tr2/output: add support for animated sprites

This uses the same logic as TR1 to allow sprites to be animated.

Resolves LostArtefacts#2401.

docs/tr2/CHANGELOG.md

@@ -7,6 +7,7 @@
 - added the ability to hold left/right to move through menus more quickly (#2298)
 - added the ability to disable exit fade effects alone (#2348)
 - added a fade-out effect when completing Lara's Home
+- added support for animated sprites (#2401)
 - changed default input bindings to let the photo mode binding be compatible with TR1X:
     | Key                           | Old binding | New binding  |
     | ----------------------------- | ----------- | ------------ |

docs/tr2/README.md

@@ -107,6 +107,7 @@ game with new enhancements and features.
 - added ability to toggle between the software/hardware renderer at runtime
 - added optional fade effects to the hardware renderer
 - added text information when changing rendering options at runtime
+- added support for animated sprites
 - changed the hardware renderer to always use 16-bit textures
 - changed the software renderer to use the picture's palette for the background pictures
 - changed fullscreen behavior to use windowed desktop mode

src/tr2/game/output.c

@@ -757,6 +757,21 @@ void Output_DoAnimateTextures(const int32_t ticks)
             g_ObjectTextures[range->textures[i]] = temp;
             range = range->next_range;
         }
+
+        for (int32_t i = 0; i < MAX_STATIC_OBJECTS; i++) {
+            const STATIC_OBJECT_2D *const object = Object_GetStaticObject2D(i);
+            if (!object->loaded || object->frame_count == 1) {
+                continue;
+            }
+
+            const int16_t frame_count = object->frame_count;
+            const SPRITE_TEXTURE temp = g_SpriteTextures[object->texture_idx];
+            for (int32_t j = 0; j < frame_count - 1; j++) {
+                g_SpriteTextures[object->texture_idx + j] =
+                    g_SpriteTextures[object->texture_idx + j + 1];
+            }
+            g_SpriteTextures[object->texture_idx + frame_count - 1] = temp;
+        }
         m_TickComp -= TICKS_PER_FRAME * 5;
     }
 }