ErrMsg.h

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/*******************************************************************************
 * @file ErrMsg.h
 *
 * @brief Defines a mechism for displaying error and warning messages onto the TFT display.
 ******************************************************************************/
 
#ifndef ERRMSG_HEADER
#define ERRMSG_HEADER
 
#include "Canvas.h"
#include "Menu.h"

#define _MAXCHARS 85
 
/******************************************************************************/
/***                                                                        ***/
/***                      Class Definition: ErrMsg                          ***/
/***                                                                        ***/
/******************************************************************************
 * @brief Provides a mechnism for displaying error and warning messages on the TFT display.
 *
 * @details
 * This is a Singleton class. Use ErrMsg::getInstance() to obtain a reference
 * to the ErrMsg instance. Warning messages give users the abiliy to acknowledge
 * the message and continue. Error messages halt the program altogether. The
 * following is an example of how to use the ErrMsg class:
 *
 * @code {.cpp}
 *   errMsg.warning()
 *     << "This is a test warning message." << ErrMsg::endl
 *     << "Value too high: " << value << ErrMsg::endl;
 *   errMsg.send();
 * @endcode
 *
 * @note It is recommended that their only be one instance of ErrMsg for a
 * given application.
 *
 ******************************************************************************/
class ErrMsg
{
 
    Canvas _canvas;              // Canvas for displaying the error message
    const uint16_t _x = 10;      // x position of the error message within _canvas
    uint16_t _y;                 // y position of the error message within _canvas
    const uint16_t _yStart = 10; // Starting position for the y cursor for a new error message within _canvas
    const uint16_t _yMax = 480;  // Maximum y position of the error message within _canvas
    const uint16_t _deltaY = 25; // Spacing between lines of each error message
 
    char _line[_MAXCHARS]; // Buffer used to build up each line of the error message
    uint8_t pos;           // Current position within the line buffer
 
    uint16_t _fontFG = 0xFFFF; // Foreground color of the font
    uint16_t _fontBG = 0x0000; // Background color of the font
 
    static ErrMsg *_instance; // The Singleton instance of ErrMsg
 
    enum ErrorType
    {
        WARNING,
        ERROR
    };
    ErrorType _type; // Tracks whether this is a warning or error message
 
    SoloMenu *_origMenu = nullptr; // The menu that was displayed before the error message was displayed
 
    // Private Constructor
    ErrMsg(void)
        : _canvas{}, _y{_yStart}, _line{""}, pos{0}, _type{ErrorType::WARNING}
    {
    }
 
    // Private Destructor
    ~ErrMsg(void) = default;
 
public:
    struct EndlToken
    {
    }; 
    static EndlToken endl; 

    static ErrMsg &getInstance(void)
    {
        if (!_instance)
            _instance = new ErrMsg();
        return *_instance;
    };

    ErrMsg(const ErrMsg &) = delete;

    ErrMsg &operator=(const ErrMsg &) = delete;

    ErrMsg &error(void);

    ErrMsg &warning(void);

    template <typename T>
    ErrMsg &operator<<(const T value)
    {
        // Ignore if this line extends past _yMax
        if (_y >= _yMax)
            return *this;
 
        // Ignore if we've run out of ro
        int16_t buffSize = _MAXCHARS - pos;
        if (buffSize <= 0)
            return *this;
 
        // Add the value to the line buffer
        _addToLine(value, buffSize);
 
        // Finished
        return *this;
    }

    void send(void);

    void checkForUserInput(void);
 
private:
    // Clears the canvas and sets the background color
    void _resetCanvas(uint16_t color);
 
    // Internal message used to send an error message to the screen
    void _sendError(void);
 
    // Internal message used to send a warning message to the screen
    void _sendWarning(void);
 
    // Adds a value to the current line. These methods provide functionality for the operator<<() method.
    void _addToLine(const char *const value, int16_t buffSize);
    void _addToLine(const int value, int16_t buffSize);
    void _addToLine(const bool value, int16_t buffSize);
    void _addToLine(const unsigned int value, int16_t buffSize);
};

template <>
ErrMsg &ErrMsg::operator<< <ErrMsg::EndlToken>(const ErrMsg::EndlToken value);

extern ErrMsg &errMsg;
 
#endif // ERRMSG_HEADER