Index: src/lang/english.txt
===================================================================
--- src/lang/english.txt	(revision 12099)
+++ src/lang/english.txt	(working copy)
@@ -3337,14 +3337,14 @@
 STR_DRIVE_THROUGH_ERROR_DIRECTION                               :{WHITE}...road facing in the wrong direction
 
 STR_TRANSPARENCY_TOOLB                                          :{WHITE}Transparency Options
-STR_TRANSPARENT_SIGNS_DESC                                      :{BLACK}Toggle transparency for station signs
-STR_TRANSPARENT_TREES_DESC                                      :{BLACK}Toggle transparency for trees
-STR_TRANSPARENT_HOUSES_DESC                                     :{BLACK}Toggle transparency for houses
-STR_TRANSPARENT_INDUSTRIES_DESC                                 :{BLACK}Toggle transparency for industries
-STR_TRANSPARENT_BUILDINGS_DESC                                  :{BLACK}Toggle transparency for buildables like stations, depots, waypoints and catenary
-STR_TRANSPARENT_BRIDGES_DESC                                    :{BLACK}Toggle transparency for bridges
-STR_TRANSPARENT_STRUCTURES_DESC                                 :{BLACK}Toggle transparency for structures like lighthouses and antennas, maybe in future for eyecandy
-STR_TRANSPARENT_LOADING_DESC                                    :{BLACK}Toggle transparency for loading indicators
+STR_TRANSPARENT_SIGNS_DESC                                      :{BLACK}Toggle transparency for station signs. CTRL-click to lock.
+STR_TRANSPARENT_TREES_DESC                                      :{BLACK}Toggle transparency for trees. CTRL-click to lock.
+STR_TRANSPARENT_HOUSES_DESC                                     :{BLACK}Toggle transparency for houses. CTRL-click to lock.
+STR_TRANSPARENT_INDUSTRIES_DESC                                 :{BLACK}Toggle transparency for industries. CTRL-click to lock.
+STR_TRANSPARENT_BUILDINGS_DESC                                  :{BLACK}Toggle transparency for buildables like stations, depots, waypoints and catenary. CTRL-click to lock.
+STR_TRANSPARENT_BRIDGES_DESC                                    :{BLACK}Toggle transparency for bridges. CTRL-click to lock.
+STR_TRANSPARENT_STRUCTURES_DESC                                 :{BLACK}Toggle transparency for structures like lighthouses and antennas. CTRL-click to lock.
+STR_TRANSPARENT_LOADING_DESC                                    :{BLACK}Toggle transparency for loading indicators. CTRL-click to lock.
 
 STR_PERCENT_UP_SMALL                                            :{TINYFONT}{WHITE}{NUM}%{UPARROW}
 STR_PERCENT_UP                                                  :{WHITE}{NUM}%{UPARROW}
Index: src/settings.cpp
===================================================================
--- src/settings.cpp	(revision 12099)
+++ src/settings.cpp	(working copy)
@@ -1283,6 +1283,7 @@
 	  SDTG_VAR("sprite_cache_size",SLE_UINT, S, 0, _sprite_cache_size,     4, 1, 64, 0, STR_NULL, NULL),
 	  SDTG_VAR("player_face",    SLE_UINT32, S, 0, _player_face,      0,0,0xFFFFFFFF,0, STR_NULL, NULL),
 	  SDTG_VAR("transparency_options", SLE_UINT8, S, 0, _transparency_opt, 0, 0,0xFF,0, STR_NULL, NULL),
+	  SDTG_VAR("transparency_locks", SLE_UINT8, S, 0, _transparency_lock, 0, 0,0xFF,0, STR_NULL, NULL),
 	  SDTG_END()
 };
 
Index: src/transparency.h
===================================================================
--- src/transparency.h	(revision 12099)
+++ src/transparency.h	(working copy)
@@ -28,6 +28,7 @@
 
 typedef byte TransparencyOptionBits; ///< transparency option bits
 extern TransparencyOptionBits _transparency_opt;
+extern TransparencyOptionBits _transparency_lock;
 
 /**
  * Check if the transparency option bit is set
@@ -43,26 +44,33 @@
 /**
  * Toggle the transparency option bit
  *
- * @param to the structure which transparency option is toggle
+ * @param to the transparency option to be toggled
  */
 static inline void ToggleTransparency(TransparencyOption to)
 {
 	ToggleBit(_transparency_opt, to);
 }
 
-/** Toggle all transparency options (except signs) or restore the stored transparencies */
+/**
+ * Toggle the transparency lock bit
+ *
+ * @param to the transparency option to be locked or unlocked
+ */
+static inline void ToggleTransparencyLock(TransparencyOption to)
+{
+	ToggleBit(_transparency_lock, to);
+}
+
+/** Set or clear all non-locked transparency options */
 static inline void ResetRestoreAllTransparency()
 {
-	/* backup of the original transparencies or if all transparencies false toggle them to true */
-	static TransparencyOptionBits trans_opt = ~0;
-
-	if (_transparency_opt == 0) {
-		/* no structure is transparent, so restore the old transparency if present otherwise set all true */
-		_transparency_opt = trans_opt;
+	/* if none of the non-locked options are set */
+	if ((_transparency_opt & ~_transparency_lock) == 0) {
+		/* set all non-locked options */
+		_transparency_opt |= ~_transparency_lock;
 	} else {
-		/* any structure is transparent, so store current transparency settings and reset it */
-		trans_opt = _transparency_opt;
-		_transparency_opt = 0;
+		/* clear all non-locked options */
+		_transparency_opt &= _transparency_lock;
 	}
 
 	MarkWholeScreenDirty();
Index: src/transparency_gui.cpp
===================================================================
--- src/transparency_gui.cpp	(revision 12099)
+++ src/transparency_gui.cpp	(working copy)
@@ -12,12 +12,10 @@
 #include "table/strings.h"
 
 TransparencyOptionBits _transparency_opt;
+TransparencyOptionBits _transparency_lock;
 
 enum TransparencyToolbarWidgets{
-	/* Widgets not toggled when pressing the X key */
 	TTW_WIDGET_SIGNS = 3,    ///< Make signs background transparent
-
-	/* Widgets toggled when pressing the X key */
 	TTW_WIDGET_TREES,        ///< Make trees transparent
 	TTW_WIDGET_HOUSES,       ///< Make houses transparent
 	TTW_WIDGET_INDUSTRIES,   ///< Make Industries transparent
@@ -39,14 +37,23 @@
 			}
 
 			DrawWindowWidgets(w);
+			for (uint i = TO_SIGNS; i < TO_END; i++) {
+				if (GB(_transparency_lock, i, 1)) DrawSprite(SPR_LOCK, PAL_NONE, w->widget[TTW_WIDGET_SIGNS + i].left + 1, w->widget[TTW_WIDGET_SIGNS + i].top + 1);
+			}
 			break;
 
 		case WE_CLICK:
 			if (e->we.click.widget >= TTW_WIDGET_SIGNS) {
-				/* toggle the bit of the transparencies variable when clicking on a widget, and play a sound */
-				ToggleTransparency((TransparencyOption)(e->we.click.widget - TTW_WIDGET_SIGNS));
-				SndPlayFx(SND_15_BEEP);
-				MarkWholeScreenDirty();
+				if (_ctrl_pressed) {
+					/* toggle the bit of the transparencies lock variable */
+					ToggleTransparencyLock((TransparencyOption)(e->we.click.widget - TTW_WIDGET_SIGNS));
+					SetWindowDirty(w);
+				} else {
+					/* toggle the bit of the transparencies variable and play a sound */
+					ToggleTransparency((TransparencyOption)(e->we.click.widget - TTW_WIDGET_SIGNS));
+					SndPlayFx(SND_15_BEEP);
+					MarkWholeScreenDirty();
+				}
 			}
 			break;
 	}