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Attempted to template this thing. Without yet a plan in place for pixel lookup timing.

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This commit is contained in:
Thomas Harte 2017-02-20 21:42:59 -05:00
parent 2bf784535c
commit 99547181f1
2 changed files with 90 additions and 8 deletions
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86
Machines/Atari2600/TIA.cpp
View File

@ -643,6 +643,92 @@ int TIA::perform_border_motion(Object &object, int start, int end)
return steps_taken;
}
template<class T> void TIA::draw_object(T &target, Object &object, int start, int end)
{
int first_pixel = first_pixel_cycle - 4 + (horizontal_blank_extend_ ? 8 : 0);
// movement works across the entire screen, so do work that falls outside of the pixel area
if(start < first_pixel)
{
target.skip_pixels(perform_border_motion(object, start, std::max(end, first_pixel)));
}
// don't continue to do any drawing if this window ends too early
if(end < first_pixel) return;
if(start < first_pixel) start = first_pixel;
if(start >= end) return;
// perform the visible part of the line, if any
if(start < 224)
{
draw_object_visible<T>(target, object, start - first_pixel_cycle + 4, std::min(end - first_pixel_cycle + 4, 160));
}
// move further if required
if(object.is_moving && end >= 224 && object.motion_time < end)
{
perform_motion_step(object);
target.skip_pixels(1);
}
}
template<class T> void TIA::draw_object_visible(T &target, Object &object, int start, int end)
{
// perform a miniature event loop on (i) triggering draws; (ii) drawing; and (iii) motion
int next_motion_time = object.motion_time - first_pixel_cycle + 4;
while(start < end)
{
int next_event_time = end;
// is the next event a movement tick?
if(object.is_moving && next_motion_time < next_event_time)
{
next_event_time = next_motion_time;
}
// is the next event a graphics trigger?
int next_copy = 160;
if(target.copy_flags)
{
if(object.position < 16 && target.copy_flags&1)
{
next_copy = 16;
} else if(object.position < 32 && target.copy_flags&2)
{
next_copy = 32;
} else if(object.position < 64 && target.copy_flags&4)
{
next_copy = 64;
}
}
int next_copy_time = start + next_copy - object.position;
if(next_copy_time < next_event_time) next_event_time = next_copy_time;
// the decision is to progress by length
const int length = next_event_time - start;
target.draw_pixels(length);
// the next interesting event is after next_event_time cycles, so progress
object.position = (object.position + length) % 160;
start = next_event_time;
// if the event is a motion tick, apply
if(object.is_moving && start == next_motion_time)
{
perform_motion_step(object);
next_motion_time += 4;
}
// if it's a draw trigger, trigger a draw
if(start == next_copy_time)
{
target.reset_pixels();
}
}
}
#pragma mark - Player output
void TIA::draw_player_visible(Player &player, Object &object, CollisionType collision_identity, int start, int end)

12
Machines/Atari2600/TIA.hpp
View File

@ -178,14 +178,7 @@ class TIA {
// indicates whether this object is currently undergoing motion
bool is_moving;
// receives a list of drawing events; 20 is a deliberately over-specified quantity
struct DrawingEvent {
int time;
int copy;
} drawing_events[20];
int draw_event_read_pointer, draw_event_write_pointer;
Object() : draw_event_read_pointer(0), draw_event_write_pointer(0), is_moving(false) {};
Object() : is_moving(false) {};
} object_[5];
enum class MotionIndex : uint8_t {
Ball,
@ -200,6 +193,9 @@ class TIA {
inline void perform_motion_step(Object &object);
// drawing methods and state
template<class T> void draw_object(T &, Object &, int start, int end);
template<class T> void draw_object_visible(T &, Object &, int start, int end);
inline void output_for_cycles(int number_of_cycles);
inline void output_line();