LibCards: Support highlighting cards of interest

For example, in Solitaire, when dragging a card around, it's common for
other implementations to highlight the card underneath the dragged card
if that other card is a valid drop target. This implementation will draw
a rounded rectangle within the edges of the highlighted card, using a
rudimentary complementary color of the board background color.

Userland/Libraries/LibCards/Card.cpp

@@ -26,7 +26,10 @@ void Card::paint(GUI::Painter& painter) const
     auto bitmap = [&]() {
         if (m_inverted)
             return m_upside_down ? card_painter.card_back_inverted() : card_painter.card_front_inverted(m_suit, m_rank);
-
+        if (m_highlighted) {
+            VERIFY(!m_upside_down);
+            return card_painter.card_front_highlighted(m_suit, m_rank);
+        }
         return m_upside_down ? card_painter.card_back() : card_painter.card_front(m_suit, m_rank);
     }();
     painter.blit(position(), bitmap, bitmap->rect());

Userland/Libraries/LibCards/Card.h

@@ -104,6 +104,7 @@ public:
     void set_moving(bool moving) { m_moving = moving; }
     void set_upside_down(bool upside_down) { m_upside_down = upside_down; }
     void set_inverted(bool inverted) { m_inverted = inverted; }
+    void set_highlighted(bool highlighted) { m_highlighted = highlighted; }
 
     void save_old_position();
 
@@ -122,6 +123,7 @@ private:
     bool m_moving { false };
     bool m_upside_down { false };
     bool m_inverted { false };
+    bool m_highlighted { false };
 };
 
 enum class Shuffle {

Userland/Libraries/LibCards/CardGame.cpp

@@ -126,5 +126,8 @@ void CardGame::set_background_color(Gfx::Color color)
     auto new_palette = palette();
     new_palette.set_color(Gfx::ColorRole::Background, color);
     set_palette(new_palette);
+
+    CardPainter::the().set_background_color(color);
 }
+
 }

Userland/Libraries/LibCards/CardPainter.cpp

@@ -102,6 +102,21 @@ NonnullRefPtr<Gfx::Bitmap> CardPainter::card_back()
     return *m_card_back;
 }
 
+NonnullRefPtr<Gfx::Bitmap> CardPainter::card_front_highlighted(Suit suit, Rank rank)
+{
+    auto suit_id = to_underlying(suit);
+    auto rank_id = to_underlying(rank);
+
+    auto& existing_bitmap = m_cards_highlighted[suit_id][rank_id];
+    if (!existing_bitmap.is_null())
+        return *existing_bitmap;
+
+    m_cards_highlighted[suit_id][rank_id] = create_card_bitmap();
+    paint_highlighted_card(*m_cards_highlighted[suit_id][rank_id], card_front(suit, rank));
+
+    return *m_cards_highlighted[suit_id][rank_id];
+}
+
 NonnullRefPtr<Gfx::Bitmap> CardPainter::card_front_inverted(Suit suit, Rank rank)
 {
     auto suit_id = to_underlying(suit);
@@ -140,6 +155,17 @@ void CardPainter::set_background_image_path(DeprecatedString path)
         paint_inverted_card(*m_card_back_inverted, *m_card_back);
 }
 
+void CardPainter::set_background_color(Color background_color)
+{
+    m_background_color = background_color;
+
+    // Clear any cached card bitmaps that depend on the background color.
+    for (auto& suit_array : m_cards_highlighted) {
+        for (auto& rank_array : suit_array)
+            rank_array = nullptr;
+    }
+}
+
 NonnullRefPtr<Gfx::Bitmap> CardPainter::create_card_bitmap()
 {
     return Gfx::Bitmap::try_create(Gfx::BitmapFormat::BGRA8888, { Card::width, Card::height }).release_value_but_fixme_should_propagate_errors();
@@ -212,4 +238,17 @@ void CardPainter::paint_inverted_card(Gfx::Bitmap& bitmap, Gfx::Bitmap const& so
     });
 }
 
+void CardPainter::paint_highlighted_card(Gfx::Bitmap& bitmap, Gfx::Bitmap const& source_to_highlight)
+{
+    Gfx::Painter painter { bitmap };
+    auto paint_rect = source_to_highlight.rect();
+    auto background_complement = m_background_color.xored(Color::White);
+
+    painter.fill_rect_with_rounded_corners(paint_rect, Color::Black, Card::card_radius);
+    paint_rect.shrink(2, 2);
+    painter.fill_rect_with_rounded_corners(paint_rect, background_complement, Card::card_radius - 1);
+    paint_rect.shrink(2, 2);
+    painter.blit({ 4, 4 }, source_to_highlight, source_to_highlight.rect().shrunken(8, 8));
+}
+
 }

Userland/Libraries/LibCards/CardPainter.h

@@ -9,6 +9,7 @@
 #include <AK/Array.h>
 #include <LibCards/Card.h>
 #include <LibGfx/Bitmap.h>
+#include <LibGfx/Color.h>
 
 namespace Cards {
 
@@ -20,8 +21,10 @@ public:
     NonnullRefPtr<Gfx::Bitmap> card_back();
     NonnullRefPtr<Gfx::Bitmap> card_front_inverted(Suit, Rank);
     NonnullRefPtr<Gfx::Bitmap> card_back_inverted();
+    NonnullRefPtr<Gfx::Bitmap> card_front_highlighted(Suit, Rank);
 
     void set_background_image_path(DeprecatedString path);
+    void set_background_color(Color);
 
 private:
     CardPainter();
@@ -29,13 +32,16 @@ private:
     void paint_card_front(Gfx::Bitmap&, Suit, Rank);
     void paint_card_back(Gfx::Bitmap&);
     void paint_inverted_card(Gfx::Bitmap& bitmap, Gfx::Bitmap const& source_to_invert);
+    void paint_highlighted_card(Gfx::Bitmap& bitmap, Gfx::Bitmap const& source_to_highlight);
 
     Array<Array<RefPtr<Gfx::Bitmap>, to_underlying(Rank::__Count)>, to_underlying(Suit::__Count)> m_cards;
     Array<Array<RefPtr<Gfx::Bitmap>, to_underlying(Rank::__Count)>, to_underlying(Suit::__Count)> m_cards_inverted;
+    Array<Array<RefPtr<Gfx::Bitmap>, to_underlying(Rank::__Count)>, to_underlying(Suit::__Count)> m_cards_highlighted;
     RefPtr<Gfx::Bitmap> m_card_back;
     RefPtr<Gfx::Bitmap> m_card_back_inverted;
 
     DeprecatedString m_background_image_path;
+    Color m_background_color;
 };
 
 }