examples: add gg/fire.v (#21784)

examples/gg/fire.v

@@ -0,0 +1,149 @@
+// Use `v -d show_fps run examples/gg/fire.v` to show a fire effect with an FPS counter.
+import gg
+import gx
+import rand
+
+const win_width = 800
+const win_height = 600
+const width = 100
+const height = 140
+const scale = 4
+const palette = [
+	gx.rgb(0x07, 0x07, 0x07),
+	gx.rgb(0x1f, 0x07, 0x07),
+	gx.rgb(0x2f, 0x0f, 0x07),
+	gx.rgb(0x47, 0x0f, 0x07),
+	gx.rgb(0x57, 0x17, 0x07),
+	gx.rgb(0x67, 0x1f, 0x07),
+	gx.rgb(0x77, 0x1f, 0x07),
+	gx.rgb(0x8f, 0x27, 0x07),
+	gx.rgb(0x9f, 0x2f, 0x07),
+	gx.rgb(0xaf, 0x3f, 0x07),
+	gx.rgb(0xbf, 0x47, 0x07),
+	gx.rgb(0xc7, 0x47, 0x07),
+	gx.rgb(0xdf, 0x4f, 0x07),
+	gx.rgb(0xdf, 0x57, 0x07),
+	gx.rgb(0xdf, 0x57, 0x07),
+	gx.rgb(0xd7, 0x5f, 0x07),
+	gx.rgb(0xd7, 0x5f, 0x07),
+	gx.rgb(0xd7, 0x67, 0x0f),
+	gx.rgb(0xcf, 0x6f, 0x0f),
+	gx.rgb(0xcf, 0x77, 0x0f),
+	gx.rgb(0xcf, 0x7f, 0x0f),
+	gx.rgb(0xcf, 0x87, 0x17),
+	gx.rgb(0xc7, 0x87, 0x17),
+	gx.rgb(0xc7, 0x8f, 0x17),
+	gx.rgb(0xc7, 0x97, 0x1f),
+	gx.rgb(0xbf, 0x9f, 0x1f),
+	gx.rgb(0xbf, 0x9f, 0x1f),
+	gx.rgb(0xbf, 0xa7, 0x27),
+	gx.rgb(0xbf, 0xa7, 0x27),
+	gx.rgb(0xbf, 0xaf, 0x2f),
+	gx.rgb(0xb7, 0xaf, 0x2f),
+	gx.rgb(0xb7, 0xb7, 0x2f),
+	gx.rgb(0xb7, 0xb7, 0x37),
+	gx.rgb(0xcf, 0xcf, 0x6f),
+	gx.rgb(0xdf, 0xdf, 0x9f),
+	gx.rgb(0xef, 0xef, 0xc7),
+	gx.rgb(0xff, 0xff, 0xff),
+]!
+
+struct App {
+mut:
+	gg    &gg.Context = unsafe { nil }
+	buf   [][]int
+	dying bool
+	tiles int
+}
+
+fn main() {
+	mut app := &App{
+		buf: [][]int{len: height - 1, init: []int{len: width}}
+	}
+	app.buf << []int{len: width, init: 36} // white fire base
+
+	app.gg = gg.new_context(
+		event_fn: event
+		frame_fn: frame
+		init_fn: retile
+		window_title: 'Fire Animation'
+		user_data: app
+		bg_color: palette[0]
+		width: win_width
+		height: win_height
+	)
+	app.gg.run()
+}
+
+fn retile(mut app App) {
+	size := app.gg.window_size()
+	app.tiles = size.width / (width * scale) + 1
+}
+
+fn (mut app App) draw() {
+	size := app.gg.window_size()
+	for t in 0 .. app.tiles {
+		app.gg.begin()
+		for y, row in app.buf {
+			for x, i in row {
+				app.gg.draw_square_filled(t * width * scale + x * scale,
+					(size.height - height * scale) + y * scale, scale, palette[i])
+			}
+		}
+		app.gg.end(
+			how: if t == 0 { .clear } else { .passthru }
+		)
+		// one pass per tile to avoid sgl vertex limit
+	}
+}
+
+@[direct_array_access]
+fn (mut app App) tick() {
+	for x in 0 .. width {
+		for y in 1 .. height {
+			if app.buf[y][x] > 0 {
+				r := rand.intn(4) or { panic('failed to generate random number') }
+				xn := ((x - r + 1) % width + width) % width
+				app.buf[y - 1][xn] = app.buf[y][x] - r % 2
+			} else {
+				app.buf[y - 1][x] = 0
+			}
+		}
+	}
+	if app.dying {
+		for x in 0 .. width {
+			y := height - 1
+			app.buf[y][x] -= rand.intn(4) or { panic('failed to generate random number') }
+			if app.buf[y][x] < 0 {
+				app.buf[y][x] = 0
+			}
+		}
+	}
+}
+
+fn event(event &gg.Event, mut app App) {
+	match event.typ {
+		.key_up {
+			match event.key_code {
+				.space {
+					if app.dying {
+						app.dying = false
+						app.buf[height - 1] = []int{len: width, init: 36}
+					} else {
+						app.dying = true
+					}
+				}
+				else {}
+			}
+		}
+		.resized {
+			retile(mut app)
+		}
+		else {}
+	}
+}
+
+fn frame(mut app App) {
+	app.draw()
+	app.tick()
+}