Implement mouse selection, copy and paste in console/terminal

[pbalduino]

Context

Add mouse-based text selection, copy and paste functionality to meniOS console and mosh shell.

Difficulty Assessment

8/10 - Complex, multi-layered feature requiring coordination across several subsystems.

Architecture Overview

This feature requires changes across multiple layers:

Hardware Layer → Input Events → Console → Clipboard → Shell

Prerequisites

1. Mouse Hardware Support

• Implement PS/2 mouse driver and input support #143 - PS/2 mouse driver
• Implement USB mouse support through HID class driver #144 - USB mouse support (alternative)
• Mouse position tracking
• Button state events (press/release)

2. Console/Framebuffer Enhancements

• Track character grid (know what character is at each position)
• Convert mouse X/Y coordinates to row/column
• Render text selection (highlight background)
• Handle scrollback buffer selection

3. Clipboard Implementation

• System-wide paste buffer
• Or per-TTY paste buffer
• Copy text to buffer
• Paste from buffer
• Handle clipboard size limits

4. Terminal Emulation

• Xterm-style mouse reporting (optional)
• Selection modes (character, word, line)
• Mouse event forwarding to applications

5. Shell Integration (mosh)

• Insert clipboard contents into line buffer
• Handle paste in middle of line
• Paste validation (no control characters)
• Visual feedback during paste

Implementation Phases

Phase 1: Console Text Selection (Core Feature)

Mouse Selection Logic

typedef struct console_selection {
    int start_row, start_col;
    int end_row, end_col;
    bool active;
    bool complete;
} console_selection_t;

Selection Rendering

• Invert colors for selected text
• Update selection in real-time as mouse drags
• Support both character-by-character and rectangular selection

User Experience

[Left-click and drag to select text]
[Text highlights as you drag]
[Release button to complete selection]

Phase 2: Clipboard Operations

Copy Operation

• Left-click drag + release - Auto-copy on selection complete
• Or: Require Ctrl+C while selected
• Or: Middle-click copies (X11 style)

Clipboard Structure

typedef struct clipboard {
    char *text;
    size_t length;
    size_t capacity;
    uint64_t timestamp;
} clipboard_t;

Copy Implementation

// Extract selected text from console buffer
int console_copy_selection(console_selection_t *sel, clipboard_t *clip);

Phase 3: Paste Operation

Paste Trigger

• Middle-click - Traditional Unix paste
• Or: Shift+Insert - Windows/modern style
• Or: Ctrl+V - Alternative

Paste to Shell

// Insert clipboard text into mosh line buffer
int mosh_paste_from_clipboard(clipboard_t *clip);

Paste Handling

• Insert at current cursor position
• Handle multi-line paste
• Filter dangerous characters (avoid auto-exec)
• Show paste preview for large pastes?

Phase 4: Advanced Features (Optional)

• Word selection: Double-click selects word
• Line selection: Triple-click selects line
• Rectangular selection: Alt+drag for column selection
• Scrollback selection: Select from scrollback buffer
• Copy formatting: Preserve color/attributes (future)

Technical Challenges

1. Character Grid Tracking

The console needs to know:

• What character is at position (x, y)
• Character attributes (color, bold, etc.)
• Mapping pixel coordinates → character cells

typedef struct console_cell {
    char ch;
    uint8_t fg_color;
    uint8_t bg_color;
    uint8_t attrs;
} console_cell_t;

console_cell_t console_buffer[ROWS][COLS];

2. Selection Rendering

Need to:

• Redraw selection region efficiently
• Handle partial character cells at edges
• Update in real-time without flicker
• Clear old selection before new one

3. Mouse Coordinate Mapping

// Convert mouse coordinates to console position
typedef struct mouse_to_console {
    int pixel_x, pixel_y;    // Mouse position
    int col, row;             // Console cell
    int char_width, char_height;  // Font metrics
} mouse_to_console_t;

void map_mouse_to_console(int x, int y, int *row, int *col) {
    *col = x / CHAR_WIDTH;
    *row = y / CHAR_HEIGHT;
}

4. Clipboard Size Management

• Limit clipboard to reasonable size (64KB?)
• Handle clipboard overflow
• Clear old clipboard on new copy

5. Multi-line Paste Safety

// Filter clipboard before paste
bool is_safe_char(char c) {
    return c >= 32 && c < 127;  // Printable ASCII
}

void filter_clipboard(char *text) {
    // Remove newlines or warn user
    // Filter control characters
    // Handle special cases
}

User Experience Design

Selection UX (X11 Style - Recommended)

1. Left-click drag - Select text (auto-copy on release)
2. Middle-click - Paste at cursor
3. Right-click - Context menu (future)

Alternative: Windows Style

1. Left-click drag - Select text only
2. Ctrl+C - Copy selection
3. Ctrl+V or Shift+Insert** - Paste

Visual Feedback

• Selected text: inverted colors
• Paste operation: brief highlight of pasted text
• Cursor position: visible caret

Dependencies

Hard Requirements

• Implement PS/2 mouse driver and input support #143 or Implement USB mouse support through HID class driver #144 - Mouse hardware support
• Framebuffer console character tracking
• Input event system for mouse

Soft Requirements

• Implement UNIX signals for process control and communication #103 - Signals (for Ctrl+C handling if used)
• Terminal scrollback buffer
• UTF-8 support for non-ASCII text (Implement UTF-8 decoding and encoding utilities #127-134)

Acceptance Criteria

• Mouse selection works on console
• Selected text is highlighted visually
• Copy operation saves to clipboard
• Paste operation inserts into mosh line buffer
• Works with both PS/2 and USB mice
• No crashes on edge cases (empty selection, large paste)
• Selection persists across terminal operations
• Paste filters dangerous characters

Timeline Estimate

With Prerequisites Complete

• Phase 1 (Selection): 2-3 weeks
• Phase 2 (Clipboard): 1 week
• Phase 3 (Paste): 1-2 weeks
• Phase 4 (Polish): 1 week
• Total: 5-7 weeks

Without Prerequisites

• Mouse driver: 3-4 weeks (Implement PS/2 mouse driver and input support #143)
• Console enhancements: 2-3 weeks
• Then above phases: 5-7 weeks
• Total: 10-14 weeks (2.5-3.5 months)

Alternative: Simpler Approach

Keyboard-Only Copy/Paste (Easier)

Skip mouse entirely, use keyboard:

• Shift+Arrow keys - Select text
• Ctrl+C - Copy
• Ctrl+V - Paste

This requires:

• Selection mode in shell
• No mouse support needed
• Much simpler implementation
• Timeline: 1-2 weeks

Recommendation

1. Short term: Implement keyboard-based copy/paste (1-2 weeks)
2. Medium term: Add mouse drivers (Implement PS/2 mouse driver and input support #143)
3. Long term: Add mouse selection (after drivers stable)

Or skip entirely if keyboard shortcuts sufficient for users.

Priority

Medium-Low - Nice to have, but not critical for shell milestone.

Mouse selection is standard in modern terminals (xterm, GNOME Terminal, Windows Terminal) but not essential for basic OS functionality.