get_tile_fid correct for backwards compatibility and flexibility

- Allow to pass elevation using the free bits of the tileNum value to access elevations 1 and 2 (instead of defaulting to dude_elevation, which is not how it worked before)
- Access roof FID and raw data using mode flags in the top 4 bits

artifacts/scripting/functions.yml

@@ -823,7 +823,11 @@
 - name: Tiles and paths
   items:
   - name: get_tile_fid
-    detail: int get_tile_fid(int tile)
+    detail: int get_tile_fid(int tileData)
+    doc: |
+      - returns FID information about the square under the given tile at elevation 0
+      - pass elevation as 4-bit number in bits 25-28 to access other elevations
+      - pass result mode in bits 29-32: 0 - Ground FID, 1 - Roof FID, 2 - Raw data.
     opcode: 0x823a
   - name: tile_under_cursor
     detail: int tile_under_cursor
@@ -850,6 +854,14 @@
       - returns the tile number at the x, y position relative to the top-left corner of the screen
       - if the position is outside of the range of tiles, it will return -1
     macro: sfall.h
+  - name: get_tile_ground_fid
+    detail: int get_tile_ground_fid(int tileNum, int elevation)
+    doc: Returns FID of a ground tile at given tileNum and elevation.
+    macro: sfall.h
+  - name: get_tile_roof_fid
+    detail: int get_tile_roof_fid(int tileNum, int elevation)
+    doc: Returns FID of a roof tile at given tileNum and elevation. Note that FID of 1 is used when there is no actual roof.
+    macro: sfall.h
 
   - name: obj_blocking_line
     detail: ObjectPtr obj_blocking_line(ObjectPtr objFrom, int tileTo, int blockingType)

artifacts/scripting/headers/sfall.h

@@ -321,6 +321,9 @@
 #define get_npc_stat_max(stat)                                  sfall_func2("get_stat_max", stat, 1)
 #define get_npc_stat_min(stat)                                  sfall_func2("get_stat_min", stat, 1)
 #define get_sfall_arg_at(argNum)                                sfall_func1("get_sfall_arg_at", argNum)
+#define get_tile_fid_ext(tile, elev, mode)                      get_tile_fid(((mode bwand 0xF) * 0x10000000) bwor ((elev bwand 0xF) * 0x1000000) bwor (tile bwand 0xFFFFFF))
+#define get_tile_ground_fid(tile, elev)                         get_tile_fid_ext(tile, elev, 0)
+#define get_tile_roof_fid(tile, elev)                           get_tile_fid_ext(tile, elev, 1)
 #define get_terrain_name(x, y)                                  sfall_func2("get_terrain_name", x, y)
 #define get_text_width(text)                                    sfall_func1("get_text_width", text)
 #define has_fake_perk_npc(npc, perk)                            sfall_func2("has_fake_perk_npc", npc, perk)

sfall/FalloutEngine/Variables_def.h

@@ -216,7 +216,7 @@ VAR_(sneak_working,              DWORD) // DWORD var
 VAR_(sound_music_path1,          char*)
 VAR_(sound_music_path2,          char*)
 VAR_(speech_volume,              DWORD)
-VARA(square,                     DWORD*, 3)
+VARA(square,                     DWORD*, 3) // use (square && 0xFFF) to get ground fid, and ((square >> 16) && 0xFFF) to get roof
 VAR_(square_rect,                fo::SquareRect) // _square_y
 VAR_(squares,                    DWORD*)
 VARA(stack,                      DWORD, 10)

sfall/Modules/Scripting/Handlers/Misc.cpp

@@ -332,13 +332,25 @@ end:
 }
 
 void op_get_tile_fid(OpcodeContext& ctx) {
-	long tileX, tileY, squareNum,
-		elevation = fo::var::obj_dude->elevation,
-		tileNum = ctx.arg(0).rawValue();
+	long tileX, tileY, squareNum, squareData, result,
+		tileAndElev = ctx.arg(0).rawValue(),
+		tileNum = tileAndElev & 0xFFFFFF,
+		elevation = (tileAndElev >> 24) & 0x0F,
+		mode = tileAndElev >> 28;
 
 	fo::func::tile_coord(tileNum, &tileX, &tileY);
 	squareNum = fo::func::square_num(tileX, tileY, elevation);
-	ctx.setReturn(fo::var::square[elevation][squareNum]);
+	squareData = fo::var::square[elevation][squareNum];
+	switch (mode) {
+	case 1:
+		result = (squareData >> 16) & 0xFFF; // roof
+		break;
+	case 2:
+		result = squareData; // raw data
+	default:
+		result = squareData & 0xFFF;  // this is how opcode worked prior to 4.3.9
+	}
+	ctx.setReturn(result);
 }
 
 void __declspec(naked) op_modified_ini() {