diff --git a/src/cocoa/cocoa_window.m b/src/cocoa/cocoa_window.m
index 4353a216..941f24ba 100644
--- a/src/cocoa/cocoa_window.m
+++ b/src/cocoa/cocoa_window.m
@@ -792,9 +792,7 @@ void _glfwPlatformRefreshWindowParams(void)
                            forAttribute:NSOpenGLPFAColorSize
                        forVirtualScreen:0];
     value -= window->alphaBits;
-    window->redBits = value / 3;
-    window->greenBits = value / 3;
-    window->blueBits = value / 3;
+    _glfwSplitBPP(value, &window->redBits, &window->greenBits, &window->blueBits);
 
     [window->NSGL.pixelFormat getValues:&value
                            forAttribute:NSOpenGLPFADepthSize
diff --git a/src/fullscreen.c b/src/fullscreen.c
index 55e9c548..8b706a9d 100644
--- a/src/fullscreen.c
+++ b/src/fullscreen.c
@@ -63,6 +63,35 @@ static int compareVideoModes(const void* firstPtr, const void* secondPtr)
     return firstSize - secondSize;
 }
 
+
+//////////////////////////////////////////////////////////////////////////
+//////                       GLFW internal API                      //////
+//////////////////////////////////////////////////////////////////////////
+
+//========================================================================
+// Convert BPP to RGB bits based on "best guess"
+//========================================================================
+
+void _glfwSplitBPP(int bpp, int* red, int* green, int* blue)
+{
+    int delta;
+
+    // We assume that by 32 they really meant 24
+    if (bpp == 32)
+        bpp = 24;
+
+    // Convert "bits per pixel" to red, green & blue sizes
+
+    *red = *green = *blue = bpp / 3;
+    delta = bpp - (*red * 3);
+    if (delta >= 1)
+        *green = *green + 1;
+
+    if (delta == 2)
+        *red = *red + 1;
+}
+
+
 //////////////////////////////////////////////////////////////////////////
 //////                        GLFW public API                       //////
 //////////////////////////////////////////////////////////////////////////
diff --git a/src/internal.h b/src/internal.h
index 3d71baac..52b5bdff 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -284,6 +284,9 @@ void* _glfwPlatformGetProcAddress(const char* procname);
 // Prototypes for platform independent internal functions
 //========================================================================
 
+// Fullscren management (fullscreen.c)
+void _glfwSplitBPP(int bpp, int* red, int* green, int* blue);
+
 // Error handling
 void _glfwSetError(int error);
 
diff --git a/src/win32/win32_fullscreen.c b/src/win32/win32_fullscreen.c
index 58f262b1..3604b8d1 100644
--- a/src/win32/win32_fullscreen.c
+++ b/src/win32/win32_fullscreen.c
@@ -34,30 +34,6 @@
 #include <limits.h>
 
 
-//========================================================================
-// Convert BPP to RGB bits based on "best guess"
-//========================================================================
-
-static void bpp2rgb(int bpp, int* r, int* g, int* b)
-{
-    int delta;
-
-    // We assume that by 32 they really meant 24
-    if (bpp == 32)
-        bpp = 24;
-
-    // Convert "bits per pixel" to red, green & blue sizes
-
-    *r = *g = *b = bpp / 3;
-    delta = bpp - (*r * 3);
-    if (delta >= 1)
-        *g = *g + 1;
-
-    if (delta == 2)
-        *r = *r + 1;
-}
-
-
 //========================================================================
 // Return closest video mode by dimensions, refresh rate and bits per pixel
 //========================================================================
@@ -226,7 +202,7 @@ int _glfwPlatformGetVideoModes(GLFWvidmode* list, int maxcount)
         if (success && dm.dmBitsPerPel >= 15)
         {
             // Convert to RGB, and back to bpp ("mask out" alpha bits etc)
-            bpp2rgb(dm.dmBitsPerPel, &r, &g, &b);
+            _glfwSplitBPP(dm.dmBitsPerPel, &r, &g, &b);
             bpp = r + g + b;
 
             // Mode "code" for this mode
@@ -289,6 +265,6 @@ void _glfwPlatformGetDesktopMode(GLFWvidmode* mode)
     // Return desktop mode parameters
     mode->width  = dm.dmPelsWidth;
     mode->height = dm.dmPelsHeight;
-    bpp2rgb(dm.dmBitsPerPel, &mode->redBits, &mode->greenBits, &mode->blueBits);
+    _glfwSplitBPP(dm.dmBitsPerPel, &mode->redBits, &mode->greenBits, &mode->blueBits);
 }
 
diff --git a/src/x11/x11_fullscreen.c b/src/x11/x11_fullscreen.c
index 5a584636..a80ed918 100644
--- a/src/x11/x11_fullscreen.c
+++ b/src/x11/x11_fullscreen.c
@@ -34,29 +34,6 @@
 #include <stdlib.h>
 
 
-//========================================================================
-// Convert BPP to RGB bits (based on "best guess")
-//========================================================================
-
-static void bpp2rgb(int bpp, int* r, int* g, int* b)
-{
-    int delta;
-
-    // Special case: BPP = 32 (I don't think this is necessary for X11??)
-    if (bpp == 32)
-        bpp = 24;
-
-    // Convert "bits per pixel" to red, green & blue sizes
-    *r = *g = *b = bpp / 3;
-    delta = bpp - (*r * 3);
-    if (delta >= 1)
-        *g = *g + 1;
-
-    if (delta == 2)
-        *r = *r + 1;
-}
-
-
 //////////////////////////////////////////////////////////////////////////
 //////                       GLFW internal API                      //////
 //////////////////////////////////////////////////////////////////////////
@@ -391,7 +368,7 @@ int _glfwPlatformGetVideoModes(GLFWvidmode* list, int maxcount)
             depth = vislist[k].depth;
 
             // Convert to RGB
-            bpp2rgb(depth, &r, &g, &b);
+            _glfwSplitBPP(depth, &r, &g, &b);
             depth = (r << 16) | (g << 8) | b;
 
             // Is this mode unique?
@@ -516,7 +493,7 @@ void _glfwPlatformGetDesktopMode(GLFWvidmode* mode)
     bpp = DefaultDepth(dpy, screen);
 
     // Convert BPP to RGB bits
-    bpp2rgb(bpp, &mode->redBits, &mode->greenBits, &mode->blueBits);
+    _glfwSplitBPP(bpp, &mode->redBits, &mode->greenBits, &mode->blueBits);
 
 #if defined(_GLFW_HAS_XRANDR)
     if (_glfwLibrary.X11.XRandR.available)