Fixed error when setting independent blend states on GLES devices that only support 4 render targets.

Author: TheMostDiligent

Graphics/GraphicsEngineOpenGL/include/GLContextState.h

@@ -77,6 +77,14 @@ class GLContextState
     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 @@ class GLContextState
         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;

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];

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 );