now just uses meta_gradient_add_alpha (draw_op_as_pixbuf): implement alpha

2002-05-31  Havoc Pennington  <hp@redhat.com>

	* src/theme.c (multiply_alpha): now just uses
	meta_gradient_add_alpha
	(draw_op_as_pixbuf): implement alpha gradients for tint, gradient,
	and image draw ops, so I can implement garrett's stuff.

	* src/gradient.c (meta_gradient_add_alpha): new function to
	multiply the alpha channel of a pixbuf by an alpha gradient

ChangeLog

@@ -1,3 +1,13 @@
+2002-05-31  Havoc Pennington  <hp@redhat.com>
+
+	* src/theme.c (multiply_alpha): now just uses
+	meta_gradient_add_alpha
+	(draw_op_as_pixbuf): implement alpha gradients for tint, gradient,
+	and image draw ops, so I can implement garrett's stuff.
+
+	* src/gradient.c (meta_gradient_add_alpha): new function to
+	multiply the alpha channel of a pixbuf by an alpha gradient
+
 2002-05-30  Havoc Pennington  <hp@redhat.com>
 
 	* src/main.c (main): verbose-log on startup whether we were

src/gradient.c

@@ -730,3 +730,176 @@ meta_gradient_create_multi_diagonal (int width, int height,
   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 ("metacity: vertical alpha channel gradient not implemented yet\n");
+      break;
+      
+    case META_GRADIENT_DIAGONAL:
+      g_printerr ("metacity: diagonal alpha channel gradient not implemented yet\n");
+      break;
+      
+    case META_GRADIENT_LAST:
+      g_assert_not_reached ();
+      break;
+    }
+}

src/gradient.h

@@ -51,4 +51,13 @@ GdkPixbuf* meta_gradient_create_interwoven (int               width,
                                             int               thickness2);
 
 
+/* Generate an alpha gradient and multiply it with the existing alpha
+ * channel of the given pixbuf
+ */
+void meta_gradient_add_alpha (GdkPixbuf       *pixbuf,
+                              const guchar    *alphas,
+                              int              n_alphas,
+                              MetaGradientType type);
+
+
 #endif

src/testgradient.c

@@ -26,11 +26,78 @@ typedef void (* RenderGradientFunc) (GdkDrawable *drawable,
                                      int          width,
                                      int          height);
 
+static void
+draw_checkerboard (GdkDrawable *drawable,
+                   int          width,
+                   int          height)
+{
+  gint i, j, xcount, ycount;
+  GdkGC *gc1, *gc2;
+  GdkColor color;
+  
+#define CHECK_SIZE 10
+#define SPACING 2  
+
+  /* It would be a bit more efficient to keep these
+   * GC's around instead of recreating on each expose, but
+   * this is the lazy/slow way.
+   */
+  gc1 = gdk_gc_new (drawable);
+  color.red = 30000;
+  color.green = 30000;
+  color.blue = 30000;
+  gdk_gc_set_rgb_fg_color (gc1, &color);
+
+  gc2 = gdk_gc_new (drawable);
+  color.red = 50000;
+  color.green = 50000;
+  color.blue = 50000;
+  gdk_gc_set_rgb_fg_color (gc2, &color);
+  
+  xcount = 0;
+  i = SPACING;
+  while (i < width)
+    {
+      j = SPACING;
+      ycount = xcount % 2; /* start with even/odd depending on row */
+      while (j < height)
+	{
+	  GdkGC *gc;
+	  
+	  if (ycount % 2)
+	    gc = gc1;
+	  else
+	    gc = gc2;
+
+	  /* If we're outside event->area, this will do nothing.
+	   * It might be mildly more efficient if we handled
+	   * the clipping ourselves, but again we're feeling lazy.
+	   */
+	  gdk_draw_rectangle (drawable,
+			      gc,
+			      TRUE,
+			      i, j,
+			      CHECK_SIZE,
+			      CHECK_SIZE);
+
+	  j += CHECK_SIZE + SPACING;
+	  ++ycount;
+	}
+
+      i += CHECK_SIZE + SPACING;
+      ++xcount;
+    }
+  
+  g_object_unref (G_OBJECT (gc1));
+  g_object_unref (G_OBJECT (gc2));
+}
+
 static void
 render_simple (GdkDrawable *drawable,
                GdkGC       *gc,
                int width, int height,
-               MetaGradientType type)
+               MetaGradientType type,
+               gboolean    with_alpha)
 {
   GdkPixbuf *pixbuf;
   GdkColor from, to;
@@ -42,6 +109,26 @@ render_simple (GdkDrawable *drawable,
                                         &from, &to,
                                         type);
 
+  if (with_alpha)
+    {
+      const unsigned char alphas[] = { 0xff, 0xaa, 0x2f, 0x0, 0xcc, 0xff, 0xff };
+      
+      if (!gdk_pixbuf_get_has_alpha (pixbuf))
+        {
+          GdkPixbuf *new_pixbuf;
+          
+          new_pixbuf = gdk_pixbuf_add_alpha (pixbuf, FALSE, 0, 0, 0);
+          g_object_unref (G_OBJECT (pixbuf));
+          pixbuf = new_pixbuf;
+        }
+      
+      meta_gradient_add_alpha (pixbuf,
+                               alphas, G_N_ELEMENTS (alphas),
+                               META_GRADIENT_HORIZONTAL);
+      
+      draw_checkerboard (drawable, width, height);
+    }
+    
   gdk_pixbuf_render_to_drawable (pixbuf,
                                  drawable,
                                  gc,
@@ -58,7 +145,7 @@ render_vertical_func (GdkDrawable *drawable,
                       GdkGC *gc,
                       int width, int height)
 {
-  render_simple (drawable, gc, width, height, META_GRADIENT_VERTICAL);
+  render_simple (drawable, gc, width, height, META_GRADIENT_VERTICAL, FALSE);
 }
 
 static void
@@ -66,7 +153,7 @@ render_horizontal_func (GdkDrawable *drawable,
                         GdkGC *gc,
                         int width, int height)
 {
-  render_simple (drawable, gc, width, height, META_GRADIENT_HORIZONTAL);
+  render_simple (drawable, gc, width, height, META_GRADIENT_HORIZONTAL, FALSE);
 }
 
 static void
@@ -74,7 +161,15 @@ render_diagonal_func (GdkDrawable *drawable,
                       GdkGC *gc,
                       int width, int height)
 {
-  render_simple (drawable, gc, width, height, META_GRADIENT_DIAGONAL);
+  render_simple (drawable, gc, width, height, META_GRADIENT_DIAGONAL, FALSE);
+}
+
+static void
+render_diagonal_alpha_func (GdkDrawable *drawable,
+                            GdkGC *gc,
+                            int width, int height)
+{
+  render_simple (drawable, gc, width, height, META_GRADIENT_DIAGONAL, TRUE);
 }
 
 static void
@@ -230,6 +325,10 @@ meta_gradient_test (void)
 
   window = create_gradient_window ("Interwoven",
                                    render_interwoven_func);
+
+  window = create_gradient_window ("Simple diagonal with horizontal multi alpha",
+                                   render_diagonal_alpha_func);
+
 }
 
 int

src/theme-parser.c

@@ -578,21 +578,80 @@ parse_angle (const char          *str,
 
 static gboolean
 parse_alpha (const char             *str,
-             double              *val,
+             MetaAlphaGradientSpec **spec_ret,
              GMarkupParseContext    *context,
              GError                **error)
 {
-  if (!parse_double (str, val, context, error))
+  char **split;
-    return FALSE;
+  int i;
+  int n_alphas;
+  MetaAlphaGradientSpec *spec;
 
-  if (*val < (0.0 - 1e6) || *val > (1.0 + 1e6))
+  *spec_ret = NULL;
+  
+  split = g_strsplit (str, ":", -1);
+
+  i = 0;
+  while (split[i])
+    ++i;
+
+  if (i == 0)
+    {
+      set_error (error, context, G_MARKUP_ERROR, G_MARKUP_ERROR_PARSE,
+                 _("Could not parse \"%s\" as a floating point number"),
+                 str);
+
+      g_strfreev (split);
+      
+      return FALSE;
+    }
+
+  n_alphas = i;
+
+  /* FIXME allow specifying horizontal/vertical/diagonal in theme format,
+   * once we implement vertical/diagonal in gradient.c
+   */
+  spec = meta_alpha_gradient_spec_new (META_GRADIENT_HORIZONTAL,
+                                       n_alphas);
+
+  i = 0;
+  while (i < n_alphas)
+    {
+      double v;
+      
+      if (!parse_double (split[i], &v, context, error))
+        {
+          set_error (error, context, G_MARKUP_ERROR, G_MARKUP_ERROR_PARSE,
+                     _("Could not parse \"%s\" as a floating point number"),
+                     split[i]);
+          
+          g_strfreev (split);
+          meta_alpha_gradient_spec_free (spec);
+          
+          return FALSE;
+        }
+
+      if (v < (0.0 - 1e6) || v > (1.0 + 1e6))
         {
           set_error (error, context, G_MARKUP_ERROR, G_MARKUP_ERROR_PARSE,
                      _("Alpha must be between 0.0 (invisible) and 1.0 (fully opaque), was %g\n"),
-                 *val);
+                     v);
+
+          g_strfreev (split);
+          meta_alpha_gradient_spec_free (spec);          
+          
           return FALSE;
         }
 
+      spec->alphas[i] = (unsigned char) (v * 255);
+      
+      ++i;
+    }  
+
+  g_strfreev (split);
+  
+  *spec_ret = spec;
+  
   return TRUE;
 }
 
@@ -1886,7 +1945,7 @@ parse_draw_op_element (GMarkupParseContext  *context,
       const char *width;
       const char *height;
       const char *alpha;
-      double alpha_val;
+      MetaAlphaGradientSpec *alpha_spec;
       MetaColorSpec *color_spec;
       
       if (!locate_attributes (context, element_name, attribute_names, attribute_values,
@@ -1952,7 +2011,8 @@ parse_draw_op_element (GMarkupParseContext  *context,
       if (!check_expression (height, FALSE, info->theme, context, error))
         return;
 
-      if (!parse_alpha (alpha, &alpha_val, context, error))
+      alpha_spec = NULL;
+      if (!parse_alpha (alpha, &alpha_spec, context, error))
         return;
       
       /* Check last so we don't have to free it when other
@@ -1961,6 +2021,9 @@ parse_draw_op_element (GMarkupParseContext  *context,
       color_spec = meta_color_spec_new_from_string (color, error);
       if (color_spec == NULL)
         {
+          if (alpha_spec)
+            meta_alpha_gradient_spec_free (alpha_spec);
+          
           add_context_to_error (error, context);
           return;
         }
@@ -1968,11 +2031,11 @@ parse_draw_op_element (GMarkupParseContext  *context,
       op = meta_draw_op_new (META_DRAW_TINT);
 
       op->data.tint.color_spec = color_spec;
+      op->data.tint.alpha_spec = alpha_spec;
       op->data.tint.x = optimize_expression (info->theme, x);
       op->data.tint.y = optimize_expression (info->theme, y);
       op->data.tint.width = optimize_expression (info->theme, width);
       op->data.tint.height = optimize_expression (info->theme, height);
-      op->data.tint.alpha = alpha_val;
 
       g_assert (info->op_list);
       
@@ -1988,7 +2051,7 @@ parse_draw_op_element (GMarkupParseContext  *context,
       const char *height;
       const char *type;
       const char *alpha;
-      double alpha_val;
+      MetaAlphaGradientSpec *alpha_spec;
       MetaGradientType type_val;
       
       if (!locate_attributes (context, element_name, attribute_names, attribute_values,
@@ -2047,10 +2110,6 @@ parse_draw_op_element (GMarkupParseContext  *context,
       if (!check_expression (height, FALSE, info->theme, context, error))
         return;
       
-      alpha_val = 1.0;
-      if (alpha && !parse_alpha (alpha, &alpha_val, context, error))
-        return;
-      
       type_val = meta_gradient_type_from_string (type);
       if (type_val == META_GRADIENT_LAST)
         {
@@ -2060,6 +2119,10 @@ parse_draw_op_element (GMarkupParseContext  *context,
           return;
         }
 
+      alpha_spec = NULL;
+      if (alpha && !parse_alpha (alpha, &alpha_spec, context, error))
+        return;
+      
       g_assert (info->op == NULL);
       info->op = meta_draw_op_new (META_DRAW_GRADIENT);
 
@@ -2068,10 +2131,9 @@ parse_draw_op_element (GMarkupParseContext  *context,
       info->op->data.gradient.width = optimize_expression (info->theme, width);
       info->op->data.gradient.height = optimize_expression (info->theme, height);
 
-      info->op->data.gradient.gradient_spec =
+      info->op->data.gradient.gradient_spec = meta_gradient_spec_new (type_val);
-        meta_gradient_spec_new (type_val);
 
-      info->op->data.gradient.alpha = alpha_val;
+      info->op->data.gradient.alpha_spec = alpha_spec;
       
       push_state (info, STATE_GRADIENT);
 
@@ -2087,7 +2149,7 @@ parse_draw_op_element (GMarkupParseContext  *context,
       const char *height;
       const char *alpha;
       const char *colorize;
-      double alpha_val;
+      MetaAlphaGradientSpec *alpha_spec;
       GdkPixbuf *pixbuf;
       MetaColorSpec *colorize_spec = NULL;
       
@@ -2147,9 +2209,6 @@ parse_draw_op_element (GMarkupParseContext  *context,
       if (!check_expression (height, TRUE, info->theme, context, error))
         return;
 
-      alpha_val = 1.0;
-      if (alpha && !parse_alpha (alpha, &alpha_val, context, error))
-        return;
       
       /* Check last so we don't have to free it when other
        * stuff fails
@@ -2174,6 +2233,13 @@ parse_draw_op_element (GMarkupParseContext  *context,
 	    }
 	}
 
+      alpha_spec = NULL;
+      if (alpha && !parse_alpha (alpha, &alpha_spec, context, error))
+        {
+          g_object_unref (G_OBJECT (pixbuf));
+          return;
+        }
+      
       op = meta_draw_op_new (META_DRAW_IMAGE);
 
       op->data.image.pixbuf = pixbuf;
@@ -2182,7 +2248,7 @@ parse_draw_op_element (GMarkupParseContext  *context,
       op->data.image.y = optimize_expression (info->theme, y);
       op->data.image.width = optimize_expression (info->theme, width);
       op->data.image.height = optimize_expression (info->theme, height);
-      op->data.image.alpha = alpha_val;
+      op->data.image.alpha_spec = alpha_spec;
 
       g_assert (info->op_list);
       
@@ -2523,7 +2589,7 @@ parse_draw_op_element (GMarkupParseContext  *context,
       const char *width;
       const char *height;
       const char *alpha;
-      double alpha_val;
+      MetaAlphaGradientSpec *alpha_spec;
       
       if (!locate_attributes (context, element_name, attribute_names, attribute_values,
                               error,
@@ -2573,8 +2639,8 @@ parse_draw_op_element (GMarkupParseContext  *context,
       if (!check_expression (height, FALSE, info->theme, context, error))
         return;
 
-      alpha_val = 1.0;
+      alpha_spec = NULL;
-      if (alpha && !parse_alpha (alpha, &alpha_val, context, error))
+      if (alpha && !parse_alpha (alpha, &alpha_spec, context, error))
         return;
       
       op = meta_draw_op_new (META_DRAW_ICON);
@@ -2583,7 +2649,7 @@ parse_draw_op_element (GMarkupParseContext  *context,
       op->data.icon.y = optimize_expression (info->theme, y);
       op->data.icon.width = optimize_expression (info->theme, width);
       op->data.icon.height = optimize_expression (info->theme, height);
-      op->data.icon.alpha = alpha_val;
+      op->data.icon.alpha_spec = alpha_spec;
 
       g_assert (info->op_list);
       

src/theme.c

@@ -753,6 +753,32 @@ meta_gradient_spec_validate (MetaGradientSpec *spec,
   return TRUE;
 }
 
+MetaAlphaGradientSpec*
+meta_alpha_gradient_spec_new (MetaGradientType       type,
+                              int                    n_alphas)
+{
+  MetaAlphaGradientSpec *spec;
+
+  g_return_val_if_fail (n_alphas > 0, NULL);
+  
+  spec = g_new0 (MetaAlphaGradientSpec, 1);
+
+  spec->type = type;
+  spec->alphas = g_new0 (unsigned char, n_alphas);
+  spec->n_alphas = n_alphas;
+
+  return spec;
+}
+
+void
+meta_alpha_gradient_spec_free (MetaAlphaGradientSpec *spec)
+{
+  g_return_if_fail (spec != NULL);
+
+  g_free (spec->alphas);
+  g_free (spec);
+}
+
 MetaColorSpec*
 meta_color_spec_new (MetaColorSpecType type)
 {
@@ -2347,6 +2373,8 @@ meta_draw_op_free (MetaDrawOp *op)
     case META_DRAW_TINT:
       if (op->data.tint.color_spec)
         meta_color_spec_free (op->data.tint.color_spec);
+      if (op->data.tint.alpha_spec)
+        meta_alpha_gradient_spec_free (op->data.tint.alpha_spec);
       g_free (op->data.tint.x);
       g_free (op->data.tint.y);
       g_free (op->data.tint.width);
@@ -2356,6 +2384,8 @@ meta_draw_op_free (MetaDrawOp *op)
     case META_DRAW_GRADIENT:
       if (op->data.gradient.gradient_spec)
         meta_gradient_spec_free (op->data.gradient.gradient_spec);
+      if (op->data.gradient.alpha_spec)
+        meta_alpha_gradient_spec_free (op->data.gradient.alpha_spec);
       g_free (op->data.gradient.x);
       g_free (op->data.gradient.y);
       g_free (op->data.gradient.width);
@@ -2363,6 +2393,8 @@ meta_draw_op_free (MetaDrawOp *op)
       break;
 
     case META_DRAW_IMAGE:
+      if (op->data.image.alpha_spec)
+        meta_alpha_gradient_spec_free (op->data.image.alpha_spec);
       if (op->data.image.pixbuf)
         g_object_unref (G_OBJECT (op->data.image.pixbuf));
       if (op->data.image.colorize_spec)
@@ -2375,7 +2407,6 @@ meta_draw_op_free (MetaDrawOp *op)
       g_free (op->data.image.height);
       break;
 
-
     case META_DRAW_GTK_ARROW:
       g_free (op->data.gtk_arrow.x);
       g_free (op->data.gtk_arrow.y);
@@ -2397,6 +2428,8 @@ meta_draw_op_free (MetaDrawOp *op)
       break;
 
     case META_DRAW_ICON:
+      if (op->data.icon.alpha_spec)
+        meta_alpha_gradient_spec_free (op->data.icon.alpha_spec);
       g_free (op->data.icon.x);
       g_free (op->data.icon.y);
       g_free (op->data.icon.width);
@@ -2464,19 +2497,19 @@ get_gc_for_primitive (GtkWidget          *widget,
 }
 
 static GdkPixbuf*
-multiply_alpha (GdkPixbuf *pixbuf,
+apply_alpha (GdkPixbuf             *pixbuf,
-                guchar     alpha,
+             MetaAlphaGradientSpec *spec,
              gboolean               force_copy)
 {
   GdkPixbuf *new_pixbuf;
-  guchar *pixels;
+  gboolean needs_alpha;
-  int rowstride;
-  int height;
-  int row;
   
   g_return_val_if_fail (GDK_IS_PIXBUF (pixbuf), NULL);
   
-  if (alpha == 255)
+  needs_alpha = spec && (spec->n_alphas > 1 ||
+                         spec->alphas[0] != 0xff);
+
+  if (!needs_alpha)
     return pixbuf;
   
   if (!gdk_pixbuf_get_has_alpha (pixbuf))
@@ -2494,36 +2527,7 @@ multiply_alpha (GdkPixbuf *pixbuf,
   
   g_assert (gdk_pixbuf_get_has_alpha (pixbuf));
 
-  pixels = gdk_pixbuf_get_pixels (pixbuf);
+  meta_gradient_add_alpha (pixbuf, spec->alphas, spec->n_alphas, spec->type);
-  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;
-    }
   
   return pixbuf;
 }
@@ -2579,7 +2583,7 @@ render_pixbuf (GdkDrawable        *drawable,
 
 static GdkPixbuf*
 scale_and_alpha_pixbuf (GdkPixbuf             *src,
-                        double         alpha,
+                        MetaAlphaGradientSpec *alpha_spec,
                         int                    width,
                         int                    height)
 {
@@ -2611,9 +2615,7 @@ scale_and_alpha_pixbuf (GdkPixbuf     *src,
     }
 
   if (pixbuf)
-    pixbuf = multiply_alpha (pixbuf,
+    pixbuf = apply_alpha (pixbuf, alpha_spec, pixbuf == src);
-                             ALPHA_TO_UCHAR (alpha),
-                             pixbuf == src);
   
   return pixbuf;
 }
@@ -2665,21 +2667,47 @@ draw_op_as_pixbuf (const MetaDrawOp    *op,
       {
         GdkColor color;
         guint32 rgba;
+        gboolean has_alpha;
 
         meta_color_spec_render (op->data.rectangle.color_spec,
                                 widget,
                                 &color);
 
+        has_alpha =
+          op->data.tint.alpha_spec &&
+          (op->data.tint.alpha_spec->n_alphas > 1 ||
+           op->data.tint.alpha_spec->alphas[0] != 0xff);
+        
         pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB,
-                                 ALPHA_TO_UCHAR (op->data.tint.alpha) < 255,
+                                 has_alpha,
                                  8, width, height);
 
+        if (!has_alpha)
+          {
             rgba = GDK_COLOR_RGBA (color);
-        rgba &= ~0xff;
-        rgba |= ALPHA_TO_UCHAR (op->data.tint.alpha);
             
             gdk_pixbuf_fill (pixbuf, rgba);
           }
+        else if (op->data.tint.alpha_spec->n_alphas == 1)
+          {
+            rgba = GDK_COLOR_RGBA (color);
+            rgba &= ~0xff;
+            rgba |= op->data.tint.alpha_spec->alphas[0];
+            
+            gdk_pixbuf_fill (pixbuf, rgba);
+          }
+        else
+          {
+            rgba = GDK_COLOR_RGBA (color);
+            
+            gdk_pixbuf_fill (pixbuf, rgba);
+
+            meta_gradient_add_alpha (pixbuf,
+                                     op->data.tint.alpha_spec->alphas,
+                                     op->data.tint.alpha_spec->n_alphas,
+                                     op->data.tint.alpha_spec->type);
+          }
+      }
       break;
 
     case META_DRAW_GRADIENT:
@@ -2687,8 +2715,8 @@ draw_op_as_pixbuf (const MetaDrawOp    *op,
         pixbuf = meta_gradient_spec_render (op->data.gradient.gradient_spec,
                                             widget, width, height);
 
-        pixbuf = multiply_alpha (pixbuf,
+        pixbuf = apply_alpha (pixbuf,
-                                 ALPHA_TO_UCHAR (op->data.gradient.alpha),
+                              op->data.gradient.alpha_spec,
                               FALSE);
       }
       break;
@@ -2720,14 +2748,14 @@ draw_op_as_pixbuf (const MetaDrawOp    *op,
             if (op->data.image.colorize_cache_pixbuf)
               {
                 pixbuf = scale_and_alpha_pixbuf (op->data.image.colorize_cache_pixbuf,
-                                                 op->data.image.alpha,
+                                                 op->data.image.alpha_spec,
                                                  width, height);
               }
 	  }
 	else
 	  {
 	    pixbuf = scale_and_alpha_pixbuf (op->data.image.pixbuf,
-					     op->data.image.alpha,
+					     op->data.image.alpha_spec,
 					     width, height);
 	  }
         break;
@@ -2743,11 +2771,11 @@ draw_op_as_pixbuf (const MetaDrawOp    *op,
           width <= gdk_pixbuf_get_width (info->mini_icon) &&
           height <= gdk_pixbuf_get_height (info->mini_icon))
         pixbuf = scale_and_alpha_pixbuf (info->mini_icon,
-                                         op->data.icon.alpha,
+                                         op->data.icon.alpha_spec,
                                          width, height);
       else if (info->icon)
         pixbuf = scale_and_alpha_pixbuf (info->icon,
-                                         op->data.icon.alpha,
+                                         op->data.icon.alpha_spec,
                                          width, height);
       break;
 
@@ -2902,13 +2930,18 @@ meta_draw_op_draw_with_env (const MetaDrawOp    *op,
     case META_DRAW_TINT:
       {
         int rx, ry, rwidth, rheight;
+        gboolean needs_alpha;
+        
+        needs_alpha = op->data.tint.alpha_spec &&
+          (op->data.tint.alpha_spec->n_alphas > 1 ||
+           op->data.tint.alpha_spec->alphas[0] != 0xff);
         
         rx = parse_x_position_unchecked (op->data.tint.x, env);
         ry = parse_y_position_unchecked (op->data.tint.y, env);
         rwidth = parse_size_unchecked (op->data.tint.width, env);
         rheight = parse_size_unchecked (op->data.tint.height, env);
 
-        if (ALPHA_TO_UCHAR (op->data.tint.alpha) == 255)
+        if (!needs_alpha)
           {
             gc = get_gc_for_primitive (widget, drawable,
                                        op->data.tint.color_spec,

src/theme.h

@@ -31,6 +31,7 @@ typedef struct _MetaFrameStyleSet MetaFrameStyleSet;
 typedef struct _MetaDrawOp MetaDrawOp;
 typedef struct _MetaDrawOpList MetaDrawOpList;
 typedef struct _MetaGradientSpec MetaGradientSpec;
+typedef struct _MetaAlphaGradientSpec MetaAlphaGradientSpec; 
 typedef struct _MetaColorSpec MetaColorSpec;
 typedef struct _MetaFrameLayout MetaFrameLayout;
 typedef struct _MetaFrameGeometry MetaFrameGeometry;
@@ -169,6 +170,13 @@ struct _MetaGradientSpec
   GSList *color_specs;
 };
 
+struct _MetaAlphaGradientSpec
+{
+  MetaGradientType type;
+  unsigned char *alphas;
+  int n_alphas;
+};
+
 struct _MetaDrawInfo
 {
   GdkPixbuf   *mini_icon;
@@ -256,7 +264,7 @@ struct _MetaDrawOp
     
     struct {
       MetaColorSpec *color_spec;
-      double alpha;
+      MetaAlphaGradientSpec *alpha_spec;
       char *x;
       char *y;
       char *width;
@@ -265,7 +273,7 @@ struct _MetaDrawOp
 
     struct {
       MetaGradientSpec *gradient_spec;
-      double alpha;
+      MetaAlphaGradientSpec *alpha_spec;
       char *x;
       char *y;
       char *width;
@@ -274,6 +282,7 @@ struct _MetaDrawOp
 
     struct {
       MetaColorSpec *colorize_spec;
+      MetaAlphaGradientSpec *alpha_spec;
       GdkPixbuf *pixbuf;
       double alpha;
       char *x;
@@ -312,7 +321,7 @@ struct _MetaDrawOp
     } gtk_vline;
 
     struct {
-      double alpha;
+      MetaAlphaGradientSpec *alpha_spec;
       char *x;
       char *y;
       char *width;
@@ -618,6 +627,10 @@ GdkPixbuf*        meta_gradient_spec_render (const MetaGradientSpec *desc,
 gboolean          meta_gradient_spec_validate (MetaGradientSpec     *spec,
                                                GError              **error);
 
+MetaAlphaGradientSpec* meta_alpha_gradient_spec_new  (MetaGradientType       type,
+                                                      int                    n_alphas);
+void                   meta_alpha_gradient_spec_free (MetaAlphaGradientSpec *spec);
+
 
 MetaFrameStyle* meta_frame_style_new   (MetaFrameStyle *parent);
 void            meta_frame_style_ref   (MetaFrameStyle *style);