Fix issue where gamma was being corrupted on windows with night light enabled

2 files changed, 23 insertions, 6 deletions

diff --git a/indra/llwindow/llwindowwin32.cpp b/indra/llwindow/llwindowwin32.cpp
index 504c1589b0..27787a51a8 100644
--- a/indra/llwindow/llwindowwin32.cpp
+++ b/indra/llwindow/llwindowwin32.cpp
@@ -425,6 +425,9 @@ LLWindowWin32::LLWindowWin32(LLWindowCallbacks* callbacks,
 	mKeyVirtualKey = 0;
 	mhDC = NULL;
 	mhRC = NULL;
+	memset(mCurrentGammaRamp, 0, sizeof(mCurrentGammaRamp));
+	memset(mPrevGammaRamp, 0, sizeof(mPrevGammaRamp));
+	mCustomGammaSet = FALSE;
 	
 	if (!SystemParametersInfo(SPI_GETMOUSEVANISH, 0, &mMouseVanish, 0))
 	{
@@ -2989,13 +2992,26 @@ F32 LLWindowWin32::getGamma()
 
 BOOL LLWindowWin32::restoreGamma()
 {
-	return SetDeviceGammaRamp(mhDC, mPrevGammaRamp);
+	if (mCustomGammaSet != FALSE)
+	{
+		mCustomGammaSet = FALSE;
+		return SetDeviceGammaRamp(mhDC, mPrevGammaRamp);
+	}
+	return TRUE;
 }
 
 BOOL LLWindowWin32::setGamma(const F32 gamma)
 {
 	mCurrentGamma = gamma;
 
+	//Get the previous gamma ramp to restore later.
+	if (mCustomGammaSet == FALSE)
+	{
+		if (GetDeviceGammaRamp(mhDC, mPrevGammaRamp) == FALSE)
+			return FALSE;
+		mCustomGammaSet = TRUE;
+	}
+
 	LL_DEBUGS("Window") << "Setting gamma to " << gamma << LL_ENDL;
 
 	for ( int i = 0; i < 256; ++i )
@@ -3007,9 +3023,9 @@ BOOL LLWindowWin32::setGamma(const F32 gamma)
 		if ( value > 0xffff )
 			value = 0xffff;
 
-		mCurrentGammaRamp [ 0 * 256 + i ] = 
-			mCurrentGammaRamp [ 1 * 256 + i ] = 
-				mCurrentGammaRamp [ 2 * 256 + i ] = ( WORD )value;
+		mCurrentGammaRamp[0][i] =
+			mCurrentGammaRamp[1][i] =
+			mCurrentGammaRamp[2][i] = (WORD) value;
 	};
 
 	return SetDeviceGammaRamp ( mhDC, mCurrentGammaRamp );
diff --git a/indra/llwindow/llwindowwin32.h b/indra/llwindow/llwindowwin32.h
index d72623a6f4..9cd16eb993 100644
--- a/indra/llwindow/llwindowwin32.h
+++ b/indra/llwindow/llwindowwin32.h
@@ -184,8 +184,9 @@ protected:
 
 	F32			mCurrentGamma;
 	U32			mFSAASamples;
-	WORD		mPrevGammaRamp[256*3];
-	WORD		mCurrentGammaRamp[256*3];
+	WORD		mPrevGammaRamp[3][256];
+	WORD		mCurrentGammaRamp[3][256];
+	BOOL		mCustomGammaSet;
 
 	LPWSTR		mIconResource;
 	BOOL		mMousePositionModified;