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Newsgroups: comp.lang.ada
Date: Wed, 21 Sep 2016 11:50:47 -0700 (PDT)
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Subject: Re: Accessing a sub-array in C from Ada in SDL
From: Lucretia <laguest9000@googlemail.com>
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Xref: news.eternal-september.org comp.lang.ada:31833
Date: 2016-09-21T11:50:47-07:00
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On Wednesday, 21 September 2016 18:31:16 UTC+1, Lucretia  wrote:
> Hi,
> 
> I'm gone back to try and get some updates on SDLAda textures (and also surfaces). 
> 
> When locking a texture you get a pointer to the array and a pitch value to the next line. Mapping a 2D or 3D texture data from C onto a 2D or 3D Ada array is quite easy for a full image, by setting the address. So, currently I have this for a full frame:
> 
> Actual_Pixels    : Texture_2D_Array (1 .. Height, 1 .. Width) with
>    Address => To_Address (Pixels);
> 
> 
> But what if you want to lock a partial area of this texture? Ideally, we'd want to be able to set a stride/pitch value in the array declaration, something like:
> 
> Actual_Pixels    : Texture_2D_Array (1 .. Height, 1 .. Width) with
>    Address => To_Address (Pixels),
>    Stride  => Pitch;
> 
> As far as I can see, this is currently not possible, but I can see this as being immensely useful when working with C libs.
> 
> Luke.

A bad doodle to picture it https://snag.gy/A7waEd.jpg