From 6bcf95042cde0cfbd26b152cf09a473fcfa06791 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 5 Feb 2017 17:51:56 -0500
Subject: [PATCH] Started trying to be a bit more explicit about usage, and to
 divide up drawing responsibility.

---
 Machines/Atari2600/TIA.cpp | 30 +++++++++++++++++++++++-------
 Machines/Atari2600/TIA.hpp | 23 +++++++++++++++++++----
 2 files changed, 42 insertions(+), 11 deletions(-)

diff --git a/Machines/Atari2600/TIA.cpp b/Machines/Atari2600/TIA.cpp
index 8398e8ca0..6a8888cac 100644
--- a/Machines/Atari2600/TIA.cpp
+++ b/Machines/Atari2600/TIA.cpp
@@ -126,7 +126,7 @@ void TIA::reset_horizontal_counter()
 
 int TIA::get_cycles_until_horizontal_blank(unsigned int from_offset)
 {
-	return cycles_per_line - (horizontal_counter_ + (int)from_offset) % cycles_per_line;
+	return 4 + (cycles_per_line - (horizontal_counter_ + (int)from_offset) % cycles_per_line);
 }
 
 void TIA::set_background_colour(uint8_t colour)
@@ -156,6 +156,8 @@ void TIA::set_playfield(uint16_t offset, uint8_t value)
 void TIA::set_playfield_control_and_ball_size(uint8_t value)
 {
 	background_half_mask_ = value & 1;
+	playfield_is_above_players_ = !!(value & 4);
+	playfield_is_in_score_mode_ = !playfield_is_above_players_ && (value & 2);
 }
 
 void TIA::set_playfield_ball_colour(uint8_t colour)
@@ -338,12 +340,8 @@ void TIA::output_for_cycles(int number_of_cycles)
 		}
 		if(pixel_target_)
 		{
-			while(output_cursor < horizontal_counter_)
-			{
-				int offset = (output_cursor - 68) >> 2;
-				pixel_target_[output_cursor - pixel_target_origin_] = ((background_[(offset/20)&background_half_mask_] >> (offset%20))&1) ? playfield_ball_colour_ : background_colour_;
-				output_cursor++;
-			}
+			draw_background(pixel_target_, output_cursor, horizontal_counter_);
+			output_cursor = horizontal_counter_;
 		} else output_cursor = horizontal_counter_;
 		if(horizontal_counter_ == cycles_per_line)
 		{
@@ -377,3 +375,21 @@ void TIA::output_line()
 		break;
 	}
 }
+
+#pragma mark - Background and playfield
+
+void TIA::draw_background(uint8_t *target, int start, int length) const
+{
+	if(!target) return;
+	int position = start;
+	while(length--)
+	{
+		int offset = (position - 68) >> 2;
+		target[position - pixel_target_origin_] = ((background_[(offset/20)&background_half_mask_] >> (offset%20))&1) ? playfield_ball_colour_ : background_colour_;
+		position++;
+	}
+}
+
+void TIA::draw_playfield(uint8_t *target, int start, int length) const
+{
+}
diff --git a/Machines/Atari2600/TIA.hpp b/Machines/Atari2600/TIA.hpp
index 6c76fc9cd..b9e56379e 100644
--- a/Machines/Atari2600/TIA.hpp
+++ b/Machines/Atari2600/TIA.hpp
@@ -23,6 +23,10 @@ class TIA {
 			NTSC, PAL
 		};
 
+		/*!
+			Advances the TIA by @c number_of_cycles cycles. Any queued setters take effect in the
+			first cycle performed.
+		*/
 		void run_for_cycles(int number_of_cycles);
 		void set_output_mode(OutputMode output_mode);
 
@@ -71,9 +75,8 @@ class TIA {
 		inline void output_for_cycles(int number_of_cycles);
 		inline void output_line();
 
-		inline void draw_background(uint8_t *target, int start, int length);
-		inline void draw_playfield(uint8_t *target, int start, int length);
-		inline void draw_background_and_playfield(uint8_t *target, int start, int length);
+		inline void draw_background(uint8_t *target, int start, int length) const;
+		inline void draw_playfield(uint8_t *target, int start, int length) const;
 
 		// the master counter; counts from 0 to 228 with all visible pixels being in the final 160
 		int horizontal_counter_;
@@ -81,14 +84,25 @@ class TIA {
 		// contains flags to indicate whether sync or blank are currently active
 		int output_mode_;
 
-		// keeps track of the target pixel buffer for this line and when it was acquired
+		// keeps track of the target pixel buffer for this line and when it was acquired, and a corresponding collision buffer
 		uint8_t *pixel_target_;
 		int pixel_target_origin_;
+		uint8_t collision_buffer_[160];
+		enum class CollisionType : uint8_t {
+			Playfield,
+			Sprite1,
+			Sprite2,
+			Missile1,
+			Missile2,
+			Ball
+		};
 
 		// playfield state
 		uint8_t playfield_ball_colour_;
 		uint8_t background_colour_;
 		int background_half_mask_;
+		bool playfield_is_in_score_mode_;
+		bool playfield_is_above_players_;
 		uint32_t background_[2];	// contains two 20-bit bitfields representing the background state;
 									// at index 0 is the left-hand side of the playfield with bit 0 being
 									// the first bit to display, bit 1 the second, etc. Index 1 contains
@@ -96,6 +110,7 @@ class TIA {
 									// mirroring mode, background_[0] will be output on the left and
 									// background_[1] on the right; otherwise background_[0] will be
 									// output twice.
+		int latched_playfield_value_;
 
 		// player state
 		struct Player {