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CLK/Machines/Atari/ST/Video.cpp
2023-12-07 11:04:18 -05:00

806 lines
27 KiB
C++

//
// Video.cpp
// Clock Signal
//
// Created by Thomas Harte on 04/10/2019.
// Copyright © 2019 Thomas Harte. All rights reserved.
//
#include "Video.hpp"
#include "../../../Outputs/Log.hpp"
#include <algorithm>
#include <cstring>
#define CYCLE(x) ((x) * 2)
using namespace Atari::ST;
namespace {
/*!
Defines the line counts at which mode-specific events will occur:
vertical enable being set and being reset, and the line on which
the frame will end.
*/
const struct VerticalParams {
const int set_enable;
const int reset_enable;
const int height;
} vertical_params[3] = {
{63, 263, 313}, // 47 rather than 63 on early machines.
{34, 234, 263},
{34, 434, 500} // Guesswork: (i) nobody ever recommends 72Hz mode for opening the top border, so it's likely to be the same as another mode; (ii) being the same as PAL feels too late.
};
/// @returns The correct @c VerticalParams for output at @c frequency.
const VerticalParams &vertical_parameters(Video::FieldFrequency frequency) {
return vertical_params[int(frequency)];
}
/*!
Defines the horizontal counts at which mode-specific events will occur:
horizontal enable being set and being reset, blank being set and reset, and the
intended length of this ine.
The caller should:
* latch line length at cycle 54 (TODO: also for 72Hz mode?);
* at (line length - 50), start sync and reset enable (usually for the second time);
* at (line length - 10), disable sync.
*/
const struct HorizontalParams {
const int set_enable;
const int reset_enable;
const int set_blank;
const int reset_blank;
const int vertical_decision;
LineLength length;
} horizontal_params[3] = {
{CYCLE(56), CYCLE(376), CYCLE(450), CYCLE(28), CYCLE(502), { CYCLE(512), CYCLE(464), CYCLE(504) }},
{CYCLE(52), CYCLE(372), CYCLE(450), CYCLE(24), CYCLE(502), { CYCLE(508), CYCLE(460), CYCLE(500) }},
{CYCLE(4), CYCLE(164), CYCLE(999), CYCLE(999), CYCLE(214), { CYCLE(224), CYCLE(194), CYCLE(212) }}
// 72Hz mode doesn't set or reset blank.
};
// Re: 'vertical_decision':
// This is cycle 502 if in 50 or 60 Hz mode; in 70 Hz mode I've put it on cycle 214
// in order to be analogous to 50 and 60 Hz mode. I have no idea where it should
// actually go.
//
// Ditto the horizontal sync timings for 72Hz are plucked out of thin air.
const HorizontalParams &horizontal_parameters(Video::FieldFrequency frequency) {
return horizontal_params[int(frequency)];
}
#ifndef NDEBUG
struct Checker {
Checker() {
for(int c = 0; c < 3; ++c) {
// Expected horizontal order of events: reset blank, enable display, disable display, enable blank (at least 50 before end of line), end of line
const auto horizontal = horizontal_parameters(Video::FieldFrequency(c));
if(c < 2) {
assert(horizontal.reset_blank < horizontal.set_enable);
assert(horizontal.set_enable < horizontal.reset_enable);
assert(horizontal.reset_enable < horizontal.set_blank);
assert(horizontal.set_blank+50 < horizontal.length.length);
} else {
assert(horizontal.set_enable < horizontal.reset_enable);
assert(horizontal.set_enable+50 <horizontal.length.length);
}
// Expected vertical order of events: reset blank, enable display, disable display, enable blank (at least 50 before end of line), end of line
const auto vertical = vertical_parameters(Video::FieldFrequency(c));
assert(vertical.set_enable < vertical.reset_enable);
assert(vertical.reset_enable < vertical.height);
}
}
} checker;
#endif
const int de_delay_period = CYCLE(28); // Amount of time after DE that observed DE changes. NB: HACK HERE. This currently incorporates the MFP recognition delay. MUST FIX.
const int vsync_x_position = CYCLE(56); // Horizontal cycle on which vertical sync changes happen.
const int line_length_latch_position = CYCLE(54);
const int hsync_delay_period = CYCLE(8); // Signal hsync at the end of the line.
const int vsync_delay_period = hsync_delay_period; // Signal vsync with the same delay as hsync.
const int load_delay_period = CYCLE(4); // Amount of time after DE that observed DE changes. NB: HACK HERE. This currently incorporates the MFP recognition delay. MUST FIX.
// "VSYNC starts 104 cycles after the start of the previous line's HSYNC, so that's 4 cycles before DE would be activated. ";
// that's an inconsistent statement since it would imply VSYNC at +54, which is 2 cycles before DE in 60Hz mode and 6 before
// in 50Hz mode. I've gone with 56, to be four cycles ahead of DE in 50Hz mode.
}
Video::Video() :
crt_(2048, 2, Outputs::Display::Type::PAL50, Outputs::Display::InputDataType::Red4Green4Blue4),
// crt_(896, 1, 500, 5, Outputs::Display::InputDataType::Red4Green4Blue4),
video_stream_(crt_, palette_) {
// Show a total of 260 lines; a little short for PAL but a compromise between that and the ST's
// usual output height of 200 lines.
crt_.set_visible_area(crt_.get_rect_for_area(33, 260, 440, 1700, 4.0f / 3.0f));
}
void Video::set_ram(uint16_t *ram, size_t size) {
ram_ = ram;
ram_mask_ = int(size - 1);
}
void Video::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
crt_.set_scan_target(scan_target);
}
Outputs::Display::ScanStatus Video::get_scaled_scan_status() const {
return crt_.get_scaled_scan_status() / 4.0f;
}
void Video::set_display_type(Outputs::Display::DisplayType display_type) {
crt_.set_display_type(display_type);
}
Outputs::Display::DisplayType Video::get_display_type() const {
return crt_.get_display_type();
}
void Video::run_for(HalfCycles duration) {
int integer_duration = int(duration.as_integral());
assert(integer_duration >= 0);
while(integer_duration) {
const auto horizontal_timings = horizontal_parameters(field_frequency_);
const auto vertical_timings = vertical_parameters(field_frequency_);
// Determine time to next event; this'll either be one of the ones informally scheduled in here,
// or something from the deferral queue.
// Seed next event to end of line.
int next_event = line_length_.length;
const int next_deferred_event = deferrer_.time_until_next_action().as<int>();
if(next_deferred_event >= 0)
next_event = std::min(next_event, next_deferred_event + x_);
// Check the explicitly-placed events.
if(horizontal_timings.reset_blank > x_) next_event = std::min(next_event, horizontal_timings.reset_blank);
if(horizontal_timings.set_blank > x_) next_event = std::min(next_event, horizontal_timings.set_blank);
if(horizontal_timings.reset_enable > x_) next_event = std::min(next_event, horizontal_timings.reset_enable);
if(horizontal_timings.set_enable > x_) next_event = std::min(next_event, horizontal_timings.set_enable);
// Check for events that are relative to existing latched state.
if(line_length_.hsync_start > x_) next_event = std::min(next_event, line_length_.hsync_start);
if(line_length_.hsync_end > x_) next_event = std::min(next_event, line_length_.hsync_end);
// Also, a vertical sync event might intercede.
if(vertical_.sync_schedule != VerticalState::SyncSchedule::None && x_ < vsync_x_position && next_event >= vsync_x_position) {
next_event = vsync_x_position;
}
// Determine current output mode and number of cycles to output for.
const int run_length = std::min(integer_duration, next_event - x_);
const bool display_enable = vertical_.enable && horizontal_.enable;
const bool hsync = horizontal_.sync;
const bool vsync = vertical_.sync;
assert(run_length > 0);
// Ensure proper fetching irrespective of the output.
if(load_) {
const int since_load = x_ - load_base_;
// There will be pixels this line, subject to the shifter pipeline.
// Divide into 8-[half-]cycle windows; at the start of each window fetch a word,
// and during the rest of the window, shift out.
int start_column = (since_load - 1) >> 3;
const int end_column = (since_load + run_length - 1) >> 3;
while(start_column != end_column) {
data_latch_[data_latch_position_] = ram_[current_address_ & ram_mask_];
data_latch_position_ = (data_latch_position_ + 1) & 127;
++current_address_;
++start_column;
}
}
if(horizontal_.sync || vertical_.sync) {
video_stream_.output(run_length, VideoStream::OutputMode::Sync);
} else if(horizontal_.blank || vertical_.blank) {
video_stream_.output(run_length, VideoStream::OutputMode::Blank);
} else if(!load_) {
video_stream_.output(run_length, VideoStream::OutputMode::Pixels);
} else {
const int start = x_ - load_base_;
const int end = start + run_length;
// There will be pixels this line, subject to the shifter pipeline.
// Divide into 8-[half-]cycle windows; at the start of each window fetch a word,
// and during the rest of the window, shift out.
int start_column = start >> 3;
const int end_column = end >> 3;
const int start_offset = start & 7;
const int end_offset = end & 7;
// Rules obeyed below:
//
// Video fetches occur as the first act of business in a column. Each
// fetch is then followed by 8 shift clocks. Whether or not the shifter
// was reloaded by the fetch depends on the FIFO.
if(start_column == end_column) {
if(!start_offset) {
push_latched_data();
}
video_stream_.output(run_length, VideoStream::OutputMode::Pixels);
} else {
// Continue the current column if partway across.
if(start_offset) {
// If at least one column boundary is crossed, complete this column.
video_stream_.output(8 - start_offset, VideoStream::OutputMode::Pixels);
++start_column; // This starts a new column, so latch a new word.
}
// Run for all columns that have their starts in this time period.
int complete_columns = end_column - start_column;
while(complete_columns--) {
push_latched_data();
video_stream_.output(8, VideoStream::OutputMode::Pixels);
}
// Output the start of the next column, if necessary.
if(end_offset) {
push_latched_data();
video_stream_.output(end_offset, VideoStream::OutputMode::Pixels);
}
}
}
// Check for whether line length should have been latched during this run.
if(x_ < line_length_latch_position && (x_ + run_length) >= line_length_latch_position) {
line_length_ = horizontal_timings.length;
}
// Make a decision about vertical state on the appropriate cycle.
if(x_ < horizontal_timings.vertical_decision && (x_ + run_length) >= horizontal_timings.vertical_decision) {
next_y_ = y_ + 1;
next_vertical_ = vertical_;
next_vertical_.sync_schedule = VerticalState::SyncSchedule::None;
// Use vertical_parameters to get parameters for the current output frequency;
// quick note: things other than the total frame size are counted in terms
// of the line they're evaluated on — i.e. the test is this line, not the next
// one. The total height constraint is obviously whether the next one would be
// too far.
if(y_ == vertical_timings.set_enable) {
next_vertical_.enable = true;
} else if(y_ == vertical_timings.reset_enable) {
next_vertical_.enable = false;
} else if(next_y_ == vertical_timings.height - 2) {
next_vertical_.sync_schedule = VerticalState::SyncSchedule::Begin;
} else if(next_y_ == vertical_timings.height) {
next_y_ = 0;
} else if(y_ == 0) {
next_vertical_.sync_schedule = VerticalState::SyncSchedule::End;
}
}
// Apply the next event.
x_ += run_length;
assert(integer_duration >= run_length);
integer_duration -= run_length;
deferrer_.advance(HalfCycles(run_length));
// Check horizontal events; the first six are guaranteed to occur separately.
if(horizontal_timings.reset_blank == x_) horizontal_.blank = false;
else if(horizontal_timings.set_blank == x_) horizontal_.blank = true;
else if(horizontal_timings.reset_enable == x_) horizontal_.enable = false;
else if(horizontal_timings.set_enable == x_) horizontal_.enable = true;
else if(line_length_.hsync_start == x_) { horizontal_.sync = true; horizontal_.enable = false; }
else if(line_length_.hsync_end == x_) horizontal_.sync = false;
// Check vertical events.
if(vertical_.sync_schedule != VerticalState::SyncSchedule::None && x_ == vsync_x_position) {
vertical_.sync = vertical_.sync_schedule == VerticalState::SyncSchedule::Begin;
vertical_.enable &= !vertical_.sync;
reset_fifo(); // TODO: remove this, probably, once otherwise stable?
}
// Check whether the terminating event was end-of-line; if so then advance
// the vertical bits of state.
if(x_ == line_length_.length) {
x_ = 0;
vertical_ = next_vertical_;
y_ = next_y_;
}
// The address is reloaded during the entire period of vertical sync.
// Cf. http://www.atari-forum.com/viewtopic.php?t=31954&start=50#p324730
if(vertical_.sync) {
current_address_ = base_address_ >> 1;
// Consider a shout out to the range observer.
if(previous_base_address_ != base_address_) {
previous_base_address_ = base_address_;
if(range_observer_) {
range_observer_->video_did_change_access_range(this);
}
}
}
// Chuck any deferred output changes into the queue.
const bool next_display_enable = vertical_.enable && horizontal_.enable;
if(display_enable != next_display_enable) {
// Schedule change in load line.
deferrer_.defer(load_delay_period, [this, next_display_enable] {
this->load_ = next_display_enable;
this->load_base_ = this->x_;
});
// Schedule change in outwardly-visible DE line.
deferrer_.defer(de_delay_period, [this, next_display_enable] {
this->public_state_.display_enable = next_display_enable;
});
}
if(horizontal_.sync != hsync) {
// Schedule change in outwardly-visible hsync line.
deferrer_.defer(hsync_delay_period, [this, next_horizontal_sync = horizontal_.sync] {
this->public_state_.hsync = next_horizontal_sync;
});
}
if(vertical_.sync != vsync) {
// Schedule change in outwardly-visible hsync line.
deferrer_.defer(vsync_delay_period, [this, next_vertical_sync = vertical_.sync] {
this->public_state_.vsync = next_vertical_sync;
});
}
}
}
void Video::push_latched_data() {
data_latch_read_position_ = (data_latch_read_position_ + 1) & 127;
if(!(data_latch_read_position_ & 3)) {
video_stream_.load(
(uint64_t(data_latch_[(data_latch_read_position_ - 4) & 127]) << 48) |
(uint64_t(data_latch_[(data_latch_read_position_ - 3) & 127]) << 32) |
(uint64_t(data_latch_[(data_latch_read_position_ - 2) & 127]) << 16) |
uint64_t(data_latch_[(data_latch_read_position_ - 1) & 127])
);
}
}
void Video::reset_fifo() {
data_latch_read_position_ = data_latch_position_ = 0;
}
bool Video::hsync() {
return public_state_.hsync;
}
bool Video::vsync() {
return public_state_.vsync;
}
bool Video::display_enabled() {
return public_state_.display_enable;
}
HalfCycles Video::next_sequence_point() {
// The next sequence point will be whenever display_enabled, vsync or hsync next changes.
// Sequence of events within a standard line:
//
// 1) blank disabled;
// 2) display enabled;
// 3) display disabled;
// 4) blank enabled;
// 5) sync enabled;
// 6) sync disabled;
// 7) end-of-line, potential vertical event.
//
// If this line has a vertical sync event on it, there will also be an event at cycle 30,
// which will always falls somewhere between (1) and (4) but might or might not be in the
// visible area.
const auto horizontal_timings = horizontal_parameters(field_frequency_);
int event_time = line_length_.length; // Worst case: report end of line.
// If any events are pending, give the first of those the chance to be next.
const auto next_deferred_item = deferrer_.time_until_next_action();
if(next_deferred_item != HalfCycles(-1)) {
event_time = std::min(event_time, x_ + next_deferred_item.as<int>());
}
// If this is a vertically-enabled line, check for the display enable boundaries, + the standard delay.
if(vertical_.enable) {
if(x_ < horizontal_timings.set_enable + de_delay_period) {
event_time = std::min(event_time, horizontal_timings.set_enable + de_delay_period);
}
else if(x_ < horizontal_timings.reset_enable + de_delay_period) {
event_time = std::min(event_time, horizontal_timings.reset_enable + de_delay_period);
}
}
// If a vertical sync event is scheduled, test for that.
if(vertical_.sync_schedule != VerticalState::SyncSchedule::None && (x_ < vsync_x_position)) {
event_time = std::min(event_time, vsync_x_position);
}
// Test for beginning and end of horizontal sync.
if(x_ < line_length_.hsync_start + hsync_delay_period) {
event_time = std::min(line_length_.hsync_start + hsync_delay_period, event_time);
}
if(x_ < line_length_.hsync_end + hsync_delay_period) {
event_time = std::min(line_length_.hsync_end + hsync_delay_period, event_time);
}
// Also factor in the line length latching time.
if(x_ < line_length_latch_position) {
event_time = std::min(line_length_latch_position, event_time);
}
// It wasn't any of those, just supply end of line. That's when the static_assert above assumes a visible hsync transition.
return HalfCycles(event_time - x_);
}
// MARK: - IO dispatch
uint16_t Video::read(int address) {
address &= 0x3f;
switch(address) {
default:
break;
case 0x00: return uint16_t(0xff00 | (base_address_ >> 16));
case 0x01: return uint16_t(0xff00 | (base_address_ >> 8));
case 0x02: return uint16_t(0xff00 | (current_address_ >> 15)); // Current address is kept in word precision internally;
case 0x03: return uint16_t(0xff00 | (current_address_ >> 7)); // the shifts here represent a conversion back to
case 0x04: return uint16_t(0xff00 | (current_address_ << 1)); // byte precision.
case 0x05: return sync_mode_ | 0xfcff;
case 0x30: return video_mode_ | 0xfcff;
case 0x20: case 0x21: case 0x22: case 0x23:
case 0x24: case 0x25: case 0x26: case 0x27:
case 0x28: case 0x29: case 0x2a: case 0x2b:
case 0x2c: case 0x2d: case 0x2e: case 0x2f: return raw_palette_[address - 0x20];
}
return 0xff;
}
void Video::write(int address, uint16_t value) {
address &= 0x3f;
switch(address) {
default: break;
// Start address.
case 0x00: base_address_ = (base_address_ & 0x00ffff) | ((value & 0xff) << 16); break;
case 0x01: base_address_ = (base_address_ & 0xff00ff) | ((value & 0xff) << 8); break;
// Sync mode and pixel mode.
case 0x05:
// Writes to sync mode have a one-cycle delay in effect.
deferrer_.defer(HalfCycles(2), [this, value] {
sync_mode_ = value;
update_output_mode();
});
break;
case 0x30:
video_mode_ = value;
update_output_mode();
break;
// Palette.
case 0x20: case 0x21: case 0x22: case 0x23:
case 0x24: case 0x25: case 0x26: case 0x27:
case 0x28: case 0x29: case 0x2a: case 0x2b:
case 0x2c: case 0x2d: case 0x2e: case 0x2f: {
if(address == 0x20) video_stream_.will_change_border_colour();
raw_palette_[address - 0x20] = value;
uint8_t *const entry = reinterpret_cast<uint8_t *>(&palette_[address - 0x20]);
entry[0] = uint8_t((value & 0x700) >> 7);
entry[1] = uint8_t((value & 0x77) << 1);
} break;
}
}
void Video::update_output_mode() {
const auto old_bpp_ = output_bpp_;
// If this is black and white mode, that's that.
switch((video_mode_ >> 8) & 3) {
case 0: output_bpp_ = OutputBpp::Four; break;
case 1: output_bpp_ = OutputBpp::Two; break;
default:
case 2: output_bpp_ = OutputBpp::One; break;
}
// 1bpp mode ignores the otherwise-programmed frequency.
if(output_bpp_ == OutputBpp::One) {
field_frequency_ = FieldFrequency::SeventyTwo;
} else {
field_frequency_ = (sync_mode_ & 0x200) ? FieldFrequency::Fifty : FieldFrequency::Sixty;
}
if(output_bpp_ != old_bpp_) {
// "the 71-Hz-switch does something like a shifter-reset." (and some people use a high-low resolutions switch instead)
reset_fifo();
video_stream_.set_bpp(output_bpp_);
}
// const int freqs[] = {50, 60, 72};
// printf("%d, %d -> %d [%d %d]\n", x_ / 2, y_, freqs[int(field_frequency_)], horizontal_.enable, vertical_.enable);
}
// MARK: - The shifter
void Video::VideoStream::output(int duration, OutputMode mode) {
// If this is a transition from sync to blank, actually transition to colour burst.
if(output_mode_ == OutputMode::Sync && mode == OutputMode::Blank) {
mode = OutputMode::ColourBurst;
}
// If this is seeming a transition from blank to colour burst, obey it only if/when
// sufficient colour burst has been output.
if(output_mode_ == OutputMode::Blank && mode == OutputMode::ColourBurst) {
if(duration_ + duration >= 40) {
const int overage = duration + duration_ - 40;
duration_ = 40;
generate(overage, OutputMode::ColourBurst, true);
} else {
mode = OutputMode::ColourBurst;
}
}
// If this is a transition, or if we're doing pixels, output whatever has been accumulated.
if(mode != output_mode_ || output_mode_ == OutputMode::Pixels) {
generate(duration, output_mode_, mode != output_mode_);
} else {
duration_ += duration;
}
// Accumulate time in the current mode.
output_mode_ = mode;
}
void Video::VideoStream::generate(int duration, OutputMode mode, bool is_terminal) {
// Three of these are trivial; deal with them upfront. They don't care about the duration of
// whatever is new, just about how much was accumulated prior to now.
if(mode != OutputMode::Pixels) {
switch(mode) {
default:
case OutputMode::Sync: crt_.output_sync(duration_*2); break;
case OutputMode::Blank: crt_.output_blank(duration_*2); break;
case OutputMode::ColourBurst: crt_.output_default_colour_burst(duration_*2); break;
}
// Reseed duration.
duration_ = duration;
// The shifter should keep running, so throw away the proper amount of content.
shift(duration_);
return;
}
// If the shifter is empty, accumulate in duration_ a promise to draw border later.
if(!output_shifter_) {
if(pixel_pointer_) {
flush_pixels();
}
duration_ += duration;
// If this is terminal, we'll need to draw now. But if it isn't, job done.
if(is_terminal) {
flush_border();
}
return;
}
// There's definitely some pixels to convey, but perhaps there's some border first?
if(duration_) {
flush_border();
}
// Time to do some pixels!
output_pixels(duration);
// If was terminal, make sure any transient storage is output.
if(is_terminal) {
flush_pixels();
}
}
void Video::VideoStream::will_change_border_colour() {
// Flush the accumulated border if it'd be adversely affected.
if(duration_ && output_mode_ == OutputMode::Pixels) {
flush_border();
}
}
void Video::VideoStream::flush_border() {
// Output colour 0 for the entirety of duration_ (or black, if this is 1bpp mode).
crt_.output_level<uint16_t>(duration_ * 2, (bpp_ != OutputBpp::One) ? palette_[0] : 0);
duration_ = 0;
}
namespace {
#if TARGET_RT_BIG_ENDIAN
constexpr int upper = 0;
#else
constexpr int upper = 1;
#endif
}
void Video::VideoStream::shift(int duration) {
switch(bpp_) {
case OutputBpp::One:
output_shifter_ <<= (duration << 1);
break;
case OutputBpp::Two:
while(duration--) {
shifter_halves_[upper] = (shifter_halves_[upper] << 1) & 0xfffefffe;
shifter_halves_[upper] |= (shifter_halves_[upper^1] & 0x80008000) >> 15;
shifter_halves_[upper^1] = (shifter_halves_[upper^1] << 1) & 0xfffefffe;
}
break;
case OutputBpp::Four:
while(duration) {
output_shifter_ = (output_shifter_ << 1) & 0xfffefffefffefffe;
duration -= 2;
}
break;
}
}
// TODO: turn this into a template on current BPP, perhaps? Would avoid reevaluation of the conditional.
void Video::VideoStream::output_pixels(int duration) {
constexpr int allocation_size = 352; // i.e. 320 plus a spare 32.
// Convert from duration to pixels.
int pixels = duration;
switch(bpp_) {
case OutputBpp::One: pixels <<= 1; break;
default: break;
case OutputBpp::Four: pixels >>= 1; break;
}
while(pixels) {
// If no buffer is currently available, attempt to allocate one.
if(!pixel_buffer_) {
pixel_buffer_ = reinterpret_cast<uint16_t *>(crt_.begin_data(allocation_size, 2));
// Stop the loop if no buffer is available.
if(!pixel_buffer_) break;
}
int pixels_to_draw = std::min(allocation_size - pixel_pointer_, pixels);
pixels -= pixels_to_draw;
switch(bpp_) {
case OutputBpp::One:
while(pixels_to_draw--) {
pixel_buffer_[pixel_pointer_] = ((output_shifter_ >> 63) & 1) * 0xffff;
output_shifter_ <<= 1;
++pixel_pointer_;
}
break;
case OutputBpp::Two:
while(pixels_to_draw--) {
pixel_buffer_[pixel_pointer_] = palette_[
((output_shifter_ >> 63) & 1) |
((output_shifter_ >> 46) & 2)
];
// This ensures that the top two words shift one to the left;
// their least significant bits are fed from the most significant bits
// of the bottom two words, respectively.
shifter_halves_[upper] = (shifter_halves_[upper] << 1) & 0xfffefffe;
shifter_halves_[upper] |= (shifter_halves_[upper^1] & 0x80008000) >> 15;
shifter_halves_[upper^1] = (shifter_halves_[upper^1] << 1) & 0xfffefffe;
++pixel_pointer_;
}
break;
case OutputBpp::Four:
while(pixels_to_draw--) {
pixel_buffer_[pixel_pointer_] = palette_[
((output_shifter_ >> 63) & 1) |
((output_shifter_ >> 46) & 2) |
((output_shifter_ >> 29) & 4) |
((output_shifter_ >> 12) & 8)
];
output_shifter_ = (output_shifter_ << 1) & 0xfffefffefffefffe;
++pixel_pointer_;
}
break;
}
// Check whether the limit has been reached.
if(pixel_pointer_ >= allocation_size - 32) {
flush_pixels();
}
}
// If duration remains, that implies no buffer was available, so
// just do the corresponding shifting and provide proper timing to the CRT.
if(pixels) {
int leftover_duration = pixels;
switch(bpp_) {
default: leftover_duration >>= 1; break;
case OutputBpp::Two: break;
case OutputBpp::Four: leftover_duration <<= 1; break;
}
shift(leftover_duration);
crt_.output_data(leftover_duration*2);
}
}
void Video::VideoStream::flush_pixels() {
// Flush only if there's something to flush.
if(pixel_pointer_) {
switch(bpp_) {
case OutputBpp::One: crt_.output_data(pixel_pointer_); break;
default: crt_.output_data(pixel_pointer_ << 1, size_t(pixel_pointer_)); break;
case OutputBpp::Four: crt_.output_data(pixel_pointer_ << 2, size_t(pixel_pointer_)); break;
}
}
pixel_pointer_ = 0;
pixel_buffer_ = nullptr;
}
void Video::VideoStream::set_bpp(OutputBpp bpp) {
// Terminate the allocated block of memory (if any).
flush_pixels();
// Reset the shifter.
// TODO: is flushing like this correct?
output_shifter_ = 0;
// Store the new BPP.
bpp_ = bpp;
}
void Video::VideoStream::load(uint64_t value) {
// In 1bpp mode, a 0 bit is white and a 1 bit is black.
// Invert the input so that the 'just output the border colour
// when the shifter is empty' optimisation works.
if(bpp_ == OutputBpp::One)
output_shifter_ = ~value;
else
output_shifter_ = value;
}
// MARK: - Range observer.
Video::Range Video::get_memory_access_range() {
Range range;
range.low_address = uint32_t(previous_base_address_);
range.high_address = range.low_address + 56994;
// 56994 is pessimistic but unscientific, being derived from the resolution of the largest
// fullscreen demo I could quickly find documentation of. TODO: calculate real number.
return range;
}
void Video::set_range_observer(RangeObserver *observer) {
range_observer_ = observer;
observer->video_did_change_access_range(this);
}