Upgrading from 0.22 to 0.26.4

[Rodrigo Robles]

Hi friends,

    I'm using Imaging version 0.22 in a game project, and now I realize that I will need the TImagingCanvas blending. So upgrade Imaging is required.
    The only thing I had to change in the source was the property TSingleImage.ImageData that was renamed to ImageDataPointer. After this the project successfully built.
    For my surprise the program emits a segmentation fault message at start. I tried to debug it, but it happens before the first line of code!
    So... I did anything wrong?

[Galfar]

Hi Rodrigo,
could you provide some details about compiler and OS you use for Mundo?
Maybe there could be some problem with code in "initialization" section in Imaging in your OS+compiler combination.

[Rodrigo Robles]

After upgrade Lazarus, I can get a stack image:


#0 ?? at :0
#1 ISGLEXTENSIONSUPPORTED(0x818c118 'GL_ARB_texture_compression') at ./Imaging/Extensions/ImagingOpenGL.pas:316
#2 GETGLTEXTURECAPS({MAXTEXTURESIZE = 135828120, NONPOWEROFTWO = true (254), DXTCOMPRESSION = true (217), ATI3DCCOMPRESSION = true (5), LATCCOMPRESSION = true (8), FLOATTEXTURES = true (84), MAXANISOTROPY = 135851124, MAXSIMULTANEOUSTEXTURES = 135828120, CLAMPTOEDGE = true (92), TEXTURELOD = true (244), VERTEXTEXTUREUNITS = 134576832}) at ./Imaging/Extensions/ImagingOpenGL.pas:340
#3 CREATEGLTEXTUREFROMMULTIIMAGE(0xb7f70778, 0, 0, true, 0, IFUNKNOWN, 0x0, 0x0) at ./Imaging/Extensions/ImagingOpenGL.pas:576
#4 CREATEGLTEXTUREFROMIMAGE({WIDTH = 0, HEIGHT = 0, FORMAT = IFUNKNOWN, SIZE = 211550273, BITS = 0xb7f60cdc, PALETTE = 0x0}, 0, 0, false, IFUNKNOWN, 0xbffff408, 0x0) at ./Imaging/Extensions/ImagingOpenGL.pas:540
#5 TTEXTUREIMAGING__LOAD(0xb7f60c28 '../client/data/font/dejavu-mono-white.png', <error reading variable>) at textureimagings.pas:34
#6 TFONTBITMAP__CREATE(0xb7f60c28 '../client/data/font/dejavu-mono-white.png', 0xb7f60c90) at fontbitmaps.pas:57
#7 TFONT__CREATE(0xb7f60c28 '../client/data/font/dejavu-mono-white.png', 0xb7f70790) at fonts.pas:52
#8 TGAME__CREATE(0xbffff408) at /media/dados/rodrigo/temp/mundo_trunk/src/common/games.pas:822
#9 GAMES_init at /media/dados/rodrigo/temp/mundo_trunk/src/common/games.pas:2370
#10 fpc_initializeunits at :0
#11 ?? at :0
#12 __libc_start_main at :0
#13 SI_C21__FPC_LIBC21_START at :0

In 0.22 version I used TSingleImage.ImageData. In 0.26 this property was apparently replaced by ImageDataPointer. This assumption is correct? So I replaced it in my source, that looks like:

procedure TTextureImaging.Load(AFileName: string);
var
  i: TSingleImage;
begin
  Debug.Msg(dlBegin, 'TTextureImaging.Load("' + AFileName + '")');
  i := nil;
  try
    i := TSingleImage.Create;
    i.LoadFromFile(AFileName);
    FWidth := i.Width;
    FHeight := i.Height;
    FId := CreateGLTextureFromImage(i.ImageDataPointer^);
    i.Free;
  except
    i.Free;
    raise;
  end;
end;

The exception is raised in the line: FId := CreateGLTextureFromImage(i.ImageDataPointer^);
Now I'm using Lazarus 0.9.30 and Ubuntu 11.10.

[Rodrigo Robles]

The solution was simple: The new Imaging  uses dglOpenGL. DglOpenGL requires initialization through InitOpenGL. After adding this initialization the access violation is gone.

[Galfar]

You can configure ImagingOpenGL to use "Gl, Glu" instead of "dglOpenGL headers if that's what you are using in Mundo.

[Rodrigo Robles]

DglOpenGL have more features than the traditional gl headers, right?

[Galfar]

dglOpenGL is still being updated so new OpenGL features are in (e.g. OpenGL 3/4),
I'm not sure if "GL, GLext" headers are. 
It doesn't matter if your game targets older hardware (where new OpenGL features are not supported
by HW anyway).