DisplayMode.hh

Go to the documentation of this file.

#ifndef DISPLAYMODE_HH
#define DISPLAYMODE_HH

#include "openmsx.hh"

namespace openmsx {

class DisplayMode
{
private:
        constexpr explicit DisplayMode(byte mode_) : mode(mode_) {}
        byte mode = 0;

public:
        enum {
                GRAPHIC1   = 0x00, // Graphic 1
                TEXT1      = 0x01, // Text 1
                MULTICOLOR = 0x02, // Multicolor
                GRAPHIC2   = 0x04, // Graphic 2
                TEXT1Q     = 0x05, // !!
                MULTIQ     = 0x06, // !!
                GRAPHIC3   = 0x08, // Graphic 3
                TEXT2      = 0x09, // Text 2
                GRAPHIC4   = 0x0C, // Graphic 4
                GRAPHIC5   = 0x10, // Graphic 5
                GRAPHIC6   = 0x14, // Graphic 6
                GRAPHIC7   = 0x1C  // Graphic 7
        };

        static constexpr byte REG0_MASK = 0x0E;

        static constexpr byte REG1_MASK = 0x18;

        static constexpr byte REG25_MASK = 0x18;

        static constexpr byte YJK = 0x20;

        static constexpr byte YAE = 0x40;

        constexpr DisplayMode() = default;

        constexpr DisplayMode(byte reg0, byte reg1, byte reg25) {
                if ((reg25 & 0x08) == 0) reg25 = 0; // If YJK is off, ignore YAE.
                mode = ((reg25 & 0x18) << 2)  // YAE YJK
                     | ((reg0  & 0x0E) << 1)  // M5..M3
                     | ((reg1  & 0x08) >> 2)  // M2
                     | ((reg1  & 0x10) >> 4); // M1
        }

        constexpr DisplayMode updateReg25(byte reg25) const {
                if ((reg25 & 0x08) == 0) reg25 = 0; // If YJK is off, ignore YAE.
                return DisplayMode(getBase() | ((reg25 & 0x18) << 2));
        }

        constexpr void reset() {
                *this = DisplayMode();
        }

        constexpr bool operator==(const DisplayMode& otherMode) const {
                return mode == otherMode.mode;
        }

        constexpr bool operator!=(const DisplayMode& otherMode) const {
                return mode != otherMode.mode;
        }

        constexpr byte getByte() const {
                return mode;
        }

        constexpr void setByte(byte mode_) {
                mode = mode_;
        }

        constexpr byte getBase() const {
                return mode & 0x1F;
        }

        constexpr bool isV9938Mode() const {
                return (mode & 0x18) != 0;
        }

        constexpr bool isTextMode() const {
                byte base = getBase();
                return (base == TEXT1) ||
                       (base == TEXT2) ||
                       (base == TEXT1Q);
        }

        constexpr bool isBitmapMode() const {
                return getBase() >= 0x0C;
        }

        constexpr bool isPlanar() const {
                // TODO: Is the display mode check OK? Profile undefined modes.
                return (mode & 0x14) == 0x14;
        }

        constexpr bool isSpriteNarrow() const {
                // TODO: Check what happens to sprites in Graphic5 + YJK/YAE.
                return mode == GRAPHIC5;
        }

        constexpr int getSpriteMode(bool isMSX1) const {
                switch (getBase()) {
                case GRAPHIC1: case MULTICOLOR: case GRAPHIC2:
                        return 1;
                case MULTIQ: // depends on VDP type
                        return isMSX1 ? 1 : 0;
                case GRAPHIC3: case GRAPHIC4: case GRAPHIC5:
                case GRAPHIC6: case GRAPHIC7:
                        return 2;
                case TEXT1: case TEXT1Q: case TEXT2:
                default: // and all other (bogus) modes
                        // Verified on real V9958: none of the bogus modes
                        // show sprites.
                        // TODO check on TMSxxxx
                        return 0;
                }
        }

        constexpr unsigned getLineWidth() const {
                // Note: Testing "mode" instead of "base mode" ensures that YJK
                //       modes are treated as 256 pixels wide.
                return mode == TEXT2 || mode == GRAPHIC5 || mode == GRAPHIC6
                        ? 512
                        : 256;
        }
};

} // namespace openmsx

#endif