[fpc-devel] graphh.inc - few questions.

Jonas Maebe jonas.maebe at elis.ugent.be
Mon Jul 16 14:01:03 CEST 2007

On 14 Jul 2007, at 16:01, Evgeniy Ivanov wrote:

> I'm doing sdlgraph - so I put my self to packages/base/graph.

graph probably has to be moved to packages/extra, so it can easily  
use things like sdl and the (Mac OS X) universal interfaces.

> I can't understand the method (where are they used?) using routines in
> TModeInfo (from graphh.inc).
> In custom graph modules it's used in such way:
>             mode.PutPixel:={$ifdef fpc}@{$endif}PutPixVESA32kOr64k;
> But in windows and go32v2 there are no any routines for PutPixel from
> interface.

They don't need to be in the interface. PutPixel is a procedure  
variable, and the only thing that needs to be in the interface (and  
it's declared in graphh.inc, which is included in the interface of  
the go32v2 and win32 unts). The procedures which are assigned to this  
procvar do not have to be in the interface.

> I mean someting like
> PutPixel       := @custom_PutPixel;   (PutPixel       :=
> @libvga_PutPixelProc;   - in the unix graph.pp).
> So, if there are no such assignations (sorry, I don't know the  
> right word)
> PutPixelDefault from graph.inc will be used...
> And it is:
>  procedure PutPixelDefault(X,Y: smallint; Color: Word);
>   begin
>     Writeln(stderr,'Error: Not in graphics mode (use InitGraph and  
> test
> GraphResult afterwards)');
>     Halt(1);
>   end;
> But windows module works...

Have a look at QueryAdapterInfo in graph.pp of go32v2. It has many  
blocks like this:

          { now add all standard VGA modes...       }
          mode.DriverNumber:= LowRes;
          mode.HardwarePages:= 0;
          mode.ModeName:='320 x 200 VGA';
          mode.MaxColor := 256;
          mode.PaletteSize := mode.MaxColor;
          mode.DirectColor := FALSE;
          mode.MaxX := 319;
          mode.MaxY := 199;
          mode.DirectPutPixel:={$ifdef fpc}@{$endif}DirectPutPixel320;
>          mode.PutPixel:={$ifdef fpc}@{$endif}PutPixel320;
          mode.GetPixel:={$ifdef fpc}@{$endif}GetPixel320;
          mode.SetRGBPalette := {$ifdef fpc}@{$endif}SetVGARGBPalette;
          mode.GetRGBPalette := {$ifdef fpc}@{$endif}GetVGARGBPalette;
          mode.SetAllPalette := {$ifdef fpc}@{$endif} 
          mode.SetVisualPage := {$ifdef fpc}@{$endif}SetVisual320;
          mode.SetActivePage := {$ifdef fpc}@{$endif}SetActive320;
          mode.InitMode := {$ifdef fpc}@{$endif}Init320;
          mode.XAspect := 10000;
          mode.YAspect := 10000;

When switching to a mode, initgraph will assign the putpixel field of  
that mode to the global putpixel procvar.


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