flight-jai/physics.jai

#import "Basic";
#import "Math";
#import "Window_Creation";
Input :: #import "Input";
Simp :: #import "Simp";

window_width  : s32 = 1280;
window_height : s32 = 720;

xy :: (x: int, y: int) -> Vector2 {
    return xy(cast(float)x, cast(float)y);
}
drawing_in_world_space: bool = false;
line :: (_from: Vector2, _to: Vector2, width: float = 1.0) {
    from := _from;
    to := _to;
    if drawing_in_world_space {
        from = world_to_screen(from);
        to = world_to_screen(to);
    }
    Simp.set_shader_for_color();
    normal := rotate(unit_vector(to - from), PI/2.0);
    Simp.immediate_quad(from + normal*width, from - normal*width, to + normal*width, to - normal*width);
}

Rect :: struct {
    pos, halfsize: Vector2; // pos is in world space
    rotation: float;
};
draw_rect :: (using r: Rect) {
    facing_to_right := rotate(xy(halfsize.x,0.0), rotation);
    facing_to_up    := rotate(xy(0.0,halfsize.y), rotation);

    upper_right := pos + facing_to_right + facing_to_up;
    upper_left  := pos - facing_to_right + facing_to_up;
    lower_left  := pos - facing_to_right - facing_to_up;
    lower_right := pos + facing_to_right - facing_to_up;

    line(upper_left, upper_right);
    line(upper_right, lower_right);
    line(lower_right, lower_left);
    line(lower_left, upper_left);
}

mouse :: () -> Vector2 {
    x, y := get_mouse_pointer_position();
    pos: Vector2 = xy(cast(float)x, cast(float)y);

    // simp is lower left is (0, 0) and y+ is up
    pos.y = window_height - pos.y;

    return pos;
}

Camera :: struct {
    pos: Vector2;
    zoom: float = 1.0;
};

camera : Camera; 
screen_to_world :: (screen: Vector2) -> Vector2 {
    using camera;
    return (screen + pos)*zoom;
}
world_to_screen :: (world: Vector2) -> Vector2 {
    using camera;
    // world = (screen + pos)*zoom;
    // world/zoom = screen + pos;
    // world/zoom - pos = screen;
    return (world/zoom) - pos;
}

main :: () {
    window := create_window(window_width, window_height, "A Window");
    // Actual render size in pixels can be different from the window dimensions we specified above (for example on high-resolution displays on macOS/iOS).
    window_width, window_height = Simp.get_render_dimensions(window);

    Simp.set_render_target(window);

    rects: [..]Rect;
    array_add(*rects, .{pos = #run xy(0.0,  0.0), halfsize = #run xy(30.0)});
    array_add(*rects, .{pos = #run xy(40.0, 0.0), halfsize = #run xy(30.0)});

    quit := false;
    last_time := get_time();
    panning: bool = false;
    last_mouse_pos := mouse();
    while !quit {
        dt := cast(float)(get_time() - last_time);
        last_time = get_time();
        Input.update_window_events();
        mouse_delta := mouse() - last_mouse_pos; // using Input.mouse_delta_x seems to incorrectly accumulate
        last_mouse_pos = mouse();

        for Input.get_window_resizes() {
            Simp.update_window(it.window);  // Simp will do nothing if it doesn't care about this window.
            
            if it.window == window {
                should_reinit := (it.width != window_width) || (it.height != window_height);

                window_width  = it.width;
                window_height = it.height;

                //if should_reinit my_init_fonts();  // Resize the font for the new window size.
            }
        }

        print("%\n", Input.mouse_delta_z);
        camera.zoom *= 1.0 - 0.1*Input.mouse_delta_z/120.0;
        if panning {
            camera.pos -= mouse_delta;

            //camera.pos -= xy(Input.mouse_delta_x, -Input.mouse_delta_y);
            
            // this doesn't fix it
            //Input.mouse_delta_x = 0;
            //Input.mouse_delta_y = 0;
        }

        rects[0].rotation += dt * 1.0;

        Simp.clear_render_target(0.0, 0.0, 0.0, 1.0);

        drawing_in_world_space = true;
        for rects draw_rect(it);
        line(xy(0.0, 0.0), screen_to_world(mouse()));
        drawing_in_world_space = false;

        Simp.swap_buffers(window);

        for Input.events_this_frame {
            if it.type == .QUIT then quit = true;

            if it.type == {
              case .KEYBOARD;
                if it.key_pressed && it.key_code == .ESCAPE {
                    quit = true;
                }
                if it.key_code == .MOUSE_BUTTON_LEFT {
                    panning = cast(bool)it.key_pressed;
                }
            }
        }

    }
}