ona/src/demos/graphics.zig

const ona = @import("ona");

const std = @import("std");

const CRT = extern struct {
    width: f32,
    height: f32,
    time: f32,
    padding: [4]u8 = undefined,
};

const State = struct {
    images: [2]ona.gfx.Images.Handle = [_]ona.gfx.Images.Handle{.default} ** 2,
    last_time: f64 = 0,
    image_index: usize = 0,
    crt_effect: ona.gfx.Effects.Handle = .default,
    loaded_image: ona.gfx.Images.Handle = .default,
};

fn load(display: ona.Write(ona.gfx.Display), state: ona.Write(State), images: ona.gfx.Images, effects: ona.gfx.Effects) !void {
    display.ptr.size = .{ 1280, 720 };

    state.ptr.loaded_image = try images.load(ona.gfx.QoiImage{
        .path = try .parse("graphics_image.qoi"),
    });

    errdefer {
        images.unload(state.ptr.images[1]);
    }

    state.ptr.crt_effect = try effects.load(ona.gfx.GlslEffect{
        .fragment = .{
            .glsl = @embedFile("crt.frag"),
            .name = "crt.frag",
        },
    });

    errdefer {
        effects.unload(state.ptr.crt_effect);
    }

    state.ptr.images[0] = try images.load(ona.gfx.CheckerImage{
        .colors = .{ .black, .purple },
        .square_size = 4,
        .width = 8,
        .height = 8,
    });

    errdefer {
        images.unload(state.ptr.images[0]);
    }

    state.ptr.images[1] = try images.load(ona.gfx.CheckerImage{
        .colors = .{ .black, .grey },
        .square_size = 4,
        .width = 8,
        .height = 8,
    });

    errdefer {
        images.unload(state.ptr.images[1]);
    }
}

pub fn main() void {
    ona.realtime_app
        .with(.initModule(ona.hid))
        .with(.initModule(ona.gfx))
        .with(.initState(State{}))
        .with(.initSystem(.load, .of(load)))
        .with(.initSystem(.render, .of(render)))
        .with(.initSystem(.update, .of(update)))
        .run();
}

fn render(scene: ona.gfx.Scene, state: ona.Read(State), display: ona.Write(ona.gfx.Display), time: ona.Read(ona.App.Time)) void {
    const width, const height = display.ptr.size;

    scene.updateEffect(state.ptr.crt_effect, CRT{
        .width = @floatFromInt(width),
        .height = @floatFromInt(height),
        .time = @floatCast(time.ptr.elapsed),
    });

    scene.drawSprite(state.ptr.images[state.ptr.image_index], .{
        .size = .{ @floatFromInt(width), @floatFromInt(height) },
        .effect = state.ptr.crt_effect,
    });
}

fn update(state: ona.Write(State), time: ona.Read(ona.App.Time)) void {
    const update_seconds = 5;

    if ((time.ptr.elapsed - state.ptr.last_time) > update_seconds) {
        state.ptr.image_index = (state.ptr.image_index + 1) % state.ptr.images.len;
        state.ptr.last_time = time.ptr.elapsed;
    }
}