public:

// Create a terminal canvas, sending to given file-descriptor.

explicit TerminalCanvas(BufferedWriteSequencer *write_sequencer);

TerminalCanvas(const TerminalCanvas &) = delete;

virtual ~TerminalCanvas();

virtual int cell_height_for_pixels(int pixels) const = 0;

// Send frame to terminal. Move to xposition (relative to the left

// of the screen, and delta y (relative to the current position) first.

virtual void Send(int x, int dy, const Framebuffer &framebuffer,

SeqType sequence_type, Duration end_of_frame) = 0;

// The following methods add content that is emitted before the next Send()

void AddPrefixNextSend(const char *data, int len);

void ClearScreen();

void CursorOff();

void CursorOn();

void MoveCursorDY(int rows); // -: up^, : downV

void MoveCursorDX(int cols); // -: <-left, : right->

protected:

char *AppendPrefixToBuffer(char *buffer);

BufferedWriteSequencer *const write_sequencer_; // not owned

private:

std::string prefix_send_;