Add feature for per render target blending

Task-number: QTBUG-130334
Change-Id: I30ae0023ce8b5c26360e4255d64c209ebe404ede
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>

src/gui/rhi/qrhi.cpp

@@ -1069,6 +1069,11 @@ Q_STATIC_LOGGING_CATEGORY(QRHI_LOG_RUB, "qt.rhi.rub")
     specification of the shading rate is supported via regular textures. In
     practice this may be supported with Direct 3D 12 and Vulkan. This enum value
     has been introduced in Qt 6.9.
+
+    \value PerRenderTargetBlending Indicates that per rendertarget blending is
+    supported i.e. different render targets in MRT framebuffer can have different
+    blending modes. Currently always returns false for OpenGL.
+    This enum value has been introduced in Qt 6.9.
  */
 
 /*!

src/gui/rhi/qrhi.h

@@ -1907,7 +1907,8 @@ public:
         ResolveDepthStencil,
         VariableRateShading,
         VariableRateShadingMap,
-        VariableRateShadingMapWithTexture
+        VariableRateShadingMapWithTexture,
+        PerRenderTargetBlending,
     };
 
     enum BeginFrameFlag {

src/gui/rhi/qrhid3d11.cpp

@@ -656,6 +656,8 @@ bool QRhiD3D11::isFeatureSupported(QRhi::Feature feature) const
     case QRhi::VariableRateShadingMap:
     case QRhi::VariableRateShadingMapWithTexture:
         return false;
+    case QRhi::PerRenderTargetBlending:
+        return true;
     default:
         Q_UNREACHABLE();
         return false;

src/gui/rhi/qrhid3d12.cpp

@@ -807,6 +807,8 @@ bool QRhiD3D12::isFeatureSupported(QRhi::Feature feature) const
     case QRhi::VariableRateShadingMap:
     case QRhi::VariableRateShadingMapWithTexture:
         return caps.vrsMap;
+    case QRhi::PerRenderTargetBlending:
+        return true;
     }
     return false;
 }

src/gui/rhi/qrhigles2.cpp

@@ -1117,6 +1117,7 @@ bool QRhiGles2::create(QRhi::Flags flags)
     }
 
     caps.unpackRowLength = !caps.gles || caps.ctxMajor >= 3;
+    caps.perRenderTargetBlending = false;
 
     nativeHandlesStruct.context = ctx;
 
@@ -1507,6 +1508,8 @@ bool QRhiGles2::isFeatureSupported(QRhi::Feature feature) const
     case QRhi::VariableRateShadingMap:
     case QRhi::VariableRateShadingMapWithTexture:
         return false;
+    case QRhi::PerRenderTargetBlending:
+        return caps.perRenderTargetBlending;
     default:
         Q_UNREACHABLE_RETURN(false);
     }

src/gui/rhi/qrhigles2_p.h

@@ -1025,7 +1025,8 @@ public:
               objectLabel(false),
               glesMultisampleRenderToTexture(false),
               glesMultiviewMultisampleRenderToTexture(false),
-              unpackRowLength(false)
+              unpackRowLength(false),
+              perRenderTargetBlending(false)
         { }
         int ctxMajor;
         int ctxMinor;
@@ -1085,6 +1086,7 @@ public:
         uint glesMultisampleRenderToTexture : 1;
         uint glesMultiviewMultisampleRenderToTexture : 1;
         uint unpackRowLength : 1;
+        uint perRenderTargetBlending : 1;
     } caps;
     QGles2SwapChain *currentSwapChain = nullptr;
     QSet<GLint> supportedCompressedFormats;

src/gui/rhi/qrhimetal.mm

@@ -867,6 +867,8 @@ bool QRhiMetal::isFeatureSupported(QRhi::Feature feature) const
         return caps.shadingRateMap;
     case QRhi::VariableRateShadingMapWithTexture:
         return false;
+    case QRhi::PerRenderTargetBlending:
+        return true;
     default:
         Q_UNREACHABLE();
         return false;

src/gui/rhi/qrhivulkan.cpp

@@ -5202,6 +5202,8 @@ bool QRhiVulkan::isFeatureSupported(QRhi::Feature feature) const
     case QRhi::VariableRateShadingMap:
     case QRhi::VariableRateShadingMapWithTexture:
         return caps.renderPass2KHR && caps.imageBasedShadingRate;
+    case QRhi::PerRenderTargetBlending:
+        return true;
     default:
         Q_UNREACHABLE_RETURN(false);
     }