From dcb75840608442ee91563d0035a85b61b9f23a83 Mon Sep 17 00:00:00 2001 From: Thomas Harte Date: Wed, 8 Feb 2017 07:30:32 -0500 Subject: [PATCH] Added the four-cycle playfield output latency and ensured you can't get smaller-than-usual pixels by rapid register value changing. --- Machines/Atari2600/TIA.cpp | 33 ++++++++++++++++++++++++--------- 1 file changed, 24 insertions(+), 9 deletions(-) diff --git a/Machines/Atari2600/TIA.cpp b/Machines/Atari2600/TIA.cpp index d24b205f7..e8692b24d 100644 --- a/Machines/Atari2600/TIA.cpp +++ b/Machines/Atari2600/TIA.cpp @@ -391,6 +391,11 @@ void TIA::output_for_cycles(int number_of_cycles) memset(collision_buffer_, 0, sizeof(collision_buffer_)); } + // accumulate an OR'dversion of the output into the collision buffer + draw_playfield(output_cursor, horizontal_counter_); + + // convert to television signals + #define Period(function, target) \ if(output_cursor < target) \ { \ @@ -446,9 +451,6 @@ void TIA::output_for_cycles(int number_of_cycles) pixel_target_ = crt_->allocate_write_area(160); } - // accumulate an OR'dversion of the output into the collision buffer - draw_playfield(output_cursor, horizontal_counter_); - // convert that into pixels if(pixel_target_) output_pixels(output_cursor, horizontal_counter_); @@ -527,15 +529,28 @@ void TIA::output_line() } } -#pragma mark - Background and playfield +#pragma mark - Playfield output void TIA::draw_playfield(int start, int end) { - int position = start; - while(position < end) + // don't do anything if this window ends too early + if(end < first_pixel_cycle - 4) return; + + // look at what needs to be output four cycles into the future, to model playfield output latency + start += 4; + end += 4; + + // clip to drawable bounds + start = std::max(start, first_pixel_cycle); + end = std::min(end, 228); + + // proceed along four-pixel boundaries, plotting four pixels at a time + int aligned_position = (start + 3)&~3; + while(aligned_position < end) { - int offset = (position - first_pixel_cycle) >> 2; - collision_buffer_[position - first_pixel_cycle] |= (background_[(offset/20)&background_half_mask_] >> (offset%20))&1; - position++; + int offset = (aligned_position - first_pixel_cycle) >> 2; + uint32_t value = ((background_[(offset/20)&background_half_mask_] >> (offset%20))&1) * 0x01010101; + *(uint32_t *)&collision_buffer_[aligned_position - first_pixel_cycle] |= value; + aligned_position += 4; } }