Switching between landscape and portait mode

SDL Development
1

I’d like to get 90 degrees rotation to use screen in portrait mode on
framebuffer device (that will be the final environment for my applcation)
and usual landscape orientation on X (I use it while developing the
application).
I know there are some graphics libraries that allowing arbitrary surface
rotation, but I don’t want to waste my CPU time more than necessary.

Which is the best option to do that?

I think also about a modified SDL_BlitSurface that blits an (Width x Height)
surface on a (Height x Width) surface. Which is the best staring point to do
this?

Thank you for any suggestion,

Alessandro Staltari

2

Alessandro Staltari wrote:

I’d like to get 90 degrees rotation to use screen in portrait mode on
framebuffer device (that will be the final environment for my applcation)
and usual landscape orientation on X (I use it while developing the
application).
I know there are some graphics libraries that allowing arbitrary surface
rotation, but I don’t want to waste my CPU time more than necessary.

Which is the best option to do that?

I think also about a modified SDL_BlitSurface that blits an (Width x Height)
surface on a (Height x Width) surface. Which is the best staring point to do
this?

Thank you for any suggestion,

Alessandro Staltari

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

Hm.

Working on Compaq iPaq, I’ve built a library for my own use that autorotates all
images on load-time, and ‘overloads’ the SDL functions and the normal
SDL_Surface with #undefs and #define 's.

Pretty slick in some ways, if I’m allowed to say such of my own code :wink: - you
can SetVideoMode to 320 * 240 and get 240 * 320 and in general your source won’t
know the difference.

Some problems:

  1. As of current, the rotation is determined at compile-time. Not real-time.
    All the functions are heavily inlined etc. and I’d have to ditch that to get it
    to switch realtime. Email me if you

  2. SDL_LockSurface/SDL_UnlockSurface are currently unsupported.

  3. Bugz. Every once in awhile I stumble across and fix a new one, but there are
    surely still afew lurking.

  4. C++ codebase. Currently requires C++ because of -one- bit of code.
    Hopefully I can fix that eventually.

Email me if you want it in it’s current state.

3

“Corona688”:

Hm.

Working on Compaq iPaq, I’ve built a library for my own use that
autorotates all
images on load-time, and ‘overloads’ the SDL functions and the normal
SDL_Surface with #undefs and #define 's.

[…]

Email me if you want it in it’s current state.

Thank you very much, but I already decided to solve the problem in another
way,
using a scratch rotated surface for drawing and then blitting those surface
rotated back to screen.
It may seem a waste of memory, but it enough for me :slight_smile:

Here is my code, it may be useful for others, or maybe, somebody may suggest
improvement. :slight_smile:
I tested it only in 16 bpp. Sorry for the bad coding style :-/

/* Crate a new rotated surface for drawing */
SDL_Surface *CreateRotatedSurface(SDL_Surface *s)
{
return(SDL_CreateRGBSurface(s->flags, s->h, s->w,
s->format->BitsPerPixel,
s->format->Rmask,
s->format->Gmask,
s->format->Bmask,
s->format->Amask));
}

/* Used to copy the rotated scratch surface to the screen */
void BlitRotatedSurface(SDL_Surface *from, SDL_Surface *to)
{

int bpp = from->format->BytesPerPixel;
int w=from->w, h=from->h, pitch=to->pitch;
int i,j;
Uint8 *pfrom, *pto, *to0;

SDL_LockSurface(from);
SDL_LockSurface(to);
pfrom=(Uint8 *)from->pixels;
to0=(Uint8 *) to->pixels+pitch*(w-1);
for (i=0; i<h; i++)
{
    to0+=bpp;
    pto=to0;
    for (j=0; j<w; j++)
    {
        if (bpp==1) *pto=*pfrom;
        else if (bpp==2) *(Uint16 *)pto=*(Uint16 *)pfrom;
        else if (bpp==4) *(Uint32 *)pto=*(Uint32 *)pfrom;
        else if (bpp==3)
            {
                pto[0]=pfrom[0];
                pto[1]=pfrom[1];
                pto[2]=pfrom[2];
            }
        pfrom+=bpp;
        pto-=pitch;
    }
}
SDL_UnlockSurface(from);
SDL_UnlockSurface(to);

}

Usage example-------------

scratch=CreateRotatedSurface(screen);

/* draw operations on scratch surface */

BlitRotatedSurface(scratch, screen);
SDL_UpdateRect(screen, 0, 0, 0, 0);