moving from https://github.com/perberos/mate-desktop-environment

1 files changed, 842 insertions, 0 deletions

diff --git a/src/ui/gradient.c b/src/ui/gradient.c
new file mode 100644
index 00000000..0e739817
--- /dev/null
+++ b/src/ui/gradient.c
@@ -0,0 +1,842 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
+
+/* Marco gradient rendering */
+
+/* 
+ * Copyright (C) 2001 Havoc Pennington, 99% copied from wrlib in
+ * WindowMaker, Copyright (C) 1997-2000 Dan Pascu and Alfredo Kojima
+ * Copyright (C) 2005 Elijah Newren
+ * 
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.  */
+
+#include "gradient.h"
+#include "util.h"
+#include <string.h>
+
+/* This is all Alfredo's and Dan's usual very nice WindowMaker code,
+ * slightly GTK-ized
+ */
+static GdkPixbuf* meta_gradient_create_horizontal       (int             width,
+                                                         int             height,
+                                                         const GdkColor *from,
+                                                         const GdkColor *to);
+static GdkPixbuf* meta_gradient_create_vertical         (int             width,
+                                                         int             height,
+                                                         const GdkColor *from,
+                                                         const GdkColor *to);
+static GdkPixbuf* meta_gradient_create_diagonal         (int             width,
+                                                         int             height,
+                                                         const GdkColor *from,
+                                                         const GdkColor *to);
+static GdkPixbuf* meta_gradient_create_multi_horizontal (int             width,
+                                                         int             height,
+                                                         const GdkColor *colors,
+                                                         int             count);
+static GdkPixbuf* meta_gradient_create_multi_vertical   (int             width,
+                                                         int             height,
+                                                         const GdkColor *colors,
+                                                         int             count);
+static GdkPixbuf* meta_gradient_create_multi_diagonal   (int             width,
+                                                         int             height,
+                                                         const GdkColor *colors,
+                                                         int             count);
+
+
+/* Used as the destroy notification function for gdk_pixbuf_new() */
+static void
+free_buffer (guchar *pixels, gpointer data)
+{
+  g_free (pixels);
+}
+
+static GdkPixbuf*
+blank_pixbuf (int width, int height, gboolean no_padding)
+{
+  guchar *buf;
+  int rowstride;
+
+  g_return_val_if_fail (width > 0, NULL);
+  g_return_val_if_fail (height > 0, NULL);
+
+  if (no_padding)
+    rowstride = width * 3;
+  else
+    /* Always align rows to 32-bit boundaries */  
+    rowstride = 4 * ((3 * width + 3) / 4);
+
+  buf = g_try_malloc (height * rowstride);
+  if (!buf)
+    return NULL;
+
+  return gdk_pixbuf_new_from_data (buf, GDK_COLORSPACE_RGB,
+                                   FALSE, 8,
+                                   width, height, rowstride,
+                                   free_buffer, NULL);
+}
+
+GdkPixbuf*
+meta_gradient_create_simple (int              width,
+                             int              height,
+                             const GdkColor  *from,
+                             const GdkColor  *to,
+                             MetaGradientType style)
+{
+  switch (style)
+    {
+    case META_GRADIENT_HORIZONTAL:
+      return meta_gradient_create_horizontal (width, height,
+                                              from, to);
+    case META_GRADIENT_VERTICAL:
+      return meta_gradient_create_vertical (width, height,
+                                            from, to);
+
+    case META_GRADIENT_DIAGONAL:
+      return meta_gradient_create_diagonal (width, height,
+                                            from, to);
+    case META_GRADIENT_LAST:
+      break;
+    }
+  g_assert_not_reached ();
+  return NULL;
+}
+
+GdkPixbuf*
+meta_gradient_create_multi (int              width,
+                            int              height,
+                            const GdkColor  *colors,
+                            int              n_colors,
+                            MetaGradientType style)
+{
+
+  if (n_colors > 2)
+    {
+      switch (style)
+        {
+        case META_GRADIENT_HORIZONTAL:
+          return meta_gradient_create_multi_horizontal (width, height, colors, n_colors);
+        case META_GRADIENT_VERTICAL:
+          return meta_gradient_create_multi_vertical (width, height, colors, n_colors);
+        case META_GRADIENT_DIAGONAL:
+          return meta_gradient_create_multi_diagonal (width, height, colors, n_colors);
+        case META_GRADIENT_LAST:
+          g_assert_not_reached ();
+          break;
+        }
+    }
+  else if (n_colors > 1)
+    {
+      return meta_gradient_create_simple (width, height, &colors[0], &colors[1],
+                                          style);
+    }
+  else if (n_colors > 0)
+    {
+      return meta_gradient_create_simple (width, height, &colors[0], &colors[0],
+                                          style);
+    }
+  g_assert_not_reached ();
+  return NULL;
+}
+
+/* Interwoven essentially means we have two vertical gradients,
+ * cut into horizontal strips of the given thickness, and then the strips
+ * are alternated. I'm not sure what it's good for, just copied since
+ * WindowMaker had it.
+ */
+GdkPixbuf*
+meta_gradient_create_interwoven (int            width,
+                                 int            height,
+                                 const GdkColor colors1[2],
+                                 int            thickness1,
+                                 const GdkColor colors2[2],
+                                 int            thickness2)
+{
+  
+  int i, j, k, l, ll;
+  long r1, g1, b1, dr1, dg1, db1;
+  long r2, g2, b2, dr2, dg2, db2;
+  GdkPixbuf *pixbuf;
+  unsigned char *ptr;
+  unsigned char *pixels;
+  int rowstride;
+  
+  pixbuf = blank_pixbuf (width, height, FALSE);
+  if (pixbuf == NULL)
+    return NULL;
+    
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  
+  r1 = colors1[0].red<<8;
+  g1 = colors1[0].green<<8;
+  b1 = colors1[0].blue<<8;
+
+  r2 = colors2[0].red<<8;
+  g2 = colors2[0].green<<8;
+  b2 = colors2[0].blue<<8;
+
+  dr1 = ((colors1[1].red-colors1[0].red)<<8)/(int)height;
+  dg1 = ((colors1[1].green-colors1[0].green)<<8)/(int)height;
+  db1 = ((colors1[1].blue-colors1[0].blue)<<8)/(int)height;
+
+  dr2 = ((colors2[1].red-colors2[0].red)<<8)/(int)height;
+  dg2 = ((colors2[1].green-colors2[0].green)<<8)/(int)height;
+  db2 = ((colors2[1].blue-colors2[0].blue)<<8)/(int)height;
+
+  for (i=0,k=0,l=0,ll=thickness1; i<height; i++)
+    {
+      ptr = pixels + i * rowstride;
+      
+      if (k == 0)
+        {
+          ptr[0] = (unsigned char) (r1>>16);
+          ptr[1] = (unsigned char) (g1>>16);
+          ptr[2] = (unsigned char) (b1>>16);
+        }
+      else
+        {
+          ptr[0] = (unsigned char) (r2>>16);
+          ptr[1] = (unsigned char) (g2>>16);
+          ptr[2] = (unsigned char) (b2>>16);
+        }
+
+      for (j=1; j <= width/2; j *= 2)
+        memcpy (&(ptr[j*3]), ptr, j*3);
+      memcpy (&(ptr[j*3]), ptr, (width - j)*3);
+
+      if (++l == ll)
+        {
+          if (k == 0)
+            {
+              k = 1;
+              ll = thickness2;
+            }
+          else
+            {
+              k = 0;
+              ll = thickness1;
+            }
+          l = 0;
+        }
+      r1+=dr1;
+      g1+=dg1;
+      b1+=db1;
+	
+      r2+=dr2;
+      g2+=dg2;
+      b2+=db2;
+    }
+
+  return pixbuf;
+}
+
+/*
+ *----------------------------------------------------------------------
+ * meta_gradient_create_horizontal--
+ * 	Renders a horizontal linear gradient of the specified size in the
+ * GdkPixbuf format with a border of the specified type. 
+ * 
+ * Returns:
+ * 	A 24bit GdkPixbuf with the gradient (no alpha channel).
+ * 
+ * Side effects:
+ * 	None
+ *---------------------------------------------------------------------- 
+ */
+static GdkPixbuf*
+meta_gradient_create_horizontal (int width, int height,
+                                 const GdkColor *from,
+                                 const GdkColor *to)
+{    
+  int i;
+  long r, g, b, dr, dg, db;
+  GdkPixbuf *pixbuf;
+  unsigned char *ptr;
+  unsigned char *pixels;
+  int r0, g0, b0;
+  int rf, gf, bf;
+  int rowstride;
+
+  pixbuf = blank_pixbuf (width, height, FALSE);
+  if (pixbuf == NULL)
+    return NULL;
+    
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  ptr = pixels;
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  
+  r0 = (guchar) (from->red / 256.0);
+  g0 = (guchar) (from->green / 256.0);
+  b0 = (guchar) (from->blue / 256.0);
+  rf = (guchar) (to->red / 256.0);
+  gf = (guchar) (to->green / 256.0);
+  bf = (guchar) (to->blue / 256.0);  
+  
+  r = r0 << 16;
+  g = g0 << 16;
+  b = b0 << 16;
+    
+  dr = ((rf-r0)<<16)/(int)width;
+  dg = ((gf-g0)<<16)/(int)width;
+  db = ((bf-b0)<<16)/(int)width;
+  /* render the first line */
+  for (i=0; i<width; i++)
+    {
+      *(ptr++) = (unsigned char)(r>>16);
+      *(ptr++) = (unsigned char)(g>>16);
+      *(ptr++) = (unsigned char)(b>>16);
+      r += dr;
+      g += dg;
+      b += db;
+    }
+
+  /* copy the first line to the other lines */
+  for (i=1; i<height; i++)
+    {
+      memcpy (&(pixels[i*rowstride]), pixels, rowstride);
+    }
+  return pixbuf;
+}
+
+/*
+ *----------------------------------------------------------------------
+ * meta_gradient_create_vertical--
+ *      Renders a vertical linear gradient of the specified size in the
+ * GdkPixbuf format with a border of the specified type.
+ *
+ * Returns:
+ *      A 24bit GdkPixbuf with the gradient (no alpha channel).
+ *
+ * Side effects:
+ *      None
+ *----------------------------------------------------------------------
+ */
+static GdkPixbuf*
+meta_gradient_create_vertical (int width, int height,
+                               const GdkColor *from,
+                               const GdkColor *to)
+{
+  int i, j;
+  long r, g, b, dr, dg, db;
+  GdkPixbuf *pixbuf;
+  unsigned char *ptr;
+  int r0, g0, b0;
+  int rf, gf, bf;
+  int rowstride;
+  unsigned char *pixels;
+  
+  pixbuf = blank_pixbuf (width, height, FALSE);
+  if (pixbuf == NULL)
+    return NULL;
+    
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  
+  r0 = (guchar) (from->red / 256.0);
+  g0 = (guchar) (from->green / 256.0);
+  b0 = (guchar) (from->blue / 256.0);
+  rf = (guchar) (to->red / 256.0);
+  gf = (guchar) (to->green / 256.0);
+  bf = (guchar) (to->blue / 256.0);
+  
+  r = r0<<16;
+  g = g0<<16;
+  b = b0<<16;
+
+  dr = ((rf-r0)<<16)/(int)height;
+  dg = ((gf-g0)<<16)/(int)height;
+  db = ((bf-b0)<<16)/(int)height;
+
+  for (i=0; i<height; i++)
+    {
+      ptr = pixels + i * rowstride;
+      
+      ptr[0] = (unsigned char)(r>>16);
+      ptr[1] = (unsigned char)(g>>16);
+      ptr[2] = (unsigned char)(b>>16);
+
+      for (j=1; j <= width/2; j *= 2)
+        memcpy (&(ptr[j*3]), ptr, j*3);
+      memcpy (&(ptr[j*3]), ptr, (width - j)*3);
+
+      r+=dr;
+      g+=dg;
+      b+=db;
+    }
+  return pixbuf;
+}
+
+
+/*
+ *----------------------------------------------------------------------
+ * meta_gradient_create_diagonal--
+ *      Renders a diagonal linear gradient of the specified size in the
+ * GdkPixbuf format with a border of the specified type.
+ *
+ * Returns:
+ *      A 24bit GdkPixbuf with the gradient (no alpha channel).
+ *
+ * Side effects:
+ *      None
+ *----------------------------------------------------------------------
+ */
+
+
+static GdkPixbuf*
+meta_gradient_create_diagonal (int width, int height,
+                               const GdkColor *from,
+                               const GdkColor *to)
+{
+  GdkPixbuf *pixbuf, *tmp;
+  int j;
+  float a, offset;
+  unsigned char *ptr;
+  unsigned char *pixels;
+  int rowstride;
+  
+  if (width == 1)
+    return meta_gradient_create_vertical (width, height, from, to);
+  else if (height == 1)
+    return meta_gradient_create_horizontal (width, height, from, to);
+
+  pixbuf = blank_pixbuf (width, height, FALSE);
+  if (pixbuf == NULL)
+    return NULL;
+    
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+
+  tmp = meta_gradient_create_horizontal (2*width-1, 1, from, to);
+  if (!tmp)
+    {
+      g_object_unref (G_OBJECT (pixbuf));
+      return NULL;
+    }
+
+  ptr = gdk_pixbuf_get_pixels (tmp);
+
+  a = ((float)(width - 1))/((float)(height - 1));
+  width = width * 3;
+
+  /* copy the first line to the other lines with corresponding offset */
+  for (j=0, offset=0.0; j<rowstride*height; j += rowstride)
+    {
+      memcpy (&(pixels[j]), &ptr[3*(int)offset], width);
+      offset += a;
+    }
+
+  g_object_unref (G_OBJECT (tmp));
+  return pixbuf;
+}
+
+
+static GdkPixbuf*
+meta_gradient_create_multi_horizontal (int width, int height,
+                                       const GdkColor *colors,
+                                       int count)
+{
+  int i, j, k;
+  long r, g, b, dr, dg, db;
+  GdkPixbuf *pixbuf;
+  unsigned char *ptr;
+  unsigned char *pixels;
+  int width2;  
+  int rowstride;
+  
+  g_return_val_if_fail (count > 2, NULL);
+
+  pixbuf = blank_pixbuf (width, height, FALSE);
+  if (pixbuf == NULL)
+    return NULL;
+    
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  ptr = pixels;
+    
+  if (count > width)
+    count = width;
+    
+  if (count > 1)
+    width2 = width/(count-1);
+  else
+    width2 = width;
+    
+  k = 0;
+
+  r = colors[0].red << 8;
+  g = colors[0].green << 8;
+  b = colors[0].blue << 8;
+
+  /* render the first line */
+  for (i=1; i<count; i++)
+    {
+      dr = ((int)(colors[i].red   - colors[i-1].red)  <<8)/(int)width2;
+      dg = ((int)(colors[i].green - colors[i-1].green)<<8)/(int)width2;
+      db = ((int)(colors[i].blue  - colors[i-1].blue) <<8)/(int)width2;
+      for (j=0; j<width2; j++)
+        {
+          *ptr++ = (unsigned char)(r>>16);
+          *ptr++ = (unsigned char)(g>>16);
+          *ptr++ = (unsigned char)(b>>16);
+          r += dr;
+          g += dg;
+          b += db;
+          k++;
+	}
+      r = colors[i].red << 8;
+      g = colors[i].green << 8;
+      b = colors[i].blue << 8;
+    }
+  for (j=k; j<width; j++)
+    {
+      *ptr++ = (unsigned char)(r>>16);
+      *ptr++ = (unsigned char)(g>>16);
+      *ptr++ = (unsigned char)(b>>16);
+    }
+    
+  /* copy the first line to the other lines */
+  for (i=1; i<height; i++)
+    {
+      memcpy (&(pixels[i*rowstride]), pixels, rowstride);
+    }
+  return pixbuf;
+}
+
+static GdkPixbuf*
+meta_gradient_create_multi_vertical (int width, int height,
+                                     const GdkColor *colors,
+                                     int count)
+{
+  int i, j, k;
+  long r, g, b, dr, dg, db;
+  GdkPixbuf *pixbuf;
+  unsigned char *ptr, *tmp, *pixels;
+  int height2;
+  int x;
+  int rowstride;
+  
+  g_return_val_if_fail (count > 2, NULL);
+
+  pixbuf = blank_pixbuf (width, height, FALSE);
+  if (pixbuf == NULL)
+    return NULL;
+    
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  ptr = pixels;
+    
+  if (count > height)
+    count = height;
+    
+  if (count > 1)
+    height2 = height/(count-1);
+  else
+    height2 = height;
+    
+  k = 0;
+
+  r = colors[0].red << 8;
+  g = colors[0].green << 8;
+  b = colors[0].blue << 8;
+
+  for (i=1; i<count; i++)
+    {
+      dr = ((int)(colors[i].red   - colors[i-1].red)  <<8)/(int)height2;
+      dg = ((int)(colors[i].green - colors[i-1].green)<<8)/(int)height2;
+      db = ((int)(colors[i].blue  - colors[i-1].blue) <<8)/(int)height2;
+
+      for (j=0; j<height2; j++)
+        {
+          ptr[0] = (unsigned char)(r>>16);
+          ptr[1] = (unsigned char)(g>>16);
+          ptr[2] = (unsigned char)(b>>16);
+
+          for (x=1; x <= width/2; x *= 2)
+            memcpy (&(ptr[x*3]), ptr, x*3);
+          memcpy (&(ptr[x*3]), ptr, (width - x)*3);
+
+          ptr += rowstride;
+          
+          r += dr;
+          g += dg;
+          b += db;
+          k++;
+	}
+      r = colors[i].red << 8;
+      g = colors[i].green << 8;
+      b = colors[i].blue << 8;
+    }
+
+  if (k<height)
+    {
+      tmp = ptr;
+
+      ptr[0] = (unsigned char) (r>>16);
+      ptr[1] = (unsigned char) (g>>16);
+      ptr[2] = (unsigned char) (b>>16);
+
+      for (x=1; x <= width/2; x *= 2)
+        memcpy (&(ptr[x*3]), ptr, x*3);
+      memcpy (&(ptr[x*3]), ptr, (width - x)*3);
+
+      ptr += rowstride;
+      
+      for (j=k+1; j<height; j++)
+        {
+          memcpy (ptr, tmp, rowstride);
+          ptr += rowstride;
+        }
+    }
+    
+  return pixbuf;
+}
+
+
+static GdkPixbuf*
+meta_gradient_create_multi_diagonal (int width, int height,
+                                     const GdkColor *colors,
+                                     int count)
+{
+  GdkPixbuf *pixbuf, *tmp;
+  float a, offset;
+  int j;
+  unsigned char *ptr;
+  unsigned char *pixels;
+  int rowstride;
+  
+  g_return_val_if_fail (count > 2, NULL);
+
+  if (width == 1)
+    return meta_gradient_create_multi_vertical (width, height, colors, count);
+  else if (height == 1)
+    return meta_gradient_create_multi_horizontal (width, height, colors, count);
+
+  pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8,
+                           width, height);
+  if (pixbuf == NULL)
+    return NULL;
+    
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  
+  if (count > width)
+    count = width;
+  if (count > height)
+    count = height;
+
+  if (count > 2)
+    tmp = meta_gradient_create_multi_horizontal (2*width-1, 1, colors, count);
+  else
+    /* wrlib multiplies these colors by 256 before passing them in, but
+     * I think it's a bug in wrlib, so changed here. I could be wrong
+     * though, if we notice two-color multi diagonals not working.
+     */
+    tmp = meta_gradient_create_horizontal (2*width-1, 1,
+                                           &colors[0], &colors[1]);
+
+  if (!tmp)
+    {
+      g_object_unref (G_OBJECT (pixbuf));
+      return NULL;
+    }
+  ptr = gdk_pixbuf_get_pixels (tmp);
+
+  a = ((float)(width - 1))/((float)(height - 1));
+  width = width * 3;
+
+  /* copy the first line to the other lines with corresponding offset */
+  for (j=0, offset=0; j<rowstride*height; j += rowstride)
+    {
+      memcpy (&(pixels[j]), &ptr[3*(int)offset], width);
+      offset += a;
+    }
+
+  g_object_unref (G_OBJECT (tmp));
+  return pixbuf;
+}
+
+static void
+simple_multiply_alpha (GdkPixbuf *pixbuf,
+                       guchar     alpha)
+{
+  guchar *pixels;
+  int rowstride;
+  int height;
+  int row;
+
+  g_return_if_fail (GDK_IS_PIXBUF (pixbuf));
+  
+  if (alpha == 255)
+    return;
+  
+  g_assert (gdk_pixbuf_get_has_alpha (pixbuf));
+  
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  height = gdk_pixbuf_get_height (pixbuf);
+
+  row = 0;
+  while (row < height)
+    {
+      guchar *p;
+      guchar *end;
+
+      p = pixels + row * rowstride;
+      end = p + rowstride;
+
+      while (p != end)
+        {
+          p += 3; /* skip RGB */
+
+          /* multiply the two alpha channels. not sure this is right.
+           * but some end cases are that if the pixbuf contains 255,
+           * then it should be modified to contain "alpha"; if the
+           * pixbuf contains 0, it should remain 0.
+           */
+          /* ((*p / 255.0) * (alpha / 255.0)) * 255; */
+          *p = (guchar) (((int) *p * (int) alpha) / (int) 255);
+          
+          ++p; /* skip A */
+        }
+
+      ++row;
+    }
+}
+
+static void
+meta_gradient_add_alpha_horizontal (GdkPixbuf           *pixbuf,
+                                    const unsigned char *alphas,
+                                    int                  n_alphas)
+{
+  int i, j;
+  long a, da;
+  unsigned char *p;
+  unsigned char *pixels;
+  int width2;  
+  int rowstride;
+  int width, height;
+  unsigned char *gradient;
+  unsigned char *gradient_p;
+  unsigned char *gradient_end;
+  
+  g_return_if_fail (n_alphas > 0);
+
+  if (n_alphas == 1)
+    {
+      /* Optimize this */
+      simple_multiply_alpha (pixbuf, alphas[0]);
+      return;
+    }
+  
+  width = gdk_pixbuf_get_width (pixbuf);
+  height = gdk_pixbuf_get_height (pixbuf);
+
+  gradient = g_new (unsigned char, width);
+  gradient_end = gradient + width;
+  
+  if (n_alphas > width)
+    n_alphas = width;
+    
+  if (n_alphas > 1)
+    width2 = width / (n_alphas - 1);
+  else
+    width2 = width;
+    
+  a = alphas[0] << 8;
+  gradient_p = gradient;
+  
+  /* render the gradient into an array */
+  for (i = 1; i < n_alphas; i++)
+    {
+      da = (((int)(alphas[i] - (int) alphas[i-1])) << 8) / (int) width2;
+
+      for (j = 0; j < width2; j++)
+        {
+          *gradient_p++ = (a >> 8);
+          
+          a += da;
+	}
+
+      a = alphas[i] << 8;
+    }
+
+  /* get leftover pixels */
+  while (gradient_p != gradient_end)
+    {
+      *gradient_p++ = a >> 8;
+    }
+    
+  /* Now for each line of the pixbuf, fill in with the gradient */
+  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  rowstride = gdk_pixbuf_get_rowstride (pixbuf);
+  
+  p = pixels;
+  i = 0;
+  while (i < height)
+    {
+      unsigned char *row_end = p + rowstride;
+      gradient_p = gradient;
+
+      p += 3;
+      while (gradient_p != gradient_end)
+        {
+          /* multiply the two alpha channels. not sure this is right.
+           * but some end cases are that if the pixbuf contains 255,
+           * then it should be modified to contain "alpha"; if the
+           * pixbuf contains 0, it should remain 0.
+           */
+          /* ((*p / 255.0) * (alpha / 255.0)) * 255; */
+          *p = (guchar) (((int) *p * (int) *gradient_p) / (int) 255);
+
+          p += 4;
+          ++gradient_p;
+        }
+
+      p = row_end;
+      ++i;
+    }
+  
+  g_free (gradient);
+}
+
+void
+meta_gradient_add_alpha (GdkPixbuf       *pixbuf,
+                         const guchar    *alphas,
+                         int              n_alphas,
+                         MetaGradientType type)
+{
+  g_return_if_fail (GDK_IS_PIXBUF (pixbuf));
+  g_return_if_fail (gdk_pixbuf_get_has_alpha (pixbuf));
+  g_return_if_fail (n_alphas > 0);
+  
+  switch (type)
+    {
+    case META_GRADIENT_HORIZONTAL:
+      meta_gradient_add_alpha_horizontal (pixbuf, alphas, n_alphas);
+      break;
+      
+    case META_GRADIENT_VERTICAL:
+      g_printerr ("marco: vertical alpha channel gradient not implemented yet\n");
+      break;
+      
+    case META_GRADIENT_DIAGONAL:
+      g_printerr ("marco: diagonal alpha channel gradient not implemented yet\n");
+      break;
+      
+    case META_GRADIENT_LAST:
+      g_assert_not_reached ();
+      break;
+    }
+}