Attempt a real slot-by-slot blit.

Machines/Amiga/Blitter.cpp

@@ -223,8 +223,9 @@ uint16_t Blitter::get_status() {
 bool Blitter::advance_dma() {
 	if(!height_) return false;
 
-	not_zero_flag_ = false;
 	if(line_mode_) {
+		not_zero_flag_ = false;
+
 		// As-yet unimplemented:
 		assert(b_data_ == 0xffff);
 
@@ -332,20 +333,23 @@ bool Blitter::advance_dma() {
 				draw_ = true;
 			}
 		}
+
+		busy_ = false;
 	} else {
 		// Copy mode.
-
-		// Quick hack: do the entire action atomically.
+		if(!busy_) {
 			sequencer_.begin();
 			a32_ = 0;
 			b32_ = 0;
 
 			y_ = 0;
 			x_ = 0;
-		int loop_index_ = -1;
+			loop_index_ = -1;
 			write_phase_ = WritePhase::Starting;
+			not_zero_flag_ = 0;
+			busy_ = true;
+		}
 
-		while(true) {
 		const auto next = sequencer_.next();
 
 		// If this is the start of a new iteration, check for end of line,
@@ -379,23 +383,22 @@ bool Blitter::advance_dma() {
 			case Channel::A:
 				a_data_ = ram_[pointer_[0] & ram_mask_];
 				pointer_[0] += direction_;
-				continue;
+			return true;
 			case Channel::B:
 				b_data_ = ram_[pointer_[1] & ram_mask_];
 				pointer_[1] += direction_;
-				continue;
+			return true;
 			case Channel::C:
 				c_data_ = ram_[pointer_[2] & ram_mask_];
 				pointer_[2] += direction_;
-				continue;
+			return true;
 			case Channel::None:
-				continue;
+			return false;
 			case Channel::Write: break;
 			case Channel::FlushPipeline:
-					// HACK. REMOVE ONCE NON-BLOCKING.
 				posit_interrupt(InterruptFlag::Blitter);
 				height_ = 0;
-					// END HACK.
+				busy_ = false;
 
 				if(write_phase_ == WritePhase::Full) {
 					ram_[write_address_ & ram_mask_] = write_value_;
@@ -461,10 +464,9 @@ bool Blitter::advance_dma() {
 				write_address_ = pointer_[3];
 				write_value_ = output;
 				pointer_[3] += direction_;
-				continue;
+			return true;
 
-				default: break;
-			}
+			default: assert(false);
 		}
 	}
 

Machines/Amiga/Blitter.hpp

@@ -215,6 +215,8 @@ class Blitter: public DMADevice<4, 4> {
 		} write_phase_;
 		int y_, x_;
 		uint16_t transient_a_mask_;
+		bool busy_ = false;
+		int loop_index_ = -1;
 };
 
 }