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Wide Color Gamut Support

Rio renders onto a wide-gamut surface on macOS (Display P3) so themes that use vivid, saturated colors can reach more of the display's range. The [window] colorspace setting controls how Rio interprets the color bytes in your config and in ANSI / direct-color escape sequences — it does not change the surface.

Configuration​

[window]
colorspace = "srgb"

Available options​

  • srgb — default. Interpret hex values (#ff0000) and ANSI direct colors as sRGB. Rio converts them to Display P3 primaries before rendering, so #ff0000 displays as the same red other apps draw (no oversaturation).
  • display-p3 — Interpret input values as already being in Display P3 primaries. A pure-red theme color will reach the full P3 red gamut and look more saturated than the sRGB standard. Use this if your theme was designed with a P3-aware color picker.
  • rec2020 — Interpret input values as Rec. 2020. Treated like display-p3 for now; a proper Rec. 2020 → Display P3 matrix is planned.

Platform support​

macOS​

On macOS, Rio always uses a DisplayP3-tagged CAMetalLayer with a gamma-correct (BGRA8Unorm_sRGB) framebuffer, regardless of the setting above. This yields linear-light alpha blending (no dark halos around text) and access to the wider-gamut range. The colorspace config only affects color interpretation.

Compatible wide-gamut displays include:

  • MacBook Pro (2016 and later)
  • iMac (2017 and later)
  • iMac Pro
  • Pro Display XDR
  • Studio Display

Linux / Windows​

The wgpu path does not yet implement the linear-light + wide-gamut pipeline. The config value is accepted but most platforms effectively behave as srgb until that path is updated.

Matching other terminals​

Rio's default (srgb) matches ghostty's window-colorspace default — meaning a given hex value renders identically in both terminals. If you want the old Rio macOS behaviour (colors treated as P3, looking more saturated), set:

[window]
colorspace = "display-p3"

Technical details​

The Metal path (sugarloaf/src/renderer/renderer.metal):

  1. Linearizes sRGB-encoded input RGB (fragment side) with the IEC 61966-2-1 transfer curve.
  2. If input_colorspace == 0 (sRGB), applies a Bradford-adapted sRGB D65 → Display P3 D65 primaries matrix in linear light.
  3. Writes the result to the _sRGB DisplayP3 drawable, so the hardware sRGB-encodes on write and alpha blends subsequent pixels in linear light.

The clear color (MTLClearColor) goes through the same transform on the Rust side (sugarloaf::prepare_output_rgb_f64) so the first cleared pixel lands in the same colorspace as shader-emitted pixels.