Signals: Add GRF restriction info bit for may reverse

docs/newgrf-additions-nml.html

@@ -116,6 +116,8 @@
 				<dd>The signal is restricted (has a routing restriction program attached)</dd>
 				<dt>RESERVE_THROUGH_ALWAYS</dt>
 				<dd>The attached routing restriction program unconditionally sets reserve through</dd>
+				<dt>MAY_REVERSE</dt>
+				<dd>The attached routing restriction program may allow trains to reverse behind this signal</dd>
 			</dl>
 		</td>
 	</tr>
@@ -428,6 +430,8 @@ item (FEAT_GLOBALVARS) {
 				<dd>The signal is restricted (has a routing restriction program attached)</dd>
 				<dt>RESERVE_THROUGH_ALWAYS</dt>
 				<dd>The attached routing restriction program unconditionally sets reserve through</dd>
+				<dt>MAY_REVERSE</dt>
+				<dd>The attached routing restriction program may allow trains to reverse behind this signal</dd>
 			</dl>
 		</td>
 	</tr>

docs/newgrf-additions.html

@@ -583,6 +583,7 @@
 	<tr><th>Bit</th><th>Value</th><th>Meaning</th></tr>
 	<tr><td>0</td><td>1</td><td>This signal has a routing restriction program attached</td></tr>
 	<tr><td>1</td><td>2</td><td>Reserve through is unconditionally set in the routing restriction program</td></tr>
+	<tr><td>2</td><td>4</td><td>The routing restriction program may allow trains to reverse behind this signal</td></tr>
 	</table>
 	</p>
 	<p>See also: <a href="#railtype_enable_restricted_signals">railtype_enable_restricted_signals property</a></p>
@@ -605,6 +606,7 @@
 	<tr><th>Bit</th><th>Value</th><th>Meaning</th></tr>
 	<tr><td>0</td><td>1</td><td>This signal has a routing restriction program attached</td></tr>
 	<tr><td>1</td><td>2</td><td>Reserve through is unconditionally set in the routing restriction program</td></tr>
+	<tr><td>2</td><td>4</td><td>The routing restriction program may allow trains to reverse behind this signal</td></tr>
 	</table>
 	</p>
 	<p>See also: <a href="#signals_enable_restricted_signals">signals_enable_restricted_signals property</a></p>

src/newgrf_newsignals.cpp

@@ -78,5 +78,6 @@ uint GetNewSignalsRestrictedSignalsInfo(const TraceRestrictProgram *prog, TileIn
 
 	uint result = 1;
 	if ((prog->actions_used_flags & TRPAUF_RESERVE_THROUGH_ALWAYS) && !IsTileType(tile, MP_TUNNELBRIDGE)) result |= 2;
+	if ((prog->actions_used_flags & TRPAUF_REVERSE) && !IsTileType(tile, MP_TUNNELBRIDGE)) result |= 4;
 	return result;
 }

src/tracerestrict.cpp

@@ -1057,7 +1057,19 @@ CommandCost TraceRestrictProgram::Validate(const std::vector<TraceRestrictItem>
 					break;
 
 				case TRIT_REVERSE:
-					actions_used_flags |= TRPAUF_REVERSE;
+					switch (static_cast<TraceRestrictReverseValueField>(GetTraceRestrictValue(item))) {
+						case TRRVF_REVERSE:
+							actions_used_flags |= TRPAUF_REVERSE;
+							break;
+
+						case TRRVF_CANCEL_REVERSE:
+							if (condstack.empty()) actions_used_flags &= ~TRPAUF_REVERSE;
+							break;
+
+						default:
+							NOT_REACHED();
+							break;
+					}
 					break;
 
 				case TRIT_SPEED_RESTRICTION:
@@ -1327,7 +1339,7 @@ void TraceRestrictCheckRefreshSignals(const TraceRestrictProgram *prog, TileInde
 {
 	if (_network_dedicated) return;
 
-	if (!((old_actions_used_flags ^ prog->actions_used_flags) & TRPAUF_RESERVE_THROUGH_ALWAYS)) return;
+	if (!((old_actions_used_flags ^ prog->actions_used_flags) & (TRPAUF_RESERVE_THROUGH_ALWAYS | TRPAUF_REVERSE))) return;
 
 	if (old_size == 0 && prog->refcount == 1) return; // Program is new, no need to refresh again