vertex color shading
• Drop shadows (rect & convex)
• Path builder (arcs, rounded rects, fill/stroke)
• Clip rectangle stack
• Texture & font stack
• D3D11 / OpenGL backend support
• Window resize handling
• Thread-safe font atlas updates

Quick Example

r2::renderer2d renderer;
renderer.init(platform_data, backend_data);

// Add font with fallback + emoji
auto* font = renderer.add_font({ .size = 20, .oversample_h = 2, .glow_radius = 8 });
font->add_font(NotoSans_Regular, NotoSans_Regular_size);
font->add_font(NotoEmoji_Regular, NotoEmoji_Regular_size);
renderer.build_fonts();
renderer.create_font_texture();

while (running) {
    renderer.reset_render_data();

    renderer.add_rect_filled(
        { 100,100 }, /* min */
        { 400,300 }, /* max */
        r2::color::white().interp(r2::color::blue(), 0.5f), /* color */
        12.f /* rounding */
    );
    renderer.add_text(
        { 120, 140}, /* pos */
        r2::color::white(), /* color */
        std::u8string_view("Hello р2 😎🚀"), /* test, any string type supported */
        false /* blurred */
    );

    renderer.render();
    renderer.update_fonts_on_frame();
}

Basic Usage Flow

renderer.init(...);
auto* font = renderer.add_font(cfg);
font->add_font(...);           // can call multiple times
renderer.build_fonts();
renderer.create_font_texture();

// per frame
renderer.reset_render_data();
renderer.setup_render_state();

// draw calls ...
renderer.add_rect_filled(...);
renderer.add_text(...);
renderer.add_image(...);
...

// submit
renderer.render();
renderer.update_fonts_on_frame();   // call every frame (must be called from render thread)

Important Methods

• init(), destroy()
• add_font(), build_fonts(), create_font_texture()
• reset_render_data(), render()
• update_fonts_on_frame()
• push/pop_clip_rect(), push/pop_font(), push/pop_texture_id()
• add_rect_filled(), add_rect(), add_line(), add_convex_filled()
• add_text(), add_text_outlined(), add_text_faded()
• path_clear(), path_rect(), path_fill_convex(), path_stroke()