added a script to test clipping of drawn lines

scripts/test_clipping.py

@@ -0,0 +1,23 @@
+# Test of line clipping
+import upiwin
+
+hdc = upiwin.DevCtxt(type='screen')
+hdc.text_color = 0xFFFFFF  # white
+hdc.rectangle(100, 100, 199, 199)
+
+clip = hdc.get_clip_rect()
+hdc.set_clip_rect(100, 100, 200, 200)
+
+hdc.text_color = 0xFF0000  # red
+hdc.move_to(0, 200)
+hdc.line_to(200, 0)
+
+hdc.set_clip_rect(clip[0], clip[1], clip[2], clip[3])
+
+msg = {}
+while upiwin.get_message(msg):
+	if msg['message'] == upiwin.WM_HWBUTTONUP:
+		bn = msg['attrs'][0]
+		if bn == 4:
+			print("Quitting the application.")
+			upiwin.post_quit_message(0)