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+/* $Xorg: CmapAlloc.c,v 1.4 2001/02/09 02:03:51 xorgcvs Exp $ */
+
+/*
+
+Copyright 1989, 1994, 1998 The Open Group
+
+Permission to use, copy, modify, distribute, and sell this software and its
+documentation for any purpose is hereby granted without fee, provided that
+the above copyright notice appear in all copies and that both that
+copyright notice and this permission notice appear in supporting
+documentation.
+
+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
+OPEN GROUP 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 Open Group 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 Open Group.
+
+*/
+/* $XFree86: xc/lib/Xmu/CmapAlloc.c,v 1.6 2001/01/17 19:42:53 dawes Exp $ */
+
+/*
+ * Author: Donna Converse, MIT X Consortium
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+#include <X11/Xlib.h>
+#include <X11/Xatom.h>
+#include <X11/Xutil.h>
+#include <X11/Xmu/StdCmap.h>
+#include <stdio.h>
+
+#define lowbit(x) ((x) & (~(x) + 1))
+
+/*
+ * Prototypes
+ */
+static void best_allocation(XVisualInfo*, unsigned long*, unsigned long*,
+ unsigned long*);
+static int default_allocation(XVisualInfo*, unsigned long*,
+ unsigned long*, unsigned long*);
+static void gray_allocation(int, unsigned long*, unsigned long*,
+ unsigned long*);
+static int icbrt(int);
+static int icbrt_with_bits(int, int);
+static int icbrt_with_guess(int, int);
+
+/* To determine the best allocation of reds, greens, and blues in a
+ * standard colormap, use XmuGetColormapAllocation.
+ * vinfo specifies visual information for a chosen visual
+ * property specifies one of the standard colormap property names
+ * red_max returns maximum red value
+ * green_max returns maximum green value
+ * blue_max returns maximum blue value
+ *
+ * XmuGetColormapAllocation returns 0 on failure, non-zero on success.
+ * It is assumed that the visual is appropriate for the colormap property.
+ */
+
+Status
+XmuGetColormapAllocation(XVisualInfo *vinfo, Atom property,
+ unsigned long *red_max,
+ unsigned long *green_max,
+ unsigned long *blue_max)
+{
+ Status status = 1;
+
+ if (vinfo->colormap_size <= 2)
+ return 0;
+
+ switch (property)
+ {
+ case XA_RGB_DEFAULT_MAP:
+ status = default_allocation(vinfo, red_max, green_max, blue_max);
+ break;
+ case XA_RGB_BEST_MAP:
+ best_allocation(vinfo, red_max, green_max, blue_max);
+ break;
+ case XA_RGB_GRAY_MAP:
+ gray_allocation(vinfo->colormap_size, red_max, green_max, blue_max);
+ break;
+ case XA_RGB_RED_MAP:
+ *red_max = vinfo->colormap_size - 1;
+ *green_max = *blue_max = 0;
+ break;
+ case XA_RGB_GREEN_MAP:
+ *green_max = vinfo->colormap_size - 1;
+ *red_max = *blue_max = 0;
+ break;
+ case XA_RGB_BLUE_MAP:
+ *blue_max = vinfo->colormap_size - 1;
+ *red_max = *green_max = 0;
+ break;
+ default:
+ status = 0;
+ }
+ return status;
+}
+
+/****************************************************************************/
+/* Determine the appropriate color allocations of a gray scale.
+ *
+ * Keith Packard, MIT X Consortium
+ */
+
+static void
+gray_allocation(int n, unsigned long *red_max, unsigned long *green_max,
+ unsigned long *blue_max)
+{
+ *red_max = (n * 30) / 100;
+ *green_max = (n * 59) / 100;
+ *blue_max = (n * 11) / 100;
+ *green_max += ((n - 1) - (*red_max + *green_max + *blue_max));
+}
+
+/****************************************************************************/
+/* Determine an appropriate color allocation for the RGB_DEFAULT_MAP.
+ * If a map has less than a minimum number of definable entries, we do not
+ * produce an allocation for an RGB_DEFAULT_MAP.
+ *
+ * For 16 planes, the default colormap will have 27 each RGB; for 12 planes,
+ * 12 each. For 8 planes, let n = the number of colormap entries, which may
+ * be 256 or 254. Then, maximum red value = floor(cube_root(n - 125)) - 1.
+ * Maximum green and maximum blue values are identical to maximum red.
+ * This leaves at least 125 cells which clients can allocate.
+ *
+ * Return 0 if an allocation has been determined, non-zero otherwise.
+ */
+
+static int
+default_allocation(XVisualInfo *vinfo, unsigned long *red,
+ unsigned long *green, unsigned long *blue)
+{
+ int ngrays; /* number of gray cells */
+
+ switch (vinfo->class) {
+ case PseudoColor:
+
+ if (vinfo->colormap_size > 65000)
+ /* intended for displays with 16 planes */
+ *red = *green = *blue = (unsigned long) 27;
+ else if (vinfo->colormap_size > 4000)
+ /* intended for displays with 12 planes */
+ *red = *green = *blue = (unsigned long) 12;
+ else if (vinfo->colormap_size < 250)
+ return 0;
+ else
+ /* intended for displays with 8 planes */
+ *red = *green = *blue = (unsigned long)
+ (icbrt(vinfo->colormap_size - 125) - 1);
+ break;
+
+ case DirectColor:
+
+ if (vinfo->colormap_size < 10)
+ return 0;
+ *red = *green = *blue = vinfo->colormap_size / 2 - 1;
+ break;
+
+ case TrueColor:
+
+ *red = vinfo->red_mask / lowbit(vinfo->red_mask);
+ *green = vinfo->green_mask / lowbit(vinfo->green_mask);
+ *blue = vinfo->blue_mask / lowbit(vinfo->blue_mask);
+ break;
+
+ case GrayScale:
+
+ if (vinfo->colormap_size > 65000)
+ ngrays = 4096;
+ else if (vinfo->colormap_size > 4000)
+ ngrays = 512;
+ else if (vinfo->colormap_size < 250)
+ return 0;
+ else
+ ngrays = 12;
+ gray_allocation(ngrays, red, green, blue);
+ break;
+
+ default:
+ return 0;
+ }
+ return 1;
+}
+
+/****************************************************************************/
+/* Determine an appropriate color allocation for the RGB_BEST_MAP.
+ *
+ * For a DirectColor or TrueColor visual, the allocation is determined
+ * by the red_mask, green_mask, and blue_mask members of the visual info.
+ *
+ * Otherwise, if the colormap size is an integral power of 2, determine
+ * the allocation according to the number of bits given to each color,
+ * with green getting more than red, and red more than blue, if there
+ * are to be inequities in the distribution. If the colormap size is
+ * not an integral power of 2, let n = the number of colormap entries.
+ * Then maximum red value = floor(cube_root(n)) - 1;
+ * maximum blue value = floor(cube_root(n)) - 1;
+ * maximum green value = n / ((# red values) * (# blue values)) - 1;
+ * Which, on a GPX, allows for 252 entries in the best map, out of 254
+ * defineable colormap entries.
+ */
+
+static void
+best_allocation(XVisualInfo *vinfo, unsigned long *red, unsigned long *green,
+ unsigned long *blue)
+{
+
+ if (vinfo->class == DirectColor || vinfo->class == TrueColor)
+ {
+ *red = vinfo->red_mask;
+ while ((*red & 01) == 0)
+ *red >>= 1;
+ *green = vinfo->green_mask;
+ while ((*green & 01) == 0)
+ *green >>=1;
+ *blue = vinfo->blue_mask;
+ while ((*blue & 01) == 0)
+ *blue >>= 1;
+ }
+ else
+ {
+ register int bits, n;
+
+ /* Determine n such that n is the least integral power of 2 which is
+ * greater than or equal to the number of entries in the colormap.
+ */
+ n = 1;
+ bits = 0;
+ while (vinfo->colormap_size > n)
+ {
+ n = n << 1;
+ bits++;
+ }
+
+ /* If the number of entries in the colormap is a power of 2, determine
+ * the allocation by "dealing" the bits, first to green, then red, then
+ * blue. If not, find the maximum integral red, green, and blue values
+ * which, when multiplied together, do not exceed the number of
+
+ * colormap entries.
+ */
+ if (n == vinfo->colormap_size)
+ {
+ register int r, g, b;
+ b = bits / 3;
+ g = b + ((bits % 3) ? 1 : 0);
+ r = b + (((bits % 3) == 2) ? 1 : 0);
+ *red = 1 << r;
+ *green = 1 << g;
+ *blue = 1 << b;
+ }
+ else
+ {
+ *red = icbrt_with_bits(vinfo->colormap_size, bits);
+ *blue = *red;
+ *green = (vinfo->colormap_size / ((*red) * (*blue)));
+ }
+ (*red)--;
+ (*green)--;
+ (*blue)--;
+ }
+ return;
+}
+
+/*
+ * integer cube roots by Newton's method
+ *
+ * Stephen Gildea, MIT X Consortium, July 1991
+ */
+
+static int
+icbrt(int a)
+{
+ register int bits = 0;
+ register unsigned n = a;
+
+ while (n)
+ {
+ bits++;
+ n >>= 1;
+ }
+ return icbrt_with_bits(a, bits);
+}
+
+
+static int
+icbrt_with_bits(int a, int bits)
+ /* bits - log 2 of a */
+{
+ return icbrt_with_guess(a, a>>2*bits/3);
+}
+
+#ifdef _X_ROOT_STATS
+int icbrt_loopcount;
+#endif
+
+/* Newton's Method: x_n+1 = x_n - ( f(x_n) / f'(x_n) ) */
+
+/* for cube roots, x^3 - a = 0, x_new = x - 1/3 (x - a/x^2) */
+
+/*
+ * Quick and dirty cube roots. Nothing fancy here, just Newton's method.
+ * Only works for positive integers (since that's all we need).
+ * We actually return floor(cbrt(a)) because that's what we need here, too.
+ */
+
+static int
+icbrt_with_guess(int a, int guess)
+{
+ register int delta;
+
+#ifdef _X_ROOT_STATS
+ icbrt_loopcount = 0;
+#endif
+ if (a <= 0)
+ return 0;
+ if (guess < 1)
+ guess = 1;
+
+ do {
+#ifdef _X_ROOT_STATS
+ icbrt_loopcount++;
+#endif
+ delta = (guess - a/(guess*guess))/3;
+#ifdef _X_ROOT_STATS
+ printf("pass %d: guess=%d, delta=%d\n", icbrt_loopcount, guess, delta);
+#endif
+ guess -= delta;
+ } while (delta != 0);
+
+ if (guess*guess*guess > a)
+ guess--;
+
+ return guess;
+}