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139 lines
4.9 KiB
C++
139 lines
4.9 KiB
C++
/*! \file
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* \brief \ref CGA provides a basic interface to display a character in
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* VGA-compatible text mode
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*/
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#pragma once
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#include "../types.h"
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/*! \brief Basic operations in the VGA-compatible text mode
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* \ingroup io
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*
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* This namespace provides an interface to access the screen in text mode
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* (also known as CGA mode), with access directly on the hardware
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* level, i.e. the video memory and the I/O ports of the graphics
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* card.
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*/
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namespace CGA {
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constexpr unsigned ROWS = 25; ///< Visible rows in text mode
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constexpr unsigned COLUMNS = 80; ///< Visible columns in text mode
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/*! \brief CGA color palette
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*
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* Colors for the attribute byte.
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* All 16 colors can be used for the foreground while the background colors
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* are limited to the first eight (from`BLACK` to `LIGHT_GREY`)
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*/
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enum Color {
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BLACK, ///< Black (fore- and background)
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BLUE, ///< Blue (fore- and background)
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GREEN, ///< Green (fore- and background)
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CYAN, ///< Cyan (fore- and background)
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RED, ///< Red (fore- and background)
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MAGENTA, ///< Magenta (fore- and background)
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BROWN, ///< Brown (fore- and background)
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LIGHT_GREY, ///< Light grey (fore- and background)
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DARK_GREY, ///< Dark grey (foreground only)
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LIGHT_BLUE, ///< Light blue (foreground only)
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LIGHT_GREEN, ///< Light green (foreground only)
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LIGHT_CYAN, ///< Light cyan (foreground only)
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LIGHT_RED, ///< Light red (foreground only)
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LIGHT_MAGENTA, ///< Light magenta (foreground only)
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YELLOW, ///< Yellow (foreground only)
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WHITE ///< White (foreground only)
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};
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/*! \brief Structure of a character attribute
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* consists of 4 bit fore- and 3 bit background color, and a single blink bit.
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*
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* [Bit fields](https://en.cppreference.com/w/cpp/language/bit_field) can
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* notably simplify the access and code readability.
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*
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* \note [Type punning](https://en.wikipedia.org/wiki/Type_punning#Use_of_union)
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* is indeed undefined behavior in C++. However, *gcc* explicitly allows
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* this construct as a [language extension](https://gcc.gnu.org/bugs/#nonbugs).
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* Some compilers ([other than
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* gcc](https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#Type%2Dpunning)
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* might allow this feature only by disabling strict aliasing
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* (`-fno-strict-aliasing`). In \StuBS we use this feature extensively due to
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* the improved code readability.
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*
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* \todo(11) Fill in the bitfield
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*/
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union Attribute {
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struct {
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uint8_t todo : 8;
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} __attribute__((packed));
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uint8_t value; ///< combined value
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/*! \brief Attribute constructor (with default values)
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*
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* \todo(11) Complete constructor
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*
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* \param foreground Foreground color (Default: \ref LIGHT_GREY)
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* \param background Background color (Default: \ref BLACK)
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* \param blink Blink if `true` (default: no blinking)
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*/
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explicit Attribute(Color foreground = LIGHT_GREY, Color background = BLACK,
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bool blink = false) { // NOLINT
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(void)foreground;
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(void)background;
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(void)blink;
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}
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} __attribute__((packed)); // prevent padding by the compiler
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/*! \brief Set the keyboard hardware cursor to absolute screen position
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*
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* \todo(11) Implement the method using \ref IOPort
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*
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* \param abs_x absolute column of the keyboard hardware cursor
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* \param abs_y absolute row of the keyboard hardware cursor
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*/
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void setCursor(unsigned abs_x, unsigned abs_y);
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/*! \brief Retrieve the keyboard hardware cursor position on screen
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*
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* \todo(11) Implement the method using the \ref IOPort
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*
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* \param abs_x absolute column of the keyboard hardware cursor
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* \param abs_y absolute row of the keyboard hardware cursor
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*/
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void getCursor(unsigned& abs_x, unsigned& abs_y);
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/*! \brief Basic output of a character at a specific position on the screen.
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*
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* This method outputs the given character at the absolute screen position
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* (`x`, `y`) with the specified color attribute.
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*
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* The position (`0`,`0`) indicates the upper left corner of the screen.
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* The attribute defines characteristics such as background color,
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* foreground color and blinking.
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*
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* \param abs_x Column (`abs_x` < \ref COLUMNS) in which the character should be
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* displayed
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* \param abs_y Row (`abs_y` < \ref ROWS) in which the character should be
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* displayed
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* \param character Character to be displayed
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* \param attrib Attribute with color settings
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*
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* \todo(11) Implement the method
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*/
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void show(unsigned abs_x, unsigned abs_y, char character,
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Attribute attrib = Attribute());
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/*! \brief Structure for a cell in text mode
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*
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* Consisting of two bytes, character and attribute
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*/
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struct Cell {
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char character;
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Attribute attribute;
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Cell(char character, Attribute attribute)
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: character(character), attribute(attribute) {}
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} __attribute__((packed));
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/*! \brief Base address for linear text buffer in video memory
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*/
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Cell* const TEXT_BUFFER_BASE = nullptr;
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}; // namespace CGA
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