cranpose-render-common 0.0.58

Common rendering contracts for Cranpose
Documentation 
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use cranpose_ui_graphics::{GraphicsLayer, Point, Rect};

use crate::graph::{quad_bounds, ProjectiveTransform};

pub(crate) fn layer_scale_x(layer: &GraphicsLayer) -> f32 {
    layer.scale * layer.scale_x
}

pub(crate) fn layer_scale_y(layer: &GraphicsLayer) -> f32 {
    layer.scale * layer.scale_y
}

pub fn layer_uniform_scale(layer: &GraphicsLayer) -> f32 {
    layer_scale_x(layer).min(layer_scale_y(layer))
}

pub fn apply_layer_affine_to_rect(rect: Rect, layer_bounds: Rect, layer: &GraphicsLayer) -> Rect {
    let offset_x = rect.x - layer_bounds.x;
    let offset_y = rect.y - layer_bounds.y;
    let scale_x = layer_scale_x(layer);
    let scale_y = layer_scale_y(layer);
    Rect {
        x: layer_bounds.x + offset_x * scale_x + layer.translation_x,
        y: layer_bounds.y + offset_y * scale_y + layer.translation_y,
        width: rect.width * scale_x,
        height: rect.height * scale_y,
    }
}

fn layer_rotation_pivot(layer_bounds: Rect, layer: &GraphicsLayer) -> (f32, f32) {
    (
        layer_bounds.x + layer_bounds.width * layer.transform_origin.pivot_fraction_x,
        layer_bounds.y + layer_bounds.height * layer.transform_origin.pivot_fraction_y,
    )
}

fn layer_has_rotation(layer: &GraphicsLayer) -> bool {
    layer.rotation_x.abs() > f32::EPSILON
        || layer.rotation_y.abs() > f32::EPSILON
        || layer.rotation_z.abs() > f32::EPSILON
}

fn apply_rotation_and_perspective(
    point: [f32; 2],
    pivot: (f32, f32),
    layer: &GraphicsLayer,
) -> [f32; 2] {
    if !layer_has_rotation(layer) {
        return point;
    }

    let mut x = point[0] - pivot.0;
    let mut y = point[1] - pivot.1;
    let mut z = 0.0f32;

    let (sin_x, cos_x) = layer.rotation_x.to_radians().sin_cos();
    let (sin_y, cos_y) = layer.rotation_y.to_radians().sin_cos();
    let (sin_z, cos_z) = layer.rotation_z.to_radians().sin_cos();

    let y_rot_x = y * cos_x - z * sin_x;
    let z_rot_x = y * sin_x + z * cos_x;
    y = y_rot_x;
    z = z_rot_x;

    let x_rot_y = x * cos_y + z * sin_y;
    let z_rot_y = -x * sin_y + z * cos_y;
    x = x_rot_y;
    z = z_rot_y;

    let x_rot_z = x * cos_z - y * sin_z;
    let y_rot_z = x * sin_z + y * cos_z;
    x = x_rot_z;
    y = y_rot_z;

    const CAMERA_DISTANCE_SCALE: f32 = 72.0;
    let camera_distance = (layer.camera_distance * CAMERA_DISTANCE_SCALE).max(1.0);
    let denom = (camera_distance - z).max(1.0);
    let perspective = camera_distance / denom;

    [pivot.0 + x * perspective, pivot.1 + y * perspective]
}

pub fn apply_layer_to_quad(rect: Rect, layer_bounds: Rect, layer: &GraphicsLayer) -> [[f32; 2]; 4] {
    let affine_rect = apply_layer_affine_to_rect(rect, layer_bounds, layer);
    let affine_layer_bounds = apply_layer_affine_to_rect(layer_bounds, layer_bounds, layer);
    let pivot = layer_rotation_pivot(affine_layer_bounds, layer);
    let quad = [
        [affine_rect.x, affine_rect.y],
        [affine_rect.x + affine_rect.width, affine_rect.y],
        [affine_rect.x, affine_rect.y + affine_rect.height],
        [
            affine_rect.x + affine_rect.width,
            affine_rect.y + affine_rect.height,
        ],
    ];

    quad.map(|point| apply_rotation_and_perspective(point, pivot, layer))
}

pub fn apply_layer_to_rect(rect: Rect, layer_bounds: Rect, layer: &GraphicsLayer) -> Rect {
    quad_bounds(apply_layer_to_quad(rect, layer_bounds, layer))
}

pub fn layer_transform_to_parent(
    local_bounds: Rect,
    placement: Point,
    layer: &GraphicsLayer,
) -> ProjectiveTransform {
    let placement_rect = Rect {
        x: placement.x,
        y: placement.y,
        width: local_bounds.width,
        height: local_bounds.height,
    };
    ProjectiveTransform::from_rect_to_quad(
        local_bounds,
        apply_layer_to_quad(placement_rect, placement_rect, layer),
    )
}

#[cfg(test)]
mod tests {
    use super::*;
    use cranpose_ui_graphics::{Rect, TransformOrigin};

    #[test]
    fn layer_transform_to_parent_maps_local_bounds_to_positioned_bounds() {
        let local_bounds = Rect {
            x: 0.0,
            y: 0.0,
            width: 30.0,
            height: 18.0,
        };
        let placement = Point { x: 12.0, y: 9.0 };
        let transform =
            layer_transform_to_parent(local_bounds, placement, &GraphicsLayer::default());

        assert_eq!(
            transform.bounds_for_rect(local_bounds),
            Rect {
                x: 12.0,
                y: 9.0,
                width: 30.0,
                height: 18.0,
            }
        );
    }

    #[test]
    fn layer_transform_to_parent_applies_rotation_about_transform_origin() {
        let local_bounds = Rect {
            x: 0.0,
            y: 0.0,
            width: 100.0,
            height: 40.0,
        };
        let layer = GraphicsLayer {
            rotation_z: 90.0,
            transform_origin: TransformOrigin::CENTER,
            ..Default::default()
        };

        let transform = layer_transform_to_parent(local_bounds, Point::default(), &layer);
        let mapped = transform.bounds_for_rect(local_bounds);

        assert!((mapped.width - 40.0).abs() < 0.01);
        assert!((mapped.height - 100.0).abs() < 0.01);
    }
}