From 146b3cff19870dfb2d1853eec4f7376c0137b1bb Mon Sep 17 00:00:00 2001
From: Alex Szpakowski <slime73@gmail.com>
Date: Thu, 27 Mar 2014 23:28:36 -0300
Subject: [PATCH] Added blend mode "screen".

---
 src/modules/graphics/Graphics.cpp        | 1 +
 src/modules/graphics/Graphics.h          | 1 +
 src/modules/graphics/opengl/Graphics.cpp | 6 ++++++
 3 files changed, 8 insertions(+)

diff --git a/src/modules/graphics/Graphics.cpp b/src/modules/graphics/Graphics.cpp
index 10f8cf8e1..516c8530c 100644
--- a/src/modules/graphics/Graphics.cpp
+++ b/src/modules/graphics/Graphics.cpp
@@ -144,6 +144,7 @@ StringMap<Graphics::BlendMode, Graphics::BLEND_MAX_ENUM>::Entry Graphics::blendM
 	{ "subtractive", Graphics::BLEND_SUBTRACTIVE },
 	{ "multiplicative", Graphics::BLEND_MULTIPLICATIVE },
 	{ "premultiplied", Graphics::BLEND_PREMULTIPLIED },
+	{ "screen", Graphics::BLEND_SCREEN },
 	{ "replace", Graphics::BLEND_REPLACE },
 };
 
diff --git a/src/modules/graphics/Graphics.h b/src/modules/graphics/Graphics.h
index e91d96e8f..95406e485 100644
--- a/src/modules/graphics/Graphics.h
+++ b/src/modules/graphics/Graphics.h
@@ -57,6 +57,7 @@ public:
 		BLEND_SUBTRACTIVE,
 		BLEND_MULTIPLICATIVE,
 		BLEND_PREMULTIPLIED,
+		BLEND_SCREEN,
 		BLEND_REPLACE,
 		BLEND_MAX_ENUM
 	};
diff --git a/src/modules/graphics/opengl/Graphics.cpp b/src/modules/graphics/opengl/Graphics.cpp
index 3630e3216..80a0c3026 100644
--- a/src/modules/graphics/opengl/Graphics.cpp
+++ b/src/modules/graphics/opengl/Graphics.cpp
@@ -642,6 +642,10 @@ void Graphics::setBlendMode(Graphics::BlendMode mode)
 		state.srcRGB = state.srcA = GL_SRC_ALPHA;
 		state.dstRGB = state.dstA = GL_ONE;
 		break;
+	case BLEND_SCREEN:
+		state.srcRGB = state.srcA = GL_ONE;
+		state.dstRGB = state.dstA = GL_ONE_MINUS_SRC_COLOR;
+		break;
 	case BLEND_REPLACE:
 	default:
 		state.srcRGB = state.srcA = GL_ONE;
@@ -669,6 +673,8 @@ Graphics::BlendMode Graphics::getBlendMode() const
 			return BLEND_MULTIPLICATIVE;
 		else if (state.srcRGB == GL_ONE && state.dstRGB == GL_ONE_MINUS_SRC_ALPHA)
 			return BLEND_PREMULTIPLIED;
+		else if (state.srcRGB == GL_ONE && state.dstRGB == GL_ONE_MINUS_SRC_COLOR)
+			return BLEND_SCREEN;
 		else if (state.srcRGB == GL_ONE && state.dstRGB == GL_ZERO)
 			return BLEND_REPLACE;
 	}