Re: Pixmap question

[Colin Thomas <colin designresources co uk>]

Hi ,

I have gone some hunting around, and have found a reference to the following
in gdktypes.h:

############################################
/* GC function types.
 *   Copy: Overwrites destination pixels with the source pixels.
 *   Invert: Inverts the destination pixels.
 *   Xor: Xor's the destination pixels with the source pixels.
 *   Clear: set pixels to 0
 *   And: source AND destination
 *   And Reverse: source AND (NOT destination)
 *   And Invert: (NOT source) AND destination
 *   Noop: destination
 *   Or: source OR destination
 *   Nor: (NOT source) AND (NOT destination)
 *   Equiv: (NOT source) XOR destination
 *   Xor Reverse: source OR (NOT destination)
 *   Copy Inverted: NOT source
 *   Xor Inverted: (NOT source) OR destination
 *   Nand: (NOT source) OR (NOT destination)
 *   Set: set pixels to 1
 */
typedef enum
{
  GDK_COPY,
  GDK_INVERT,
  GDK_XOR,
  GDK_CLEAR,
  GDK_AND,
  GDK_AND_REVERSE,
  GDK_AND_INVERT,
  GDK_NOOP,
  GDK_OR,
  GDK_EQUIV,
  GDK_OR_REVERSE,
  GDK_COPY_INVERT,
  GDK_OR_INVERT,
  GDK_NAND,
  GDK_SET
} GdkFunction;
############################################

If I read it correctly, it seems you can overlay pixels on existing pixels
ANDing the colour ? (Which is what I am after...)

Is this the correct way it was intended? If so has anyone used the above, 
and how in gtk+ ?

I also would like to have dashed lines in rectangles et al. There seems to
be the following, but again can it be used in gdk: I assume somehow it is
called in the GC which the rectangle is drawn in ?? (Either of my 2 gtk+ books
go into this depth)

############################################
typedef enum
{
  GDK_LINE_SOLID,
  GDK_LINE_ON_OFF_DASH,
  GDK_LINE_DOUBLE_DASH
} GdkLineStyle;
############################################


Many thanks in advance...

Colin Thomas
------------- Begin Forwarded Message -------------

Date: Tue, 09 Jan 2001 11:49:54 -0800
From: "Timothy M. Shead" <tshead k-3d com>
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To: Paul Barton-Davis <pbd Op Net>
Cc: Colin Thomas <colin designresources co uk>, gtk-list gnome org
Subject: Re: Pixmap question
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Paul Barton-Davis wrote:

>> I need to develop Display window which can a number of coloured layers.
>> ( the various layers used in IC design).
>> 
>> Where each layer overlaps another, I want to see the correct ANDING of
>> the colours.
>> 
>> I need to be able to repaint with an odd layer removed from display.
>> 
>> I can see that if I have multiple pixmaps (one for each layer to be
>> displayed), but just sending the desired pixmaps to the screen I should 
>> be able to achieve this.
> 
> 
> 1) I believe that no part of X (or GDK) current supports such
>    things. This generally goes by the name "alpha channel", and X
>    doesn't support it. A pixel in a Drawable is either completely
>    transparent or completely opaque (with its own particular color).
> 

The X Render extension should support these types of operations (with 
hardware support, when available). However, you're talking about 
bleeding edge (it only just appeared in XFree86 4.0.2) X calls - no 
support from GTK+, etc. Check out the release notes and link at 
http://www.xfree86.org

Regards,
Tim

------------- End Forwarded Message -------------


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| Colin Thomas. 
| Design Consultant.                             
|                                           
| Email   : colin designresources co uk     
| Tele    : (44) 1234 240562 
| Fax     : (44) 1234 241262               
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|           United Kingdom.                 
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