[SDL] Hello, new member reporting

[Donny Viszneki]

You can do what you're proposing if the pixels pointer is actually
editable, but I'm betting on most platforms it is not. That is, of
course, for the display surface, not for an ordinary surface. Why
would you want to do this with an ordinary surface?

On Mon, Jan 26, 2009 at 8:39 AM, Antonio Marcos <amcmr2003 at yahoo.com.br> wrote:
>> Hey, welcome to the community!
>
> Hey, Thanks! :)
>
>> I don't know how it would work in video memory, but it
>> sounds like something
>> that can be done (in software, at least) by twiddling with
>> void*
>> SDL_Surface::pixels and Uint16 SDL_Surface::pitch.
>
> I was thinking about something like that, but I have no idea how the inner workings would proceed to know if its doing th actual thing. I was thinking about creating a bigger resolution surface with the SetVideoMode, get the pointer, and then reset to a lower resolution. The problem with this is that SDL have privileges to work with the hardware (at least on some OS'es i guess), and this would probably bypass it.. also, I dont know if the 'freed' parts of the memory would be used by something else.
>
>> I've never tried it, of
>> course, but I hope you can find a way to achieve your
>> desired effect.
>>
> It would be nice because changing a "camera view" would just be a matter of  incrementing/decrementing a pointer :)
>
>> Jonny D
>
> AM.
>
> --- Em seg, 26/1/09, Jonathan Dearborn <grimfang4 at gmail.com> escreveu:
>
>> De: Jonathan Dearborn <grimfang4 at gmail.com>
>> Assunto: Re: [SDL] Hello, new member reporting
>> Para: "A list for developers using the SDL library. (includes SDL-announce)" <sdl at lists.libsdl.org>
>> Data: Segunda-feira, 26 de Janeiro de 2009, 11:03
>> Hey, welcome to the community!
>> I don't know how it would work in video memory, but it
>> sounds like something
>> that can be done (in software, at least) by twiddling with
>> void*
>> SDL_Surface::pixels and Uint16 SDL_Surface::pitch.
>> I've never tried it, of
>> course, but I hope you can find a way to achieve your
>> desired effect.
>>
>> Jonny D
>>
>>
>> On Sun, Jan 25, 2009 at 4:22 PM, David Olofson
>> <david at olofson.net> wrote:
>>
>> > On Sunday 25 January 2009, Donny Viszneki wrote:
>> > [...hardware scrolling...]
>> > > I could be wrong, but I don't think modern
>> graphics hardware
>> > > supports this.
>> >
>> > Actually, most hardware does support it, but it's
>> only used
>> > for "virtual desktop" (desktop larger than
>> the display) and things
>> > like that... Probably not very portable or reliable
>> stuff, if it's at
>> > all accessible to normal applications. (From what
>> I've seen of this
>> > stuff on Windows, it may as well be internal driver
>> hacks.)
>> >
>> > So, full screen redrawing it is!
>> >
>> > If performance is an issue, you could implement it
>> over OpenGL or
>> > Direct3D, for hardware blitting and keeping it all in
>> VRAM. With SDL
>> > 1.3/2.0, you don't even have to touch those APIs
>> directly to do this,
>> > and it'll still work with
>> "software-only" displays as a fallback.
>> >
>> > On the bright side, using blitting instead of hardware
>> scrolling gives
>> > you a lot more freedom when it comes to layering,
>> screen layout,
>> > blending effects etc.
>> >
>> >
>> > //David Olofson - Programmer, Composer, Open Source
>> Advocate
>> >
>> > .-------  http://olofson.net - Games, SDL examples
>> -------.
>> > |        http://zeespace.net - 2.5D rendering engine
>>     |
>> > |       http://audiality.org - Music/audio engine
>>     |
>> > |     http://eel.olofson.net - Real time scripting
>>     |
>> > '--  http://www.reologica.se - Rheology
>> instrumentation  --'
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>> >
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