From d3457f45080c7735dd7dac007730942dbb3a72f1 Mon Sep 17 00:00:00 2001
From: "alexey.lysiuk" <alexey.lysiuk@gmail.com>
Date: Sun, 31 Jul 2016 12:19:08 +0300
Subject: [PATCH] Implemented hardware gamma support for macOS

Hardware gamma is limited to main display only, use shader-based correction for other displays
---
 src/posix/cocoa/i_video.mm   | 30 ++++++++++++++++++++++++++++++
 src/posix/cocoa/sdlglvideo.h |  7 ++++++-
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/src/posix/cocoa/i_video.mm b/src/posix/cocoa/i_video.mm
index 3b04c64a0..242cb489b 100644
--- a/src/posix/cocoa/i_video.mm
+++ b/src/posix/cocoa/i_video.mm
@@ -1086,6 +1086,20 @@ SDLGLFB::SDLGLFB(void*, const int width, const int height, int, int, const bool
 , m_lock(-1)
 , m_isUpdatePending(false)
 {
+	CGGammaValue gammaTable[GAMMA_TABLE_SIZE];
+	uint32_t actualChannelSize;
+
+	const CGError result = CGGetDisplayTransferByTable(kCGDirectMainDisplay, GAMMA_CHANNEL_SIZE,
+		gammaTable, &gammaTable[GAMMA_CHANNEL_SIZE], &gammaTable[GAMMA_CHANNEL_SIZE * 2], &actualChannelSize);
+	m_supportsGamma = kCGErrorSuccess == result && GAMMA_CHANNEL_SIZE == actualChannelSize;
+
+	if (m_supportsGamma)
+	{
+		for (uint32_t i = 0; i < GAMMA_TABLE_SIZE; ++i)
+		{
+			m_originalGamma[i] = static_cast<WORD>(gammaTable[i] * 65535.0f);
+		}
+	}
 }
 
 SDLGLFB::SDLGLFB()
@@ -1169,10 +1183,26 @@ void SDLGLFB::SwapBuffers()
 
 void SDLGLFB::SetGammaTable(WORD* table)
 {
+	if (m_supportsGamma)
+	{
+		CGGammaValue gammaTable[GAMMA_TABLE_SIZE];
+
+		for (uint32_t i = 0; i < GAMMA_TABLE_SIZE; ++i)
+		{
+			gammaTable[i] = static_cast<CGGammaValue>(table[i] / 65535.0f);
+		}
+
+		CGSetDisplayTransferByTable(kCGDirectMainDisplay, GAMMA_CHANNEL_SIZE,
+			gammaTable, &gammaTable[GAMMA_CHANNEL_SIZE], &gammaTable[GAMMA_CHANNEL_SIZE * 2]);
+	}
 }
 
 void SDLGLFB::ResetGammaTable()
 {
+	if (m_supportsGamma)
+	{
+		SetGammaTable(m_originalGamma);
+	}
 }
 
 int SDLGLFB::GetClientWidth()
diff --git a/src/posix/cocoa/sdlglvideo.h b/src/posix/cocoa/sdlglvideo.h
index 4a63a9193..cab846a15 100644
--- a/src/posix/cocoa/sdlglvideo.h
+++ b/src/posix/cocoa/sdlglvideo.h
@@ -71,7 +71,12 @@ protected:
 	int                 m_lock;
 	bool                m_isUpdatePending;
 
-	static const bool   m_supportsGamma = false;
+	static const uint32_t GAMMA_CHANNEL_SIZE = 256;
+	static const uint32_t GAMMA_CHANNEL_COUNT = 3;
+	static const uint32_t GAMMA_TABLE_SIZE = GAMMA_CHANNEL_SIZE * GAMMA_CHANNEL_COUNT;
+
+	bool				m_supportsGamma;
+	WORD				m_originalGamma[GAMMA_TABLE_SIZE];
 
 	SDLGLFB();