examples: add examples/gg/random.v demonstrating how to stream images/pixels

examples/gg/random.v

@@ -0,0 +1,63 @@
+import gg
+import time
+
+const pwidth = 800
+
+const pheight = 600
+
+const pbytes = 4
+
+struct AppState {
+mut:
+	gg          &gg.Context = 0
+	istream_idx int
+	pixels      [pwidth][pheight]u32
+}
+
+[direct_array_access]
+fn (mut state AppState) update() {
+	mut rcolor := u64(state.gg.frame)
+	for {
+		for x in 0 .. pwidth {
+			for y in 0 .. pheight {
+				rcolor = rcolor * 1664525 + 1013904223
+				state.pixels[x][y] = u32(rcolor & 0x0000_0000_FFFF_FFFF) | 0x1010AFFF
+			}
+		}
+		time.sleep(33 * time.millisecond)
+	}
+}
+
+fn (mut state AppState) draw() {
+	mut istream_image := state.gg.get_cached_image_by_idx(state.istream_idx)
+	istream_image.update_pixel_data(&state.pixels)
+	size := gg.window_size()
+	state.gg.draw_image(0, 0, size.width, size.height, istream_image)
+}
+
+// gg callbacks:
+
+fn graphics_init(mut state AppState) {
+	state.istream_idx = state.gg.new_streaming_image(pwidth, pheight, pbytes)
+}
+
+fn graphics_frame(mut state AppState) {
+	state.gg.begin()
+	state.draw()
+	state.gg.end()
+}
+
+fn main() {
+	mut state := &AppState{}
+	state.gg = gg.new_context(
+		width: 800
+		height: 600
+		create_window: true
+		window_title: 'Random Static'
+		init_fn: graphics_init
+		frame_fn: graphics_frame
+		user_data: state
+	)
+	go state.update()
+	state.gg.run()
+}