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Ask the platform what colour the screen actually is

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FR-DSP-8's acquisition half. `dr_plat::display` surveys the session's
displays and reduces each one's profile to an output space the pipeline
can encode into, stating the mechanism per display server as
FR-PLAT-LIN-2 requires:

  - X11 reads the `_ICC_PROFILE` / `_ICC_PROFILE_<n>` root-window
    properties, enumerating and numbering the outputs through RandR,
    which also yields the rectangles a window move is measured against.
  - Wayland binds `wp_color_manager_v1` and asks each `wl_output` for
    its image description, accepting either an ICC profile on a file
    descriptor or primaries stated as chromaticities.
  - Where neither answers, sRGB is assumed and the reason travels with
    it as data rather than into a log, so the About page can say which
    path the session is on.

A display profile is a measurement of one panel and is none of the four
spaces the pipeline knows. Rather than grow an ICC engine, the profile
is reduced to D50-adapted colorants and matched against the four; a
match that is merely nearest is marked as such and shown as such.

Verified on this machine: mutter 50 advertises the colour-management
global and reports eDP-1 as sRGB, and the same session forced onto X11
enumerates the output through RandR and correctly finds no atom.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
This commit is contained in:
dtourolle
2026-08-27 18:20:28 +02:00
co-authored by Claude Opus 5
parent 725f7bf77f
commit e4875498ca
10 changed files with 1561 additions and 2 deletions
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platform/dr-plat/examples/display_probe.rs
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//! What this machine's display server will say about its monitors.
//!
//! The same probe the application runs at startup, printed instead of used.
//! It exists for the reason `keyring_check` does: the answer depends entirely
//! on the desktop the code is running on, so the only way to know which
//! acquisition path a given machine takes is to ask it there.
//!
//! cargo run -p dr-plat --example display_probe
fn main() {
env_logger::init();
let survey = dr_plat::DisplaySurvey::probe();
println!("display server: {}", survey.server.label());
println!();
for (index, display) in survey.displays.iter().enumerate() {
println!("[{index}] {}", display.name);
println!(" space: {}", display.profile.space.label());
println!(" reading: {}", display.profile.describe());
println!(
" source: {:?} measured: {} approximated: {}",
display.profile.source,
display.profile.source.is_measured(),
display.profile.approximated
);
match display.bounds {
Some(b) => println!(
" bounds: {}×{} at ({}, {})",
b.width, b.height, b.x, b.y
),
// Expected on Wayland; see `DisplaySurvey::containing`.
None => println!(" bounds: not stated by this display server"),
}
println!();
}
}