add alpha test

Author: pmp-p

src/test_alpha.py

@@ -0,0 +1,52 @@
+# /// script
+# dependencies = [
+#  "pygame-ce",
+# ]
+# ///
+
+import pygame
+import asyncio
+import platform, sys
+
+if sys.platform in ('emscripten', 'wasi'):
+    platform.document.body.style.background = "#00FF00"
+    platform.window.canvas.style.imageRendering = "pixelated"
+
+import pygame
+pygame.init()
+
+async def main():
+    screen = pygame.display.set_mode((800, 600))
+    clock = pygame.time.Clock()
+    BLUE = pygame.Color('dodgerblue4')
+    # I just create the background surface in the following lines.
+    background = pygame.Surface(screen.get_size())
+    background.fill((90, 120, 140))
+    for y in range(0, 600, 20):
+        for x in range(0, 800, 20):
+            pygame.draw.rect(background, BLUE, (x, y, 20, 20), 1)
+
+    # This dark gray surface will be blitted above the background surface.
+    surface = pygame.Surface(screen.get_size(), pygame.SRCALPHA)
+    surface.fill(pygame.Color('gray11'))
+
+    done = False
+    while not done:
+        for event in pygame.event.get():
+            if event.type == pygame.QUIT:
+                done = True
+            elif event.type == pygame.MOUSEMOTION:
+                surface.fill(pygame.Color('gray11'))  # Clear the gray surface ...
+                # ... and draw a transparent circle onto it to create a hole.
+                pygame.draw.circle(surface, (255, 255, 255, 0), event.pos, 90)
+
+        screen.blit(background, (0, 0))
+        screen.blit(surface, (0, 0))
+
+        pygame.display.flip()
+        clock.tick(30)
+        await asyncio.sleep(0)
+
+    pygame.quit()
+
+asyncio.run(main())