+#define TRANS_OPACITY 0.75
+#define SHADOW_RADIUS 15
+#define SHADOW_OPACITY 0.75
+#define SHADOW_OFFSET_X (-SHADOW_RADIUS)
+#define SHADOW_OFFSET_Y (-SHADOW_RADIUS)
+
+
+double
+gaussian (double r, double x, double y)
+{
+ return ((1 / (sqrt (2 * M_PI * r))) *
+ exp ((- (x * x + y * y)) / (2 * r * r)));
+}
+
+typedef struct _conv {
+ int size;
+ double *data;
+} conv;
+
+conv *
+make_gaussian_map (Display *dpy, double r)
+{
+ conv *c;
+ int size = ((int) ceil ((r * 3)) + 1) & ~1;
+ int center = size / 2;
+ int x, y;
+ double t;
+ double g;
+
+ c = malloc (sizeof (conv) + size * size * sizeof (double));
+ c->size = size;
+ c->data = (double *) (c + 1);
+ for (y = 0; y < size; y++)
+ for (x = 0; x < size; x++)
+ {
+ g = gaussian (r, (double) (x - center), (double) (y - center));
+ t += g;
+ c->data[y * size + x] = g;
+ }
+ printf ("gaussian total %f\n", t);
+ for (y = 0; y < size; y++)
+ for (x = 0; x < size; x++)
+ {
+ c->data[y*size + x] /= t;
+ }
+ return c;
+}
+
+/*
+ * A picture will help
+ *
+ * -center 0 width width+center
+ * -center +-----+-------------------+-----+
+ * | | | |
+ * | | | |
+ * 0 +-----+-------------------+-----+
+ * | | | |
+ * | | | |
+ * | | | |
+ * height +-----+-------------------+-----+
+ * | | | |
+ * height+ | | | |
+ * center +-----+-------------------+-----+
+ */
+
+unsigned int
+sum_gaussian (conv *map, double opacity, int x, int y, int width, int height)
+{
+ int fx, fy;
+ int sx, sy;
+ double *g_data;
+ double *g_line = map->data;
+ int g_size = map->size;
+ int center = g_size / 2;
+ int fx_start, fx_end;
+ int fy_start, fy_end;
+ double v;
+
+ /*
+ * Compute set of filter values which are "in range",
+ * that's the set with:
+ * 0 <= x + (fx-center) && x + (fx-center) < width &&
+ * 0 <= y + (fy-center) && y + (fy-center) < height
+ *
+ * 0 <= x + (fx - center) x + fx - center < width
+ * center - x <= fx fx < width + center - x
+ */
+
+ fx_start = center - x;
+ if (fx_start < 0)
+ fx_start = 0;
+ fx_end = width + center - x;
+ if (fx_end > g_size)
+ fx_end = g_size;
+
+ fy_start = center - y;
+ if (fy_start < 0)
+ fy_start = 0;
+ fy_end = height + center - y;
+ if (fy_end > g_size)
+ fy_end = g_size;
+
+ g_line = g_line + fy_start * g_size + fx_start;
+
+ v = 0;
+ for (fy = fy_start; fy < fy_end; fy++)
+ {
+ g_data = g_line;
+ g_line += g_size;
+
+ for (fx = fx_start; fx < fx_end; fx++)
+ v += *g_data++;
+ }
+ if (v > 1)
+ v = 1;
+
+ return ((unsigned int) (v * opacity * 255.0)) << 24;
+}
+
+XImage *
+make_shadow (Display *dpy, double opacity, double r, int width, int height)
+{
+ conv *map = make_gaussian_map (dpy, r);
+ XImage *ximage;
+ double *gdata = map->data;
+ unsigned int *data;
+ int gsize = map->size;
+ int ylimit, xlimit;
+ int swidth = width + gsize;
+ int sheight = height + gsize;
+ int center = gsize / 2;
+ int x, y;
+ int fx, fy;
+ int sx, sy;
+ unsigned int d;
+ double v;
+ unsigned char c;
+
+ data = malloc (swidth * sheight * sizeof (int));
+ ximage = XCreateImage (dpy,
+ DefaultVisual(dpy, DefaultScreen(dpy)),
+ 32,
+ ZPixmap,
+ 0,
+ (char *) data,
+ swidth, sheight, 32, swidth * sizeof (int));
+ /*
+ * Build the gaussian in sections
+ */
+
+ /*
+ * corners
+ */
+ ylimit = gsize;
+ if (ylimit > sheight / 2)
+ ylimit = (sheight + 1) / 2;
+ xlimit = gsize;
+ if (xlimit > swidth / 2)
+ xlimit = (swidth + 1) / 2;
+
+ for (y = 0; y < ylimit; y++)
+ for (x = 0; x < xlimit; x++)
+ {
+ d = sum_gaussian (map, opacity, x - center, y - center, width, height);
+ data[y * swidth + x] = d;
+ data[(sheight - y - 1) * swidth + x] = d;
+ data[(sheight - y - 1) * swidth + (swidth - x - 1)] = d;
+ data[y * swidth + (swidth - x - 1)] = d;
+ }
+
+ /*
+ * top/bottom
+ */
+ for (y = 0; y < ylimit; y++)
+ {
+ d = sum_gaussian (map, opacity, center, y - center, width, height);
+ for (x = gsize; x < swidth - gsize; x++)
+ {
+ data[y * swidth + x] = d;
+ data[(sheight - y - 1) * swidth + x] = d;
+ }
+ }
+
+ /*
+ * sides
+ */
+
+ for (x = 0; x < xlimit; x++)
+ {
+ d = sum_gaussian (map, opacity, x - center, center, width, height);
+ for (y = gsize; y < sheight - gsize; y++)
+ {
+ data[y * swidth + x] = d;
+ data[y * swidth + (swidth - x - 1)] = d;
+ }
+ }
+
+ /*
+ * center
+ */
+
+ d = sum_gaussian (map, opacity, center, center, width, height);
+ for (y = ylimit; y < sheight - ylimit; y++)
+ for (x = xlimit; x < swidth - xlimit; x++)
+ data[y * swidth + x] = d;
+
+ free (map);
+ return ximage;
+}
+
+Picture
+shadow_picture (Display *dpy, double opacity, double r, int width, int height, int *wp, int *hp)
+{
+ XImage *shadowImage = make_shadow (dpy, opacity, r, width, height);
+ Pixmap shadowPixmap = XCreatePixmap (dpy, root,
+ shadowImage->width,
+ shadowImage->height,
+ 32);
+ Picture shadowPicture = XRenderCreatePicture (dpy, shadowPixmap,
+ XRenderFindStandardFormat (dpy, PictStandardARGB32),
+ 0, 0);
+ GC gc = XCreateGC (dpy, shadowPixmap, 0, 0);
+
+ XPutImage (dpy, shadowPixmap, gc, shadowImage, 0, 0, 0, 0,
+ shadowImage->width,
+ shadowImage->height);
+ *wp = shadowImage->width;
+ *hp = shadowImage->height;
+ XFreeGC (dpy, gc);
+ XDestroyImage (shadowImage);
+ XFreePixmap (dpy, shadowPixmap);
+ return shadowPicture;
+}