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For VCL components, when running on a palette-based device (typically, a 256-color video mode), Delphi controls automatically support palette realization. That is, if you have a control that has a palette, you can use two methods inherited from TControl to control how Windows accommodates that palette.
Palette support for controls has these two aspects:
Most controls have no need for a palette, but controls that contain "rich color" graphic images (such as the image control) might need to interact with Windows and the screen device driver to ensure the proper appearance of the control. Windows refers to this process as realizing palettes.
Realizing palettes is the process of ensuring that the foremost window uses its full palette, and that windows in the background use as much of their palettes as possible, then map any other colors to the closest available colors in the "real" palette. As windows move in front of one another, Windows continually realizes the palettes.
Note: Delphi itself provides no specific support for creating or maintaining palettes, other than in bitmaps. If you have a palette handle, however, Delphi controls can manage it for you.