Refactor menu/automap background shading for optimization

The trick is simple - a local copy of global variables of I_VideoBuffer (basically, "screen pixel") and shading factors are used inside 'for' loops. This is faster for the overall loop processing.
JNechaevsky · Jan 1, 2025 · 12c574b · 12c574b
1 parent c797197
commit 12c574b
Show file tree

Hide file tree

Showing 6 changed files with 59 additions and 32 deletions.
diff --git a/src/doom/am_map.c b/src/doom/am_map.c
@@ -1225,17 +1225,21 @@ static void AM_clearFB (void)
 
 static void AM_shadeBackground (void)
 {
-    const int height = dp_screen_size > 10 ?
-                       SCREENHEIGHT : (SCREENHEIGHT - (ST_HEIGHT * vid_resolution));
+    pixel_t *dest = I_VideoBuffer;
+    const int shade = automap_shading;
+    const int scr = (dp_screen_size > 10)
+                  ? SCREENWIDTH * SCREENHEIGHT
+                  : SCREENWIDTH * (SCREENHEIGHT - ST_HEIGHT * vid_resolution);
 
-        for (int y = 0; y < SCREENWIDTH * height ; y++)
-        {
+    for (int i = 0; i < scr; i++)
+    {
 #ifndef CRISPY_TRUECOLOR
-            I_VideoBuffer[y] = colormaps[((automap_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
+        *dest = colormaps[((automap_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
 #else
-            I_VideoBuffer[y] = I_BlendDark(I_VideoBuffer[y], I_ShadeFactor[automap_shading]);
+        *dest = I_BlendDark(*dest, I_ShadeFactor[shade]);
 #endif
-        }
+        ++dest;
+    }
 }
 
 // -----------------------------------------------------------------------------

diff --git a/src/doom/m_menu.c b/src/doom/m_menu.c
@@ -928,13 +928,18 @@ static void M_ShadeBackground (void)
 {
     if (dp_menu_shading)
     {
-        for (int y = 0; y < SCREENWIDTH * SCREENHEIGHT; y++)
+        pixel_t *dest = I_VideoBuffer;
+        const int shade = dp_menu_shading;
+        const int scr = SCREENWIDTH * SCREENHEIGHT;
+
+        for (int i = 0; i < scr; i++)
         {
 #ifndef CRISPY_TRUECOLOR
-            I_VideoBuffer[y] = colormaps[((dp_menu_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
+            *dest = colormaps[((dp_menu_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
 #else
-            I_VideoBuffer[y] = I_BlendDark(I_VideoBuffer[y], I_ShadeFactor[dp_menu_shading]);
+            *dest = I_BlendDark(*dest, I_ShadeFactor[shade]);
 #endif
+            ++dest;
         }
     }
 }

diff --git a/src/heretic/am_map.c b/src/heretic/am_map.c
@@ -1202,17 +1202,21 @@ static void AM_drawBackground (void)
 
 static void AM_shadeBackground (void)
 {
-    const int height = dp_screen_size > 10 ?
-                       SCREENHEIGHT : (SCREENHEIGHT - (42 * vid_resolution));
+    pixel_t *dest = I_VideoBuffer;
+    const int shade = automap_shading;
+    const int scr = (dp_screen_size > 10)
+                  ? SCREENWIDTH * SCREENHEIGHT
+                  : SCREENWIDTH * (SCREENHEIGHT - SBARHEIGHT);
 
-        for (int y = 0; y < SCREENWIDTH * height ; y++)
-        {
+    for (int i = 0; i < scr; i++)
+    {
 #ifndef CRISPY_TRUECOLOR
-            I_VideoBuffer[y] = colormaps[((automap_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
+        *dest = colormaps[((automap_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
 #else
-            I_VideoBuffer[y] = I_BlendDark(I_VideoBuffer[y], I_ShadeFactor[automap_shading]);
+        *dest = I_BlendDark(*dest, I_ShadeFactor[shade]);
 #endif
-        }
+        ++dest;
+    }
 }
 
 // -----------------------------------------------------------------------------

diff --git a/src/heretic/mn_menu.c b/src/heretic/mn_menu.c
@@ -792,18 +792,23 @@ static void M_ScrollPages (boolean direction)
 // [JN] Delay before shading.
 static int shade_wait;
 
-// [JN] Shade background while in CRL menu.
+// [JN] Shade background while in active menu.
 static void M_ShadeBackground (void)
 {
     if (dp_menu_shading)
     {
-        for (int y = 0; y < SCREENWIDTH * SCREENHEIGHT; y++)
+        pixel_t *dest = I_VideoBuffer;
+        const int shade = dp_menu_shading;
+        const int scr = SCREENWIDTH * SCREENHEIGHT;
+
+        for (int i = 0; i < scr; i++)
         {
 #ifndef CRISPY_TRUECOLOR
-            I_VideoBuffer[y] = colormaps[((dp_menu_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
+            *dest = colormaps[((dp_menu_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
 #else
-            I_VideoBuffer[y] = I_BlendDark(I_VideoBuffer[y], I_ShadeFactor[dp_menu_shading]);
+            *dest = I_BlendDark(*dest, I_ShadeFactor[shade]);
 #endif
+            ++dest;
         }
     }
 }

diff --git a/src/hexen/am_map.c b/src/hexen/am_map.c
@@ -1074,17 +1074,21 @@ static void AM_drawBackground (void)
 
 static void AM_shadeBackground (void)
 {
-    const int height = dp_screen_size > 10 ?
-                       SCREENHEIGHT : (SCREENHEIGHT - SBARHEIGHT);
+    pixel_t *dest = I_VideoBuffer;
+    const int shade = automap_shading;
+    const int scr = (dp_screen_size > 10)
+                  ? SCREENWIDTH * SCREENHEIGHT
+                  : SCREENWIDTH * (SCREENHEIGHT - SBARHEIGHT);
 
-        for (int y = 0; y < SCREENWIDTH * height ; y++)
-        {
+    for (int i = 0; i < scr; i++)
+    {
 #ifndef CRISPY_TRUECOLOR
-            I_VideoBuffer[y] = colormaps[((automap_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
+        *dest = colormaps[((automap_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
 #else
-            I_VideoBuffer[y] = I_BlendDark(I_VideoBuffer[y], I_ShadeFactor[automap_shading]);
+        *dest = I_BlendDark(*dest, I_ShadeFactor[shade]);
 #endif
-        }
+        ++dest;
+    }
 }
 
 // -----------------------------------------------------------------------------

diff --git a/src/hexen/mn_menu.c b/src/hexen/mn_menu.c
@@ -744,18 +744,23 @@ static void M_ScrollPages (boolean direction)
 // [JN] Delay before shading.
 static int shade_wait;
 
-// [JN] Shade background while in CRL menu.
+// [JN] Shade background while in active menu.
 static void M_ShadeBackground (void)
 {
     if (dp_menu_shading)
     {
-        for (int y = 0; y < SCREENWIDTH * SCREENHEIGHT; y++)
+        pixel_t *dest = I_VideoBuffer;
+        const int shade = dp_menu_shading;
+        const int scr = SCREENWIDTH * SCREENHEIGHT;
+
+        for (int i = 0; i < scr; i++)
         {
 #ifndef CRISPY_TRUECOLOR
-            I_VideoBuffer[y] = colormaps[((dp_menu_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
+            *dest = colormaps[((dp_menu_shading + 3) * 2) * 256 + I_VideoBuffer[y]];
 #else
-            I_VideoBuffer[y] = I_BlendDark(I_VideoBuffer[y], I_ShadeFactor[dp_menu_shading]);
+            *dest = I_BlendDark(*dest, I_ShadeFactor[shade]);
 #endif
+            ++dest;
         }
     }
 }