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Attempted to factor out parts I expect to reuse for missiles and the ball.

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This commit is contained in:
Thomas Harte 2017-02-12 11:31:17 -05:00
parent ac444a3f34
commit 40954d6a2a
2 changed files with 39 additions and 33 deletions
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70
Machines/Atari2600/TIA.cpp
View File

@ -574,47 +574,59 @@ void TIA::draw_playfield(int start, int end)
}
}
#pragma mark - Motion
void TIA::perform_motion_step(int identity, int movement_time)
{
int movement_step = (movement_time - horizontal_move_start_time_) >> 2;
if(movement_step == (motion_[identity] ^ 8))
is_moving_[identity] = false;
else
position_[identity] ++;
}
int TIA::perform_border_motion(int identity, int start, int end, int &movement_time)
{
movement_time = (start + 3) & ~3;
if(!is_moving_[identity]) return 0;
int steps_taken = 0;
int first_pixel = first_pixel_cycle + (horizontal_blank_extend_ ? 8 : 0);
// round up to the next H@1 cycle
while(is_moving_[identity] && movement_time < end && movement_time < first_pixel)
{
perform_motion_step(identity, movement_time);
movement_time += 4;
}
position_[identity] %= 160;
return steps_taken;
}
#pragma mark - Player output
void TIA::draw_player(Player &player, CollisionType collision_identity, const int position_identity, int start, int end)
{
int &position = position_[position_identity];
int &motion = motion_[position_identity];
bool &is_moving = is_moving_[position_identity];
// movement works across the entire screen, so do work that falls outside of the pixel area
int first_pixel = first_pixel_cycle + (horizontal_blank_extend_ ? 8 : 0);
int movement_time = (start + 3) & ~3;
if(is_moving)
{
// round up to the next H@1 cycle
while(movement_time < end && movement_time < first_pixel)
{
int movement = (movement_time - horizontal_move_start_time_) >> 2;
if(movement == (motion ^ 8))
{
is_moving = false;
break;
}
position ++;
movement_time += 4;
}
position %= 160;
}
int movement_time;
perform_border_motion(position_identity, start, end, movement_time);
// don't continue to do any drawing if this window ends too early
int first_pixel = first_pixel_cycle + (horizontal_blank_extend_ ? 8 : 0);
if(end < first_pixel) return;
if(start < first_pixel) start = first_pixel;
// perform a miniature event loop on (i) triggering draws; (ii) drawing; and (iii) motion
if(is_moving || player.graphic)
if(is_moving_[position_identity] || player.graphic)
{
while(start < end)
{
int next_event_time = end;
// is the next event a movement tick?
if(is_moving && movement_time + 4 < next_event_time)
if(is_moving_[position_identity] && movement_time + 4 < next_event_time)
{
next_event_time = movement_time + 4;
}
@ -643,18 +655,10 @@ void TIA::draw_player(Player &player, CollisionType collision_identity, const in
start = next_event_time;
// if the event is a motion tick, apply
if(is_moving && start == movement_time + 4)
if(is_moving_[position_identity] && start == movement_time + 4)
{
int movement_step = (movement_time - horizontal_move_start_time_) >> 2;
if(movement_step == (motion ^ 8))
{
is_moving = false;
}
else
{
position ++;
movement_time += 4;
}
perform_motion_step(position_identity, movement_time);
movement_time += 4;
}
// if it's a draw trigger, draw (TODO: use the actual graphic)

2
Machines/Atari2600/TIA.hpp
View File

@ -154,6 +154,8 @@ class TIA {
Missile0,
Missile1
};
inline int perform_border_motion(int identity, int start, int end, int &movement_time);
inline void perform_motion_step(int identity, int movement_time);
// drawing methods and state
inline void output_for_cycles(int number_of_cycles);