Chess+GameSettings: Optionally highlight the king when in check

When either king is in check, its square is now highlighted with a red
background. This behavior can be toggled in GameSettings.

3 files changed, 22 insertions, 2 deletions

diff --git a/Userland/Games/Chess/ChessWidget.cpp b/Userland/Games/Chess/ChessWidget.cpp
index 4ce5458728..aeb952c79e 100644
--- a/Userland/Games/Chess/ChessWidget.cpp
+++ b/Userland/Games/Chess/ChessWidget.cpp
@@ -62,8 +62,20 @@ void ChessWidget::paint_event(GUI::PaintEvent& event)
 
         painter.fill_rect(tile_rect, (sq.is_light()) ? board_theme().light_square_color : board_theme().dark_square_color);
 
-        if (active_board.last_move().has_value() && (active_board.last_move().value().to == sq || active_board.last_move().value().from == sq)) {
-            painter.fill_rect(tile_rect, m_move_highlight_color);
+        if (active_board.last_move().has_value()) {
+            auto const last_move = active_board.last_move().value();
+            if (last_move.to == sq || last_move.from == sq)
+                painter.fill_rect(tile_rect, m_move_highlight_color);
+
+            auto const piece = active_board.get_piece(sq);
+            if (m_highlight_checks && last_move.is_check && piece.type == Chess::Type::King && piece.color == active_board.turn()) {
+                Array<Gfx::ColorStop, 2> colors = {
+                    Gfx::ColorStop { .color = Color::Red, .position = 0.16f },
+                    Gfx::ColorStop { .color = Color::Transparent, .position = .66f }
+                };
+
+                painter.fill_rect_with_radial_gradient(tile_rect, colors, tile_rect.center() - tile_rect.top_left(), tile_rect.size());
+            }
         }
 
         if (m_coordinates) {
@@ -750,5 +762,8 @@ void ChessWidget::config_bool_did_change(DeprecatedString const& domain, Depreca
     if (key == "ShowCoordinates"sv) {
         set_coordinates(value);
         update();
+    } else if (key == "HighlightChecks"sv) {
+        set_highlight_checks(value);
+        update();
     }
 }
diff --git a/Userland/Games/Chess/ChessWidget.h b/Userland/Games/Chess/ChessWidget.h
index 7beb6a23bc..95731c5adb 100644
--- a/Userland/Games/Chess/ChessWidget.h
+++ b/Userland/Games/Chess/ChessWidget.h
@@ -89,6 +89,9 @@ public:
     void set_coordinates(bool coordinates) { m_coordinates = coordinates; }
     bool coordinates() const { return m_coordinates; }
 
+    void set_highlight_checks(bool highlight_checks) { m_highlight_checks = highlight_checks; }
+    bool highlight_checks() const { return m_highlight_checks; }
+
     struct BoardMarking {
         Chess::Square from { 50, 50 };
         Chess::Square to { 50, 50 };
@@ -146,4 +149,5 @@ private:
     Vector<Chess::Square> m_available_moves;
     RefPtr<Engine> m_engine;
     bool m_coordinates { true };
+    bool m_highlight_checks { true };
 };
diff --git a/Userland/Games/Chess/main.cpp b/Userland/Games/Chess/main.cpp
index ba19020741..e591c1cfc6 100644
--- a/Userland/Games/Chess/main.cpp
+++ b/Userland/Games/Chess/main.cpp
@@ -87,6 +87,7 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
     widget->set_board_theme(Config::read_string("Games"sv, "Chess"sv, "BoardTheme"sv, "Beige"sv));
     widget->set_coordinates(Config::read_bool("Games"sv, "Chess"sv, "ShowCoordinates"sv, true));
     widget->set_show_available_moves(Config::read_bool("Games"sv, "Chess"sv, "ShowAvailableMoves"sv, true));
+    widget->set_highlight_checks(Config::read_bool("Games"sv, "Chess"sv, "HighlightChecks"sv, true));
 
     auto game_menu = TRY(window->try_add_menu("&Game"_short_string));