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 Text output does not work 
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Joined: Tue Apr 20, 2010 9:08 am
Posts: 20
Post Text output does not work
Somehow I can't get text output to work right.

I made functions that print a character set the color, set the position, but I just can't get printing strings and scrolling to work.

The OS is booted using GRUB, so it's in 32-bit Protected Mode.


Mon Apr 26, 2010 12:39 pm
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Joined: Tue Apr 20, 2010 1:39 pm
Posts: 17
Post Re: Text output does not work
Show code.
You are writing to B800:0000, right?


Mon Apr 26, 2010 5:07 pm
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Joined: Tue Apr 20, 2010 9:08 am
Posts: 20
Post Re: Text output does not work
The scroll() function simply does not work, and when I position it to near the end of the screen and print a few characters it prints the first few characters in two places on the screen and does not scroll.

kernel.c

Code:
#include "vga.h"

void kernel_main( void* mbd, unsigned int magic )
{
   if ( magic != 0x2BADB002 ) { // if the bootloader is not Multiboot-compatible
   }

   // char* boot_loader_name = (char*) ((long*) mbd)[16];
   set_color(COLOR_LTAQUA | (COLOR_AQUA << 4));
   set_cur(78, 24);
   put_character('H');
   put_character('e');
   put_character('l');
   put_character('l');
   put_character('o');
}


vga.c

Code:
#include "vga.h"

int curx=0, cury=0;
unsigned char curc = COLOR_GRAY | (COLOR_BLACK << 4);
unsigned short* videoram = (unsigned short*) 0xB8000;
#define videoram_get(x, y) videoram[x + (y * COLS)]

void scroll() {
   int x, y;
   for(y=1; y<LINES; y++) {
      for(x=0; x<COLS; x++) {
         videoram_get(x, y-1) = videoram_get(x, y);
      }
   }
}

void set_color(unsigned char color) {
   curc = color;
}

void set_cur(int x, int y) {
   curx = x;
   cury = y;
}

void put_character(char c) {
   if(c == '\n') {
      curx = 0;
      cury++;
   } else {
      videoram_get(curx, cury) = c | (curc << 8);
      if(++curx == COLS) {
         curx = 0;
         if(cury+1 == LINES) scroll(); else cury++;
      }
   }
}

void clear_screen() {
   int i;
   for(i=0; i<LINES*COLS; i++) {
      videoram[i] = ' ' | (curc << 8);
   }
}


The (improper) output is attached.


Attachments:
hello.jpg
hello.jpg [ 37.41 KiB | Viewed 12027 times ]
Mon Apr 26, 2010 7:56 pm
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Joined: Tue Apr 20, 2010 1:39 pm
Posts: 17
Post Re: Text output does not work
Code:

void put_character(char c) {
   if(c == '\n') {
      curx = 0;
      cury++;
      if(cury+1 == LINES || cury == LINES){scroll();}
   } else {
      videoram_get(curx, cury) = c | (curc << 8);
      if(++curx == COLS) {
         curx = 0;
         if(cury+1 == LINES || cury == LINES) scroll(); else cury++;
      }
   }
}

Try that.


Mon Apr 26, 2010 9:45 pm
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Joined: Tue Apr 20, 2010 9:08 am
Posts: 20
Post Re: Text output does not work
smeezekitty wrote:
Code:

void put_character(char c) {
   if(c == '\n') {
      curx = 0;
      cury++;
      if(cury+1 == LINES || cury == LINES){scroll();}
   } else {
      videoram_get(curx, cury) = c | (curc << 8);
      if(++curx == COLS) {
         curx = 0;
         if(cury+1 == LINES || cury == LINES) scroll(); else cury++;
      }
   }
}

Try that.


What's the purpose of checking if cury AND cury+1 equals LINES? Why not >=, which will be simpler and more efficient?


Tue Apr 27, 2010 5:26 am
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Site Admin

Joined: Sat Jul 25, 2009 7:44 am
Posts: 274
Location: United Kingdom
Post Re: Text output does not work
Id go with >= too :P

_________________
Thank you for reading,

Kieran C G Foot


Tue Apr 27, 2010 5:41 am
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Joined: Tue Apr 20, 2010 9:08 am
Posts: 20
Post Re: Text output does not work
Code:
void scroll() {
   int x, y;
   for(y=1; y<LINES; y++) {
      for(x=0; x<COLS; x++) {
         videoram_get(x, y-1) = videoram_get(x, y);
      }
   }
   cury--;
}

void put_character(char c) {
   if (c == '\n') {
      curx = 0;
      if (++cury == LINES) scroll();
   } else {
      videoram_get(curx, cury) = c | (curc << 8);
      if (++curx == COLS) {
         curx = 0;
         if (++cury == LINES) scroll();
      }
   }
}


Newer version, but still the same result.


Tue Apr 27, 2010 5:52 am
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Joined: Tue Apr 20, 2010 9:08 am
Posts: 20
Post Re: Text output does not work
Anyone?

I would like to search it, but I just don't know what. I tried things like "vga characher output" and stuff but 99.9% of the results are completely irrelavent.


Tue Apr 27, 2010 7:23 pm
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Joined: Wed Feb 10, 2010 6:32 am
Posts: 26
Post Re: Text output does not work
Code:
int8u attrib = 0x0F;

void scroll(){
    int32u blank = ' ' | (attrib << 8);
    if(csr_y >= 25){
           int16u i;
           for (i = 0; i < 24*80; i++){
               vga_ptr[i] = vga_ptr[i+80];
           }
           for (i = 24*80; i < 25*80; i++){
               vga_ptr[i] = blank;
           }
           csr_y = 24;
       }
    move_csr();
}


I did it like that, maybe it helps you.
bye Sharpner


Thu Apr 29, 2010 3:38 am
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