as requested by Soliton,

use kotkey ctrl+l to toggle the mouse scrolling preference

renamed disable mouse scroll to prevent double-negative logic (disable(false))

data/game.cfg

@@ -249,6 +249,11 @@ default=yes
     cmd=yes
     [/hotkey]
     [hotkey]
+    command=mousescroll
+    key=l
+    cmd=yes
+    [/hotkey]
+    [hotkey]
     command=mute
     key=m
     cmd=yes
@@ -434,6 +439,11 @@ default=yes
     ctrl=yes
     [/hotkey]
     [hotkey]
+    command=mousescroll
+    key=l
+    ctrl=yes
+    [/hotkey]
+    [hotkey]
     command=mute
     key=m
     ctrl=yes

data/themes/editor.cfg

@@ -60,6 +60,14 @@ name=editor
 	shift=no
 	[/hotkey]
 
+	[hotkey]
+	command="mousescroll"
+	key="l"
+	cmd=yes
+	alt=no
+	shift=no
+	[/hotkey]
+
 	[hotkey]
 	command="editsavemap"
 	key="s"
@@ -269,6 +277,14 @@ name=editor
 	shift=no
 	[/hotkey]
 
+	[hotkey]
+	command="mousescroll"
+	key="l"
+	ctrl=yes
+	alt=no
+	shift=no
+	[/hotkey]
+
 	[hotkey]
 	command="editsavemap"
 	key="s"

src/editor/editor.cpp

@@ -728,6 +728,7 @@ bool map_editor::can_execute_command(hotkey::HOTKEY_COMMAND command) const {
 	case hotkey::HOTKEY_FULLSCREEN:
 	case hotkey::HOTKEY_SCREENSHOT:
 	case hotkey::HOTKEY_TOGGLE_GRID:
+	case hotkey::HOTKEY_MOUSE_SCROLL:
 	case hotkey::HOTKEY_PREFERENCES:
 	case hotkey::HOTKEY_EDIT_SAVE_MAP:
 	case hotkey::HOTKEY_EDIT_SAVE_AS:

src/hotkeys.cpp

@@ -68,6 +68,7 @@ const struct {
 	{ hotkey::HOTKEY_RECALL, "recall", N_("Recall"), false },
 	{ hotkey::HOTKEY_ENDTURN, "endturn", N_("End Turn"), false },
 	{ hotkey::HOTKEY_TOGGLE_GRID, "togglegrid", N_("Toggle Grid"), false },
+	{ hotkey::HOTKEY_MOUSE_SCROLL, "mousescroll", N_("Mouse Scrolling"), false },
 	{ hotkey::HOTKEY_STATUS_TABLE, "statustable", N_("Status Table"), false },
 	{ hotkey::HOTKEY_MUTE, "mute", N_("Mute"), false },
 	{ hotkey::HOTKEY_SPEAK, "speak", N_("Speak"), false },
@@ -572,6 +573,9 @@ void execute_command(display& disp, HOTKEY_COMMAND command, command_executor* ex
 			if(executor)
 				executor->toggle_grid();
 			break;
+		case HOTKEY_MOUSE_SCROLL:
+			preferences::enable_mouse_scroll(!preferences::mouse_scroll_enabled());
+			break;
 		case HOTKEY_STATUS_TABLE:
 			if(executor)
 				executor->status_table();

src/hotkeys.hpp

@@ -35,7 +35,7 @@ enum HOTKEY_COMMAND {
 	HOTKEY_FULLSCREEN, HOTKEY_SCREENSHOT, HOTKEY_ACCELERATED,
 	HOTKEY_UNIT_DESCRIPTION, HOTKEY_RENAME_UNIT, HOTKEY_SAVE_GAME, HOTKEY_LOAD_GAME,
 	HOTKEY_RECRUIT, HOTKEY_REPEAT_RECRUIT, HOTKEY_RECALL, HOTKEY_ENDTURN,
-	HOTKEY_TOGGLE_GRID, HOTKEY_STATUS_TABLE, HOTKEY_MUTE,
+	HOTKEY_TOGGLE_GRID, HOTKEY_STATUS_TABLE, HOTKEY_MUTE, HOTKEY_MOUSE_SCROLL,
 	HOTKEY_SPEAK, HOTKEY_CREATE_UNIT, HOTKEY_CHANGE_UNIT_SIDE, HOTKEY_PREFERENCES,
 	HOTKEY_OBJECTIVES, HOTKEY_UNIT_LIST, HOTKEY_STATISTICS, HOTKEY_QUIT_GAME,
 	HOTKEY_LABEL_TERRAIN, HOTKEY_CLEAR_LABELS,HOTKEY_SHOW_ENEMY_MOVES, HOTKEY_BEST_ENEMY_MOVES,

src/play_controller.cpp

@@ -437,6 +437,7 @@ bool play_controller::can_execute_command(hotkey::HOTKEY_COMMAND command) const
 	case hotkey::HOTKEY_SCREENSHOT:
 	case hotkey::HOTKEY_ACCELERATED:
 	case hotkey::HOTKEY_TOGGLE_GRID:
+	case hotkey::HOTKEY_MOUSE_SCROLL:
 	case hotkey::HOTKEY_STATUS_TABLE:
 	case hotkey::HOTKEY_MUTE:
 	case hotkey::HOTKEY_PREFERENCES:
@@ -599,7 +600,7 @@ void play_controller::play_slice()
 	SDL_GetMouseState(&mousex,&mousey);
 	tooltips::process(mousex, mousey);
 
-	const int scroll_threshold = (preferences::mouse_scroll_disabled()) ? 0 : 5;
+	const int scroll_threshold = (preferences::mouse_scroll_enabled()) ? 5 : 0;
 
 	if(key[SDLK_UP] || mousey < scroll_threshold)
 		gui_->scroll(0,-preferences::scroll_speed());

src/preferences.cpp

@@ -762,12 +762,15 @@ bool show_floating_labels()
 	return prefs["floating_labels"] != "no";
 }
 
-bool mouse_scroll_disabled()
+bool mouse_scroll_enabled()
 {
-	//enabled by default
-	return prefs["mouse_scrolling"] == "no";
+	return prefs["mouse_scrolling"] != "no";
 }
 
+void enable_mouse_scroll(bool value)
+{
+	prefs["mouse_scrolling"] = value ? "yes" : "no";
+}
 
 void set_show_floating_labels(bool value)
 {

src/preferences.hpp

@@ -101,6 +101,8 @@ namespace preferences {
 
 	int scroll_speed();
 	void set_scroll_speed(int scroll);
+	bool mouse_scroll_enabled();
+	void enable_mouse_scroll(bool value);
 
 	bool turn_bell();
 	void set_turn_bell(bool ison);
@@ -199,7 +201,6 @@ namespace preferences {
 	void set_chat_lines(int lines);
 
 	bool compress_saves();
-	bool mouse_scroll_disabled();
 
 	std::set<std::string> &encountered_units();
 	std::set<std::string> &encountered_terrains();