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UI

UI​

The UI struct handles all rendering and user interaction for the chess game. It manages cursor position, piece selection, and renders the board, move history, and captured pieces.

Responsibilities​

The UI struct manages:

  • Board rendering - Chess board with pieces, highlights, and colors
  • Move history display - Algebraic notation move list
  • Captured pieces display - Shows taken pieces for each side
  • Cursor and selection - Keyboard and mouse interaction
  • Display modes - DEFAULT (Unicode) and ASCII rendering

Key Fields​

pub struct UI {
    pub cursor_coordinates: Coord,           // Current cursor position
    pub selected_square: Option<Square>,      // Currently selected piece square
    pub selected_piece_cursor: i8,           // Cursor for authorized moves
    pub promotion_cursor: i8,                // Cursor for promotion selection
    pub old_cursor_position: Coord,           // Previous cursor (for unselect)
    pub top_x: u16,                          // Board top-left X coordinate
    pub top_y: u16,                          // Board top-left Y coordinate
    pub width: u16,                          // Cell width
    pub height: u16,                         // Cell height
    pub mouse_used: bool,                     // Whether last action was mouse
    pub display_mode: DisplayMode,           // DEFAULT or ASCII
    pub prompt: Prompt,                      // Text input prompt
}

Key Methods​

Cursor Management​

  • cursor_up/down/left/right(authorized_positions: Vec<Coord>)

    • Moves cursor in specified direction
    • If piece is selected, moves through authorized positions only
    • Otherwise, moves freely on the board

  • move_selected_piece_cursor(first_time_moving: bool, direction: i8, authorized_positions: Vec<Coord>)

    • Moves cursor through legal moves when piece is selected
    • Cycles through available destination squares

  • cursor_left_promotion() / cursor_right_promotion()

    • Navigates promotion piece selection (Queen, Rook, Bishop, Knight)

Selection​

  • is_cell_selected() -> bool - Checks if a piece is currently selected
  • unselect_cell() - Deselects piece and restores cursor position

Rendering Methods​

Board Rendering​

  • board_render(area: Rect, frame: &mut Frame, logic: &GameLogic)
    • Main board rendering method
    • Handles board flipping for perspective
    • Renders pieces using Unicode or ASCII
    • Highlights:
      • Blue - Current cursor position
      • Green - Selected piece or last move squares
      • Grey - Available move destinations
      • Magenta - King in check (with blinking)

Label Rendering​

  • render_rank_labels(frame: &mut Frame, area: Rect, is_flipped: bool)

    • Renders rank labels (1-8) on the left side of the board
    • Order adjusts based on board flip state

  • render_file_labels(frame: &mut Frame, area: Rect, is_flipped: bool)

    • Renders file labels (A-H) below the board
    • Order adjusts based on board flip state

History Rendering​

  • history_render(area: Rect, frame: &mut Frame, game: &Game)
    • Displays move history in Standard Algebraic Notation
    • Shows move number, piece symbol, and move (e.g., "1. ♙ e4 ♟ e5")
    • Formats moves in pairs (white, black)
    • Uses fixed-width formatting to ensure consistent column alignment:
      • Line numbers: Right-aligned in 3 characters + ". " (5 chars total)
      • White moves: Icon + space + move notation in 10 characters (left-aligned)
      • Black moves: Icon + space + move notation in 10 characters (left-aligned)
    • Maintains alignment regardless of move length or piece type

Material Rendering​

  • white_material_render(area: Rect, frame: &mut Frame, white_taken_pieces: &[Role])

    • Displays captured white pieces
    • Shows piece symbols for taken pieces
    • Displays "Press ? for help" at the bottom

  • black_material_render(area: Rect, frame: &mut Frame, black_taken_pieces: &[Role])

    • Displays captured black pieces
    • Shows piece symbols for taken pieces

Piece Rendering​

  • render_piece_paragraph(piece_type: Option<Role>, piece_color: Option<Color>, square: Rect) -> Paragraph
    • Renders individual piece based on display mode
    • DEFAULT mode: Multi-line Unicode art
    • ASCII mode: Single character (K, Q, R, B, N, P)

Utility​

  • reset() - Resets all UI state to defaults

Display Modes​

DEFAULT Mode​

  • Uses Unicode chess piece symbols (♔ ♕ ♖ ♗ ♘ ♙)
  • Multi-line piece art for board rendering
  • Color-coded pieces (white/black)

ASCII Mode​

  • Single character representation (K, Q, R, B, N, P)
  • Uppercase for white, lowercase for black
  • Underlined for white pieces

Coordinate System​

The UI handles coordinate conversion between:

  • Visual coordinates - What the user sees (may be flipped)
  • Standard coordinates - Internal shakmaty coordinates (a1-h8)

The is_flipped flag in GameBoard determines if coordinates need conversion when:

  • Selecting pieces
  • Moving pieces
  • Rendering the board

Integration with Game​

The UI is owned by the Game struct alongside GameLogic:

pub struct Game {
    pub logic: GameLogic,
    pub ui: UI,
}

The UI reads game state from GameLogic but doesn't modify it directly. All game state changes go through Game methods which coordinate between UI and logic.