Add: Allow to configure modifier keys

src/gfx_type.h

@@ -351,4 +351,11 @@ enum StringAlignment {
 };
 DECLARE_ENUM_AS_BIT_SET(StringAlignment)
 
+enum ModifierKey : byte {
+	None      = 0, ///< No key configured
+	Shift     = 1, ///< Shift key
+	Ctrl      = 2, ///< Ctrl key
+	Alt       = 3, ///< Alt key
+};
+
 #endif /* GFX_TYPE_H */

src/lang/english.txt

@@ -1766,6 +1766,18 @@ STR_CONFIG_SETTING_FAST_FORWARD_SPEED_LIMIT_VAL                 :{NUM}% normal g
 ###setting-zero-is-special
 STR_CONFIG_SETTING_FAST_FORWARD_SPEED_LIMIT_ZERO                :No limit (as fast as your computer allows)
 
+STR_CONFIG_SETTING_MODIFIER_FN                                  :Function modifier key: {STRING2}
+STR_CONFIG_SETTING_MODIFIER_FN_HELPTEXT                         :Modifier key for accessing additional functions.
+STR_CONFIG_SETTING_MODIFIER_REMOVE                              :Remove modifier key: {STRING2}
+STR_CONFIG_SETTING_MODIFIER_REMOVE_HELPTEXT                     :Modifier key for removal mode on building tools.
+STR_CONFIG_SETTING_MODIFIER_ESTIMATE                            :Estimate modifier key: {STRING2}
+STR_CONFIG_SETTING_MODIFIER_ESTIMATE_HELPTEXT                   :Modifier key for estimating action cost.
+STR_CONFIG_SETTING_MODIFIER_NONE                                :None
+STR_CONFIG_SETTING_MODIFIER_SHIFT                               :Shift
+STR_CONFIG_SETTING_MODIFIER_CTRL                                :Ctrl
+STR_CONFIG_SETTING_MODIFIER_ALT                                 :Alt
+STR_CONFIG_SETTING_MODIFIER_ALREADY_IN_USE                      :{WHITE}This modifier key is already in use.
+
 STR_CONFIG_SETTING_SOUND_TICKER                                 :News ticker: {STRING2}
 STR_CONFIG_SETTING_SOUND_TICKER_HELPTEXT                        :Play sound for summarised news messages
 

src/settings_gui.cpp

@@ -2041,6 +2041,9 @@ static SettingsContainer &GetSettingsTree()
 			interface->Add(new SettingEntry("gui.timetable_arrival_departure"));
 			interface->Add(new SettingEntry("gui.show_newgrf_name"));
 			interface->Add(new SettingEntry("gui.show_cargo_in_vehicle_lists"));
+			viewports->Add(new SettingEntry("gui.fn_modifier"));
+			viewports->Add(new SettingEntry("gui.remove_modifier"));
+			viewports->Add(new SettingEntry("gui.estimate_modifier"));
 		}
 
 		SettingsPage *advisors = main->Add(new SettingsPage(STR_CONFIG_SETTING_ADVISORS));

src/settings_table.cpp

@@ -483,6 +483,33 @@ static bool CheckMaxHeightLevel(int32_t &new_value)
 	return true;
 }
 
+static bool CheckModifier(int32_t new_value, ModifierKey other1, ModifierKey other2)
+{
+	ModifierKey key = (ModifierKey)new_value;
+	if (key == ModifierKey::None) return true;
+	if (other1 == key || other2 == key) {
+		ShowErrorMessage(STR_CONFIG_SETTING_MODIFIER_ALREADY_IN_USE, INVALID_STRING_ID, WL_ERROR);
+		return false;
+	}
+
+	return true;
+}
+
+static bool CheckFnModifier(int32_t &new_value)
+{
+	return CheckModifier(new_value, _settings_client.gui.remove_modifier, _settings_client.gui.estimate_modifier);
+}
+
+static bool CheckRemoveModifier(int32_t &new_value)
+{
+	return CheckModifier(new_value, _settings_client.gui.fn_modifier, _settings_client.gui.estimate_modifier);
+}
+
+static bool CheckEstimateModifier(int32_t &new_value)
+{
+	return CheckModifier(new_value, _settings_client.gui.fn_modifier, _settings_client.gui.remove_modifier);
+}
+
 static void StationCatchmentChanged(int32_t)
 {
 	Station::RecomputeCatchmentForAll();

src/settings_type.h

@@ -23,6 +23,7 @@
 #include "rail_gui.h"
 #include "signal_type.h"
 #include "timetable.h"
+#include "gfx_type.h"
 
 /* Used to validate sizes of "max" value in settings. */
 const size_t MAX_SLE_UINT8 = UINT8_MAX;
@@ -220,6 +221,9 @@ struct GUISettings {
 	uint8_t  newgrf_default_palette;           ///< default palette to use for NewGRFs without action 14 palette information
 
 	bool   scale_bevels;                     ///< bevels are scaled with GUI scale.
+	ModifierKey fn_modifier;                 ///< function modifier key
+	ModifierKey remove_modifier;             ///< remove modifier key
+	ModifierKey estimate_modifier;           ///< estimate modifier key
 
 	/**
 	 * Returns true when the user has sufficient privileges to edit newgrfs on a running game

src/table/settings/gui_settings.ini

@@ -16,10 +16,14 @@ static void InvalidateCompanyLiveryWindow(int32_t new_value);
 static void InvalidateNewGRFChangeWindows(int32_t new_value);
 static void ZoomMinMaxChanged(int32_t new_value);
 static void SpriteZoomMinChanged(int32_t new_value);
+static bool CheckFnModifier(int32_t &new_value);
+static bool CheckRemoveModifier(int32_t &new_value);
+static bool CheckEstimateModifier(int32_t &new_value);
 
 static constexpr std::initializer_list<const char*> _osk_activation{"disabled", "double", "single", "immediately"};
 static constexpr std::initializer_list<const char*> _savegame_date{"long", "short", "iso"};
 static constexpr std::initializer_list<const char*> _right_click_close{"no", "yes", "except sticky"};
+static constexpr std::initializer_list<const char*> _mod_keys{"none", "shift", "ctrl", "alt"};
 
 static const SettingVariant _gui_settings_table[] = {
 [post-amble]
@@ -903,3 +907,44 @@ post_cb  = [](auto) { SetupWidgetDimensions(); ReInitAllWindows(true); }
 cat      = SC_BASIC
 startup  = true
 
+[SDTC_OMANY]
+var      = gui.fn_modifier
+type     = SLE_UINT8
+flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC | SF_GUI_DROPDOWN
+full     = _mod_keys
+def      = 2
+min      = 0
+max      = 3
+str      = STR_CONFIG_SETTING_MODIFIER_FN
+strhelp  = STR_CONFIG_SETTING_MODIFIER_FN_HELPTEXT
+strval   = STR_CONFIG_SETTING_MODIFIER_NONE
+pre_cb   = CheckFnModifier
+cat      = SC_ADVANCED
+
+[SDTC_OMANY]
+var      = gui.remove_modifier
+type     = SLE_UINT8
+flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC | SF_GUI_DROPDOWN
+full     = _mod_keys
+def      = 3
+min      = 0
+max      = 3
+str      = STR_CONFIG_SETTING_MODIFIER_REMOVE
+strhelp  = STR_CONFIG_SETTING_MODIFIER_REMOVE_HELPTEXT
+strval   = STR_CONFIG_SETTING_MODIFIER_NONE
+pre_cb   = CheckRemoveModifier
+cat      = SC_ADVANCED
+
+[SDTC_OMANY]
+var      = gui.estimate_modifier
+type     = SLE_UINT8
+flags    = SF_NOT_IN_SAVE | SF_NO_NETWORK_SYNC | SF_GUI_DROPDOWN
+full     = _mod_keys
+def      = 1
+min      = 0
+max      = 3
+str      = STR_CONFIG_SETTING_MODIFIER_ESTIMATE
+strhelp  = STR_CONFIG_SETTING_MODIFIER_ESTIMATE_HELPTEXT
+strval   = STR_CONFIG_SETTING_MODIFIER_NONE
+pre_cb   = CheckEstimateModifier
+cat      = SC_ADVANCED

src/window.cpp

@@ -2613,6 +2613,25 @@ void HandleKeypress(uint keycode, char32_t key)
 	HandleGlobalHotkeys(key, keycode);
 }
 
+/**
+ * Select the right state for the requested modifier key.
+ */
+static bool SelectModifierKey(ModifierKey key, bool shift_pressed, bool ctrl_pressed, bool alt_pressed)
+{
+	switch (key) {
+		case ModifierKey::None:
+			return false;
+		case ModifierKey::Shift:
+			return shift_pressed;
+		case ModifierKey::Ctrl:
+			return ctrl_pressed;
+		case ModifierKey::Alt:
+			return alt_pressed;
+		default:
+			NOT_REACHED();
+	}
+}
+
 /**
  * Handle the modifier key state changes.
  */
@@ -2623,10 +2642,9 @@ void HandleModifierKeys(bool shift_pressed, bool ctrl_pressed, bool alt_pressed)
 
 	_shift_pressed = shift_pressed;
 
-	/* Hardwire modifier keys. */
+	_fn_pressed = SelectModifierKey(_settings_client.gui.fn_modifier, shift_pressed, ctrl_pressed, alt_pressed);
-	_fn_pressed = ctrl_pressed;
+	_remove_pressed = SelectModifierKey(_settings_client.gui.remove_modifier, shift_pressed, ctrl_pressed, alt_pressed);
-	_remove_pressed = alt_pressed;
+	_estimate_pressed = SelectModifierKey(_settings_client.gui.estimate_modifier, shift_pressed, ctrl_pressed, alt_pressed);
-	_estimate_pressed = shift_pressed;
 
 	if (old_fn_pressed != _fn_pressed) {
 		/* Call the event, start with the uppermost window. */