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From: Stefan Soos <stefan.soos@gmx.de>
Newsgroups: comp.lang.ada
Subject: Re: AdaSDL and glTexImage2D
Date: Thu, 30 Jan 2003 10:52:39 +0100
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Date: 2003-01-30T10:52:39+01:00
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Hello,

On Wed, 29 Jan 2003 15:15:44 -0500, Chad R. Meiners wrote:
> In AdaSDL-Video-Drawing.adb around line 273 you will find:
>             declare
>                subtype Current_Screen is Screen_Eight(1..Array_Size);
>                package Convert is new  System.Address_To_Access_Conversions
>                  (Current_Screen);
>             begin
>                Eight_Bit_Draw
>                  ( On => Convert.To_Pointer (Item.Item.Pixels).all,  -- The
> important conversion
>                    Colors => To_Palette_Provider (Item),
>                    Coordinates => Coords);
>             end;
> 
> Here is a example of converting the Image.Pixels (in this case
> Item.Item.Pixels ;) into an access to an array of size Array_Size.  Notice
> that we had to declare a subtype of the Screen_Eight array with a specified
> range so that the compiler can reconstruct the range information.

I've only looked at the thin binding in adsdl.ad[bs] and
adsdl_framebuf and there he's doing some tricky stuff with
SDL.Types.Uint[8|16|32]_Ptrs. I've seen the package
Address_To_Access_Conversions in varios sources before but I didn't
know what it was good for ;)


> Now I am guessing that GLubyte_Array is an array of bytes.  So for your code
> your solution might look like this
> 
> declare
>     Bytes_Per_Pixel : constant := 4;  -- I believe RGBA is 32 bit color, but
> if I am wrong in your case change this value
>     subtype Current_Buffer is
> GLubyte_Array(0..(Width*Height*Bytes_Per_Pixel)-1);
>     package Convert is new
> System.Address_To_Access_Conversions(Current_Buffer);
> begin
>           glTexImage2D (GL_TEXTURE_2D,
>                         0,
>                         GLint (GL_RGBA),
>                         GLsizei (Width), GLsizei (Height),
>                         0,
>                         GL_RGBA,
>                         GL_UNSIGNED_BYTE,
>                         Convert.To_Pointer (Image.Pixels).all);
> end;

That's exactly how it works. Thank you very much.
The Bytes_Per_Pixel information is stored in Image.format.BytesPerPixel.

> Now remember this might need some tinkering to get it right since I don't
> have the packages to test this out.

There was a little bit of tinkering because I have to do some color
conversion and flipping of the textures but your code worked just
right out of the box ;) Again, thank you so much.


> I hope this solves your problem,
> 
> Chad R. Meiners

Indeed, it did. Thanks and bye,
Stefan


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