Re: Question..

[raster redhat com]

On 11 Sep, Christopher Blizzard shouted:
->  Michael O'Reilly wrote:
->  > 
->  > Some dumb questions:
->  > 
->  > #1. What is a visual? I'm having trouble finding any documentation on
->  > the details of such things.
->  > 
->  
->  A visual is defined in the Xlib programming manual as:
->  
->  "The specifications for color handling for a drawable, including visual
->  class, depth, RGB/Pixel, etc., are collectively referred to as a
->  visual..."  Ok, so what this mess means is that a visual is the
->  representation of two really big things: a visual class and the color
->  depth.
->  
->  The visual class is a description of the hardware.  Basically, the
->  visual class answers two questions:
->  
->  o Is the display grayscale, have a single index for color, or have a
->  decomposed index for color?
->  
->  o Is the colormap read-only or is it read/write?
->  
->  The color depth is something you're probably more familiar with; It's
->  how many colors are supported on a particular display expressed as
->  planes, from 1 to 24, I think.
->  
->  A single display has at least one visual but can also support more than
->  one.
->  
->  > #2. What exactly does the following code do?
->  > 
->  >   gnomefe_depth = gdk_visual_get_best_depth();
->  >   gnomefe_visual = gdk_visual_get_best_with_depth(gnomefe_depth);
->  > 
->  >   gtk_widget_set_default_visual(gnomefe_visual);
->  > 
->  
->  This code basically says "get me the best available depth for my
->  display".  Because displays can handle more than one depth, you want the
->  best one.  Then it says "get the best visual class with said depth." 
->  You want the best visual class for that depth as well.  Remember that
->  you can have different visuals at different depths.  Then it sets the
->  default visual for the toolkit with the information that it has gathered
->  from the previous calls.
->  
->  > #3. Why is this code better/different/worse than the above?
->  > 
->  >   gtk_widget_push_visual(gdk_imlib_get_visual());
->  >   gtk_widget_push_colormap(gdk_imlib_get_colormap());
->  > 
->  
->  Honestly, I don't know.  Raster?  Is there any difference?  Does imlib
->  play any heuristical games to choose a better colormap/visual than the
->  best?

imlib tries to chose the best - but what it thinks the best is might
not be what gdk/gtk thinks... ie sometiems you have 2 visuals of the
same depth - same attributes - under accelerated X one can be hware
gamma corrected, the other, not. I made damn sure imlib does not go
picking these gamma corrected visual cause my god it can look ugly. I
dont knwo abotu gdk -but it may just pick them by accident.. basically
I dont trust anytone to do it for me - i do it myself.

->  --Chris
->  

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