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Reduce repetition, map dark yellow to brown.
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Thomas Harte
parent
48d1fa7eab
commit
c5745f71f6
@ -15,7 +15,41 @@
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namespace PCCompatible {
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// TODO: border colour isn't currently honoured.
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static constexpr uint8_t DarkCyan = 0b00'10'10;
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static constexpr uint8_t DarkMagenta = 0b10'00'10;
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static constexpr uint8_t DarkGrey = 0b10'10'10;
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static constexpr uint8_t DarkGreen = 0b00'10'00;
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static constexpr uint8_t DarkRed = 0b10'00'00;
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static constexpr uint8_t DarkYellow = 0b10'10'00;
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static constexpr uint8_t Brown = 0b10'01'00;
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/// @returns @c Brown if @c source is @c DarkYellow; @c source otherwise.
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constexpr uint8_t yellow_to_brown(uint8_t source) {
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return (source == DarkYellow) ? Brown : source;
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}
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/// @returns The brightened (i.e. high intensity) version of @c source.
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constexpr uint8_t bright(uint8_t source) {
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return source | (source >> 1);
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}
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/// Maps the RGB TTL triplet @c source to an appropriate output colour.
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constexpr uint8_t rgb(uint8_t source) {
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return uint8_t(
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((source & 0x01) << 1) |
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((source & 0x02) << 2) |
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((source & 0x04) << 3)
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);
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}
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/// Maps the RGBI value in @c source to an appropriate output colour, including potential yellow-to-brown conversion.
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constexpr uint8_t rgbi(uint8_t source) {
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const uint8_t result = rgb(source);
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return (source & 0x10) ? bright(result) : yellow_to_brown(result);
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}
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class CGA {
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public:
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CGA() : crtc_(Motorola::CRTC::Personality::HD6845S, outputter_) {}
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@ -126,37 +160,14 @@ class CGA {
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pixels_per_tick = 8;
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}
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clock_divider = 1 + !(control & 0x01);
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// Both graphics mode and monochrome/colour may have changed, so update the palette.
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update_palette();
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}
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void set_colours(uint8_t value) {
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// b5: 320x200 palette.
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if(value & 0x20) {
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palette320[1] = 0b00'10'10;
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palette320[2] = 0b10'00'10;
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palette320[3] = 0b10'10'10;
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} else {
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palette320[1] = 0b00'10'00;
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palette320[2] = 0b10'00'00;
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palette320[3] = 0b10'10'00; // TODO: brown, here and elsewhere.
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}
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// b4: set 320x200 palette into high intensity.
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if(value & 0x10) {
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palette320[1] |= palette320[1] >> 1;
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palette320[2] |= palette320[2] >> 1;
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palette320[3] |= palette320[3] >> 1;
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}
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// b3–b0: set background, border, monochrome colour.
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palette320[0] = uint8_t(
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((value & 0x01) << 1) |
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((value & 0x02) << 2) |
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((value & 0x04) << 3)
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);
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if(value & 0x08) {
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palette320[0] |= palette320[0] >> 1;
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}
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palette640[1] = palette320[0];
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colours_ = value;
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update_palette();
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}
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uint8_t control() {
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@ -180,9 +191,9 @@ class CGA {
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} else if(!state.display_enable || !(control_&0x08)) {
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new_state = OutputState::Border;
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// TODO: I'm pretty sure this isn't correct for colour burst positioning, though
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// TODO: this isn't correct for colour burst positioning, though
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// it happens to fool the particular CRT I've implemented.
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if(!(control_&4) && cycles_since_hsync <= 4) {
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if(!(control_&4) && cycles_since_hsync <= 6) {
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new_state = OutputState::ColourBurst;
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}
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} else {
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@ -198,12 +209,24 @@ class CGA {
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const OutputState new_state = implied_state(state);
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// Upon either a state change or just having accumulated too much local time...
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if(new_state != output_state || active_pixels_per_tick != pixels_per_tick || active_clock_divider != clock_divider || count > 912) {
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if(
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new_state != output_state ||
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active_pixels_per_tick != pixels_per_tick ||
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active_clock_divider != clock_divider ||
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active_border_colour != border_colour ||
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count > 912
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) {
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// (1) flush preexisting state.
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if(count) {
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switch(output_state) {
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case OutputState::Sync: crt.output_sync(count * active_clock_divider); break;
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case OutputState::Border: crt.output_blank(count * active_clock_divider); break;
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case OutputState::Border:
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if(active_border_colour) {
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crt.output_blank(count * active_clock_divider);
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} else {
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crt.output_level<uint8_t>(count * active_clock_divider, active_border_colour);
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}
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break;
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case OutputState::ColourBurst: crt.output_colour_burst(count * active_clock_divider, 0); break;
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case OutputState::Pixels: flush_pixels(); break;
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}
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@ -213,6 +236,7 @@ class CGA {
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output_state = new_state;
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active_pixels_per_tick = pixels_per_tick;
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active_clock_divider = clock_divider;
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active_border_colour = border_colour;
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count = 0;
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}
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@ -307,15 +331,7 @@ class CGA {
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const uint8_t glyph = ram[((state.refresh_address << 1) + 0) & 0x3fff];
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const uint8_t row = font[(glyph * 8) + state.row_address];
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uint8_t colours[2] = {
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uint8_t(((attributes & 0x40) >> 1) | ((attributes & 0x20) >> 2) | ((attributes & 0x10) >> 3)),
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uint8_t(((attributes & 0x04) << 3) | ((attributes & 0x02) << 2) | ((attributes & 0x01) << 1)),
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};
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// Apply foreground intensity.
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if(attributes & 0x08) {
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colours[1] |= colours[1] >> 1;
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}
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uint8_t colours[2] = { rgb(attributes >> 4), rgbi(attributes) };
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// Apply blink or background intensity.
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if(control_ & 0x20) {
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@ -324,10 +340,13 @@ class CGA {
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}
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} else {
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if(attributes & 0x80) {
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colours[0] |= colours[0] >> 1;
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colours[0] = bright(colours[0]);
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}
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}
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// Potentially remap dark yellow to brown.
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colours[0] = yellow_to_brown(colours[0]);
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// Draw according to ROM contents.
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pixel_pointer[0] = (row & 0x80) ? colours[1] : colours[0];
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pixel_pointer[1] = (row & 0x40) ? colours[1] : colours[0];
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@ -347,6 +366,7 @@ class CGA {
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uint8_t *pixel_pointer = nullptr;
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int active_pixels_per_tick = 8;
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int active_clock_divider = 1;
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uint8_t active_border_colour = 0;
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// Source data.
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const uint8_t *ram = nullptr;
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@ -362,6 +382,7 @@ class CGA {
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// Current Programmer-set parameters.
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int clock_divider = 1;
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int pixels_per_tick = 8;
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uint8_t colours_ = 0;
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uint8_t control_ = 0;
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enum class Mode {
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Pixels640, Pixels320, Text,
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@ -369,6 +390,40 @@ class CGA {
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uint8_t palette320[4]{};
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uint8_t palette640[2]{};
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uint8_t border_colour;
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void update_palette() {
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// b5: 320x200 palette, unless in monochrome mode.
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if(control_ & 0x04) {
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palette320[1] = DarkCyan;
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palette320[2] = DarkRed;
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palette320[3] = DarkGrey;
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} else {
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if(colours_ & 0x20) {
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palette320[1] = DarkCyan;
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palette320[2] = DarkMagenta;
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palette320[3] = DarkGrey;
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} else {
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palette320[1] = DarkGreen;
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palette320[2] = DarkRed;
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palette320[3] = DarkYellow;
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}
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}
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// b4: set 320x200 palette into high intensity.
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if(colours_ & 0x10) {
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palette320[1] = bright(palette320[1]);
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palette320[2] = bright(palette320[2]);
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palette320[3] = bright(palette320[3]);
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} else {
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// Remap dark yellow to brown if applicable.
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palette320[3] = yellow_to_brown(palette320[3]);
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}
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// b3–b0: set background, border, monochrome colour.
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palette640[1] = palette320[0] = rgbi(colours_);
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border_colour = (mode_ != Mode::Pixels640) ? palette320[0] : 0;
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}
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} outputter_;
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Motorola::CRTC::CRTC6845<CRTCOutputter, Motorola::CRTC::CursorType::MDA> crtc_;
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