GBHawk: update clearing screen for subgbhawk and linked modes

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawk/GBHawk.IEmulator.cs

@@ -167,21 +167,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			// GBC games need to clear slow enough that games that turn the screen off briefly for cinematics still look smooth
 			if (ppu.clear_screen)
 			{
-				if (is_GBC)
-				{
-					for (int j = 0; j < frame_buffer.Length; j++) { frame_buffer[j] = (int)(frame_buffer[j] | (0x30303 << (clear_counter * 2))); }
-
-					clear_counter++;
-					if (clear_counter == 4)
-					{
-						ppu.clear_screen = false;
-					}				
-				}
-				else
-				{
-					for (int j = 0; j < frame_buffer.Length; j++) { frame_buffer[j] = (int)ppu.color_palette[0]; }
-					ppu.clear_screen = false;
-				}
+				clear_screen_func();
 			}
 		}
 
@@ -369,6 +355,25 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawk
 			}
 		}
 
+		public void clear_screen_func()
+		{
+			if (is_GBC)
+			{
+				for (int j = 0; j < frame_buffer.Length; j++) { frame_buffer[j] = (int)(frame_buffer[j] | (0x30303 << (clear_counter * 2))); }
+
+				clear_counter++;
+				if (clear_counter == 4)
+				{
+					ppu.clear_screen = false;
+				}
+			}
+			else
+			{
+				for (int j = 0; j < frame_buffer.Length; j++) { frame_buffer[j] = (int)ppu.color_palette[0]; }
+				ppu.clear_screen = false;
+			}
+		}
+
 		public void SetIntRegs(byte r)
 		{
 			// For timer interrupts or serial interrupts that occur on the same cycle as the IRQ clear

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawkLink/GBHawkLink.IEmulator.cs

@@ -84,7 +84,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawkLink
 				FillVideoBuffer();
 			}
 
-
 			_islag = L._islag & R._islag;
 
 			if (_islag)
@@ -202,6 +201,19 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawkLink
 					do_frame_fill = true;
 				}
 			}
+
+			// clear the screens as needed
+			if (L.ppu.clear_screen)
+			{
+				L.clear_screen_func();
+				do_frame_fill = true;
+			}
+
+			if (R.ppu.clear_screen)
+			{
+				R.clear_screen_func();
+				do_frame_fill = true;
+			}
 		}
 
 		public void GetControllerState(IController controller)

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawkLink3x/GBHawkLink3x.IEmulator.cs

@@ -389,6 +389,25 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawkLink3x
 					do_frame_fill = true;
 				}
 			}
+
+			// clear the screens as needed
+			if (L.ppu.clear_screen)
+			{
+				L.clear_screen_func();
+				do_frame_fill = true;
+			}
+
+			if (C.ppu.clear_screen)
+			{
+				C.clear_screen_func();
+				do_frame_fill = true;
+			}
+
+			if (R.ppu.clear_screen)
+			{
+				R.clear_screen_func();
+				do_frame_fill = true;
+			}
 		}
 
 		public void GetControllerState(IController controller)

src/BizHawk.Emulation.Cores/Consoles/Nintendo/GBHawkLink4x/GBHawkLink4x.IEmulator.cs

@@ -960,7 +960,32 @@ namespace BizHawk.Emulation.Cores.Nintendo.GBHawkLink4x
 					D.vblank_rise = false;
 					do_frame_fill = true;
 				}
-			}			
+			}
+
+			// clear the screens as needed
+			if (A.ppu.clear_screen)
+			{
+				A.clear_screen_func();
+				do_frame_fill = true;
+			}
+
+			if (B.ppu.clear_screen)
+			{
+				B.clear_screen_func();
+				do_frame_fill = true;
+			}
+
+			if (C.ppu.clear_screen)
+			{
+				C.clear_screen_func();
+				do_frame_fill = true;
+			}
+
+			if (D.ppu.clear_screen)
+			{
+				D.clear_screen_func();
+				do_frame_fill = true;
+			}
 		}
 
 		public void GetControllerState(IController controller)

src/BizHawk.Emulation.Cores/Consoles/Nintendo/SubGBHawk/SubGBHawk.IEmulator.cs

@@ -60,7 +60,17 @@ namespace BizHawk.Emulation.Cores.Nintendo.SubGBHawk
 
 			bool ret = pass_a_frame;
 
-			if (pass_a_frame) { frame_cycle = 0; }
+			if (pass_a_frame) 
+			{
+				// clear the screen as needed
+				if (_GBCore.ppu.clear_screen)
+				{
+					_GBCore.clear_screen_func();
+				}
+
+				// reset the frame cycle counter
+				frame_cycle = 0; 
+			}
 			current_cycle = 0;
 			
 			_isLag = pass_a_frame;