Merge pull request #1394 from TomHarte/ElectronFlicker

Electron: don't miss interrupts early in the frame.
TomHarte · Aug 27, 2024 · 7e3a331 · 7e3a331
2 parents 051f054 + b5932ed
commit 7e3a331
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Showing 2 changed files with 23 additions and 11 deletions.
diff --git a/Machines/Acorn/Electron/Electron.cpp b/Machines/Acorn/Electron/Electron.cpp
@@ -687,6 +687,9 @@ template <bool has_scsi_bus> class ConcreteMachine:
 		}
 
 		inline void signal_interrupt(Interrupt interrupt) {
+			if(!interrupt) {
+				return;
+			}
 			interrupt_status_ |= interrupt;
 			evaluate_interrupts();
 		}

diff --git a/Machines/Acorn/Electron/Video.cpp b/Machines/Acorn/Electron/Video.cpp
@@ -237,18 +237,27 @@ void VideoOutput::run_for(const Cycles cycles) {
 	const auto start_position = output_position_;
 	output_position_ = (output_position_ + number_of_cycles) % cycles_per_frame;
 
-	if(
-		(start_position < real_time_clock_interrupt_1 && output_position_ >= real_time_clock_interrupt_1) ||
-		(start_position < real_time_clock_interrupt_2 && output_position_ >= real_time_clock_interrupt_2)
-	) {
-		interrupts_ = Electron::Interrupt(interrupts_ | Electron::Interrupt::RealTimeClock);
-	}
+	const auto test_range = [&](int start, int end) {
+		if(
+			(start < real_time_clock_interrupt_1 && end >= real_time_clock_interrupt_1) ||
+			(start < real_time_clock_interrupt_2 && end >= real_time_clock_interrupt_2)
+		) {
+			interrupts_ = Electron::Interrupt(interrupts_ | Electron::Interrupt::RealTimeClock);
+		}
 
-	if(
-		(start_position < display_end_interrupt_1 && output_position_ >= display_end_interrupt_1) ||
-		(start_position < display_end_interrupt_2 && output_position_ >= display_end_interrupt_2)
-	) {
-		interrupts_ = Electron::Interrupt(interrupts_ | Electron::Interrupt::DisplayEnd);
+		if(
+			(start < display_end_interrupt_1 && end >= display_end_interrupt_1) ||
+			(start < display_end_interrupt_2 && end >= display_end_interrupt_2)
+		) {
+			interrupts_ = Electron::Interrupt(interrupts_ | Electron::Interrupt::DisplayEnd);
+		}
+	};
+
+	if(output_position_ >= start_position) {
+		test_range(start_position, output_position_);
+	} else {
+		test_range(start_position, cycles_per_frame);
+		test_range(0, output_position_);
 	}
 
 	while(number_of_cycles) {