Q140588: INFO: Differences Between Full Screen and Windowed Mode Palettes

Article: Q140588
Product(s): Miscellaneous Software Development Kits
Version(s): 1.0
Operating System(s): 
Keyword(s): kbcode
Last Modified: 08-NOV-2001

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The information in this article applies to:

- Microsoft Game Software Development Kit (SDK), version 1.0 
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SUMMARY
=======

You can use the Game SDK function CreatePalette() to create a DIRECTDRAWPALETTE
object for a DirectDraw object.

When in full screen mode, you have control over the complete physical palette
except for the first and last colors, black and white. When in full screen mode,
the first and last entries of the palette will be set to black and white no
matter what the user has specified for these entries.

You can over-ride this feature by specifying DDPCAPS_ALLOW256 in the flags field
for the CreatePalette() call. This flag should be used with caution. On some
video cards, setting palette entry 0 to a color other than black could change
the color of the overscan region, the area of the display tube outside of the
normal video display. When you are running in windowed mode (DDSCL_NORMAL), you
will not be able to change the first and last 10 colors of the physical palette.
This means that when your application goes between the full screen and windowed
modes, you need to change the bits of your bitmap data before you will be able
to display them properly.

MORE INFORMATION
================

Use the following code to create a gray-scale palette with 256 colors:

     for( i=0; i<256; i++ )

     {
     ape[i].peRed   = (BYTE)i;
     ape[i].peGreen = (BYTE)i;
     ape[i].peBlue  = (BYTE)i;
     ape[i].peFlags = 0;
     }

     ddrval = IDirectDraw_CreatePalette(lpDD, DDPCAPS_8BIT, ape,

                                        &ppal, NULL);

Now, when in full screen mode, all 256 colors will be set -- the larger the
palette index number, the brighter the color. All of your offscreen surfaces
(bitmaps) will contain bytes that map to these 256 colors correctly.

However, when you go into windowed mode, your bitmaps will no longer map to the
colors correctly because the 256 palette entries you specified in "ape" are
mapped to the physical palette like a GDI logical palette is mapped to the
physical palette when RealizePalette() is called.

In windowed mode, there is no way to know how your 256 colors will get mapped
unless you use the PC_NOCOLLAPSE flag for your entries. This way, you can ensure
that entry 1 will map to physical entry 10, entry 2 will map to physical entry
11, entry 3 will map to physical entry 12, and so on. You should rely only on
the first 236 colors, though, because there are only 236 free entries in the
physical palette when in windowed mode.

For example, you could call the following code when your application switches to
windowed mode:

     for( i=0; i<256; i++ )

     {
     ape[i].peRed   = (BYTE)i;
     ape[i].peGreen = (BYTE)i;
     ape[i].peBlue  = (BYTE)i;
     ape[i].peFlags = PC_NOCOLLAPSE;
     }

     ddrval = IDirectDraw_CreatePalette(lpDD, DDPCAPS_8BIT, ape,

                                        &ppal, NULL);

Now you need to add 10 to all of the bytes in all of your bitmap data because all
colors are now offset by 10. Once you have done so, your bitmap images will
display correctly.

Additional query words: 1.00 kbinf DDraw DirectDraw Palette

======================================================================
Keywords          : kbcode 
Technology        : kbAudDeveloper _IKkbbogus kbSDKSearch kbSDKGame
Version           : :1.0
Issue type        : kbinfo

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