v/examples/fireworks/fireworks.v

import os
import objects
import gg
import gx
import rand
import sokol.sapp

struct App {
mut:
	gg      &gg.Context       = 0
	ui      &objects.UIParams = 0
	rockets []objects.Rocket
	frames  [][]objects.Rocket
	// i thought about using a fixed fifo queue for the frames but the array
	// seemed to work fine, if you'd like a challenge try implementing it with the queue :)
}

fn on_frame(mut app App) {
	app.gg.begin()

	// drawing previous frames
	for mut frame in app.frames {
		for mut rocket in frame {
			if !rocket.exploded {
				rocket.color.a = byte(f32_max(rocket.color.a - 8, 0))
				rocket.draw(mut app.gg)
			}
		}
	}

	// chance of firing new rocket
	if rand.intn(30) == 0 {
		app.rockets << objects.new_rocket()
	}
	// simulating rockets
	app.rockets = app.rockets.filter(!it.dead)

	for mut rocket in app.rockets {
		rocket.tick(mut app.gg)
	}

	// adding frame
	mut frame := app.rockets.clone()

	for mut rocket in frame {
		rocket.particles = []
	}

	app.frames << frame

	// trimming out frames
	if app.frames.len > 30 {
		app.frames.delete(0)
	}

	app.gg.end()
}

fn on_event(e &sapp.Event, mut app App) {
	match e.typ {
		.resized, .restored, .resumed { app.resize() }
		else {}
	}
}

fn (mut app App) resize() {
	mut s := sapp.dpi_scale()
	if s == 0.0 {
		s = 1.0
	}
	w := int(sapp.width() / s)
	h := int(sapp.height() / s)
	app.ui.dpi_scale = s
	app.ui.width = w
	app.ui.height = h
}

fn main() {
	mut font_path := os.resource_abs_path(os.join_path('../assets/fonts/', 'RobotoMono-Regular.ttf'))
	$if android {
		font_path = 'fonts/RobotoMono-Regular.ttf'
	}

	mut app := &App{}
	app.ui = objects.get_params()

	app.gg = gg.new_context(
		width: app.ui.width
		height: app.ui.height
		window_title: 'Fireworks!'
		bg_color: gx.black
		use_ortho: true
		user_data: app
		frame_fn: on_frame
		event_fn: on_event
		font_path: font_path
	)

	app.gg.run()
}