DarkRoom/core/dr-pipeline/tests/tone_curve.rs

//! TRACES: FR-DEV-3
//! The tone curve's four curves, seen from outside the crate.
//!
//! The unit tests beside the operation assert what one `ToneCurve` does. These
//! assert the two properties that only show up once it is a node in a chain
//! with a sidecar under it: that a file written before the per-channel curves
//! existed still describes the edit it described, and that the three new
//! curves cost a photograph that does not use them precisely nothing.

use dr_pipeline::ops::curve::{self, Axis, Channel};
use dr_pipeline::{EditGraph, Sidecar};

/// A version block carrying `params`, in the on-disk spelling.
fn sidecar_with(params: &[(&str, f32)]) -> String {
    let mut text =
        String::from("drsc 1\n\n[version u1]\nname = Default\nrevision = 2\nmodified = 0\n");
    for (key, value) in params {
        text.push_str(&format!("{key} = {value}\n"));
    }
    text
}

fn apply(text: &str) -> EditGraph {
    let sidecar = Sidecar::parse(text).expect("a valid sidecar");
    let mut graph = EditGraph::default_chain();
    sidecar
        .default_version()
        .expect("a default version")
        .apply(&mut graph);
    graph
}

/// TRACES: FR-CAT-8
/// **The compatibility guarantee, end to end.**
///
/// An edit made before this build existed has to produce the same image now.
/// Asserted on the generated shader rather than on the parameter values,
/// because that is what the photograph is actually made of: same source, same
/// uniforms, same picture.
#[test]
fn an_edit_written_before_the_channel_curves_renders_as_it_did() {
    let from_file = apply(&sidecar_with(&[
        ("tone_curve.p1_y", 0.15),
        ("tone_curve.p3_y", 0.85),
    ]));

    let mut by_hand = EditGraph::default_chain();
    by_hand.set_param(curve::ID, curve::P1_Y, 0.15);
    by_hand.set_param(curve::ID, curve::P3_Y, 0.85);

    let restored = from_file.compose();
    let expected = by_hand.compose();
    assert_eq!(restored.source, expected.source);
    assert_eq!(restored.uniforms, expected.uniforms);
    assert_eq!(restored.structure_hash, expected.structure_hash);
}

/// **Neutral means absent, and stays absent with four times as much to be
/// neutral about.**
///
/// The curve carries forty parameters now. An image edited with an S-curve and
/// nothing else must generate the shader it generated when it carried ten:
/// three untouched curves are not three identity evaluations, they are nothing
/// at all.
#[test]
fn three_untouched_curves_cost_nothing() {
    let mut graph = EditGraph::default_chain();
    graph.set_param(curve::ID, curve::P2_Y, 0.62);
    let shader = graph.compose();

    assert!(
        shader.source.contains("---- tone_curve ----"),
        "the master curve must reach the shader"
    );
    assert!(
        !shader.source.contains("channel_curve"),
        "an untouched channel curve reached the shader:\n{}",
        shader.source
    );
    for prefix in ["r_", "g_", "b_"] {
        assert!(
            !shader.source.contains(&format!("tone_curve_{prefix}")),
            "an untouched channel curve declared uniforms:\n{}",
            shader.source
        );
    }
}

/// And with none of them touched, the operation is not there at all — the
/// property `a_fresh_graph_is_neutral` asserts for the chain, restated for the
/// node that just quadrupled in size.
#[test]
fn a_curve_at_its_defaults_is_absent_from_the_shader() {
    let graph = EditGraph::default_chain();
    assert!(graph.is_neutral());
    assert!(!graph.compose().source.contains("tone_curve"));

    // Including when every one of the forty parameters has been explicitly
    // written to its own default, which is what a sidecar round trip through
    // a build with a different idea of "default" would produce.
    let mut written = EditGraph::default_chain();
    for cap in written.capabilities() {
        if cap.id != curve::ID {
            continue;
        }
        for p in &cap.params {
            written.set_param(curve::ID, p.id, p.default);
        }
    }
    assert!(written.is_neutral());
}

/// A grade with no tonal work is a real edit, and it must not drag the
/// luminance path in behind it.
#[test]
fn a_channel_curve_reaches_the_shader_on_its_own() {
    let mut graph = EditGraph::default_chain();
    graph.set_param(
        curve::ID,
        curve::coordinate(Channel::Blue, 0, Axis::Y),
        0.08,
    );

    let shader = graph.compose();
    assert!(shader.source.contains("c.b = channel_curve(c.b,"));
    assert!(
        !shader.source.contains("apply_tone_gain"),
        "the identity master curve reached the shader:\n{}",
        shader.source
    );
    // Blue's ten points, and nothing else: the other two curves are at the
    // identity and contribute no slot to the uniform block.
    for prefix in ["r_", "g_"] {
        assert!(
            !shader.source.contains(&format!("tone_curve_{prefix}")),
            "an untouched channel curve declared uniforms:\n{}",
            shader.source
        );
    }
    for point in 0..curve::POINTS {
        assert!(
            shader.source.contains(&format!("tone_curve_b_x{point}")),
            "blue's point {point} is missing from the uniform block"
        );
    }
}

/// Each curve is its own shader, so the pipeline cache cannot hand the red
/// curve's compiled program to an edit that moved the green one.
#[test]
fn every_curve_generates_a_distinct_shader() {
    let mut hashes: Vec<u64> = Vec::new();
    for channel in Channel::ALL {
        let mut graph = EditGraph::default_chain();
        graph.set_param(curve::ID, curve::coordinate(channel, 2, Axis::Y), 0.62);
        hashes.push(graph.compose().structure_hash);
    }
    let before = hashes.len();
    hashes.sort_unstable();
    hashes.dedup();
    assert_eq!(before, hashes.len(), "two curves share a compiled shader");
}

/// The forty parameters all persist, and the file names each one once.
#[test]
fn every_point_of_every_curve_round_trips_through_a_sidecar() {
    let mut graph = EditGraph::default_chain();
    // A different y per coordinate, so a point wired to the wrong channel
    // cannot pass by holding the value it was supposed to hold anyway.
    // Thirty-secondths because they survive both the decimal the file is
    // written in and the binary32 it is read back into exactly — this test is
    // about which parameter a value lands in, and a rounding difference here
    // would fail it for an unrelated reason.
    let mut step = 1;
    for channel in Channel::ALL {
        for point in 0..curve::POINTS {
            graph.set_param(
                curve::ID,
                curve::coordinate(channel, point, Axis::Y),
                step as f32 / 32.0,
            );
            step += 1;
        }
    }

    let mut sidecar = Sidecar::new();
    sidecar.put(dr_pipeline::sidecar::Version::from_graph(
        "u1", "Default", &graph,
    ));
    let restored = apply(&sidecar.to_text());

    for channel in Channel::ALL {
        for point in 0..curve::POINTS {
            let id = curve::coordinate(channel, point, Axis::Y);
            assert_eq!(
                restored.param(curve::ID, id),
                graph.param(curve::ID, id),
                "{id} did not survive the sidecar"
            );
        }
    }
}