Re: [BLACKBOX] GdkGC *fg_gc[5] in CP?

From: [at]} <Wojtek>
Date: Sun, 27 Mar 2011 22:38:31 -0400

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> 'GdkColor fg[5];':
> As this C construct is a pointer to the first array element, I thought it
> should be translated to
> 'fg*: POINTER TO ARRAY [untagged] 5 OF Gdk.Color'
> and got a 'NIL reference' trap when trying to print out the color of fg[0].
> When I omitted 'POINTER TO' I got the correct values (0,0,0) for (R,G,B).

The array "GdkColor fg[5]" is an array. In C it should be accessed as
fg[0] through fg[4]. No need to use pointers in C, and therefore in CP
either.

A POINTER TO a five-element array would be declared in C like this:

GdkColor * fg[5];

If it crashed on:

> Gdk.draw_arc (
> widget.window, widget.style.fg_gc[ORD(widget.state)],
> G.TRUE, 0, 0, widget.allocation.width, widget.allocation.height,
> 0, 64 * 360);

perhaps it is a NIL pointer? Can you examine it with SYSTEM?

> I guess you
> all have the .h files of the corresponding C source on your computers, but I
> can post those too if wanted.

I do not. It makes little sense to post questions to this list
without providing necessary info. It is hard to guess what you are doing
without seeing the .h file and then your translation.


> I simply have no idea how to continue.

Perhaps the last few slides of my very long presentation can be of some
help? Start with slide 77.

http://www.pas.rochester.edu/~skulski/Presentations/BB_Class.pdf

Hope it helps,

Wojtek

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Received on Mon Mar 28 2011 - 04:38:31 UTC