Makes a first attempt to box out the ST display area.

Machines/AtariST/AtariST.cpp

@@ -267,6 +267,7 @@ class ConcreteMachine:
 
 		void flush() {
 			audio_queue_.perform();
+			video_.flush();
 		}
 
 	private:

Machines/AtariST/Video.cpp

@@ -8,10 +8,47 @@
 
 #include "Video.hpp"
 
+#include <algorithm>
+
 using namespace Atari::ST;
 
+namespace {
+
+struct ModeParams {
+	const int lines_per_frame;
+
+	const int first_video_line;
+	const int final_video_line;
+
+	const int line_length;
+
+	const int end_of_blank;
+
+	const int start_of_display_enable;
+	const int end_of_display_enable;
+
+	const int start_of_output;
+	const int end_of_output;
+
+	const int start_of_blank;
+
+	const int start_of_hsync;
+	const int end_of_hsync;
+} modes[3] = {
+	{313,	56, 256,	1024,		64,		116, 116+640,	116+48, 116+48+640,		904,	928, 1008	},
+	{},
+	{}
+};
+
+const ModeParams &mode_params_for_mode() {
+	// TODO: rest of potential combinations, and accept mode as a paramter.
+	return modes[0];
+}
+
+}
+
 Video::Video() :
-	crt_(512, 1, Outputs::Display::Type::PAL50, Outputs::Display::InputDataType::Red4Green4Blue4) {
+	crt_(1024, 1, Outputs::Display::Type::PAL50, Outputs::Display::InputDataType::Red4Green4Blue4) {
 }
 
 void Video::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
@@ -19,4 +56,67 @@ void Video::set_scan_target(Outputs::Display::ScanTarget *scan_target) {
 }
 
 void Video::run_for(HalfCycles duration) {
+	int integer_duration = duration.as_int();
+	const auto mode_params = mode_params_for_mode();
+
+#define Period(lower, upper, type)	\
+	if(x >= lower && x < upper) {	\
+		const auto target = std::min(upper, final_x);	\
+		type(target - x);	\
+		x = target;	\
+	}
+
+	while(integer_duration) {
+		const int final_x = std::min(x + integer_duration, mode_params.line_length);
+		integer_duration -= (final_x - x);
+
+		if(y >= mode_params.first_video_line && y < mode_params.final_video_line) {
+			// TODO: Prior to output: collect all necessary data, obeying start_of_display_enable and end_of_display_enable.
+
+			Period(0, 							mode_params.end_of_blank, 		crt_.output_blank);
+			Period(mode_params.end_of_blank, 	mode_params.start_of_output, 	output_border);
+
+			if(x >= mode_params.start_of_output && x < mode_params.end_of_output) {
+				const auto target = std::min(mode_params.end_of_output, final_x);
+				x = target;
+
+				if(x == mode_params.end_of_output) {
+					uint16_t *colour_pointer = reinterpret_cast<uint16_t *>(crt_.begin_data(1));
+					if(colour_pointer) *colour_pointer = 0xffff;
+					crt_.output_level(mode_params.end_of_output - mode_params.start_of_output);
+				}
+			}
+
+			Period(mode_params.end_of_output, 	mode_params.start_of_blank, 	output_border);
+			Period(mode_params.start_of_blank, 	mode_params.start_of_hsync,		crt_.output_blank);
+			Period(mode_params.start_of_hsync,	mode_params.start_of_blank,		crt_.output_sync);
+			Period(mode_params.start_of_blank, 	mode_params.line_length,		crt_.output_blank);
+		} else {
+			// Hard code the first three lines as vertical sync.
+			if(y < 3) {
+				Period(0,							mode_params.start_of_hsync,	crt_.output_sync);
+				Period(mode_params.start_of_hsync,	mode_params.end_of_hsync,	crt_.output_blank);
+				Period(mode_params.end_of_hsync,	mode_params.line_length,	crt_.output_sync);
+			} else {
+				Period(0, 							mode_params.end_of_blank, 		crt_.output_blank);
+				Period(mode_params.end_of_blank, 	mode_params.start_of_blank, 	output_border);
+				Period(mode_params.start_of_blank, 	mode_params.start_of_hsync,		crt_.output_blank);
+				Period(mode_params.start_of_hsync,	mode_params.start_of_blank,		crt_.output_sync);
+				Period(mode_params.start_of_blank, 	mode_params.line_length,		crt_.output_blank);
+			}
+		}
+
+		if(x == mode_params.line_length) {
+			x = 0;
+			y = (y + 1) % mode_params.lines_per_frame;
+		}
+	}
+
+#undef Period
+}
+
+void Video::output_border(int duration) {
+	uint16_t *colour_pointer = reinterpret_cast<uint16_t *>(crt_.begin_data(1));
+	if(colour_pointer) *colour_pointer = 0x333;
+	crt_.output_level(duration);
 }

Machines/AtariST/Video.hpp

@@ -6,8 +6,8 @@
 //  Copyright © 2019 Thomas Harte. All rights reserved.
 //
 
-#ifndef Video_hpp
-#define Video_hpp
+#ifndef Atari_ST_Video_hpp
+#define Atari_ST_Video_hpp
 
 #include "../../Outputs/CRT/CRT.hpp"
 #include "../../ClockReceiver/ClockReceiver.hpp"
@@ -29,11 +29,24 @@ class Video {
 		*/
 		void run_for(HalfCycles duration);
 
+		/*!
+			@returns the number of cycles until there is next a change in the hsync,
+			vsync or display_enable outputs.
+		*/
+		HalfCycles get_next_sequence_point();
+
+		bool hsync();
+		bool vsync();
+		bool display_enabled();
+
 	private:
 		Outputs::CRT::CRT crt_;
+
+		int x = 0, y = 0;
+		void output_border(int duration);
 };
 
 }
 }
 
-#endif /* Video_hpp */
+#endif /* Atari_ST_Video_hpp */