Query before destroying important structures (rail stations and industries)

Prior to this change, the use of NewObjects often lead to the problem of players trying to clear those and accidentally destroying a rail station or (when using magic bulldozer) an industry. This action cannot be undone.

This change shows a query making sure the player actually wants to destroy the station or industry.

NOTE: The switch to a std::function no longer allows for the inequality check in ShowQuery in misc_gui. If this was required a different solution has to be found.

src/lang/english.txt

@@ -5550,6 +5550,10 @@ STR_ERROR_NAME_MUST_BE_UNIQUE                                   :{WHITE}Name mus
 STR_ERROR_GENERIC_OBJECT_IN_THE_WAY                             :{WHITE}{1:STRING} in the way
 STR_ERROR_NOT_ALLOWED_WHILE_PAUSED                              :{WHITE}Not allowed while paused
 
+# Clear area query
+STR_QUERY_CLEAR_AREA_CAPTION                                    :{WHITE}Clear area
+STR_CLEAR_AREA_CONFIRMATION_TEXT                                :{YELLOW}You are about to destroy an important structure. Are you sure?
+
 # Local authority errors
 STR_ERROR_LOCAL_AUTHORITY_REFUSES_TO_ALLOW_THIS                 :{WHITE}{TOWN} local authority refuses to allow this
 STR_ERROR_LOCAL_AUTHORITY_REFUSES_AIRPORT                       :{WHITE}{TOWN} local authority refuses to allow another airport to be built in this town

src/misc_gui.cpp

@@ -12,6 +12,8 @@
 #include "landscape.h"
 #include "error.h"
 #include "gui.h"
+
+#include <utility>
 #include "command_func.h"
 #include "company_func.h"
 #include "town.h"
@@ -1230,19 +1232,19 @@ void ShowQueryString(StringID str, StringID caption, uint maxsize, Window *paren
  * Window used for asking the user a YES/NO question.
  */
 struct QueryWindow : public Window {
-	QueryCallbackProc *proc; ///< callback function executed on closing of popup. Window* points to parent, bool is true if 'yes' clicked, false otherwise
+	QueryCallbackProc proc;  ///< callback function executed on closing of popup. Window* points to parent, bool is true if 'yes' clicked, false otherwise
 	uint64 params[10];       ///< local copy of #_global_string_params
 	StringID message;        ///< message shown for query window
 	StringID caption;        ///< title of window
 
-	QueryWindow(WindowDesc *desc, StringID caption, StringID message, Window *parent, QueryCallbackProc *callback) : Window(desc)
+	QueryWindow(WindowDesc *desc, StringID caption, StringID message, Window *parent, QueryCallbackProc callback) : Window(desc)
 	{
 		/* Create a backup of the variadic arguments to strings because it will be
 		 * overridden pretty often. We will copy these back for drawing */
 		CopyOutDParam(this->params, 0, lengthof(this->params));
 		this->caption = caption;
 		this->message = message;
-		this->proc    = callback;
+		this->proc    = std::move(callback);
 		this->parent  = parent;
 
 		this->InitNested(WN_CONFIRM_POPUP_QUERY);
@@ -1299,7 +1301,7 @@ struct QueryWindow : public Window {
 			case WID_Q_YES: {
 				/* in the Generate New World window, clicking 'Yes' causes
 				 * DeleteNonVitalWindows() to be called - we shouldn't be in a window then */
-				QueryCallbackProc *proc = this->proc;
+				QueryCallbackProc proc = this->proc;
 				Window *parent = this->parent;
 				/* Prevent the destructor calling the callback function */
 				this->proc = nullptr;
@@ -1364,9 +1366,9 @@ static WindowDesc _query_desc(
  * @param message string that will be shown for the window
  * @param parent pointer to parent window, if this pointer is nullptr the parent becomes
  * the main window WC_MAIN_WINDOW
- * @param callback callback function pointer to set in the window descriptor
+ * @param callback callback function to set in the window descriptor
  */
-void ShowQuery(StringID caption, StringID message, Window *parent, QueryCallbackProc *callback)
+void ShowQuery(StringID caption, StringID message, Window *parent, QueryCallbackProc callback)
 {
 	if (parent == nullptr) parent = FindWindowById(WC_MAIN_WINDOW, 0);
 
@@ -1374,7 +1376,7 @@ void ShowQuery(StringID caption, StringID message, Window *parent, QueryCallback
 		if (w->window_class != WC_CONFIRM_POPUP_QUERY) continue;
 
 		const QueryWindow *qw = (const QueryWindow *)w;
-		if (qw->parent != parent || qw->proc != callback) continue;
+		if (qw->parent != parent) continue;
 
 		delete qw;
 		break;

src/network/network_gui.cpp

@@ -2141,7 +2141,7 @@ public:
 
 			case WID_CL_MATRIX: {
 				StringID text = STR_NULL;
-				QueryCallbackProc *callback = nullptr;
+				QueryCallbackProc callback = nullptr;
 
 				switch (index) {
 					case DD_CLIENT_ADMIN_KICK:

src/terraform_gui.cpp

@@ -30,6 +30,7 @@
 #include "hotkeys.h"
 #include "engine_base.h"
 #include "terraform_gui.h"
+#include "cheat_func.h"
 #include "town_gui.h"
 #include "zoom_func.h"
 
@@ -95,6 +96,30 @@ static void GenerateRockyArea(TileIndex end, TileIndex start)
 	if (success && _settings_client.sound.confirm) SndPlayTileFx(SND_1F_CONSTRUCTION_OTHER, end);
 }
 
+/** Checks if the area contains any structures that are important enough to query about first */
+static bool IsIndustryOrRailStationInArea(TileIndex start_tile, TileIndex end_tile, bool diagonal)
+{
+	std::unique_ptr<TileIterator> tile_iterator;
+
+	if (diagonal) {
+		tile_iterator = std::make_unique<DiagonalTileIterator>(end_tile, start_tile);
+	} else {
+		tile_iterator = std::make_unique<OrthogonalTileIterator>(end_tile, start_tile);
+	}
+
+	bool destroying_industry_or_station = false;
+
+	for (; *tile_iterator != INVALID_TILE; ++(*tile_iterator)) {
+		if ((_cheats.magic_bulldozer.value && IsTileType(*tile_iterator, MP_INDUSTRY)) ||
+		    IsRailStationTile(*tile_iterator)) {
+			destroying_industry_or_station = true;
+			break;
+		}
+	}
+
+	return destroying_industry_or_station;
+}
+
 /**
  * A central place to handle all X_AND_Y dragged GUI functions.
  * @param proc       Procedure related to the dragging
@@ -114,9 +139,23 @@ bool GUIPlaceProcDragXY(ViewportDragDropSelectionProcess proc, TileIndex start_t
 	}
 
 	switch (proc) {
-		case DDSP_DEMOLISH_AREA:
+		case DDSP_DEMOLISH_AREA: {
+			const bool should_query_first = IsIndustryOrRailStationInArea(start_tile, end_tile, _ctrl_pressed);
+
+			const auto cmd_clear_area = [=](Window*, bool confirmed) {
+				if (confirmed) {
 					DoCommandP(end_tile, start_tile, _ctrl_pressed ? 1 : 0, CMD_CLEAR_AREA | CMD_MSG(STR_ERROR_CAN_T_CLEAR_THIS_AREA), CcPlaySound_EXPLOSION);
+				}
+			};
+
+			if (should_query_first) {
+				ShowQuery(STR_QUERY_CLEAR_AREA_CAPTION, STR_CLEAR_AREA_CONFIRMATION_TEXT, nullptr, cmd_clear_area);
+			} else {
+				cmd_clear_area(nullptr, true);
+			}
+
 			break;
+		}
 		case DDSP_RAISE_AND_LEVEL_AREA:
 			DoCommandP(end_tile, start_tile, LM_RAISE << 1 | (_ctrl_pressed ? 1 : 0), CMD_LEVEL_LAND | CMD_MSG(STR_ERROR_CAN_T_RAISE_LAND_HERE), CcTerraform);
 			break;

src/textbuf_gui.h

@@ -10,10 +10,13 @@
 #ifndef TEXTBUF_GUI_H
 #define TEXTBUF_GUI_H
 
-#include "window_type.h"
 #include "string_type.h"
 #include "strings_type.h"
 
+#include <functional>
+
+struct Window;
+
 /** Flags used in ShowQueryString() call */
 enum QueryStringFlags {
 	QSF_NONE             =    0,
@@ -26,10 +29,10 @@ enum QueryStringFlags {
 DECLARE_ENUM_AS_BIT_SET(QueryStringFlags)
 
 /** Callback procedure for the ShowQuery method. */
-typedef void QueryCallbackProc(Window*, bool);
+typedef std::function<void(Window*, bool)> QueryCallbackProc;
 
 void ShowQueryString(StringID str, StringID caption, uint max_len, Window *parent, CharSetFilter afilter, QueryStringFlags flags);
-void ShowQuery(StringID caption, StringID message, Window *w, QueryCallbackProc *callback);
+void ShowQuery(StringID caption, StringID message, Window *w, QueryCallbackProc callback);
 
 /** The number of 'characters' on the on-screen keyboard. */
 static const uint OSK_KEYBOARD_ENTRIES = 50;