Video debug overlay: Add information on where the display vs CPU memory banks are

Author: joncampbell123

CHANGELOG

@@ -1,4 +1,8 @@
 NEXT VERSION
+  - Video debug overlay: For Tandy and PCjr emulation, add information on
+    the screen that shows the line mask, display and cpu memory banks and
+    the corresponding segment values, which may aid in debugging issues
+    with games and reveal any remapping or page flipping (joncampbell123).
   - Tandy emulation: Add the string "Tandy" somewhere in the DOS kernel
     at startup if machine=tandy. The game "The Train: Escape to Normandy"
     scans from FFFF:0000 for the string "Tandy" which of course wraps

src/gui/render.cpp

@@ -1006,6 +1006,9 @@ void RENDER_SetSize(Bitu width,Bitu height,Bitu bpp,float fps,double scrn_ratio)
 		width += 8*32;
 		width += 4;
 	}
+	else if (machine == MCH_TANDY || machine == MCH_PCJR) {
+		height += 8*3;
+	}
 	else {
 		height += 8*2;
 	}

src/hardware/vga_draw.cpp

@@ -5062,6 +5062,28 @@ void VGA_sof_debug_video_info(void) {
 				/* would be redundant copy of HWPAL */
 			}
 
+			x = 4;
+			y += 8;
+
+			{
+				uint16_t drawseg,memseg;
+
+				drawseg = vga.tandy.draw_bank * 0x400u;
+				memseg = vga.tandy.mem_bank * 0x400u;
+				if (machine == MCH_TANDY) {
+					drawseg += 0x8000u;
+					memseg += 0x8000u;
+				}
+
+				sprintf(tmp,"LM=%X DB=%u(%04X) MB=%u(%04X)",
+					(unsigned int)vga.tandy.line_mask,
+					(unsigned int)vga.tandy.draw_bank,
+					(unsigned int)drawseg,
+					(unsigned int)vga.tandy.mem_bank,
+					(unsigned int)memseg);
+				x = VGA_debug_screen_puts8(x,y,tmp,white) + 8;
+			}
+
 			x += 8;
 		}
 	}