Accessing a sub-array in C from Ada in SDL

Accessing a sub-array in C from Ada in SDL

[Lucretia]

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.

Re: Accessing a sub-array in C from Ada in SDL

[Lucretia]

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