Refactor: Moved gamma tables to DisplayMode class

Since SDL is going away, we cannot rely on it for setting display color
transfer tables. Moved the old gamma code from gl_main.c and added
new native OS X color table routines.

doomsday/engine/mac/src/displaymode_macx.mm

@@ -195,3 +195,39 @@ void DisplayMode_Native_Raise(void* nativeHandle)
     NSWindow* wnd = [handle window];
     [wnd setLevel:CGShieldingWindowLevel()];
 }
+
+void DisplayMode_Native_GetColorTransfer(displaycolortransfer_t* colors)
+{
+    const uint size = 256;
+    CGGammaValue red[size];
+    CGGammaValue green[size];
+    CGGammaValue blue[size];
+    uint32_t count = 0;
+
+    CGGetDisplayTransferByTable(kCGDirectMainDisplay, size, red, green, blue, &count);
+    assert(count == size);
+
+    for(uint i = 0; i < size; ++i)
+    {
+        colors->table[i]          = (unsigned short) (red[i]   * 0xffff);
+        colors->table[i + size]   = (unsigned short) (green[i] * 0xffff);
+        colors->table[i + 2*size] = (unsigned short) (blue[i]  * 0xffff);
+    }
+}
+
+void DisplayMode_Native_SetColorTransfer(const displaycolortransfer_t* colors)
+{
+    const uint size = 256;
+    CGGammaValue red[size];
+    CGGammaValue green[size];
+    CGGammaValue blue[size];
+
+    for(uint i = 0; i < size; ++i)
+    {
+        red[i]   = colors->table[i]/float(0xffff);
+        green[i] = colors->table[i + size]/float(0xffff);
+        blue[i]  = colors->table[i + 2*size]/float(0xffff);
+    }
+
+    CGSetDisplayTransferByTable(kCGDirectMainDisplay, size, red, green, blue);
+}

doomsday/engine/portable/include/displaymode.h

@@ -42,6 +42,10 @@ typedef struct displaymode_s {
     int ratioY;
 } DisplayMode;
 
+typedef struct displaycolortransfer_s {
+    unsigned short table[3 * 256]; // 0-255:red, 256-511:green, 512-767:blue (range: 0..ffff)
+} displaycolortransfer_t;
+
 /**
  * Initializes the DisplayMode class. Enumerates all available display modes and
  * saves the current display mode. Must be called at engine startup.
@@ -114,6 +118,20 @@ boolean DisplayMode_IsEqual(const DisplayMode* a, const DisplayMode* b);
  */
 int DisplayMode_Change(const DisplayMode* mode, boolean shouldCapture);
 
+/**
+ * Gets the current color transfer table.
+ *
+ * @param colors  Color transfer.
+ */
+void DisplayMode_GetColorTransfer(displaycolortransfer_t* colors);
+
+/**
+ * Sets the color transfer table.
+ *
+ * @param colors  Color transfer.
+ */
+void DisplayMode_SetColorTransfer(const displaycolortransfer_t* colors);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif

doomsday/engine/portable/include/displaymode_native.h

@@ -34,6 +34,8 @@ extern "C" {
 
 void DisplayMode_Native_Init(void);
 
+void DisplayMode_Native_Shutdown(void);
+
 int DisplayMode_Native_Count(void);
 
 void DisplayMode_Native_GetMode(int index, DisplayMode* mode);
@@ -42,7 +44,9 @@ void DisplayMode_Native_GetCurrentMode(DisplayMode* mode);
 
 int DisplayMode_Native_Change(const DisplayMode* mode, boolean shouldCapture);
 
-void DisplayMode_Native_Shutdown(void);
+void DisplayMode_Native_GetColorTransfer(displaycolortransfer_t* colors);
+
+void DisplayMode_Native_SetColorTransfer(const displaycolortransfer_t* colors);
 
 #ifdef MACOSX
 void DisplayMode_Native_Raise(void* handle);

doomsday/engine/portable/src/displaymode.cpp

@@ -28,6 +28,7 @@
 #include <de/Log>
 
 static bool inited = false;
+static displaycolortransfer_t originalColorTransfer;
 
 static float differenceToOriginalHz(float hz);
 
@@ -149,6 +150,7 @@ int DisplayMode_Init(void)
 
     captured = false;
     DisplayMode_Native_Init();
+    DisplayMode_Native_GetColorTransfer(&originalColorTransfer);
 
     // This is used for sorting the mode set (Hz).
     originalMode = Mode::fromCurrent();
@@ -183,6 +185,8 @@ void DisplayMode_Shutdown(void)
     // Back to the original mode.
     DisplayMode_Change(&originalMode, false /*release captured*/);
 
+    DisplayMode_Native_SetColorTransfer(&originalColorTransfer);
+
     modes.clear();
 
     DisplayMode_Native_Shutdown();
@@ -272,3 +276,19 @@ int DisplayMode_Change(const DisplayMode* mode, boolean shouldCapture)
     captured = shouldCapture;
     return DisplayMode_Native_Change(mode, shouldCapture || (originalMode != *mode));
 }
+
+void DisplayMode_GetColorTransfer(displaycolortransfer_t* colors)
+{
+    /// @todo  Factor in the original color transfer function, which may be
+    /// set up specifically by the user.
+
+    DisplayMode_Native_GetColorTransfer(colors);
+}
+
+void DisplayMode_SetColorTransfer(const displaycolortransfer_t* colors)
+{
+    /// @todo  Factor in the original color transfer function, which may be
+    /// set up specifically by the user.
+
+    DisplayMode_Native_SetColorTransfer(colors);
+}