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[directfb-users] Re: Displaying buffer contents
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[directfb-users] Re: Displaying buffer contents

Sven Neumann <> writes:

> You got me wrong obviously. Your solution is the one that needs
> internal headers. What I am suggesting works with the exported
> DirectFB API.

OK. Thanks for your patience.

> The API reference manual could indeed be improved but it covers all
> the functions I mentioned. All you need for my first suggestion is
> IDirectFBSurface::Lock() and IDirectFB::UnLock() while the second one
> uses IDirectFB::CreateSurface() only.
> Lock the surface, write the data to it, then unlock it.

How do i write data to a surface (with the public API)? Maybe i'm
quite blind, but i don't see it. The only way i found to write
data to an existing surface is either with private API or via
ImageProvider. What am i missing?

>> What is the pitch field for, what does it mean, which values are
>> valid?

> Ugh, do I really need to explain this? This is a basic principle of
> computer graphics. Perhaps you know it under the name "rowstride".
> Basically it's the number of bytes that you need to advance to get
> from one row to the next. And, no, this is not necessarily equal to
> the number of columns multiplied by the number of bytes per pixel.

Hmmm... it's quite some time ago i'm working with graphics on this
low level (ah, C64 times -- that was fun :)).

If i have RGB24 or RGB32 surface then is the pitch cols*bpp? Or am
i missing something here, too?

BTW: DirectFB is a nice project and i really like it (for my
project i looked to quite some libraries) -- but mixing one
library with sparse documentation with another library with even
less documentation sometimes become really frustrating (even more
because it's not to easy to debug my application).

But i appreciate your help very much. Thanks.

Until the next mail...,

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