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Technote 1024

FEBRUARY 1996

This Technote is of interest to developers designing general-purpose applications who want to use palettes for their windows but who don't want to deal with the hassles of setting up a new palette for each and every window.

Although the Palette Manager is documented in the Palette Manager chapter of Inside Macintosh:Advanced Color Imaging , this Technote sheds light on issues that may remain unclear after reading that chapter.

Contents

• Enhancements to the Palette Manager
  
• Summary
  

Application Default Palettes

The application palette feature is especially handy in cases where a color application uses old-style dialogs and alerts because without an application palette, the system will use its own default palette, which may not be the appropriate colors, to define the color environment. Since the system uses the default palette, the color environment may change (will change in 16-color mode) and cause some "cosmic" colors to appear in the active window. Defining a default application palette with two colors, black and white, solves this problem.

If the system needs a palette to define a color environment, it looks in the resource fork of the application for the 'pltt' ID = 0 resource and uses the palette contained therein. If the system cannot find this resource in the application's resource fork, it will use its own default palette (resource 'pltt' ID = 0 in the System file) if present, or, if necessary, it will use the Palette Manager's built-in palette.

Once an application has set its color environment (by calling InitMenus, or InitPalettes) it can find the default palette by calling

GetPalette (WindowRef) -1);

SetPalette ((WindowRef) -1, srcPalette, true); 

Note:

The initialization of the Palette Manager with a call to InitMenus is contrary to the way Inside Macintosh: Advanced Color Imaging, "The Palette Manager" documents it.

One Palette, Many Ports

Although this ability to associate one palette with multiple ports and windows will allow the use of calls like PmForeColor and PmBackColor, calling ActivatePalette with an off-screen port will associate the palette with the port but will not cause any change in the color environment.

An important implication of this feature is that DisposeWindow (DisposWindow) will no longer dispose of the associated palette automatically, since it may be allocated to other ports or windows. The only exception to this behavior is when an application has used GetNewCWindow to create the window, there is a 'pltt' resource with the same ID as the window, and the application has not called GetPalette for the window.

Color Updates

void NSetPalette (WindowPtr dstWindow, PaletteHandle srcPalette, 
					short nCUpdates)

You have more flexibility in setting window updates for your application:

• If you want dstWindow to be updated whenever its color environment changes, set nCUpdates to pmAllUpdates.

• If you are only interested in updates when dstWindow is the active window, set nCUpdates to pmFgUpdates.

• If you are only interested in updates when dstWindow is not the active window, set nCUpdates to pmBkUpdates.

{NSetPalette Update Constants }

pmNoUpdates = 0x8000 {no updates}
pmBkUpdates = 0xA000 {background updates only}
pmFgUpdates = 0xC000 {foreground updates only}
pmAllUpdates = 0xE000 {all updates}

void SetPalette (WindowPtr dstWindow, PaletteHandle srcPalette, 
				Boolean CUpdates)

Important:

The trap words for NSetPalette and SetPalette are identical.

CopyPalette

void CopyPalette (PaletteHandle srcPalette, PaletteHandle dstPalette,
			short srcEntry, short dstEntry, short dstLength); 

CopyPalette does not call ActivatePalette, so the application is free to do a number of palette changes without causing a series of intermediate changes to the color environment; the application should call ActivatePalette after completing all palette changes.

If either of the palette handles are NIL, CopyPalette does nothing.

Summary

Further References

• Inside Macintosh: Advanced Color Imaging , Palette Manager chapter.

Change History

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