gg: update draw polygon test (#14880)

vlib/gg/testdata/draw_simple_polygons.vv

@@ -1,14 +1,20 @@
+module main
+
 import gg
 import gx
 
 struct App {
 mut:
-	gg       &gg.Context = 0
+	gg       &gg.Context = unsafe { 0 }
 	rotation f32 = f32(0)
+	edge     int = 3
 }
 
 [console]
 fn main() {
+	println('rotation: left arrow key, right arrow key')
+	println('center polygon edge: up arrow key, down arrow key')
+
 	mut app := &App{}
 
 	app.gg = gg.new_context(
@@ -33,14 +39,19 @@ fn render(app &App) {
 		b: 0
 		a: 200
 	}
-	mut shape := 3
-	for i := 1; i < 5; i++ {
-		for j := 1; j < 5; j++ {
-			app.gg.draw_polygon_filled(100 * j, 100 * i, 30, shape, app.rotation, color)
-			shape++
+	mut edge := 3
+	for i := 0; i <= 5; i++ {
+		for j := 0; j <= 5; j++ {
+			if i == 0 || j == 0 || i == 5 || j == 5 {
+				app.gg.draw_polygon_filled(50 + 80 * i, 50 + 80 * j, 30, edge, app.rotation,
+					color)
+				edge++
+			}
 		}
 	}
 
+	app.gg.draw_polygon_filled(250, 250, 150, app.edge, app.rotation, color)
+
 	app.gg.end()
 }
 
@@ -48,13 +59,25 @@ fn event(e &gg.Event, mut app App) {
 	match e.typ {
 		.key_down {
 			match e.key_code {
-				.right { app.rotation++ }
-				.left { app.rotation-- }
-				.escape { app.gg.quit() }
+				.up {
+					app.edge++
+				}
+				.down {
+					if app.edge > 3 {
+						app.edge--
+					}
+				}
+				.right {
+					app.rotation++
+				}
+				.left {
+					app.rotation--
+				}
+				.escape {
+					app.gg.quit()
+				}
 				else {}
 			}
-			print('rotation: ')
-			println(app.rotation)
 		}
 		else {}
 	}