code: 9ferno

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cga cursor move bug in vmx

vmx is moving the cursor by 2 characters for each character pressed
vmx debug prints show the position moved by 1
0x3d4 val 14
0x3d5 val 7
0x3d4 val 15
0x3d5 val 132
0x3d4 val 14
0x3d5 val 7
0x3d4 val 15
0x3d5 val 133
0x3d4 val 14
0x3d5 val 7
0x3d4 val 15
0x3d5 val 134
but the display is moving by 2.

Also, cgascreenputc is only used by cgascreenputs. Hence, doing the movetocursor() after the string is printed

--- a/os/pc/cga.c

+++ b/os/pc/cga.c

@@ -31,7 +31,7 @@

 						 */

 };

-#define CGASCREENBASE	((uchar*)KADDR(0xB8000))

+#define CGASCREENBASE	((uchar*)0xB8000)

 static int cgapos;

 static Lock cgascreenlock;

@@ -50,11 +50,6 @@

 	outb(0x3D4+1, data);

 }

-/* TODO BUG the cursor is 2 characters beyond

- * could use pos = cgapos -2

- * but skips a character when 'd' is pressed

- * is it a bug in the shell prompt?

- */

 static void

 movecursor(void)

 {

@@ -97,12 +92,14 @@

 		}

 		cgapos = Width*(Height-1);

 	}

-	movecursor();

 }

 static void

 cgascreenputs(char* s, int n)

 {

+	int i,j;

+	/*char pre[512] = "";*/

+

 	if(!islo()){

 		/*

 		 * Don't deadlock trying to

@@ -114,6 +111,10 @@

 	else

 		lock(&cgascreenlock);

+	/*j = snprint(pre,512,"-%d %d-",n, cgapos);

+	for(i=0;i<j&&i<512;i++){

+		outb(0x3D6, pre[i]);

+	}*/

 	while(n-- > 0){

 		outb(0x3D6, *s);

 		// outb(0x3D6, '-');

@@ -120,6 +121,7 @@

 		cgascreenputc(*s++);

 		// outb(0x3D6, '_');

 	}

+	movecursor();

 	unlock(&cgascreenlock);

 		// outb(0x3D6, ',');