Fix display of zoning overlay sprites on half-tile foundations

Partly based on commit 598b781259a5c1ad25cf3de85807b9c79e9f08fe

src/viewport.cpp

@@ -149,14 +149,6 @@ struct ChildScreenSpriteToDraw {
 	int next;                       ///< next child to draw (-1 at the end)
 };
 
-/** Enumeration of multi-part foundations */
-enum FoundationPart {
-	FOUNDATION_PART_NONE     = 0xFF,  ///< Neither foundation nor groundsprite drawn yet.
-	FOUNDATION_PART_NORMAL   = 0,     ///< First part (normal foundation or no foundation)
-	FOUNDATION_PART_HALFTILE = 1,     ///< Second part (halftile foundation)
-	FOUNDATION_PART_END
-};
-
 /**
  * Mode of "sprite combining"
  * @see StartSpriteCombine
@@ -1015,16 +1007,17 @@ static void AddStringToDraw(int x, int y, StringID string, uint64 params_1, uint
  * @param ti TileInfo Tile that is being drawn
  * @param z_offset Z offset relative to the groundsprite. Only used for the sprite position, not for sprite sorting.
  * @param foundation_part Foundation part the sprite belongs to.
+ * @param sub Sub-section of sprite to draw.
  */
-static void DrawSelectionSprite(SpriteID image, PaletteID pal, const TileInfo *ti, int z_offset, FoundationPart foundation_part)
+void DrawSelectionSprite(SpriteID image, PaletteID pal, const TileInfo *ti, int z_offset, FoundationPart foundation_part, const SubSprite *sub)
 {
 	/* FIXME: This is not totally valid for some autorail highlights that extend over the edges of the tile. */
 	if (_vd.foundation[foundation_part] == -1) {
 		/* draw on real ground */
-		AddTileSpriteToDraw(image, pal, ti->x, ti->y, ti->z + z_offset);
+		AddTileSpriteToDraw(image, pal, ti->x, ti->y, ti->z + z_offset, sub);
 	} else {
 		/* draw on top of foundation */
-		AddChildSpriteToFoundation(image, pal, NULL, foundation_part, 0, -z_offset * ZOOM_LVL_BASE);
+		AddChildSpriteToFoundation(image, pal, sub, foundation_part, 0, -z_offset * ZOOM_LVL_BASE);
 	}
 }
 
@@ -1034,7 +1027,7 @@ static void DrawSelectionSprite(SpriteID image, PaletteID pal, const TileInfo *t
  * @param ti TileInfo Tile that is being drawn
  * @param pal Palette to apply.
  */
-static void DrawTileSelectionRect(const TileInfo *ti, PaletteID pal)
+void DrawTileSelectionRect(const TileInfo *ti, PaletteID pal)
 {
 	if (!IsValidTile(ti->tile)) return;
 

src/viewport_func.h

@@ -19,6 +19,8 @@
 #include "station_type.h"
 #include "vehicle_base.h"
 
+struct TileInfo;
+
 static const int TILE_HEIGHT_STEP = 50; ///< One Z unit tile height difference is displayed as 50m.
 
 void SetSelectionRed(bool);
@@ -98,4 +100,7 @@ void ShowTooltipForTile(Window *w, const TileIndex tile);
 void ViewportMapClearTunnelCache();
 void ViewportMapInvalidateTunnelCacheByTile(const TileIndex tile);
 
+void DrawTileSelectionRect(const TileInfo *ti, PaletteID pal);
+void DrawSelectionSprite(SpriteID image, PaletteID pal, const TileInfo *ti, int z_offset, FoundationPart foundation_part, const SubSprite *sub = NULL);
+
 #endif /* VIEWPORT_FUNC_H */

src/viewport_type.h

@@ -149,4 +149,12 @@ enum ViewportScrollTarget {
 	VST_CLIENT,   ///< Single player
 };
 
+/** Enumeration of multi-part foundations */
+enum FoundationPart {
+	FOUNDATION_PART_NONE     = 0xFF,  ///< Neither foundation nor groundsprite drawn yet.
+	FOUNDATION_PART_NORMAL   = 0,     ///< First part (normal foundation or no foundation)
+	FOUNDATION_PART_HALFTILE = 1,     ///< Second part (halftile foundation)
+	FOUNDATION_PART_END
+};
+
 #endif /* VIEWPORT_TYPE_H */

src/zoning_cmd.cpp

@@ -26,6 +26,7 @@
 #include "tracerestrict.h"
 #include "window_func.h"
 #include "zoning.h"
+#include "viewport_func.h"
 #include "3rdparty/cpp-btree/btree_set.h"
 
 Zoning _zoning;
@@ -391,11 +392,34 @@ void DrawTileZoning(const TileInfo *ti)
 	}
 
 	if (_zoning.outer != ZEM_NOTHING) {
-		DrawZoningSprites(SPR_SELECT_TILE, TileZoningSpriteEvaluationCached(ti->tile, _local_company, _zoning.outer, false), ti);
+		const SpriteID colour = TileZoningSpriteEvaluationCached(ti->tile, _local_company, _zoning.outer, false);
+
+		if (colour != ZONING_INVALID_SPRITE_ID) {
+			DrawTileSelectionRect(ti, colour);
+		}
 	}
 
 	if (_zoning.inner != ZEM_NOTHING) {
-		DrawZoningSprites(SPR_ZONING_INNER_HIGHLIGHT_BASE, TileZoningSpriteEvaluationCached(ti->tile, _local_company, _zoning.inner, true), ti);
+		const SpriteID colour = TileZoningSpriteEvaluationCached(ti->tile, _local_company, _zoning.inner, true);
+
+		if (colour != ZONING_INVALID_SPRITE_ID) {
+			SpriteID sprite = SPR_ZONING_INNER_HIGHLIGHT_BASE;
+
+			if (IsHalftileSlope(ti->tileh)) {
+				const int INF = 1000;
+				static const SubSprite sub_sprites[4] = {
+					{ -INF    , -INF   , 32 - 33, INF     }, // CORNER_W, clip 33 pixels from right
+					{ -INF    ,  0 + 22, INF    , INF     }, // CORNER_S, clip 22 pixels from top
+					{ -31 + 34, -INF   , INF    , INF     }, // CORNER_E, clip 34 pixels from left
+					{ -INF    , -INF   , INF    , 30 - 8  }  // CORNER_N, clip  8 pixels from bottom
+				};
+
+				DrawSelectionSprite(sprite, colour, ti, 7 + TILE_HEIGHT, FOUNDATION_PART_HALFTILE, &(sub_sprites[GetHalftileSlopeCorner(ti->tileh)]));
+			} else {
+				sprite += SlopeToSpriteOffset(ti->tileh);
+			}
+			DrawSelectionSprite(sprite, colour, ti, 7, FOUNDATION_PART_NORMAL);
+		}
 	}
 }