Plotting desktop

[St8ic]

I want to see if I can develop a GUI in 16-bit real mode (don't ask why...), but I'm stuck at the very start. I'm trying to draw the desktop, wich sounds like an easy enough task, but I can't get it quite right. I have cleared the screen and set VGA mode 12h. Now I just need a routine to plot a colored box that covers the whole 640x480 screen.

Can anyone give some code or snippets for this simple task? Thanks in advance!

(P.S. I know that graphics in real mode are slow, but I just want to give it a try.)

[ASHLEY4]

Hi
First no one will give you code,as this will not help you,second if you have cleared your 640x480x16 screen,
then by puting the right color in the reg, will do what you want.
You would also be best useing 13 mode,to start with as it will be easyer for you.
Also you should tell people what language you use.
Here alink that may help you make a gui in real mode(get "obmaker.zip")

http://www.tomaskovic.com/other.html

PS. real mode graphics are not slow.

ASHLEY4.

[St8ic]

Thanks for the reply

1. I'm sorry for not saying what language I use: I was going to say that it could be in C or asm, but I thought you'd assume that.

2. That obmaker thing didn't export any useful code, mainly just jibberish.

3. Could you possibly provide an example for clearing the screen and filling it with a color? Thanks!

[bubach]

Some links:

Mouse in mode 12h:
http://www.programmersheaven.com/zone5/cat710/1423.htm

how does it work:
http://www.programmersheaven.com/search/download.asp?FileID=6376

Code: Select all

      mov ax, 0xA000
      mov es, ax 
      mov di, 0 

      mov dx, 0x03C4      ; Enable write to all bitplanes 
      mov ax, 0x0F02 
      out dx, ax 

      mov cx, 0x8000 
      mov ax, 0x0000       ; color = 0 = black
      rep stosw

[St8ic]

Bubach,
Thanks for the links, those should prove useful later in my GUI development. As for the code: what video mode is it intended for? I changed the color to 0x9. It works on 12h and 13h, but on both modes the screen is striped blue and black, instead of solid blue! Is this supposed to happen or is it a mode problem?

Thanks again!

[ASHLEY4]

Try it like this:

Code: Select all

   
     mov ax, 0xA000
      mov es, ax 
      mov di, 0 

      mov dx, 0x03C4      ; Enable write to all bitplanes 
      mov ax, 0x0F02 
      out dx, ax 

      mov cx, 0x8000 
      mov ax, 0x0909       ;<TRY THIS color = 0 = black
      rep stosw

Also try this to get 640x480x256

Code: Select all

; uses vesa (1 
; assembles in NASM

mov ax,4f02h   ;set vesa 1.0 screen mode
mov bx,101h   ;640*480*256
int 10h

mov dx,0xa000
mov ds,dx               ;sets up registers
call window
rain:
xor dx,dx       ;(pages-1)

mouse:
push dx
call window
xor bx,bx
mov al, 0cch
call dog
pop dx
cmp dx,4
je rain
inc dx
mov ah,01h
int 16h
jz mouse

mov ax,0003h
int 10h

mov ax,4c00h      ; This is just 
int 21h                 ; for test ,take it out in your OS

window:
mov ax,4f05h    ;vesa 1 window select
mov bx,0
int 10h         ;dx is  the reqired window
xor bx,bx
ret

dog:         ;(4*2^16)+45056 pixels
mov [bx],al
inc bx
cmp bx,$00000
jne dog
ret

ASHLEY4.

[Pype.Clicker]

in mode 12, you have four planes of bits. Each bit is one of the color's bits, so if you want to draw something in dark-ceylan (0011), you need to write a '1' at that pixel's bit in plane #0, a '1' in plane #1, a '0' in plane #2 and a '0' in plane #3.

This means that your drawing function will require a lot of optimization (they always do, anyway to be efficient: the approach

Code: Select all

virtual_offset = x+y*640;
for (i=0;i<4;i++, color=color/2) {
   switch_plane(i)
   video[virtual_offset/8]=((video[virtual_offset/8]& ~(1<<i)) | color)
}

should be restricted to single-pixel plotting. Drawing boxes, lines, bitmaps, etc. should take the advantage they're accessing several bits from the same character in video[] (reducing VRAM read and writes), and could benefit of 'operating mode = AND/OR/XOR' setting on the VGA card (so that you just write X and the video memory become new_content = old_content & X in a single memory cycle).

I strongly suggest you consider using 256 colors approach instead. And if you can afford it, turn in unreal mode and use the LinearFrameBuffer to forget about banking, etc. and unleash the power of your VESA card with 1024x768x16M

[yub]

whats's in your function switch_plane()

[Candy]

in mode 12, you have four planes of bits. Each bit is one of the color's bits, so if you want to draw something in dark-ceylan (0011), you need to write a '1' at that pixel's bit in plane #0, a '1' in plane #1, a '0' in plane #2 and a '0' in plane #3.

The color's called cyan

FYI, the colors are coded with LSB = blue, bit 1 = green, bit 2 = rood, MSB = bright. So 0001 is dark blue and 1010 is bright green.

[Solar]

FYI, the colors are coded with LSB = blue, bit 1 = green, bit 2 = rood...

The color's called "red". ;D

[Pype.Clicker]

The color's called cyan
The color's called red ;D

*rofl*
damn't where did i lost that that blleue pill again

[Candy]

FYI, the colors are coded with LSB = blue, bit 1 = green, bit 2 = rood...

The color's called "red". ;D

thanks, missed that

*roflmao irl*

So, the second bit is red

[Pype.Clicker]

So, the second bit is red

and it's actually the *third* one as bit 0 is the first one ;D

btw, that's somehow fun ... but aren't we hitchhiking the forum from it's initial intent (somehow).

[Chris Giese]

Fast 16-color graphics code = large, hard-to-understand code (this is also true for banked framebuffer code). But here ya go:

http://my.execpc.com/~geezer/osd/graphics/grdemo.c

Should work with 16-bit Turbo C. For filled rectangles, the functions you want are fill_rect4p(), fill_plane(), and set_plane()

If you don't understand fill_rect4p() and fill_plane(), there is also a write_pixel4p() in there, but it's much slower (four plane-switches for each pixel!)