gecko-dev/gfx/webrender/res/rect.glsl

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

struct RectWithSize {
    vec2 p0;
    vec2 size;
};

struct RectWithEndpoint {
    vec2 p0;
    vec2 p1;
};

RectWithEndpoint to_rect_with_endpoint(RectWithSize rect) {
    RectWithEndpoint result;
    result.p0 = rect.p0;
    result.p1 = rect.p0 + rect.size;

    return result;
}

RectWithSize to_rect_with_size(RectWithEndpoint rect) {
    RectWithSize result;
    result.p0 = rect.p0;
    result.size = rect.p1 - rect.p0;

    return result;
}

RectWithSize transform_rect(RectWithSize rect, mat2 transform) {
    vec2 center = transform * (rect.p0 + rect.size * 0.5);
    vec2 radius = mat2(abs(transform[0]), abs(transform[1])) * (rect.size * 0.5);
    return RectWithSize(center - radius, radius * 2.0);
}

RectWithSize intersect_rects(RectWithSize a, RectWithSize b) {
    RectWithSize result;
    result.p0 = max(a.p0, b.p0);
    result.size = min(a.p0 + a.size, b.p0 + b.size) - result.p0;

    return result;
}

bool rect_inside_rect(RectWithSize little, RectWithSize big) {
    return all(lessThanEqual(vec4(big.p0, little.p0 + little.size),
                             vec4(little.p0, big.p0 + big.size)));
}