diff --git a/ChangeLog b/ChangeLog
index 9115c8b9ff..044aa4ce31 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Fri Jul 24 19:36:33 BST 1998  Adam D. Moss <adam@gimp.org>
+
+	* app/appenv.h app/brightness_contrast.c app/color_balance.c
+	app/curves.c app/gdisplay.h app/gdisplay_ops.c
+	app/hue_saturation.c app/paint_core.c app/paint_funcs.c
+	app/undo.c: Attempt to speed-up and/or sanitize
+	MAX/MIN/CLAMP macro usage throughout gimp-core.
+
 Fri Jul 24 12:01:31 CDT 1998  Larry Ewing  <lewing@gimp.org>
 
 	* app/gdisplay.c (gdisplay_update_cursor): Fixed a string
diff --git a/app/appenv.h b/app/appenv.h
index 364e420f08..3197d68d14 100644
--- a/app/appenv.h
+++ b/app/appenv.h
@@ -18,16 +18,24 @@
 #ifndef __APPENV_H__
 #define __APPENV_H__
 
+#include "glib.h"
 #include "gdk/gdkx.h"
 #include "gtk/gtk.h"
 #include "gimpsetF.h"
 
 #define DISPLAY              ((Display *) GDK_DISPLAY())
 
-/*   important macros  */
-#define BOUNDS(a,x,y)  ((a < x) ? x : ((a > y) ? y : a))
-#define MINIMUM(x,y) ((x < y) ? x : y)
-#define MAXIMUM(x,y) ((x > y) ? x : y)
+/*   important macros - we reuse the ones from glib */
+#define BOUNDS(a,x,y)  CLAMP(a,x,y)
+#define MINIMUM(x,y)   MIN(x,y)
+#define MAXIMUM(x,y)   MAX(x,y)
+
+/* limit a (0->511) int to 255 */
+#define MAX255(a)  (a | ((a & 256) - ((a & 256) >> 8)))
+
+/* clamp a int32-range int between 0 and 255 inclusive */
+#define CLAMP0255(a)  ((a&256)? (~(a>>31)) : a)
+
 
 typedef enum {
   MESSAGE_BOX,
diff --git a/app/base/color-balance.c b/app/base/color-balance.c
index 2b6c839252..178ec52906 100644
--- a/app/base/color-balance.c
+++ b/app/base/color-balance.c
@@ -154,25 +154,25 @@ color_balance (PixelRegion *srcPR,
 	  b = b_n = s[BLUE_PIX];
 
 	  r_n += cbd->cyan_red[SHADOWS] * cyan_red_transfer[SHADOWS][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 	  r_n += cbd->cyan_red[MIDTONES] * cyan_red_transfer[MIDTONES][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 	  r_n += cbd->cyan_red[HIGHLIGHTS] * cyan_red_transfer[HIGHLIGHTS][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 
 	  g_n += cbd->magenta_green[SHADOWS] * magenta_green_transfer[SHADOWS][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 	  g_n += cbd->magenta_green[MIDTONES] * magenta_green_transfer[MIDTONES][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 	  g_n += cbd->magenta_green[HIGHLIGHTS] * magenta_green_transfer[HIGHLIGHTS][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 
 	  b_n += cbd->yellow_blue[SHADOWS] * yellow_blue_transfer[SHADOWS][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 	  b_n += cbd->yellow_blue[MIDTONES] * yellow_blue_transfer[MIDTONES][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 	  b_n += cbd->yellow_blue[HIGHLIGHTS] * yellow_blue_transfer[HIGHLIGHTS][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 
 	  if (cbd->preserve_luminosity)
 	    {
diff --git a/app/base/curves.c b/app/base/curves.c
index fe057c648f..15512ec6f6 100644
--- a/app/base/curves.c
+++ b/app/base/curves.c
@@ -757,8 +757,8 @@ curves_plot_curve (CurvesDialog *cd,
       dy += dy2;
       dy2 += dy3;
 
-      newx = BOUNDS ((ROUND (x)), 0, 255);
-      newy = BOUNDS ((ROUND (y)), 0, 255);
+      newx = CLAMP0255 (ROUND (x));
+      newy = CLAMP0255 (ROUND (y));
 
       /* if this point is different than the last one...then draw it */
       if ((lastx != newx) || (lasty != newy))
@@ -914,7 +914,7 @@ curves_smooth_callback (GtkWidget *w,
       /*  pick representative points from the curve and make them control points  */
       for (i = 0; i <= 8; i++)
 	{
-	  index = BOUNDS ((i * 32), 0, 255);
+	  index = CLAMP0255 (i * 32);
 	  cd->points[cd->channel][i * 2][0] = index;
 	  cd->points[cd->channel][i * 2][1] = cd->curve[cd->channel][index];
 	}
diff --git a/app/base/hue-saturation.c b/app/base/hue-saturation.c
index e09bcbb2c0..9b37b8b4b0 100644
--- a/app/base/hue-saturation.c
+++ b/app/base/hue-saturation.c
@@ -163,7 +163,7 @@ hue_saturation_calculate_transfers (HueSaturationDialog *hsd)
 	value = (hsd->saturation[0] + hsd->saturation[hue + 1]) * 255.0 / 100.0;
 	value = BOUNDS (value, -255, 255);
 #if 0
-        saturation_transfer[hue][i] = (unsigned char) (BOUNDS ((i * (255 + value)) / 255, 0, 255));
+        saturation_transfer[hue][i] = (unsigned char) (CLAMP0255 ((i * (255 + value)) / 255));
 #else
 	if (value < 0)
 	  saturation_transfer[hue][i] = (unsigned char) ((i * (255 + value)) / 255);
diff --git a/app/brightness_contrast.c b/app/brightness_contrast.c
index 66bc9d5f84..3e0de2157f 100644
--- a/app/brightness_contrast.c
+++ b/app/brightness_contrast.c
@@ -133,7 +133,7 @@ brightness_contrast (PixelRegion *srcPR,
 	value = (i > 127) ? (255 - i) : i;
 	value = (int) (127.0 * pow ((double) (value ? value : 1) / 127.0,
 				    (double) (127 + bcd->contrast) / 127.0));
-	value = BOUNDS (value, 0, 255);
+	value = CLAMP0255 (value);
 	contrast[i] = (i > 127) ? (255 - value) : value;
       }
   else
@@ -142,7 +142,7 @@ brightness_contrast (PixelRegion *srcPR,
 	value = (i > 127) ? (255 - i) : i;
 	power = (bcd->contrast == 127) ? 127 : 127.0 / (127 - bcd->contrast);
 	value = (int) (127.0 * pow ((double) value / 127.0, power));
-	value = BOUNDS (value, 0, 255);
+	value = CLAMP0255 (value);
 	contrast[i] = (i > 127) ? (255 - value) : value;
       }
 
diff --git a/app/color_balance.c b/app/color_balance.c
index 2b6c839252..178ec52906 100644
--- a/app/color_balance.c
+++ b/app/color_balance.c
@@ -154,25 +154,25 @@ color_balance (PixelRegion *srcPR,
 	  b = b_n = s[BLUE_PIX];
 
 	  r_n += cbd->cyan_red[SHADOWS] * cyan_red_transfer[SHADOWS][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 	  r_n += cbd->cyan_red[MIDTONES] * cyan_red_transfer[MIDTONES][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 	  r_n += cbd->cyan_red[HIGHLIGHTS] * cyan_red_transfer[HIGHLIGHTS][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 
 	  g_n += cbd->magenta_green[SHADOWS] * magenta_green_transfer[SHADOWS][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 	  g_n += cbd->magenta_green[MIDTONES] * magenta_green_transfer[MIDTONES][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 	  g_n += cbd->magenta_green[HIGHLIGHTS] * magenta_green_transfer[HIGHLIGHTS][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 
 	  b_n += cbd->yellow_blue[SHADOWS] * yellow_blue_transfer[SHADOWS][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 	  b_n += cbd->yellow_blue[MIDTONES] * yellow_blue_transfer[MIDTONES][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 	  b_n += cbd->yellow_blue[HIGHLIGHTS] * yellow_blue_transfer[HIGHLIGHTS][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 
 	  if (cbd->preserve_luminosity)
 	    {
diff --git a/app/core/gimpimage-undo-push.c b/app/core/gimpimage-undo-push.c
index b7deea7280..facc59be9b 100644
--- a/app/core/gimpimage-undo-push.c
+++ b/app/core/gimpimage-undo-push.c
@@ -513,6 +513,7 @@ undo_push_image_mod (GImage *gimage,
 		     int     sparse)
 {
   long size;
+  int dwidth, dheight;
   Undo * new;
   ImageUndo *image_undo;
   TileManager *tiles;
@@ -524,10 +525,13 @@ undo_push_image_mod (GImage *gimage,
   if (! tiles_ptr)
     return FALSE;
 
-  x1 = BOUNDS (x1, 0, drawable_width (drawable));
-  y1 = BOUNDS (y1, 0, drawable_height (drawable));
-  x2 = BOUNDS (x2, 0, drawable_width (drawable));
-  y2 = BOUNDS (y2, 0, drawable_height (drawable));
+  dwidth = drawable_width (drawable);
+  dheight = drawable_height (drawable);
+
+  x1 = BOUNDS (x1, 0, dwidth);
+  y1 = BOUNDS (y1, 0, dheight);
+  x2 = BOUNDS (x2, 0, dwidth);
+  y2 = BOUNDS (y2, 0, dheight);
 
   tiles = (TileManager *) tiles_ptr;
   size = tiles->levels[0].width * tiles->levels[0].height *
diff --git a/app/core/gimpprojection.h b/app/core/gimpprojection.h
index 723a91a386..cd9467d48a 100644
--- a/app/core/gimpprojection.h
+++ b/app/core/gimpprojection.h
@@ -35,7 +35,7 @@
 #define  UNSCALE(g,x)   ((x * SCALESRC(g)) / SCALEDEST(g))
 
 #define LOWPASS(x) ((x>0) ? x : 0)
-#define HIGHPASS(x,y) ((x>y) ? y : x)
+/* #define HIGHPASS(x,y) ((x>y) ? y : x) */ /* unused - == MIN */
 
 
 typedef enum
diff --git a/app/curves.c b/app/curves.c
index fe057c648f..15512ec6f6 100644
--- a/app/curves.c
+++ b/app/curves.c
@@ -757,8 +757,8 @@ curves_plot_curve (CurvesDialog *cd,
       dy += dy2;
       dy2 += dy3;
 
-      newx = BOUNDS ((ROUND (x)), 0, 255);
-      newy = BOUNDS ((ROUND (y)), 0, 255);
+      newx = CLAMP0255 (ROUND (x));
+      newy = CLAMP0255 (ROUND (y));
 
       /* if this point is different than the last one...then draw it */
       if ((lastx != newx) || (lasty != newy))
@@ -914,7 +914,7 @@ curves_smooth_callback (GtkWidget *w,
       /*  pick representative points from the curve and make them control points  */
       for (i = 0; i <= 8; i++)
 	{
-	  index = BOUNDS ((i * 32), 0, 255);
+	  index = CLAMP0255 (i * 32);
 	  cd->points[cd->channel][i * 2][0] = index;
 	  cd->points[cd->channel][i * 2][1] = cd->curve[cd->channel][index];
 	}
diff --git a/app/display/gimpdisplay-ops.c b/app/display/gimpdisplay-ops.c
index 116141142b..efa65b26e2 100644
--- a/app/display/gimpdisplay-ops.c
+++ b/app/display/gimpdisplay-ops.c
@@ -154,8 +154,8 @@ gdisplay_shrink_wrap (GDisplay *gdisp)
       shell_width = width + border_x;
       shell_height = height + border_y;
 
-      x = HIGHPASS (shell_x, BOUNDS (s_width - shell_width, border_x, s_width));
-      y = HIGHPASS (shell_y, BOUNDS (s_height - shell_height, border_y, s_height));
+      x = MINIMUM (shell_x, BOUNDS (s_width - shell_width, border_x, s_width));
+      y = MINIMUM (shell_y, BOUNDS (s_height - shell_height, border_y, s_height));
 
       if (x != shell_x || y != shell_y)
 	gdk_window_move (gdisp->shell->window, x, y);
@@ -183,8 +183,8 @@ gdisplay_shrink_wrap (GDisplay *gdisp)
       shell_width = width + border_x;
       shell_height = height + border_y;
 
-      x = HIGHPASS (shell_x, BOUNDS (s_width - shell_width, border_x, s_width));
-      y = HIGHPASS (shell_y, BOUNDS (s_height - shell_height, border_y, s_height));
+      x = MINIMUM (shell_x, BOUNDS (s_width - shell_width, border_x, s_width));
+      y = MINIMUM (shell_y, BOUNDS (s_height - shell_height, border_y, s_height));
 
       if (x != shell_x || y != shell_y)
 	gdk_window_move (gdisp->shell->window, x, y);
@@ -219,8 +219,8 @@ gdisplay_resize_image (GDisplay *gdisp)
   /*  Calculate the width and height of the new canvas  */
   sx = SCALE (gdisp, gdisp->gimage->width);
   sy = SCALE (gdisp, gdisp->gimage->height);
-  width = HIGHPASS (sx, gdisp->disp_width);
-  height = HIGHPASS (sy, gdisp->disp_height);
+  width = MINIMUM (sx, gdisp->disp_width);
+  height = MINIMUM (sy, gdisp->disp_height);
 
   /* if the new dimensions of the ximage are different than the old...resize */
   if (width != gdisp->disp_width || height != gdisp->disp_height)
diff --git a/app/display/gimpdisplay.h b/app/display/gimpdisplay.h
index 723a91a386..cd9467d48a 100644
--- a/app/display/gimpdisplay.h
+++ b/app/display/gimpdisplay.h
@@ -35,7 +35,7 @@
 #define  UNSCALE(g,x)   ((x * SCALESRC(g)) / SCALEDEST(g))
 
 #define LOWPASS(x) ((x>0) ? x : 0)
-#define HIGHPASS(x,y) ((x>y) ? y : x)
+/* #define HIGHPASS(x,y) ((x>y) ? y : x) */ /* unused - == MIN */
 
 
 typedef enum
diff --git a/app/gdisplay.h b/app/gdisplay.h
index 723a91a386..cd9467d48a 100644
--- a/app/gdisplay.h
+++ b/app/gdisplay.h
@@ -35,7 +35,7 @@
 #define  UNSCALE(g,x)   ((x * SCALESRC(g)) / SCALEDEST(g))
 
 #define LOWPASS(x) ((x>0) ? x : 0)
-#define HIGHPASS(x,y) ((x>y) ? y : x)
+/* #define HIGHPASS(x,y) ((x>y) ? y : x) */ /* unused - == MIN */
 
 
 typedef enum
diff --git a/app/gdisplay_ops.c b/app/gdisplay_ops.c
index 116141142b..efa65b26e2 100644
--- a/app/gdisplay_ops.c
+++ b/app/gdisplay_ops.c
@@ -154,8 +154,8 @@ gdisplay_shrink_wrap (GDisplay *gdisp)
       shell_width = width + border_x;
       shell_height = height + border_y;
 
-      x = HIGHPASS (shell_x, BOUNDS (s_width - shell_width, border_x, s_width));
-      y = HIGHPASS (shell_y, BOUNDS (s_height - shell_height, border_y, s_height));
+      x = MINIMUM (shell_x, BOUNDS (s_width - shell_width, border_x, s_width));
+      y = MINIMUM (shell_y, BOUNDS (s_height - shell_height, border_y, s_height));
 
       if (x != shell_x || y != shell_y)
 	gdk_window_move (gdisp->shell->window, x, y);
@@ -183,8 +183,8 @@ gdisplay_shrink_wrap (GDisplay *gdisp)
       shell_width = width + border_x;
       shell_height = height + border_y;
 
-      x = HIGHPASS (shell_x, BOUNDS (s_width - shell_width, border_x, s_width));
-      y = HIGHPASS (shell_y, BOUNDS (s_height - shell_height, border_y, s_height));
+      x = MINIMUM (shell_x, BOUNDS (s_width - shell_width, border_x, s_width));
+      y = MINIMUM (shell_y, BOUNDS (s_height - shell_height, border_y, s_height));
 
       if (x != shell_x || y != shell_y)
 	gdk_window_move (gdisp->shell->window, x, y);
@@ -219,8 +219,8 @@ gdisplay_resize_image (GDisplay *gdisp)
   /*  Calculate the width and height of the new canvas  */
   sx = SCALE (gdisp, gdisp->gimage->width);
   sy = SCALE (gdisp, gdisp->gimage->height);
-  width = HIGHPASS (sx, gdisp->disp_width);
-  height = HIGHPASS (sy, gdisp->disp_height);
+  width = MINIMUM (sx, gdisp->disp_width);
+  height = MINIMUM (sy, gdisp->disp_height);
 
   /* if the new dimensions of the ximage are different than the old...resize */
   if (width != gdisp->disp_width || height != gdisp->disp_height)
diff --git a/app/hue_saturation.c b/app/hue_saturation.c
index e09bcbb2c0..9b37b8b4b0 100644
--- a/app/hue_saturation.c
+++ b/app/hue_saturation.c
@@ -163,7 +163,7 @@ hue_saturation_calculate_transfers (HueSaturationDialog *hsd)
 	value = (hsd->saturation[0] + hsd->saturation[hue + 1]) * 255.0 / 100.0;
 	value = BOUNDS (value, -255, 255);
 #if 0
-        saturation_transfer[hue][i] = (unsigned char) (BOUNDS ((i * (255 + value)) / 255, 0, 255));
+        saturation_transfer[hue][i] = (unsigned char) (CLAMP0255 ((i * (255 + value)) / 255));
 #else
 	if (value < 0)
 	  saturation_transfer[hue][i] = (unsigned char) ((i * (255 + value)) / 255);
diff --git a/app/paint-funcs/paint-funcs.c b/app/paint-funcs/paint-funcs.c
index 716529182e..623fddb06f 100644
--- a/app/paint-funcs/paint-funcs.c
+++ b/app/paint-funcs/paint-funcs.c
@@ -725,7 +725,7 @@ divide_pixels (unsigned char *src1,
     {
       for (b = 0; b < alpha; b++) {
 	result = ((src1[b] * 256) / (1+src2[b]));
-        dest[b] = (result > 255) ? 255 : result;
+        dest[b] = MINIMUM(result, 255);
       }
 
       if (ha1 && ha2)
@@ -827,7 +827,9 @@ add_pixels (unsigned char *src1,
       for (b = 0; b < alpha; b++)
 	{
 	  sum = src1[b] + src2[b];
-	  dest[b] = (sum > 255) ? 255 : sum;
+	  dest[b] = MAX255 (sum);
+	  /* dest[b] = sum | ((sum&256) - ((sum&256) >> 8)); */
+	  /* dest[b] = (sum > 255) ? 255 : sum; */ /* older, little slower */
 	}
 
       if (ha1 && ha2)
diff --git a/app/paint_core.c b/app/paint_core.c
index f38908d4dd..cf23777e63 100644
--- a/app/paint_core.c
+++ b/app/paint_core.c
@@ -603,6 +603,7 @@ paint_core_get_paint_area (paint_core, drawable)
   int x, y;
   int x1, y1, x2, y2;
   int bytes;
+  int dwidth, dheight;
 
   bytes = drawable_has_alpha (drawable) ?
     drawable_bytes (drawable) : drawable_bytes (drawable) + 1;
@@ -611,12 +612,15 @@ paint_core_get_paint_area (paint_core, drawable)
   x = (int) paint_core->curx - (paint_core->brush->mask->width >> 1);
   y = (int) paint_core->cury - (paint_core->brush->mask->height >> 1);
 
-  x1 = BOUNDS (x - 1, 0, drawable_width (drawable));
-  y1 = BOUNDS (y - 1, 0, drawable_height (drawable));
+  dwidth = drawable_width (drawable);
+  dheight = drawable_height (drawable);
+
+  x1 = BOUNDS (x - 1, 0, dwidth);
+  y1 = BOUNDS (y - 1, 0, dheight);
   x2 = BOUNDS (x + paint_core->brush->mask->width + 1,
-	       0, drawable_width (drawable));
+	       0, dwidth);
   y2 = BOUNDS (y + paint_core->brush->mask->height + 1,
-	       0, drawable_height (drawable));
+	       0, dheight);
 
   /*  configure the canvas buffer  */
   if ((x2 - x1) && (y2 - y1))
@@ -640,18 +644,24 @@ paint_core_get_orig_image (paint_core, drawable, x1, y1, x2, y2)
   int h;
   int refd;
   int pixelwidth;
+  int dwidth, dheight;
   unsigned char * s, * d;
   void * pr;
 
   orig_buf = temp_buf_resize (orig_buf, drawable_bytes (drawable),
 			      x1, y1, (x2 - x1), (y2 - y1));
-  x1 = BOUNDS (x1, 0, drawable_width (drawable));
-  y1 = BOUNDS (y1, 0, drawable_height (drawable));
-  x2 = BOUNDS (x2, 0, drawable_width (drawable));
-  y2 = BOUNDS (y2, 0, drawable_height (drawable));
+
+  dwidth = drawable_width (drawable);
+  dheight = drawable_height (drawable);
+
+  x1 = BOUNDS (x1, 0, dwidth);
+  y1 = BOUNDS (y1, 0, dheight);
+  x2 = BOUNDS (x2, 0, dwidth);
+  y2 = BOUNDS (y2, 0, dheight);
 
   /*  configure the pixel regions  */
-  pixel_region_init (&srcPR, drawable_data (drawable), x1, y1, (x2 - x1), (y2 - y1), FALSE);
+  pixel_region_init (&srcPR, drawable_data (drawable), x1, y1,
+		     (x2 - x1), (y2 - y1), FALSE);
   destPR.bytes = orig_buf->bytes;
   destPR.x = 0; destPR.y = 0;
   destPR.w = (x2 - x1); destPR.h = (y2 - y1);
@@ -659,14 +669,18 @@ paint_core_get_orig_image (paint_core, drawable, x1, y1, x2, y2)
   destPR.data = temp_buf_data (orig_buf) +
     (y1 - orig_buf->y) * destPR.rowstride + (x1 - orig_buf->x) * destPR.bytes;
 
-  for (pr = pixel_regions_register (2, &srcPR, &destPR); pr != NULL; pr = pixel_regions_process (pr))
+  for (pr = pixel_regions_register (2, &srcPR, &destPR);
+       pr != NULL;
+       pr = pixel_regions_process (pr))
     {
       /*  If the undo tile corresponding to this location is valid, use it  */
-      undo_tile = tile_manager_get_tile (undo_tiles, srcPR.x, srcPR.y, 0, FALSE, FALSE);
+      undo_tile = tile_manager_get_tile (undo_tiles, srcPR.x, srcPR.y,
+					 0, FALSE, FALSE);
       if (undo_tile->valid == TRUE)
 	{
 	  refd = 1;
-	  undo_tile = tile_manager_get_tile (undo_tiles, srcPR.x, srcPR.y, 0, TRUE, FALSE);
+	  undo_tile = tile_manager_get_tile (undo_tiles, srcPR.x, srcPR.y,
+					     0, TRUE, FALSE);
 	  s = undo_tile->data + srcPR.rowstride * (srcPR.y % TILE_HEIGHT) +
 	    srcPR.bytes * (srcPR.x % TILE_WIDTH);
 	}
@@ -810,7 +824,7 @@ paint_core_subsample_mask (mask, x, y)
 	      while (s--)
 		{
 		  new_val = *d + ((*m * *k++) >> 8);
-		  *d++ = (new_val > 255) ? 255 : new_val;
+		  *d++ = MINIMUM (new_val, 255);
 		}
 	    }
 	  m++;
diff --git a/app/paint_funcs.c b/app/paint_funcs.c
index 716529182e..623fddb06f 100644
--- a/app/paint_funcs.c
+++ b/app/paint_funcs.c
@@ -725,7 +725,7 @@ divide_pixels (unsigned char *src1,
     {
       for (b = 0; b < alpha; b++) {
 	result = ((src1[b] * 256) / (1+src2[b]));
-        dest[b] = (result > 255) ? 255 : result;
+        dest[b] = MINIMUM(result, 255);
       }
 
       if (ha1 && ha2)
@@ -827,7 +827,9 @@ add_pixels (unsigned char *src1,
       for (b = 0; b < alpha; b++)
 	{
 	  sum = src1[b] + src2[b];
-	  dest[b] = (sum > 255) ? 255 : sum;
+	  dest[b] = MAX255 (sum);
+	  /* dest[b] = sum | ((sum&256) - ((sum&256) >> 8)); */
+	  /* dest[b] = (sum > 255) ? 255 : sum; */ /* older, little slower */
 	}
 
       if (ha1 && ha2)
diff --git a/app/tools/brightness_contrast.c b/app/tools/brightness_contrast.c
index 66bc9d5f84..3e0de2157f 100644
--- a/app/tools/brightness_contrast.c
+++ b/app/tools/brightness_contrast.c
@@ -133,7 +133,7 @@ brightness_contrast (PixelRegion *srcPR,
 	value = (i > 127) ? (255 - i) : i;
 	value = (int) (127.0 * pow ((double) (value ? value : 1) / 127.0,
 				    (double) (127 + bcd->contrast) / 127.0));
-	value = BOUNDS (value, 0, 255);
+	value = CLAMP0255 (value);
 	contrast[i] = (i > 127) ? (255 - value) : value;
       }
   else
@@ -142,7 +142,7 @@ brightness_contrast (PixelRegion *srcPR,
 	value = (i > 127) ? (255 - i) : i;
 	power = (bcd->contrast == 127) ? 127 : 127.0 / (127 - bcd->contrast);
 	value = (int) (127.0 * pow ((double) value / 127.0, power));
-	value = BOUNDS (value, 0, 255);
+	value = CLAMP0255 (value);
 	contrast[i] = (i > 127) ? (255 - value) : value;
       }
 
diff --git a/app/tools/color_balance.c b/app/tools/color_balance.c
index 2b6c839252..178ec52906 100644
--- a/app/tools/color_balance.c
+++ b/app/tools/color_balance.c
@@ -154,25 +154,25 @@ color_balance (PixelRegion *srcPR,
 	  b = b_n = s[BLUE_PIX];
 
 	  r_n += cbd->cyan_red[SHADOWS] * cyan_red_transfer[SHADOWS][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 	  r_n += cbd->cyan_red[MIDTONES] * cyan_red_transfer[MIDTONES][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 	  r_n += cbd->cyan_red[HIGHLIGHTS] * cyan_red_transfer[HIGHLIGHTS][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 
 	  g_n += cbd->magenta_green[SHADOWS] * magenta_green_transfer[SHADOWS][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 	  g_n += cbd->magenta_green[MIDTONES] * magenta_green_transfer[MIDTONES][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 	  g_n += cbd->magenta_green[HIGHLIGHTS] * magenta_green_transfer[HIGHLIGHTS][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 
 	  b_n += cbd->yellow_blue[SHADOWS] * yellow_blue_transfer[SHADOWS][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 	  b_n += cbd->yellow_blue[MIDTONES] * yellow_blue_transfer[MIDTONES][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 	  b_n += cbd->yellow_blue[HIGHLIGHTS] * yellow_blue_transfer[HIGHLIGHTS][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 
 	  if (cbd->preserve_luminosity)
 	    {
diff --git a/app/tools/curves.c b/app/tools/curves.c
index fe057c648f..15512ec6f6 100644
--- a/app/tools/curves.c
+++ b/app/tools/curves.c
@@ -757,8 +757,8 @@ curves_plot_curve (CurvesDialog *cd,
       dy += dy2;
       dy2 += dy3;
 
-      newx = BOUNDS ((ROUND (x)), 0, 255);
-      newy = BOUNDS ((ROUND (y)), 0, 255);
+      newx = CLAMP0255 (ROUND (x));
+      newy = CLAMP0255 (ROUND (y));
 
       /* if this point is different than the last one...then draw it */
       if ((lastx != newx) || (lasty != newy))
@@ -914,7 +914,7 @@ curves_smooth_callback (GtkWidget *w,
       /*  pick representative points from the curve and make them control points  */
       for (i = 0; i <= 8; i++)
 	{
-	  index = BOUNDS ((i * 32), 0, 255);
+	  index = CLAMP0255 (i * 32);
 	  cd->points[cd->channel][i * 2][0] = index;
 	  cd->points[cd->channel][i * 2][1] = cd->curve[cd->channel][index];
 	}
diff --git a/app/tools/gimpbrightnesscontrasttool.c b/app/tools/gimpbrightnesscontrasttool.c
index 66bc9d5f84..3e0de2157f 100644
--- a/app/tools/gimpbrightnesscontrasttool.c
+++ b/app/tools/gimpbrightnesscontrasttool.c
@@ -133,7 +133,7 @@ brightness_contrast (PixelRegion *srcPR,
 	value = (i > 127) ? (255 - i) : i;
 	value = (int) (127.0 * pow ((double) (value ? value : 1) / 127.0,
 				    (double) (127 + bcd->contrast) / 127.0));
-	value = BOUNDS (value, 0, 255);
+	value = CLAMP0255 (value);
 	contrast[i] = (i > 127) ? (255 - value) : value;
       }
   else
@@ -142,7 +142,7 @@ brightness_contrast (PixelRegion *srcPR,
 	value = (i > 127) ? (255 - i) : i;
 	power = (bcd->contrast == 127) ? 127 : 127.0 / (127 - bcd->contrast);
 	value = (int) (127.0 * pow ((double) value / 127.0, power));
-	value = BOUNDS (value, 0, 255);
+	value = CLAMP0255 (value);
 	contrast[i] = (i > 127) ? (255 - value) : value;
       }
 
diff --git a/app/tools/gimpcolorbalancetool.c b/app/tools/gimpcolorbalancetool.c
index 2b6c839252..178ec52906 100644
--- a/app/tools/gimpcolorbalancetool.c
+++ b/app/tools/gimpcolorbalancetool.c
@@ -154,25 +154,25 @@ color_balance (PixelRegion *srcPR,
 	  b = b_n = s[BLUE_PIX];
 
 	  r_n += cbd->cyan_red[SHADOWS] * cyan_red_transfer[SHADOWS][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 	  r_n += cbd->cyan_red[MIDTONES] * cyan_red_transfer[MIDTONES][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 	  r_n += cbd->cyan_red[HIGHLIGHTS] * cyan_red_transfer[HIGHLIGHTS][r_n];
-	  r_n = BOUNDS (r_n, 0, 255);
+	  r_n = CLAMP0255 (r_n);
 
 	  g_n += cbd->magenta_green[SHADOWS] * magenta_green_transfer[SHADOWS][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 	  g_n += cbd->magenta_green[MIDTONES] * magenta_green_transfer[MIDTONES][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 	  g_n += cbd->magenta_green[HIGHLIGHTS] * magenta_green_transfer[HIGHLIGHTS][g_n];
-	  g_n = BOUNDS (g_n, 0, 255);
+	  g_n = CLAMP0255 (g_n);
 
 	  b_n += cbd->yellow_blue[SHADOWS] * yellow_blue_transfer[SHADOWS][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 	  b_n += cbd->yellow_blue[MIDTONES] * yellow_blue_transfer[MIDTONES][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 	  b_n += cbd->yellow_blue[HIGHLIGHTS] * yellow_blue_transfer[HIGHLIGHTS][b_n];
-	  b_n = BOUNDS (b_n, 0, 255);
+	  b_n = CLAMP0255 (b_n);
 
 	  if (cbd->preserve_luminosity)
 	    {
diff --git a/app/tools/gimpcurvestool.c b/app/tools/gimpcurvestool.c
index fe057c648f..15512ec6f6 100644
--- a/app/tools/gimpcurvestool.c
+++ b/app/tools/gimpcurvestool.c
@@ -757,8 +757,8 @@ curves_plot_curve (CurvesDialog *cd,
       dy += dy2;
       dy2 += dy3;
 
-      newx = BOUNDS ((ROUND (x)), 0, 255);
-      newy = BOUNDS ((ROUND (y)), 0, 255);
+      newx = CLAMP0255 (ROUND (x));
+      newy = CLAMP0255 (ROUND (y));
 
       /* if this point is different than the last one...then draw it */
       if ((lastx != newx) || (lasty != newy))
@@ -914,7 +914,7 @@ curves_smooth_callback (GtkWidget *w,
       /*  pick representative points from the curve and make them control points  */
       for (i = 0; i <= 8; i++)
 	{
-	  index = BOUNDS ((i * 32), 0, 255);
+	  index = CLAMP0255 (i * 32);
 	  cd->points[cd->channel][i * 2][0] = index;
 	  cd->points[cd->channel][i * 2][1] = cd->curve[cd->channel][index];
 	}
diff --git a/app/tools/gimphuesaturationtool.c b/app/tools/gimphuesaturationtool.c
index e09bcbb2c0..9b37b8b4b0 100644
--- a/app/tools/gimphuesaturationtool.c
+++ b/app/tools/gimphuesaturationtool.c
@@ -163,7 +163,7 @@ hue_saturation_calculate_transfers (HueSaturationDialog *hsd)
 	value = (hsd->saturation[0] + hsd->saturation[hue + 1]) * 255.0 / 100.0;
 	value = BOUNDS (value, -255, 255);
 #if 0
-        saturation_transfer[hue][i] = (unsigned char) (BOUNDS ((i * (255 + value)) / 255, 0, 255));
+        saturation_transfer[hue][i] = (unsigned char) (CLAMP0255 ((i * (255 + value)) / 255));
 #else
 	if (value < 0)
 	  saturation_transfer[hue][i] = (unsigned char) ((i * (255 + value)) / 255);
diff --git a/app/tools/hue_saturation.c b/app/tools/hue_saturation.c
index e09bcbb2c0..9b37b8b4b0 100644
--- a/app/tools/hue_saturation.c
+++ b/app/tools/hue_saturation.c
@@ -163,7 +163,7 @@ hue_saturation_calculate_transfers (HueSaturationDialog *hsd)
 	value = (hsd->saturation[0] + hsd->saturation[hue + 1]) * 255.0 / 100.0;
 	value = BOUNDS (value, -255, 255);
 #if 0
-        saturation_transfer[hue][i] = (unsigned char) (BOUNDS ((i * (255 + value)) / 255, 0, 255));
+        saturation_transfer[hue][i] = (unsigned char) (CLAMP0255 ((i * (255 + value)) / 255));
 #else
 	if (value < 0)
 	  saturation_transfer[hue][i] = (unsigned char) ((i * (255 + value)) / 255);
diff --git a/app/tools/paint_core.c b/app/tools/paint_core.c
index f38908d4dd..cf23777e63 100644
--- a/app/tools/paint_core.c
+++ b/app/tools/paint_core.c
@@ -603,6 +603,7 @@ paint_core_get_paint_area (paint_core, drawable)
   int x, y;
   int x1, y1, x2, y2;
   int bytes;
+  int dwidth, dheight;
 
   bytes = drawable_has_alpha (drawable) ?
     drawable_bytes (drawable) : drawable_bytes (drawable) + 1;
@@ -611,12 +612,15 @@ paint_core_get_paint_area (paint_core, drawable)
   x = (int) paint_core->curx - (paint_core->brush->mask->width >> 1);
   y = (int) paint_core->cury - (paint_core->brush->mask->height >> 1);
 
-  x1 = BOUNDS (x - 1, 0, drawable_width (drawable));
-  y1 = BOUNDS (y - 1, 0, drawable_height (drawable));
+  dwidth = drawable_width (drawable);
+  dheight = drawable_height (drawable);
+
+  x1 = BOUNDS (x - 1, 0, dwidth);
+  y1 = BOUNDS (y - 1, 0, dheight);
   x2 = BOUNDS (x + paint_core->brush->mask->width + 1,
-	       0, drawable_width (drawable));
+	       0, dwidth);
   y2 = BOUNDS (y + paint_core->brush->mask->height + 1,
-	       0, drawable_height (drawable));
+	       0, dheight);
 
   /*  configure the canvas buffer  */
   if ((x2 - x1) && (y2 - y1))
@@ -640,18 +644,24 @@ paint_core_get_orig_image (paint_core, drawable, x1, y1, x2, y2)
   int h;
   int refd;
   int pixelwidth;
+  int dwidth, dheight;
   unsigned char * s, * d;
   void * pr;
 
   orig_buf = temp_buf_resize (orig_buf, drawable_bytes (drawable),
 			      x1, y1, (x2 - x1), (y2 - y1));
-  x1 = BOUNDS (x1, 0, drawable_width (drawable));
-  y1 = BOUNDS (y1, 0, drawable_height (drawable));
-  x2 = BOUNDS (x2, 0, drawable_width (drawable));
-  y2 = BOUNDS (y2, 0, drawable_height (drawable));
+
+  dwidth = drawable_width (drawable);
+  dheight = drawable_height (drawable);
+
+  x1 = BOUNDS (x1, 0, dwidth);
+  y1 = BOUNDS (y1, 0, dheight);
+  x2 = BOUNDS (x2, 0, dwidth);
+  y2 = BOUNDS (y2, 0, dheight);
 
   /*  configure the pixel regions  */
-  pixel_region_init (&srcPR, drawable_data (drawable), x1, y1, (x2 - x1), (y2 - y1), FALSE);
+  pixel_region_init (&srcPR, drawable_data (drawable), x1, y1,
+		     (x2 - x1), (y2 - y1), FALSE);
   destPR.bytes = orig_buf->bytes;
   destPR.x = 0; destPR.y = 0;
   destPR.w = (x2 - x1); destPR.h = (y2 - y1);
@@ -659,14 +669,18 @@ paint_core_get_orig_image (paint_core, drawable, x1, y1, x2, y2)
   destPR.data = temp_buf_data (orig_buf) +
     (y1 - orig_buf->y) * destPR.rowstride + (x1 - orig_buf->x) * destPR.bytes;
 
-  for (pr = pixel_regions_register (2, &srcPR, &destPR); pr != NULL; pr = pixel_regions_process (pr))
+  for (pr = pixel_regions_register (2, &srcPR, &destPR);
+       pr != NULL;
+       pr = pixel_regions_process (pr))
     {
       /*  If the undo tile corresponding to this location is valid, use it  */
-      undo_tile = tile_manager_get_tile (undo_tiles, srcPR.x, srcPR.y, 0, FALSE, FALSE);
+      undo_tile = tile_manager_get_tile (undo_tiles, srcPR.x, srcPR.y,
+					 0, FALSE, FALSE);
       if (undo_tile->valid == TRUE)
 	{
 	  refd = 1;
-	  undo_tile = tile_manager_get_tile (undo_tiles, srcPR.x, srcPR.y, 0, TRUE, FALSE);
+	  undo_tile = tile_manager_get_tile (undo_tiles, srcPR.x, srcPR.y,
+					     0, TRUE, FALSE);
 	  s = undo_tile->data + srcPR.rowstride * (srcPR.y % TILE_HEIGHT) +
 	    srcPR.bytes * (srcPR.x % TILE_WIDTH);
 	}
@@ -810,7 +824,7 @@ paint_core_subsample_mask (mask, x, y)
 	      while (s--)
 		{
 		  new_val = *d + ((*m * *k++) >> 8);
-		  *d++ = (new_val > 255) ? 255 : new_val;
+		  *d++ = MINIMUM (new_val, 255);
 		}
 	    }
 	  m++;
diff --git a/app/undo.c b/app/undo.c
index b7deea7280..facc59be9b 100644
--- a/app/undo.c
+++ b/app/undo.c
@@ -513,6 +513,7 @@ undo_push_image_mod (GImage *gimage,
 		     int     sparse)
 {
   long size;
+  int dwidth, dheight;
   Undo * new;
   ImageUndo *image_undo;
   TileManager *tiles;
@@ -524,10 +525,13 @@ undo_push_image_mod (GImage *gimage,
   if (! tiles_ptr)
     return FALSE;
 
-  x1 = BOUNDS (x1, 0, drawable_width (drawable));
-  y1 = BOUNDS (y1, 0, drawable_height (drawable));
-  x2 = BOUNDS (x2, 0, drawable_width (drawable));
-  y2 = BOUNDS (y2, 0, drawable_height (drawable));
+  dwidth = drawable_width (drawable);
+  dheight = drawable_height (drawable);
+
+  x1 = BOUNDS (x1, 0, dwidth);
+  y1 = BOUNDS (y1, 0, dheight);
+  x2 = BOUNDS (x2, 0, dwidth);
+  y2 = BOUNDS (y2, 0, dheight);
 
   tiles = (TileManager *) tiles_ptr;
   size = tiles->levels[0].width * tiles->levels[0].height *