(svn r22923) -Codechange: Move application of the construction stage into TileLayoutSpriteGroup::ProcessRegisters().

1 files changed, 19 insertions, 0 deletions

diff --git a/src/newgrf_commons.h b/src/newgrf_commons.h
index ec669d907..a77da3cd2 100644
--- a/src/newgrf_commons.h
+++ b/src/newgrf_commons.h
@@ -70,6 +70,25 @@ enum TileLayoutFlags {
 DECLARE_ENUM_AS_BIT_SET(TileLayoutFlags)
 
 /**
+ * Determines which sprite to use from a spriteset for a specific construction stage.
+ * @param construction_stage Construction stage 0 - 3.
+ * @param num_sprites Number of available sprites to select stage from.
+ * @return Sprite to use
+ */
+static inline uint GetConstructionStageOffset(uint construction_stage, uint num_sprites)
+{
+	assert(num_sprites > 0);
+	if (num_sprites > 4) num_sprites = 4;
+	switch (construction_stage) {
+		case 0: return 0;
+		case 1: return num_sprites > 2 ? 1 : 0;
+		case 2: return num_sprites > 2 ? num_sprites - 2 : 0;
+		case 3: return num_sprites - 1;
+		default: NOT_REACHED();
+	}
+}
+
+/**
  * Additional modifiers for items in sprite layouts.
  */
 struct TileLayoutRegisters {