First implementation of interlaced mode and switching display modes by pressing Select.

Still a bit buggy, not sure what I'm doing wrong. Will have to revisit this after performance is improved.

display.c

@@ -106,6 +106,24 @@ void display_reset(u_char interlaced, int *outScreenHeight)
 		aspect_scale.vy = 256 * ONE / 240;
 	}
 
+	if (interlaced)
+	{
+		screenHeight <<= 1;
+		yOffset <<= 1;
+		aspect_scale.vy <<= 1;
+
+		// Define display environments, interlaced images cover the same area in VRAM
+		SetDefDispEnv(&disp[0], 0, 0, SCREENWIDTH, screenHeight);
+		SetDefDispEnv(&disp[1], 0, 0, SCREENWIDTH, screenHeight);
+
+		// Define drawing environments, interlaced images cover the same area in VRAM
+		SetDefDrawEnv(&draw[0], 0, 0, SCREENWIDTH, screenHeight);
+		SetDefDrawEnv(&draw[1], 0, 0, SCREENWIDTH, screenHeight);
+
+		disp[0].isinter = disp[1].isinter = 1;
+	}
+	else
+	{
 		// Define display environments, first on top and second on bottom
 		SetDefDispEnv(&disp[0], 0, 0, SCREENWIDTH, screenHeight);
 		SetDefDispEnv(&disp[1], 0, screenHeight, SCREENWIDTH, screenHeight);
@@ -114,6 +132,9 @@ void display_reset(u_char interlaced, int *outScreenHeight)
 		SetDefDrawEnv(&draw[0], 0, screenHeight, SCREENWIDTH, screenHeight);
 		SetDefDrawEnv(&draw[1], 0, 0, SCREENWIDTH, screenHeight);
 
+		disp[0].isinter = disp[1].isinter = 0;
+	}
+
 	disp[0].screen.y = disp[1].screen.y = yOffset;
 	disp[0].screen.h = disp[1].screen.h = screenHeight;
 

input.c

@@ -1,6 +1,7 @@
 #include "common.h"
 #include "input.h"
 #include "time.h"
+#include "display.h"
 
 #include <psxpad.h>
 
@@ -10,6 +11,9 @@ static const int moveSpeed = 1024;
 static const short rotSpeed = 1024;
 static const char deadZone = 0x30;
 
+static u_char disp_interlace = 0;
+static u_char dispmode_held = 0;
+
 void input_init()
 {
 	InitPAD(padBuffer[0], 34, padBuffer[1], 34);
@@ -96,6 +100,20 @@ void input_process()
 		// Look up
 		cam_rot.vx += rotInterval;
 	}
+    if (!(buttons & PAD_SELECT))
+    {
+        // Switch display mode
+        if (!dispmode_held)
+        {
+            dispmode_held = 1;
+            disp_interlace = !disp_interlace;
+            display_reset(disp_interlace, NULL);
+        }
+    }
+    else
+    {
+        dispmode_held = 0;
+    }
 	
 	// Check for analog controller
 	u_char padType = padBuffer[0][1] >> 4;