Highlight unit movement area while holding a key modifier

src/fheroes2/battle/battle_cell.cpp

@@ -173,6 +173,12 @@ Battle::Position Battle::Position::GetReachable( const Unit & unit, const int32_
             return {};
         };
 
+        Position headPos = tryHead();
+
+        if ( headPos.GetHead() != nullptr && headPos.GetTail() != nullptr ) {
+            return headPos;
+        }
+
         const auto tryTail = [&unit, dst, &checkCells]() -> Position {
             const CellDirection headDirection = unit.isReflect() ? CellDirection::LEFT : CellDirection::RIGHT;
 
@@ -186,12 +192,6 @@ Battle::Position Battle::Position::GetReachable( const Unit & unit, const int32_
             return {};
         };
 
-        Position headPos = tryHead();
-
-        if ( headPos.GetHead() != nullptr && headPos.GetTail() != nullptr ) {
-            return headPos;
-        }
-
         return tryTail();
     }
 

src/fheroes2/battle/battle_interface.cpp

@@ -1182,7 +1182,7 @@ void Battle::Status::clear()
     _lastMessage = "";
 }
 
-bool Battle::TurnOrder::queueEventProcessing( Interface & interface, std::string & msg, const fheroes2::Point & offset ) const
+bool Battle::TurnOrder::queueEventProcessing( Interface & interface, std::string & msg, const fheroes2::Point & offset, const bool highlightUnitMomevementArea ) const
 {
     LocalEvent & le = LocalEvent::Get();
 
@@ -1196,6 +1196,10 @@ bool Battle::TurnOrder::queueEventProcessing( Interface & interface, std::string
 
             interface.setUnitTobeHighlighted( unit );
 
+            if ( highlightUnitMomevementArea ) {
+                interface.setUnitToShowMovementArea( unit );
+            }
+
             // Process mouse buttons events.
             if ( le.MouseClickLeft( unitRoi ) ) {
                 Dialog::ArmyInfo( *unit, Dialog::BUTTONS, unit->isReflect() );
@@ -1431,6 +1435,7 @@ Battle::Interface::Interface( Arena & battleArena, const int32_t tileIndex )
     _hexagonShadow = DrawHexagonShadow( 4, 2 );
     // Shadow that fits the hexagon grid.
     _hexagonGridShadow = DrawHexagonShadow( 4, 1 );
+    _hexagonHighlightShadow = DrawHexagonShadow( 2, 2 );
 
     _buttonAuto.setICNInfo( ICN::TEXTBAR, 4, 5 );
     _buttonSettings.setICNInfo( ICN::TEXTBAR, 6, 7 );
@@ -2392,21 +2397,79 @@ void Battle::Interface::_redrawCoverStatic()
 {
     fheroes2::Copy( _battleGround, _mainSurface );
 
+    if ( _movingUnit != nullptr ) {
+        // Do not show movement area while units are in action.
+        return;
+    }
+
     const Settings & conf = Settings::Get();
+    if ( !conf.BattleShowMoveShadow() ) {
+        // Display movement area only if the associated option is enabled.
+        return;
+    }
 
-    // Movement shadow.
-    if ( !_movingUnit && conf.BattleShowMoveShadow() && _currentUnit && !( _currentUnit->GetCurrentControl() & CONTROL_AI ) ) {
-        const fheroes2::Image & shadowImage = conf.BattleShowGrid() ? _hexagonGridShadow : _hexagonShadow;
-        const Board & board = *Arena::GetBoard();
+    if ( _currentUnit == nullptr || ( _currentUnit->GetCurrentControl() & CONTROL_AI ) ) {
+        // No current unit is selected or this unit is controlled by AI.
+        return;
+    }
+
+    Board & board = *Arena::GetBoard();
+
+    std::array<bool, Board::sizeInCells> processedCells{ false };
+    assert( board.size() == processedCells.size() );
+
+    if ( _highlightUnitMovementArea != nullptr ) {
+        Unit * foundUnit = nullptr;
+        for ( Cell & cell : board ) {
+            Unit * unit = cell.GetUnit();
+            if ( unit != nullptr && unit == _highlightUnitMovementArea ) {
+                foundUnit = unit;
+                break;
+            }
+        }
+
+        // If we hit this assertion then the unit doesn't even exist.
+        assert( foundUnit != nullptr );
+
+        // The highlighted unit might have moved. We want to display the real movement area.
+        const bool isMoved = foundUnit->Modes( Battle::TR_MOVED );
 
+        foundUnit->ResetModes( Battle::TR_MOVED );
+
+        // To avoid pathfinder re-evaluation we need to run the same loop separately for the selected unit and then for the current unit.
+        // In this case we do re-evaluation only once.
         for ( const Cell & cell : board ) {
-            const Position pos = Position::GetReachable( *_currentUnit, cell.GetIndex() );
+            const Position pos = Position::GetReachable( *_highlightUnitMovementArea, cell.GetIndex() );
+
             if ( pos.GetHead() != nullptr ) {
-                assert( pos.isValidForUnit( _currentUnit ) );
+                assert( pos.isValidForUnit( _highlightUnitMovementArea ) );
 
-                fheroes2::Blit( shadowImage, _mainSurface, cell.GetPos().x, cell.GetPos().y );
+                // To separate enemy movement from the current unit we apply the shadow twice.
+                fheroes2::Blit( _hexagonHighlightShadow, _mainSurface, cell.GetPos().x, cell.GetPos().y );
+                fheroes2::Blit( _hexagonHighlightShadow, _mainSurface, cell.GetPos().x, cell.GetPos().y );
+
+                processedCells[cell.GetIndex()] = true;
             }
         }
+
+        if ( isMoved ) {
+            foundUnit->SetModes( Battle::TR_MOVED );
+        }
+    }
+
+    const fheroes2::Image & shadowImage = conf.BattleShowGrid() ? _hexagonGridShadow : _hexagonShadow;
+
+    for ( const Cell & cell : board ) {
+        if ( processedCells[cell.GetIndex()] ) {
+            continue;
+        }
+
+        const Position pos = Position::GetReachable( *_currentUnit, cell.GetIndex() );
+        if ( pos.GetHead() != nullptr ) {
+            assert( pos.isValidForUnit( _currentUnit ) );
+
+            fheroes2::Blit( shadowImage, _mainSurface, cell.GetPos().x, cell.GetPos().y );
+        }
     }
 }
 
@@ -2689,7 +2752,7 @@ void Battle::Interface::RedrawKilled()
     }
 }
 
-int Battle::Interface::GetBattleCursor( std::string & statusMsg ) const
+int Battle::Interface::GetBattleCursor( std::string & statusMsg, const bool highlightUnitMomevementArea )
 {
     statusMsg.clear();
 
@@ -2707,6 +2770,10 @@ int Battle::Interface::GetBattleCursor( std::string & statusMsg ) const
 
         const Unit * unit = cell->GetUnit();
 
+        if ( highlightUnitMomevementArea ) {
+            _highlightUnitMovementArea = unit;
+        }
+
         if ( unit == nullptr || _currentUnit == unit ) {
             const Position pos = Position::GetReachable( *_currentUnit, _currentCellIndex );
             if ( pos.GetHead() != nullptr ) {
@@ -2978,6 +3045,10 @@ void Battle::Interface::HumanBattleTurn( const Unit & unit, Actions & actions, s
 
     BoardActionIntentUpdater boardActionIntentUpdater( _boardActionIntent, le.isMouseEventFromTouchpad() );
 
+    // Make sure to reset currently selected unit every time we do rendering.
+    _highlightUnitMovementArea = nullptr;
+    const bool highlightUnitMovementArea = Game::HotKeyHoldEvent( Game::HotKeyEvent::BATTLE_HIGHLIGHT_UNIT_AREA_MODIFIER );
+
     _buttonAuto.drawOnState( le.isMouseLeftButtonPressedAndHeldInArea( _buttonAuto.area() ) );
     _buttonSettings.drawOnState( le.isMouseLeftButtonPressedAndHeldInArea( _buttonSettings.area() ) );
     _buttonSkip.drawOnState( le.isMouseLeftButtonPressedAndHeldInArea( _buttonSkip.area() ) );
@@ -3069,7 +3140,7 @@ void Battle::Interface::HumanBattleTurn( const Unit & unit, Actions & actions, s
     }
     else if ( conf.BattleShowTurnOrder() && le.isMouseCursorPosInArea( _turnOrder.getRenderingRoi() ) ) {
         cursor.SetThemes( Cursor::POINTER );
-        if ( _turnOrder.queueEventProcessing( *this, msg, _interfacePosition.getPosition() ) ) {
+        if ( _turnOrder.queueEventProcessing( *this, msg, _interfacePosition.getPosition(), highlightUnitMovementArea ) ) {
             humanturn_redraw = true;
         }
     }
@@ -3193,7 +3264,7 @@ void Battle::Interface::HumanBattleTurn( const Unit & unit, Actions & actions, s
         }
     }
     else if ( le.isMouseCursorPosInArea( battleFieldRect ) ) {
-        int themes = GetBattleCursor( msg );
+        int themes = GetBattleCursor( msg, highlightUnitMovementArea );
 
         if ( _swipeAttack.isValid() ) {
             // The swipe attack motion is either in progress or has finished.

src/fheroes2/battle/battle_interface.h

@@ -243,7 +243,7 @@ namespace Battle
 
         void redraw( const Unit * current, const uint8_t currentUnitColor, const Unit * underCursor, fheroes2::Image & output, const fheroes2::Rect & dialogRoi );
 
-        bool queueEventProcessing( Interface & interface, std::string & msg, const fheroes2::Point & offset ) const;
+        bool queueEventProcessing( Interface & interface, std::string & msg, const fheroes2::Point & offset, const bool highlightUnitMomevementArea ) const;
 
         const fheroes2::Rect & getRenderingRoi() const
         {
@@ -351,6 +351,11 @@ namespace Battle
             _unitToHighlight = unit;
         }
 
+        void setUnitToShowMovementArea( const Unit * unit )
+        {
+            _highlightUnitMovementArea = unit;
+        }
+
         void SetOrderOfUnits( const std::shared_ptr<const Units> & units );
         void FadeArena( const bool clearMessageLog );
 
@@ -459,7 +464,7 @@ namespace Battle
         void MouseLeftClickBoardAction( const int themes, const Cell & cell, const bool isConfirmed, Actions & actions );
         bool MousePressRightBoardAction( const Cell & cell ) const;
 
-        int GetBattleCursor( std::string & statusMsg ) const;
+        int GetBattleCursor( std::string & statusMsg, const bool highlightUnitMomevementArea );
         int GetBattleSpellCursor( std::string & statusMsg ) const;
 
         void _startAutoCombat( const Unit & unit, Actions & actions );
@@ -476,6 +481,7 @@ namespace Battle
         fheroes2::Image _hexagonShadow;
         fheroes2::Image _hexagonGridShadow;
         fheroes2::Image _hexagonCursorShadow;
+        fheroes2::Image _hexagonHighlightShadow;
 
         int _battleGroundIcn{ ICN::UNKNOWN };
         int _borderObjectsIcn{ ICN::UNKNOWN };
@@ -509,6 +515,7 @@ namespace Battle
         const Unit * _movingUnit{ nullptr };
         const Unit * _flyingUnit{ nullptr };
         const Unit * _unitToHighlight{ nullptr };
+        const Unit * _highlightUnitMovementArea{ nullptr };
         const fheroes2::Sprite * _spriteInsteadCurrentUnit{ nullptr };
         fheroes2::Point _movingPos;
         fheroes2::Point _flyingPos;

src/fheroes2/game/game_hotkeys.cpp

@@ -298,6 +298,8 @@ namespace
             = { Game::HotKeyCategory::BATTLE, gettext_noop( "hotkey|cast battle spell" ), fheroes2::Key::KEY_C };
         hotKeyEventInfo[hotKeyEventToInt( Game::HotKeyEvent::BATTLE_TOGGLE_TURN_ORDER_DISPLAY )]
             = { Game::HotKeyCategory::BATTLE, gettext_noop( "hotkey|toggle display of battle turn order" ), fheroes2::Key::KEY_T };
+        hotKeyEventInfo[hotKeyEventToInt( Game::HotKeyEvent::BATTLE_HIGHLIGHT_UNIT_AREA_MODIFIER )]
+            = { Game::HotKeyCategory::BATTLE, gettext_noop( "hotkey|hold to highlight unit movement area" ), fheroes2::Key::KEY_LEFT_SHIFT };
 
         hotKeyEventInfo[hotKeyEventToInt( Game::HotKeyEvent::TOWN_DWELLING_LEVEL_1 )]
             = { Game::HotKeyCategory::TOWN, gettext_noop( "hotkey|dwelling level 1" ), fheroes2::Key::KEY_1 };

src/fheroes2/game/game_hotkeys.h

@@ -156,6 +156,7 @@ namespace Game
         BATTLE_SKIP,
         BATTLE_CAST_SPELL,
         BATTLE_TOGGLE_TURN_ORDER_DISPLAY,
+        BATTLE_HIGHLIGHT_UNIT_AREA_MODIFIER,
 
         TOWN_DWELLING_LEVEL_1,
         TOWN_DWELLING_LEVEL_2,