From af77e4f49de804e9a37bbadb40bd3668d96a8d8c Mon Sep 17 00:00:00 2001
From: Egor <egor.yusov@gmail.com>
Date: Mon, 19 Feb 2018 15:47:19 -0800
Subject: Fixed error when setting independent blend states on GLES devices
 that only support 4 render targets.

---
 .../GraphicsEngineOpenGL/include/GLContextState.h  | 14 ++++++++-----
 .../src/DeviceContextGLImpl.cpp                    |  6 +++++-
 .../GraphicsEngineOpenGL/src/GLContextState.cpp    | 24 ++++++++++++++++++++--
 3 files changed, 36 insertions(+), 8 deletions(-)

(limited to 'Graphics/GraphicsEngineOpenGL')

diff --git a/Graphics/GraphicsEngineOpenGL/include/GLContextState.h b/Graphics/GraphicsEngineOpenGL/include/GLContextState.h
index ab985d1d..919f73ce 100644
--- a/Graphics/GraphicsEngineOpenGL/include/GLContextState.h
+++ b/Graphics/GraphicsEngineOpenGL/include/GLContextState.h
@@ -77,6 +77,14 @@ public:
     void SetCurrentGLContext(GLContext::NativeGLContextType Context) { m_CurrentGLContext = Context; }
     GLContext::NativeGLContextType GetCurrentGLContext()const { return m_CurrentGLContext; }
 
+    struct ContextCaps
+    {
+        bool bFillModeSelectionSupported = True;
+        GLint m_iMaxCombinedTexUnits = 0;
+        GLint m_iMaxDrawBuffers = 0;
+    };
+    const ContextCaps& GetContextCaps(){return m_Caps;}
+
 private:
     // It is unsafe to use GL handle to keep track of bound objects
     // When an object is released, GL is free to reuse its handle for 
@@ -195,11 +203,7 @@ private:
         EnableStateHelper ScissorTestEnable;
     }m_RSState;
 
-    struct ContextCaps
-    {
-        bool bFillModeSelectionSupported = True;
-        GLint m_iMaxCombinedTexUnits = 0;
-    }m_Caps;
+    ContextCaps m_Caps;
 
     Uint32 m_ColorWriteMasks[MaxRenderTargets] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
     EnableStateHelper m_bIndependentWriteMasks;
diff --git a/Graphics/GraphicsEngineOpenGL/src/DeviceContextGLImpl.cpp b/Graphics/GraphicsEngineOpenGL/src/DeviceContextGLImpl.cpp
index 155758a5..f30b43b3 100644
--- a/Graphics/GraphicsEngineOpenGL/src/DeviceContextGLImpl.cpp
+++ b/Graphics/GraphicsEngineOpenGL/src/DeviceContextGLImpl.cpp
@@ -301,8 +301,12 @@ namespace Diligent
 
             Uint32 NumRenderTargets = m_NumBoundRenderTargets;
             VERIFY(NumRenderTargets < MaxRenderTargets, "Too many render targets (", NumRenderTargets, ") are being set");
-
             NumRenderTargets = std::min(NumRenderTargets, MaxRenderTargets);
+
+            const auto& CtxCaps = m_ContextState.GetContextCaps();
+            VERIFY(NumRenderTargets < CtxCaps.m_iMaxDrawBuffers, "This device only supports ", CtxCaps.m_iMaxDrawBuffers, " draw buffers, but ", NumRenderTargets, " are being set");
+            NumRenderTargets = std::min(NumRenderTargets, static_cast<Uint32>(CtxCaps.m_iMaxDrawBuffers));
+
             ITextureView *pBoundRTVs[MaxRenderTargets] = {};
             for (Uint32 rt = 0; rt < NumRenderTargets; ++rt)
                 pBoundRTVs[rt] = m_pBoundRenderTargets[rt];
diff --git a/Graphics/GraphicsEngineOpenGL/src/GLContextState.cpp b/Graphics/GraphicsEngineOpenGL/src/GLContextState.cpp
index a12373aa..1b8e3a36 100644
--- a/Graphics/GraphicsEngineOpenGL/src/GLContextState.cpp
+++ b/Graphics/GraphicsEngineOpenGL/src/GLContextState.cpp
@@ -46,6 +46,11 @@ namespace Diligent
             glGetIntegerv( GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS, &m_Caps.m_iMaxCombinedTexUnits );
             CHECK_GL_ERROR( "Failed to get max combined tex image units count" );
             VERIFY_EXPR(m_Caps.m_iMaxCombinedTexUnits > 0);
+
+            m_Caps.m_iMaxDrawBuffers = 0;
+            glGetIntegerv( GL_MAX_DRAW_BUFFERS, &m_Caps.m_iMaxDrawBuffers );
+            CHECK_GL_ERROR( "Failed to get max draw buffers count" );
+            VERIFY_EXPR(m_Caps.m_iMaxDrawBuffers > 0);
         }
 
         m_BoundTextures.reserve( m_Caps.m_iMaxCombinedTexUnits );
@@ -577,8 +582,15 @@ namespace Diligent
                 const auto& RT = BSDsc.RenderTargets[i];
                 if( RT.BlendEnable )
                     bEnableBlend = true;
-                                    
-                SetColorWriteMask(i, RT.RenderTargetWriteMask, True);
+
+                if(i < m_Caps.m_iMaxDrawBuffers)
+                {
+                    SetColorWriteMask(i, RT.RenderTargetWriteMask, True);
+                }
+                else
+                {
+                    VERIFY(RT.RenderTargetWriteMask == RenderTargetBlendDesc().RenderTargetWriteMask, "Render target write mask is specified for buffer ", i, " but this device only supports ", m_Caps.m_iMaxDrawBuffers, " draw buffers");
+                }
             }
         }
         else
@@ -610,6 +622,14 @@ namespace Diligent
                 for( int i = 0; i < BSDsc.MaxRenderTargets; ++i )
                 {
                     const auto& RT = BSDsc.RenderTargets[i];
+
+                    if(i >= m_Caps.m_iMaxDrawBuffers)
+                    {
+                        if( RT.BlendEnable )
+                            LOG_ERROR_MESSAGE("Blend is enabled for render target ", i, " but this device only supports ", m_Caps.m_iMaxDrawBuffers, " draw buffers");
+                        continue;
+                    }
+
                     if( RT.BlendEnable )
                     {
                         glEnablei( GL_BLEND, i );
-- 
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