Question: Is it a good practice to save the value of the registers that you change inside a function? or thats not important?

using putpixes is not a good idea especially in order to fill big areas with the same collor.
Use dword chunks of data. For 24 bit color this is not very convenient, but still can be implemented - use 4pixel array, that is exactly 3 dwords load them in 3 registers and then fill the area on dword basis.

yep.

use a double buffer in 32 bits.
and just transfer pixels for 24 bpp with dwords.

basically, you can create a virtual screen, of any resolution (very big is possible), in 32 bpp, and only vsync will do the refresh to the target resolution and bpp.

----

double buffer fixed resolution and bpp > vsync > resolution and bpp convert to screen

this can be a method.

    drawfillrect:
        mov  eax,[esp+2*4] ;y
        add  eax,[esp+4*4] ;h
        mov  ebx,[esp+1*4] ;x
        call moveTo
        mov  eax,[esp+5*4] ;c
        ;shl  eax,8  ; if i uncomment this line i got right colors, except the last one.
        mov  edx,[esp+3*4] ;w
        shl  edx,1
        add  edx,[esp+3*4] ;w   edx = w * 3bytes
        mov  ecx,[esp+4*4] ;h
  .for: mov  ebx,edx
    @@: mov  dword[edi+ebx],eax ;c
        sub  ebx,3
        jnz  @b
        sub  edi,1280*3
        dec  ecx
        jnz  .for
        ret  5*4     

mov  eax, $33112233
mov  ebx, $22331122
mov  ecx, $11332211
    

mov  [edi], eax
mov  [edi+4], ebx
mov  [edi+8], ecx
    

3: you transfert pixels from buffer to screen memory periodically

4: you can read pixel without reading to screen memory

john found: nice trick, i will try it one day..

the 2D HW acceleration is a set of basic commands, passed to the GPU. and is specific to each model of GPU, not like the instruction set of X86.

if you want to exploit the HW acceleration, it is better to use OPENGL, direct draw, win32, X, GTK, QT within an OS like windows or linux. for the moment, maybe latter, there will be a good way in BOOT asm.

GPU acceleration is a set of instructions and data structures used in the GPU, exactlly as instructions and datas for the CPU, but close to the video DAC (digital to analog converter), and very different because it is a purpose specific processor, just made to compute faster the pixels in 3D, and fill faster the screen in 2D.

the 2D HW acceleration is a set of basic commands, passed to the GPU.
for example to draw a line, fill a rectangle, put a bitmap,write font... and is specific to each model of GPU, not like the instruction set of X86.

if you want to exploit the HW acceleration, it is better to use OPENGL, direct draw, win32, X, GTK, QT within an OS like windows or linux. for the moment, maybe latter, there will be a good way in BOOT asm.