Add gallery testcase.

testcases/game/mygallery.rpy

@@ -0,0 +1,45 @@
+image b0 red = "#f00"
+image b0 green = "#0f0"
+image b0 blue = "#00f"
+image b1 red = "#f00"
+image b1 green = "#0f0"
+image b1 blue = "#00f"
+image b2 red = "#f00"
+image b2 green = "#0f0"
+image b2 blue = "#00f"
+
+
+init python:
+    g = Gallery()
+
+    g.button("b0")
+    g.unlock_image("b0 red")
+    g.unlock_image("b0 green")
+    g.unlock_image("b0 blue")
+
+    g.button("b1")
+    g.unlock_image("b1 red")
+    g.unlock_image("b1 green")
+    g.unlock_image("b1 blue")
+
+    g.button("b2")
+    g.unlock_image("b2 red")
+    g.unlock_image("b2 green")
+    g.unlock_image("b2 blue")
+
+
+screen gallery:
+    vbox:
+        textbutton "b0" action g.Action("b0")
+        textbutton "b1" action g.Action("b1")
+        textbutton "b2" action g.Action("b2")
+
+label gallery:
+    show b0 green
+    show b0 blue
+    hide b0
+
+    call screen gallery
+
+    return
+