Three things, sorry. SDL composite texture bugfix, sprite offset position, some Grid render efficiencies

tests/unit/entity_sprite_offset_test.py

@@ -0,0 +1,91 @@
+"""Test Entity sprite_offset property (#233 sub-feature 1)"""
+import mcrfpy
+import sys
+
+passed = 0
+failed = 0
+
+def test(name, condition):
+    global passed, failed
+    if condition:
+        passed += 1
+    else:
+        failed += 1
+        print(f"FAIL: {name}")
+
+# Setup: create a grid and texture for entity tests
+scene = mcrfpy.Scene("test")
+mcrfpy.current_scene = scene
+tex = mcrfpy.Texture("assets/kenney_tinydungeon.png", 16, 16)
+grid = mcrfpy.Grid(grid_size=(10, 10), texture=tex, pos=(0, 0), size=(160, 160))
+scene.children.append(grid)
+
+# Test 1: Default sprite_offset is (0, 0)
+e = mcrfpy.Entity(grid_pos=(3, 3), texture=tex, sprite_index=0, grid=grid)
+test("default sprite_offset is (0,0)",
+     e.sprite_offset.x == 0.0 and e.sprite_offset.y == 0.0)
+
+# Test 2: Set sprite_offset via tuple
+e.sprite_offset = (-8, -16)
+test("set sprite_offset via tuple",
+     e.sprite_offset.x == -8.0 and e.sprite_offset.y == -16.0)
+
+# Test 3: Read individual components
+test("sprite_offset_x component", e.sprite_offset_x == -8.0)
+test("sprite_offset_y component", e.sprite_offset_y == -16.0)
+
+# Test 4: Set individual components
+e.sprite_offset_x = 4.5
+e.sprite_offset_y = -3.0
+test("set sprite_offset_x", e.sprite_offset_x == 4.5)
+test("set sprite_offset_y", e.sprite_offset_y == -3.0)
+test("individual set reflects in vector",
+     e.sprite_offset.x == 4.5 and e.sprite_offset.y == -3.0)
+
+# Test 5: Constructor kwarg
+e2 = mcrfpy.Entity(grid_pos=(1, 1), texture=tex, sprite_index=0,
+                    grid=grid, sprite_offset=(-8, -16))
+test("constructor kwarg sprite_offset",
+     e2.sprite_offset.x == -8.0 and e2.sprite_offset.y == -16.0)
+
+# Test 6: Constructor default when not specified
+e3 = mcrfpy.Entity(grid_pos=(2, 2), texture=tex, sprite_index=0, grid=grid)
+test("constructor default (0,0)",
+     e3.sprite_offset.x == 0.0 and e3.sprite_offset.y == 0.0)
+
+# Test 7: Animation support - verify property is animatable
+try:
+    e.animate("sprite_offset_x", -8.0, 0.5, "linear")
+    test("animate sprite_offset_x accepted", True)
+except Exception as ex:
+    test(f"animate sprite_offset_x accepted: {ex}", False)
+
+try:
+    e.animate("sprite_offset_y", -16.0, 0.5, "linear")
+    test("animate sprite_offset_y accepted", True)
+except Exception as ex:
+    test(f"animate sprite_offset_y accepted: {ex}", False)
+
+# Test 8: Animation actually changes value (step the game loop)
+e.sprite_offset_x = 0.0
+e.animate("sprite_offset_x", 10.0, 0.1, "linear")
+# Step enough to complete the animation
+for _ in range(5):
+    mcrfpy.step(0.05)
+test("animation changes sprite_offset_x", abs(e.sprite_offset_x - 10.0) < 0.1)
+
+# Test 9: Type errors
+try:
+    e.sprite_offset_x = "bad"
+    test("type error on string", False)
+except TypeError:
+    test("type error on string", True)
+
+# Summary
+print(f"\n{passed} passed, {failed} failed out of {passed + failed} tests")
+if failed:
+    print("FAIL")
+    sys.exit(1)
+else:
+    print("PASS")
+    sys.exit(0)