dear-imgui-glow

Glow (OpenGL) renderer for Dear ImGui.

Quick Start

use dear_imgui_rs::Context;
use dear_imgui_glow::GlowRenderer;
use glow::HasContext;

let gl = unsafe { glow::Context::from_loader_function(|s| loader.get_proc_address(s) as *const _) };
let mut imgui = Context::create();
let mut renderer = GlowRenderer::new(gl, &mut imgui)?;

// per-frame
let draw_data = imgui.render();
renderer.new_frame()?;
renderer.render(&draw_data)?;

What You Get

• ImGui v1.92 texture system integration (font atlas upload + dynamic texture updates)
• OpenGL 2.1+/ES 2.0+ compatible shaders and state setup
• Full GL state backup/restore around ImGui rendering

sRGB / Gamma

• Pipeline choice

  • Linear FB: keep FRAMEBUFFER_SRGB disabled (default). Colors are passed through without gamma.
  • sRGB FB: request an sRGB-capable surface and enable FRAMEBUFFER_SRGB.

    renderer.set_framebuffer_srgb_enabled(true) // enabled during render, disabled after
    

  • Pick exactly one path to avoid double correction.

• Vertex color gamma (auto + override)

  • The renderer applies gamma to ImGui vertex colors in the fragment shader via a ColorGamma uniform.
  • Auto (default):
    • 2.2 when FRAMEBUFFER_SRGB is enabled (decode vertex colors from sRGB → linear before write)
    • 1.0 when FRAMEBUFFER_SRGB is disabled (pass-through)
  • Override if needed:

    // Force a custom gamma (e.g., 2.2 or 1.0). Use None to restore auto.
    renderer.set_color_gamma_override(Some(2.2));
    renderer.set_color_gamma_override(None);
    

• Clear color

  • gl.clear_color(r,g,b,a) is specified in linear space. With sRGB FB, the driver encodes it on write, so the on-screen hex may not equal r,g,b * 255 exactly (this is expected).

Notes

• Alpha8 textures currently expand to RGBA8 for broad compatibility. On GL 3.3+/GLES 3.0+, RED + texture swizzle can reduce memory (see code comments).
• Multi-viewport support is feature-gated (off by default).

Compatibility

See also: docs/COMPATIBILITY.md for the full workspace matrix.

Features

• Default (core): bind_vertex_array_support, vertex_offset_support
• Extras (opt-in as a group): enable extras to include gl_extensions_support, bind_sampler_support, clip_origin_support, polygon_mode_support, primitive_restart_support
• Debug helper: debug_message_insert_support (no-op if disabled)
• Multi-viewport: multi-viewport (declared but currently not fully supported; off by default)

Rule of thumb: use the defaults; turn on extras only if you need those GL knobs.