xf86cmap.c   [plain text]

/*
 * Copyright (c) 1998-2001 by The XFree86 Project, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * Except as contained in this notice, the name of the copyright holder(s)
 * and author(s) shall not be used in advertising or otherwise to promote
 * the sale, use or other dealings in this Software without prior written
 * authorization from the copyright holder(s) and author(s).
 */

#ifdef HAVE_XORG_CONFIG_H
#include <xorg-config.h>
#endif

#if defined(_XOPEN_SOURCE) || defined(sun) && defined(__SVR4)
#include <math.h>
#else
#define _XOPEN_SOURCE   /* to get prototype for pow on some systems */
#include <math.h>
#undef _XOPEN_SOURCE
#endif

#include <X11/X.h>
#include "misc.h"
#include <X11/Xproto.h>
#include "colormapst.h"
#include "scrnintstr.h"

#include "resource.h"

#include "xf86.h"
#include "xf86_OSproc.h"
#include "xf86str.h"
#include "micmap.h"

#ifdef XFreeXDGA
#define _XF86DGA_SERVER_
#include <X11/extensions/xf86dgastr.h>
#include "dgaproc.h"
#endif

#include "xf86cmap.h"

#define SCREEN_PROLOGUE(pScreen, field) ((pScreen)->field = \
    ((CMapScreenPtr)dixLookupPrivate(&(pScreen)->devPrivates, CMapScreenKey))->field)
#define SCREEN_EPILOGUE(pScreen, field, wrapper)\
    ((pScreen)->field = wrapper)

#define LOAD_PALETTE(pmap, index) \
    ((pmap == miInstalledMaps[index]) && \
     ((pScreenPriv->flags & CMAP_LOAD_EVEN_IF_OFFSCREEN) || \
      xf86Screens[index]->vtSema || pScreenPriv->isDGAmode))


typedef struct _CMapLink {
  ColormapPtr		cmap;
  struct _CMapLink	*next;
} CMapLink, *CMapLinkPtr;

typedef struct {
  ScrnInfoPtr			pScrn;
  CloseScreenProcPtr		CloseScreen;
  CreateColormapProcPtr 	CreateColormap;
  DestroyColormapProcPtr	DestroyColormap;
  InstallColormapProcPtr	InstallColormap;
  StoreColorsProcPtr		StoreColors;
  Bool				(*EnterVT)(int, int);
  Bool				(*SwitchMode)(int, DisplayModePtr, int);
  int				(*SetDGAMode)(int, int, DGADevicePtr);
  int				maxColors;
  int				sigRGBbits;
  int				gammaElements;
  LOCO				*gamma;
  int				*PreAllocIndices;
  CMapLinkPtr			maps;
  unsigned int			flags;
  Bool				isDGAmode;
} CMapScreenRec, *CMapScreenPtr;

typedef struct {
  int		numColors;
  LOCO		*colors;
  Bool		recalculate;
  int		overscan;
} CMapColormapRec, *CMapColormapPtr;

static int CMapScreenKeyIndex;
static DevPrivateKey CMapScreenKey;
static int CMapColormapKeyIndex;
static DevPrivateKey CMapColormapKey = &CMapColormapKeyIndex;

static void CMapInstallColormap(ColormapPtr);
static void CMapStoreColors(ColormapPtr, int, xColorItem *);
static Bool CMapCloseScreen (int, ScreenPtr);
static Bool CMapCreateColormap (ColormapPtr);
static void CMapDestroyColormap (ColormapPtr);

static Bool CMapEnterVT(int, int);
static Bool CMapSwitchMode(int, DisplayModePtr, int);
static int  CMapSetDGAMode(int, int, DGADevicePtr);
static int  CMapChangeGamma(int, Gamma);

static void ComputeGamma(CMapScreenPtr);
static Bool CMapAllocateColormapPrivate(ColormapPtr);
static void CMapRefreshColors(ColormapPtr, int, int*);
static void CMapSetOverscan(ColormapPtr, int, int *);
static void CMapReinstallMap(ColormapPtr);
static void CMapUnwrapScreen(ScreenPtr pScreen);



_X_EXPORT Bool xf86HandleColormaps(
    ScreenPtr pScreen,
    int maxColors,
    int sigRGBbits,
    xf86LoadPaletteProc *loadPalette,
    xf86SetOverscanProc *setOverscan,
    unsigned int flags
){
    ScrnInfoPtr pScrn = xf86Screens[pScreen->myNum];
    ColormapPtr pDefMap = NULL;
    CMapScreenPtr pScreenPriv;  
    LOCO *gamma; 
    int *indices; 
    int elements;

    if(!maxColors || !sigRGBbits || !loadPalette)
	return FALSE;

    CMapScreenKey = &CMapScreenKeyIndex;

    elements = 1 << sigRGBbits;

    if(!(gamma = xalloc(elements * sizeof(LOCO))))
    	return FALSE;

    if(!(indices = xalloc(maxColors * sizeof(int)))) {
	xfree(gamma);
	return FALSE;
    }
      
    if(!(pScreenPriv = xalloc(sizeof(CMapScreenRec)))) {
	xfree(gamma);
	xfree(indices);
	return FALSE;     
    }

    dixSetPrivate(&pScreen->devPrivates, CMapScreenKey, pScreenPriv);
     
    pScreenPriv->CloseScreen = pScreen->CloseScreen;
    pScreenPriv->CreateColormap = pScreen->CreateColormap;
    pScreenPriv->DestroyColormap = pScreen->DestroyColormap;
    pScreenPriv->InstallColormap = pScreen->InstallColormap;
    pScreenPriv->StoreColors = pScreen->StoreColors;
    pScreen->CloseScreen = CMapCloseScreen;
    pScreen->CreateColormap = CMapCreateColormap;
    pScreen->DestroyColormap = CMapDestroyColormap;
    pScreen->InstallColormap = CMapInstallColormap;
    pScreen->StoreColors = CMapStoreColors;

    pScreenPriv->pScrn = pScrn;
    pScrn->LoadPalette = loadPalette;
    pScrn->SetOverscan = setOverscan;
    pScreenPriv->maxColors = maxColors;
    pScreenPriv->sigRGBbits = sigRGBbits;
    pScreenPriv->gammaElements = elements;
    pScreenPriv->gamma = gamma;
    pScreenPriv->PreAllocIndices = indices;
    pScreenPriv->maps = NULL;
    pScreenPriv->flags = flags;
    pScreenPriv->isDGAmode = FALSE;

    pScreenPriv->EnterVT = pScrn->EnterVT;
    pScreenPriv->SwitchMode = pScrn->SwitchMode;
    pScreenPriv->SetDGAMode = pScrn->SetDGAMode;    

    if (!(flags & CMAP_LOAD_EVEN_IF_OFFSCREEN)) {
	pScrn->EnterVT = CMapEnterVT;
	if ((flags & CMAP_RELOAD_ON_MODE_SWITCH) && pScrn->SwitchMode) 
	    pScrn->SwitchMode = CMapSwitchMode;
    }
#ifdef XFreeXDGA
    pScrn->SetDGAMode = CMapSetDGAMode;
#endif
    pScrn->ChangeGamma = CMapChangeGamma;
 
    ComputeGamma(pScreenPriv);

    /* get the default map */

    pDefMap = (ColormapPtr) LookupIDByType(pScreen->defColormap, RT_COLORMAP);
    
    if(!CMapAllocateColormapPrivate(pDefMap)) {
        CMapUnwrapScreen(pScreen);
	return FALSE;
    }

    /* Force the initial map to be loaded */
    miInstalledMaps[pScreen->myNum] = NULL;
    CMapInstallColormap(pDefMap);
    return TRUE;
}


/**** Screen functions ****/


static Bool
CMapCloseScreen (int i, ScreenPtr pScreen)
{
    CMapUnwrapScreen(pScreen);

    return (*pScreen->CloseScreen) (i, pScreen);
}

static Bool
CMapColormapUseMax(VisualPtr pVisual, CMapScreenPtr pScreenPriv)
{
    if (pVisual->nplanes > 16)
        return TRUE;
    return ((1 << pVisual->nplanes) > pScreenPriv->maxColors);
}

static Bool
CMapAllocateColormapPrivate(ColormapPtr pmap)
{
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pmap->pScreen->devPrivates, CMapScreenKey);
    CMapColormapPtr pColPriv;
    CMapLinkPtr pLink;
    int numColors;
    LOCO *colors;

    if (CMapColormapUseMax(pmap->pVisual, pScreenPriv))
	numColors = pmap->pVisual->ColormapEntries;
    else 
	numColors = 1 << pmap->pVisual->nplanes; 

    if(!(colors = xalloc(numColors * sizeof(LOCO))))
	return FALSE;

    if(!(pColPriv = xalloc(sizeof(CMapColormapRec)))) {
	xfree(colors);
	return FALSE;
    }	

    dixSetPrivate(&pmap->devPrivates, CMapColormapKey, pColPriv);
 
    pColPriv->numColors = numColors;
    pColPriv->colors = colors;
    pColPriv->recalculate = TRUE;
    pColPriv->overscan = -1;

    /* add map to list */
    pLink = xalloc(sizeof(CMapLink));
    if(pLink) {
	pLink->cmap = pmap;
	pLink->next = pScreenPriv->maps;
	pScreenPriv->maps = pLink;
    }

    return TRUE;
}

static Bool 
CMapCreateColormap (ColormapPtr pmap)
{
    ScreenPtr pScreen = pmap->pScreen;
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pScreen->devPrivates, CMapScreenKey);
    Bool ret = FALSE;

    pScreen->CreateColormap = pScreenPriv->CreateColormap;
    if((*pScreen->CreateColormap)(pmap)) { 
	if(CMapAllocateColormapPrivate(pmap)) 
	   ret = TRUE;
    }
    pScreen->CreateColormap = CMapCreateColormap;

    return ret;
}

static void
CMapDestroyColormap (ColormapPtr cmap)
{
    ScreenPtr pScreen = cmap->pScreen;
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pScreen->devPrivates, CMapScreenKey);
    CMapColormapPtr pColPriv = (CMapColormapPtr)dixLookupPrivate(
	&cmap->devPrivates, CMapColormapKey);
    CMapLinkPtr prevLink = NULL, pLink = pScreenPriv->maps;

    if(pColPriv) {
	if(pColPriv->colors) xfree(pColPriv->colors);
	xfree(pColPriv);
    }
   
    /* remove map from list */
    while(pLink) {
	if(pLink->cmap == cmap) {
	   if(prevLink)
		prevLink->next = pLink->next;
	   else
		pScreenPriv->maps = pLink->next;
	   xfree(pLink);
	   break;
	}
	prevLink = pLink;
	pLink = pLink->next;
    }

    if(pScreenPriv->DestroyColormap) {
    	pScreen->DestroyColormap = pScreenPriv->DestroyColormap;
	(*pScreen->DestroyColormap)(cmap);
    	pScreen->DestroyColormap = CMapDestroyColormap;
    }
}



static void
CMapStoreColors(
     ColormapPtr	pmap,
     int		ndef,
     xColorItem	        *pdefs
){
    ScreenPtr 	pScreen = pmap->pScreen;
    VisualPtr	pVisual = pmap->pVisual;
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pScreen->devPrivates, CMapScreenKey);
    int 	*indices = pScreenPriv->PreAllocIndices;
    int		num = ndef;

    /* At the moment this isn't necessary since there's nobody below us */
    pScreen->StoreColors = pScreenPriv->StoreColors;
    (*pScreen->StoreColors)(pmap, ndef, pdefs); 
    pScreen->StoreColors = CMapStoreColors;

    /* should never get here for these */
    if(	(pVisual->class == TrueColor) ||
	(pVisual->class == StaticColor) ||
	(pVisual->class == StaticGray))
	return;

    if(pVisual->class == DirectColor) {
	CMapColormapPtr pColPriv = (CMapColormapPtr)dixLookupPrivate(
	    &pmap->devPrivates, CMapColormapKey);
	int i;

	if (CMapColormapUseMax(pVisual, pScreenPriv)) {
	    int index;

	    num = 0;
	    while(ndef--) {
		if(pdefs[ndef].flags & DoRed) {
		    index = (pdefs[ndef].pixel & pVisual->redMask) >>
					pVisual->offsetRed;
		    i = num;
		    while(i--)
			if(indices[i] == index) break;
		    if(i == -1)
			indices[num++] = index;
		}
		if(pdefs[ndef].flags & DoGreen) {
		    index = (pdefs[ndef].pixel & pVisual->greenMask) >>
					pVisual->offsetGreen;
		    i = num;
		    while(i--)
			if(indices[i] == index) break;
		    if(i == -1)
			indices[num++] = index;
		}
		if(pdefs[ndef].flags & DoBlue) {
		    index = (pdefs[ndef].pixel & pVisual->blueMask) >>
					pVisual->offsetBlue;
		    i = num;
		    while(i--)
			if(indices[i] == index) break;
		    if(i == -1)
			indices[num++] = index;
		}
	    }

	} else {
	    /* not really as overkill as it seems */
	    num = pColPriv->numColors;
	    for(i = 0; i < pColPriv->numColors; i++)
		indices[i] = i;
	}
    } else {
	while(ndef--)
	   indices[ndef] = pdefs[ndef].pixel;
    } 

    CMapRefreshColors(pmap, num, indices);
}


static void
CMapInstallColormap(ColormapPtr pmap)
{
    ScreenPtr 	  pScreen = pmap->pScreen;
    int		  index = pScreen->myNum;
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pScreen->devPrivates, CMapScreenKey);

    if (pmap == miInstalledMaps[index])
	return;

    pScreen->InstallColormap = pScreenPriv->InstallColormap;
    (*pScreen->InstallColormap)(pmap);
    pScreen->InstallColormap = CMapInstallColormap;

    /* Important. We let the lower layers, namely DGA, 
       overwrite the choice of Colormap to install */
    if (miInstalledMaps[index])
	pmap = miInstalledMaps[index];

    if (!(pScreenPriv->flags & CMAP_PALETTED_TRUECOLOR) &&
	 (pmap->pVisual->class == TrueColor) &&
	 CMapColormapUseMax(pmap->pVisual, pScreenPriv))
	return;

    if(LOAD_PALETTE(pmap, index))
	CMapReinstallMap(pmap);
}


/**** ScrnInfoRec functions ****/

static Bool 
CMapEnterVT(int index, int flags)
{
    ScreenPtr pScreen = screenInfo.screens[index];
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pScreen->devPrivates, CMapScreenKey);

    if((*pScreenPriv->EnterVT)(index, flags)) {
	if(miInstalledMaps[index])
	    CMapReinstallMap(miInstalledMaps[index]);
	return TRUE;
    }
    return FALSE;
}


static Bool 
CMapSwitchMode(int index, DisplayModePtr mode, int flags)
{
    ScreenPtr pScreen = screenInfo.screens[index];
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pScreen->devPrivates, CMapScreenKey);

    if((*pScreenPriv->SwitchMode)(index, mode, flags)) {
	if(miInstalledMaps[index])
	    CMapReinstallMap(miInstalledMaps[index]);
	return TRUE;
    }
    return FALSE;
}

#ifdef XFreeXDGA
static int  
CMapSetDGAMode(int index, int num, DGADevicePtr dev)
{
    ScreenPtr pScreen = screenInfo.screens[index];
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pScreen->devPrivates, CMapScreenKey);
    int ret;

    ret = (*pScreenPriv->SetDGAMode)(index, num, dev);

    pScreenPriv->isDGAmode = DGAActive(index);

    if(!pScreenPriv->isDGAmode && miInstalledMaps[index] 
         && xf86Screens[pScreen->myNum]->vtSema)
	CMapReinstallMap(miInstalledMaps[index]);

    return ret;
}
#endif


/**** Utilities ****/

static void
CMapReinstallMap(ColormapPtr pmap)
{
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pmap->pScreen->devPrivates, CMapScreenKey);
    CMapColormapPtr cmapPriv = (CMapColormapPtr)dixLookupPrivate(
	&pmap->devPrivates, CMapColormapKey);
    ScrnInfoPtr pScrn = xf86Screens[pmap->pScreen->myNum];
    int i = cmapPriv->numColors;
    int *indices = pScreenPriv->PreAllocIndices;

    while(i--)
	indices[i] = i;
   
    if(cmapPriv->recalculate)
	CMapRefreshColors(pmap, cmapPriv->numColors, indices);
    else {
	(*pScrn->LoadPalette)(pScrn, cmapPriv->numColors,
 			indices, cmapPriv->colors, pmap->pVisual);
	if (pScrn->SetOverscan) {
#ifdef DEBUGOVERSCAN
	    ErrorF("SetOverscan() called from CMapReinstallMap\n");
#endif
	    pScrn->SetOverscan(pScrn, cmapPriv->overscan);
	}
    }

    cmapPriv->recalculate = FALSE;
}


static void 
CMapRefreshColors(ColormapPtr pmap, int defs, int* indices)
{
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pmap->pScreen->devPrivates, CMapScreenKey);
    CMapColormapPtr pColPriv = (CMapColormapPtr)dixLookupPrivate(
	&pmap->devPrivates, CMapColormapKey);
    VisualPtr pVisual = pmap->pVisual;
    ScrnInfoPtr pScrn = xf86Screens[pmap->pScreen->myNum];
    int numColors, i;
    LOCO *gamma, *colors;
    EntryPtr entry;
    int reds, greens, blues, maxValue, index, shift;

    numColors = pColPriv->numColors;
    shift = 16 - pScreenPriv->sigRGBbits;
    maxValue = (1 << pScreenPriv->sigRGBbits) - 1;
    gamma = pScreenPriv->gamma;
    colors = pColPriv->colors;

    reds = pVisual->redMask >> pVisual->offsetRed;
    greens = pVisual->greenMask >> pVisual->offsetGreen;
    blues = pVisual->blueMask >> pVisual->offsetBlue;

    switch(pVisual->class) {
    case StaticGray:
	for(i = 0; i <= numColors - 1; i++) { 
	    index = i * maxValue / numColors;
	    colors[i].red   = gamma[index].red;
	    colors[i].green = gamma[index].green;
	    colors[i].blue  = gamma[index].blue;
	}
	break;
    case TrueColor:
        if (CMapColormapUseMax(pVisual, pScreenPriv)) {
	    for(i = 0; i <= reds; i++) 
		colors[i].red   = gamma[i * maxValue / reds].red;
	    for(i = 0; i <= greens; i++) 
		colors[i].green = gamma[i * maxValue / greens].green;
	    for(i = 0; i <= blues; i++) 
		colors[i].blue  = gamma[i * maxValue / blues].blue;
	    break;
	}
	for(i = 0; i < numColors; i++) {
	    colors[i].red   = gamma[((i >> pVisual->offsetRed) & reds) * 
					maxValue / reds].red;
	    colors[i].green = gamma[((i >> pVisual->offsetGreen) & greens) * 
					maxValue / greens].green;
	    colors[i].blue  = gamma[((i >> pVisual->offsetBlue) & blues) * 
					maxValue / blues].blue;
	}
	break;
    case StaticColor:
    case PseudoColor:
    case GrayScale:
	for(i = 0; i < defs; i++) { 
	    index = indices[i];
	    entry = (EntryPtr)&pmap->red[index];

	    if(entry->fShared) {
		colors[index].red = 
			gamma[entry->co.shco.red->color >> shift].red;
		colors[index].green = 
			gamma[entry->co.shco.green->color >> shift].green;
		colors[index].blue = 
			gamma[entry->co.shco.blue->color >> shift].blue;
	    } else {
		colors[index].red   = 
				gamma[entry->co.local.red >> shift].red;
		colors[index].green = 
				gamma[entry->co.local.green >> shift].green;
		colors[index].blue  = 
				gamma[entry->co.local.blue >> shift].blue;
	    }
	}
	break;
    case DirectColor:
        if (CMapColormapUseMax(pVisual, pScreenPriv)) {
	    for(i = 0; i < defs; i++) { 
		index = indices[i];
		if(index <= reds)
		    colors[index].red   = 
			gamma[pmap->red[index].co.local.red >> shift].red;
		if(index <= greens)
		    colors[index].green = 
			gamma[pmap->green[index].co.local.green >> shift].green;
		if(index <= blues)
		    colors[index].blue   = 
			gamma[pmap->blue[index].co.local.blue >> shift].blue;

	    }
	    break;
	}
	for(i = 0; i < defs; i++) { 
	    index = indices[i];

	    colors[index].red   = gamma[pmap->red[
				(index >> pVisual->offsetRed) & reds
				].co.local.red >> shift].red;
	    colors[index].green = gamma[pmap->green[
				(index >> pVisual->offsetGreen) & greens
				].co.local.green >> shift].green;
	    colors[index].blue  = gamma[pmap->blue[
				(index >> pVisual->offsetBlue) & blues
				].co.local.blue >> shift].blue;
	}
	break;
    }


    if(LOAD_PALETTE(pmap, pmap->pScreen->myNum))
	(*pScrn->LoadPalette)(pScreenPriv->pScrn, defs, indices,
 					colors, pmap->pVisual);

    if (pScrn->SetOverscan)
	CMapSetOverscan(pmap, defs, indices);

}

static Bool
CMapCompareColors(LOCO *color1, LOCO *color2)
{
    /* return TRUE if the color1 is "closer" to black than color2 */
#ifdef DEBUGOVERSCAN
    ErrorF("#%02x%02x%02x vs #%02x%02x%02x (%d vs %d)\n",
	color1->red, color1->green, color1->blue,
	color2->red, color2->green, color2->blue,
	color1->red + color1->green + color1->blue,
	color2->red + color2->green + color2->blue);
#endif
    return (color1->red + color1->green + color1->blue <
	    color2->red + color2->green + color2->blue);
}

static void
CMapSetOverscan(ColormapPtr pmap, int defs, int *indices)
{
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pmap->pScreen->devPrivates, CMapScreenKey);
    CMapColormapPtr pColPriv = (CMapColormapPtr)dixLookupPrivate(
	&pmap->devPrivates, CMapColormapKey);
    ScrnInfoPtr pScrn = xf86Screens[pmap->pScreen->myNum];
    VisualPtr pVisual = pmap->pVisual;
    int i;
    LOCO *colors;
    int index;
    Bool newOverscan = FALSE;
    int overscan, tmpOverscan;

    colors = pColPriv->colors;
    overscan = pColPriv->overscan;

    /*
     * Search for a new overscan index in the following cases:
     *
     *   - The index hasn't yet been initialised.  In this case search
     *     for an index that is black or a close match to black.
     *
     *   - The colour of the old index is changed.  In this case search
     *     all indices for a black or close match to black.
     *
     *   - The colour of the old index wasn't black.  In this case only
     *     search the indices that were changed for a better match to black.
     */

    switch (pVisual->class) {
    case StaticGray:
    case TrueColor:
	/* Should only come here once.  Initialise the overscan index to 0 */
	overscan = 0;
	newOverscan = TRUE;
	break;
    case StaticColor:
	/*
         * Only come here once, but search for the overscan in the same way
         * as for the other cases.
	 */
    case DirectColor:
    case PseudoColor:
    case GrayScale:
	if (overscan < 0 || overscan > pScreenPriv->maxColors - 1) {
	    /* Uninitialised */
	    newOverscan = TRUE;
	} else {
	    /* Check if the overscan was changed */
	    for (i = 0; i < defs; i++) {
		index = indices[i];
		if (index == overscan) {
		    newOverscan = TRUE;
		    break;
		}
	    }
	}
	if (newOverscan) {
	    /* The overscan is either uninitialised or it has been changed */

	    if (overscan < 0 || overscan > pScreenPriv->maxColors - 1)
		tmpOverscan = pScreenPriv->maxColors - 1;
	    else
		tmpOverscan = overscan;

	    /* search all entries for a close match to black */
	    for (i = pScreenPriv->maxColors - 1; i >= 0; i--) {
		if (colors[i].red == 0 && colors[i].green == 0 &&
		    colors[i].blue == 0) {
		    overscan = i;
#ifdef DEBUGOVERSCAN
		    ErrorF("Black found at index 0x%02x\n", i);
#endif
		    break;
		} else {
#ifdef DEBUGOVERSCAN
		    ErrorF("0x%02x: ", i);
#endif
		    if (CMapCompareColors(&colors[i], &colors[tmpOverscan])) {
			tmpOverscan = i;
#ifdef DEBUGOVERSCAN
			ErrorF("possible \"Black\" at index 0x%02x\n", i);
#endif
		    }
		}
	    }
	    if (i < 0)
		overscan = tmpOverscan;
	} else {
	    /* Check of the old overscan wasn't black */
	    if (colors[overscan].red != 0 || colors[overscan].green != 0 ||
		colors[overscan].blue != 0) {
		int oldOverscan = tmpOverscan = overscan;
		/* See of there is now a better match */
		for (i = 0; i < defs; i++) {
		    index = indices[i];
		    if (colors[index].red == 0 && colors[index].green == 0 &&
			colors[index].blue == 0) {
			overscan = index;
#ifdef DEBUGOVERSCAN
			ErrorF("Black found at index 0x%02x\n", index);
#endif
			break;
		    } else {
#ifdef DEBUGOVERSCAN
			ErrorF("0x%02x: ", index);
#endif
			if (CMapCompareColors(&colors[index],
					      &colors[tmpOverscan])) {
			    tmpOverscan = index;
#ifdef DEBUGOVERSCAN
			    ErrorF("possible \"Black\" at index 0x%02x\n",
				   index);
#endif
			}
		    }
		}
		if (i == defs)
		    overscan = tmpOverscan;
		if (overscan != oldOverscan)
		    newOverscan = TRUE;
	    }
	}
	break;
    }
    if (newOverscan) {
	pColPriv->overscan = overscan;
	if (LOAD_PALETTE(pmap, pmap->pScreen->myNum)) {
#ifdef DEBUGOVERSCAN
	    ErrorF("SetOverscan() called from CmapSetOverscan\n");
#endif
	    pScrn->SetOverscan(pScreenPriv->pScrn, overscan);
	}
    }
}

static void
CMapUnwrapScreen(ScreenPtr pScreen)
{
    CMapScreenPtr pScreenPriv = (CMapScreenPtr)dixLookupPrivate(
	&pScreen->devPrivates, CMapScreenKey);
    ScrnInfoPtr pScrn = xf86Screens[pScreen->myNum];

    pScreen->CloseScreen = pScreenPriv->CloseScreen;
    pScreen->CreateColormap = pScreenPriv->CreateColormap;
    pScreen->DestroyColormap = pScreenPriv->DestroyColormap;
    pScreen->InstallColormap = pScreenPriv->InstallColormap;
    pScreen->StoreColors = pScreenPriv->StoreColors;

    pScrn->EnterVT = pScreenPriv->EnterVT; 
    pScrn->SwitchMode = pScreenPriv->SwitchMode; 
    pScrn->SetDGAMode = pScreenPriv->SetDGAMode; 

    xfree(pScreenPriv->gamma);
    xfree(pScreenPriv->PreAllocIndices);
    xfree(pScreenPriv);
}


static void 
ComputeGamma(CMapScreenPtr priv)
{
    int elements = priv->gammaElements - 1;
    double RedGamma, GreenGamma, BlueGamma;
    int i;

#ifndef DONT_CHECK_GAMMA
    /* This check is to catch drivers that are not initialising pScrn->gamma */
    if (priv->pScrn->gamma.red < GAMMA_MIN ||
	priv->pScrn->gamma.red > GAMMA_MAX ||
	priv->pScrn->gamma.green < GAMMA_MIN ||
	priv->pScrn->gamma.green > GAMMA_MAX ||
	priv->pScrn->gamma.blue < GAMMA_MIN ||
	priv->pScrn->gamma.blue > GAMMA_MAX) {

	xf86DrvMsgVerb(priv->pScrn->scrnIndex, X_WARNING, 0,
	    "The %s driver didn't call xf86SetGamma() to initialise\n"
	    "\tthe gamma values.\n", priv->pScrn->driverName);
	xf86DrvMsgVerb(priv->pScrn->scrnIndex, X_WARNING, 0,
	    "PLEASE FIX THE `%s' DRIVER!\n", priv->pScrn->driverName);
	priv->pScrn->gamma.red = 1.0;
	priv->pScrn->gamma.green = 1.0;
	priv->pScrn->gamma.blue = 1.0;
    }
#endif

    RedGamma = 1.0 / (double)priv->pScrn->gamma.red;
    GreenGamma = 1.0 / (double)priv->pScrn->gamma.green;
    BlueGamma = 1.0 / (double)priv->pScrn->gamma.blue;
    
    for(i = 0; i <= elements; i++) {
	if(RedGamma == 1.0)  
	    priv->gamma[i].red = i;
	else
	    priv->gamma[i].red = (CARD16)(pow((double)i/(double)elements,
			RedGamma) * (double)elements + 0.5);

	if(GreenGamma == 1.0)  
	    priv->gamma[i].green = i;
	else
	    priv->gamma[i].green = (CARD16)(pow((double)i/(double)elements,
			GreenGamma) * (double)elements + 0.5);

	if(BlueGamma == 1.0)  
	    priv->gamma[i].blue = i;
	else
	    priv->gamma[i].blue = (CARD16)(pow((double)i/(double)elements,
			BlueGamma) * (double)elements + 0.5);
    }
}


int
CMapChangeGamma(
   int index,
   Gamma gamma
){
    ScrnInfoPtr pScrn = xf86Screens[index];
    ScreenPtr pScreen = pScrn->pScreen;
    CMapColormapPtr pColPriv;
    CMapScreenPtr pScreenPriv;
    CMapLinkPtr pLink;
        
    /* Is this sufficient checking ? */
    if(CMapScreenKey == NULL)
	return BadImplementation;

    pScreenPriv = (CMapScreenPtr)dixLookupPrivate(&pScreen->devPrivates,
						  CMapScreenKey);
    if(!pScreenPriv)
	return BadImplementation;
 
    if (gamma.red < GAMMA_MIN || gamma.red > GAMMA_MAX ||
	gamma.green < GAMMA_MIN || gamma.green > GAMMA_MAX ||
	gamma.blue < GAMMA_MIN || gamma.blue > GAMMA_MAX)
	return BadValue;

    pScrn->gamma.red = gamma.red;
    pScrn->gamma.green = gamma.green;
    pScrn->gamma.blue = gamma.blue;

    ComputeGamma(pScreenPriv);

    /* mark all colormaps on this screen */
    pLink = pScreenPriv->maps;
    while(pLink) {
    	pColPriv = (CMapColormapPtr)dixLookupPrivate(&pLink->cmap->devPrivates,
						     CMapColormapKey);
	pColPriv->recalculate = TRUE;
	pLink = pLink->next;
    }

    if(miInstalledMaps[pScreen->myNum] && 
       ((pScreenPriv->flags & CMAP_LOAD_EVEN_IF_OFFSCREEN) ||
	pScrn->vtSema || pScreenPriv->isDGAmode)) {
	ColormapPtr pMap = miInstalledMaps[pScreen->myNum];

	if (!(pScreenPriv->flags & CMAP_PALETTED_TRUECOLOR) &&
	    (pMap->pVisual->class == TrueColor) &&
	    CMapColormapUseMax(pMap->pVisual, pScreenPriv)) {

	    /* if the current map doesn't have a palette look
		for another map to change the gamma on. */

	    pLink = pScreenPriv->maps;
	    while(pLink) {
		if(pLink->cmap->pVisual->class == PseudoColor)
		    break;
		pLink = pLink->next;
	    }

	    if(pLink) {
		/* need to trick CMapRefreshColors() into thinking 
		   this is the currently installed map */
		miInstalledMaps[pScreen->myNum] = pLink->cmap;
		CMapReinstallMap(pLink->cmap);
		miInstalledMaps[pScreen->myNum] = pMap;
	    }
	} else
	    CMapReinstallMap(pMap);
    }

    return Success;
}


static void
ComputeGammaRamp (
    CMapScreenPtr priv,
    unsigned short *red,
    unsigned short *green,
    unsigned short *blue
){
    int elements = priv->gammaElements;
    LOCO *entry = priv->gamma;
    int shift = 16 - priv->sigRGBbits;

    while(elements--) {
	entry->red = *(red++) >> shift;
	entry->green = *(green++) >> shift;
	entry->blue = *(blue++) >> shift;
	entry++;
    }
}

_X_EXPORT int
xf86ChangeGammaRamp(
   ScreenPtr pScreen,
   int size,
   unsigned short *red, 
   unsigned short *green,
   unsigned short *blue
){
    ScrnInfoPtr pScrn = xf86Screens[pScreen->myNum];
    CMapColormapPtr pColPriv;
    CMapScreenPtr pScreenPriv;
    CMapLinkPtr pLink;

    if(CMapScreenKey == NULL)
        return BadImplementation;

    pScreenPriv = (CMapScreenPtr)dixLookupPrivate(&pScreen->devPrivates,
						  CMapScreenKey);
    if(!pScreenPriv)
        return BadImplementation;

    if(pScreenPriv->gammaElements != size)
	return BadValue;

    ComputeGammaRamp(pScreenPriv, red, green, blue);

    /* mark all colormaps on this screen */
    pLink = pScreenPriv->maps;
    while(pLink) {
    	pColPriv = (CMapColormapPtr)dixLookupPrivate(&pLink->cmap->devPrivates,
						     CMapColormapKey);
        pColPriv->recalculate = TRUE;
        pLink = pLink->next;
    }

    if(miInstalledMaps[pScreen->myNum] &&
       ((pScreenPriv->flags & CMAP_LOAD_EVEN_IF_OFFSCREEN) ||
        pScrn->vtSema || pScreenPriv->isDGAmode)) {
        ColormapPtr pMap = miInstalledMaps[pScreen->myNum];

        if (!(pScreenPriv->flags & CMAP_PALETTED_TRUECOLOR) &&
            (pMap->pVisual->class == TrueColor) &&
	    CMapColormapUseMax(pMap->pVisual, pScreenPriv)) {

            /* if the current map doesn't have a palette look
                for another map to change the gamma on. */

            pLink = pScreenPriv->maps;
            while(pLink) {
                if(pLink->cmap->pVisual->class == PseudoColor)
                    break;
                pLink = pLink->next;
            }

            if(pLink) {
                /* need to trick CMapRefreshColors() into thinking
                   this is the currently installed map */
                miInstalledMaps[pScreen->myNum] = pLink->cmap;
                CMapReinstallMap(pLink->cmap);
                miInstalledMaps[pScreen->myNum] = pMap;
            }
        } else
            CMapReinstallMap(pMap);
    }

    return Success;
}

_X_EXPORT int
xf86GetGammaRampSize(ScreenPtr pScreen)
{
    CMapScreenPtr pScreenPriv;

    if(CMapScreenKey == NULL) return 0;

    pScreenPriv = (CMapScreenPtr)dixLookupPrivate(&pScreen->devPrivates,
						  CMapScreenKey);
    if(!pScreenPriv) return 0;

    return pScreenPriv->gammaElements;
}

_X_EXPORT int
xf86GetGammaRamp(
   ScreenPtr pScreen,
   int size,
   unsigned short *red,
   unsigned short *green,
   unsigned short *blue
){
    CMapScreenPtr pScreenPriv;
    LOCO *entry;
    int shift, sigbits;

    if(CMapScreenKey == NULL) 
	return BadImplementation;

    pScreenPriv = (CMapScreenPtr)dixLookupPrivate(&pScreen->devPrivates,
						  CMapScreenKey);
    if(!pScreenPriv) 
	return BadImplementation;

    if(size > pScreenPriv->gammaElements)
	return BadValue;

    entry = pScreenPriv->gamma;
    sigbits = pScreenPriv->sigRGBbits;

    while(size--) {
	*red = entry->red << (16 - sigbits);
	*green = entry->green << (16 - sigbits);
	*blue = entry->blue << (16 - sigbits);
	shift = sigbits;
	while(shift < 16) {
	    *red |= *red >> shift;
	    *green |= *green >> shift;
	    *blue |= *blue >> shift;
	    shift += sigbits;
	}
	red++; green++; blue++;
        entry++;
    }

    return Success;
}

int
xf86ChangeGamma(
   ScreenPtr pScreen,
   Gamma gamma
){
    ScrnInfoPtr pScrn = xf86Screens[pScreen->myNum];

    if(pScrn->ChangeGamma)
	return (*pScrn->ChangeGamma)(pScreen->myNum, gamma);

    return Success; /* Success? */
}