Add NewGRF global flag to allow rocky tiles in tropic desert zones

docs/newgrf-additions-nml.html

@@ -323,6 +323,11 @@ item (FEAT_GLOBALVARS) {
 			Some station names are always used first even when this is non-zero.
 		</td>
 	</tr>
+	<tr><td>allow_rocks_in_desert</td><td>0 or 1</td>
+		<td>
+			Sets whether rocky tiles are allowed to generate in and remain in desert zones (tropical climate).
+		</td>
+	</tr>
 	</table>
 	<p>Syntax example:
 		<pre class="code">

docs/newgrf-additions.html

@@ -361,6 +361,11 @@
 	The Action 0 ID field is ignored. The property length is 1 byte.
 	</p>
 	<p>This is indicated by the feature name: <font face="monospace">action0_global_default_object_generate_amount</font>, version 1</p>
+	<h4 id="global_allow_rocks_in_desert">Allow rocky tiles in desert zones (tropical climate) (mappable property: global_allow_rocks_in_desert)</h4>
+	<p>This sets whether rocky tiles are allowed to generate in and remain in desert zones (tropical climate).<br />
+	The Action 0 ID field is ignored. The property length is 1 byte. 0 is disabled (default). 1 is enabled.
+	</p>
+	<p>This is indicated by the feature name: <font face="monospace">action0_global_allow_rocks_in_desert</font>, version 1</p>
 	<br />
 	<h3 id="a0signals"><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0">Action 0 - Signals (Feature 0E)</a></h3>
 	<p>Note that Action 0 feature 0E is not supported (does nothing) in standard OpenTTD.</p>

src/clear_cmd.cpp

@@ -24,6 +24,8 @@
 
 #include "safeguards.h"
 
+bool _allow_rocks_desert = false;
+
 static CommandCost ClearTile_Clear(TileIndex tile, DoCommandFlag flags)
 {
 	static const Price clear_price_table[] = {
@@ -298,6 +300,8 @@ static void TileLoopClearDesert(TileIndex tile)
 
 	if (current == expected) return;
 
+	if (_allow_rocks_desert && IsClearGround(tile, CLEAR_ROCKS)) return;
+
 	if (expected == 0) {
 		SetClearGroundDensity(tile, CLEAR_GRASS, 3);
 	} else {
@@ -404,7 +408,7 @@ void GenerateClearTile()
 				do {
 					if (--j == 0) goto get_out;
 					tile_new = tile + TileOffsByDiagDir((DiagDirection)GB(Random(), 0, 2));
-				} while (!IsTileType(tile_new, MP_CLEAR) || IsClearGround(tile_new, CLEAR_DESERT));
+				} while (!IsTileType(tile_new, MP_CLEAR) || (!_allow_rocks_desert && IsClearGround(tile_new, CLEAR_DESERT)));
 				tile = tile_new;
 			}
 get_out:;

src/gfxinit.cpp

@@ -167,6 +167,9 @@ void InitGRFGlobalVars()
 
 	extern uint8 _extra_station_names_probability;
 	_extra_station_names_probability = 0;
+
+	extern bool _allow_rocks_desert;
+	_allow_rocks_desert = false;
 }
 
 /** Actually load the sprite tables. */

src/newgrf.cpp

@@ -2850,6 +2850,13 @@ static ChangeInfoResult GlobalVarChangeInfo(uint gvid, int numinfo, int prop, co
 				break;
 			}
 
+			case A0RPI_GLOBALVAR_ALLOW_ROCKS_DESERT: {
+				if (MappedPropertyLengthMismatch(buf, 1, mapping_entry)) break;
+				extern bool _allow_rocks_desert;
+				_allow_rocks_desert = (buf->ReadByte() != 0);
+				break;
+			}
+
 			default:
 				ret = HandleAction0PropertyDefault(buf, prop);
 				break;
@@ -2922,6 +2929,7 @@ static ChangeInfoResult GlobalVarReserveInfo(uint gvid, int numinfo, int prop, c
 			case A0RPI_GLOBALVAR_EXTRA_STATION_NAMES_PROBABILITY:
 			case A0RPI_GLOBALVAR_LIGHTHOUSE_GENERATE_AMOUNT:
 			case A0RPI_GLOBALVAR_TRANSMITTER_GENERATE_AMOUNT:
+			case A0RPI_GLOBALVAR_ALLOW_ROCKS_DESERT:
 				buf->Skip(buf->ReadExtendedByte());
 				break;
 

src/newgrf_extension.cpp

@@ -42,6 +42,7 @@ extern const GRFFeatureInfo _grf_feature_list[] = {
 	GRFFeatureInfo("varaction2_railtype_signal_context", 1),
 	GRFFeatureInfo("action0_global_extra_station_names", 2),
 	GRFFeatureInfo("action0_global_default_object_generate_amount", 1),
+	GRFFeatureInfo("action0_global_allow_rocks_in_desert", 1),
 	GRFFeatureInfo("action0_signals_programmable_signals", 1),
 	GRFFeatureInfo("action0_signals_no_entry_signals", 1),
 	GRFFeatureInfo("action0_signals_restricted_signals", 2),
@@ -86,6 +87,7 @@ extern const GRFPropertyMapDefinition _grf_action0_remappable_properties[] = {
 	GRFPropertyMapDefinition(GSF_GLOBALVAR, A0RPI_GLOBALVAR_EXTRA_STATION_NAMES_PROBABILITY, "global_extra_station_names_probability"),
 	GRFPropertyMapDefinition(GSF_GLOBALVAR, A0RPI_GLOBALVAR_LIGHTHOUSE_GENERATE_AMOUNT, "global_lighthouse_generate_amount"),
 	GRFPropertyMapDefinition(GSF_GLOBALVAR, A0RPI_GLOBALVAR_TRANSMITTER_GENERATE_AMOUNT, "global_transmitter_generate_amount"),
+	GRFPropertyMapDefinition(GSF_GLOBALVAR, A0RPI_GLOBALVAR_ALLOW_ROCKS_DESERT, "global_allow_rocks_in_desert"),
 	GRFPropertyMapDefinition(GSF_SIGNALS, A0RPI_SIGNALS_ENABLE_PROGRAMMABLE_SIGNALS, "signals_enable_programmable_signals"),
 	GRFPropertyMapDefinition(GSF_SIGNALS, A0RPI_SIGNALS_ENABLE_NO_ENTRY_SIGNALS, "signals_enable_no_entry_signals"),
 	GRFPropertyMapDefinition(GSF_SIGNALS, A0RPI_SIGNALS_ENABLE_RESTRICTED_SIGNALS, "signals_enable_restricted_signals"),

src/newgrf_extension.h

@@ -30,6 +30,7 @@ enum Action0RemapPropertyIds {
 	A0RPI_GLOBALVAR_EXTRA_STATION_NAMES_PROBABILITY,
 	A0RPI_GLOBALVAR_LIGHTHOUSE_GENERATE_AMOUNT,
 	A0RPI_GLOBALVAR_TRANSMITTER_GENERATE_AMOUNT,
+	A0RPI_GLOBALVAR_ALLOW_ROCKS_DESERT,
 	A0RPI_SIGNALS_ENABLE_PROGRAMMABLE_SIGNALS,
 	A0RPI_SIGNALS_ENABLE_NO_ENTRY_SIGNALS,
 	A0RPI_SIGNALS_ENABLE_RESTRICTED_SIGNALS,