Fixed an issue when using wireframe without a full screen render target in HDRP

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDUtils.cs

             return Matrix4x4.Transpose(worldToViewMatrix.transpose * viewSpaceRasterTransform);
         }
 
+        private static void SetViewportAndClear(CommandBuffer cmd, HDCamera camera, RTHandle buffer, ClearFlag clearFlag, Color clearColor)
+        {
+            // Clearing a partial viewport currently does not go through the hardware clear.
+            // Instead it goes through a quad rendered with a specific shader.
+            // When enabling wireframe mode in the scene view, unfortunately it overrides this shader thus breaking every clears.
+            // That's why in the editor we don't set the viewport before clearing (it's set to full screen by the previous SetRenderTarget) but AFTER so that we benefit from un-bugged hardware clear.
+            // We consider that the small loss in performance is acceptable in the editor.
+            // A refactor of wireframe is needed before we can fix this properly (with not doing anything!)
+#if !UNITY_EDITOR
+            SetViewport(cmd, camera, buffer);
+#endif
+            CoreUtils.ClearRenderTarget(cmd, clearFlag, clearColor);
+#if UNITY_EDITOR
+            SetViewport(cmd, camera, buffer);
+#endif
+        }
+
-            SetViewport(cmd, camera, buffer);
-            CoreUtils.ClearRenderTarget(cmd, clearFlag, clearColor);
+            SetViewportAndClear(cmd, camera, buffer, clearFlag, clearColor);
         }
 
         public static void SetRenderTarget(CommandBuffer cmd, HDCamera camera, RTHandle buffer, ClearFlag clearFlag = ClearFlag.None, int miplevel = 0, CubemapFace cubemapFace = CubemapFace.Unknown, int depthSlice = 0)
         public static void SetRenderTarget(CommandBuffer cmd, HDCamera camera, RTHandle colorBuffer, RTHandle depthBuffer, ClearFlag clearFlag, Color clearColor, int miplevel = 0, CubemapFace cubemapFace = CubemapFace.Unknown, int depthSlice = 0)
         {
             CoreUtils.SetRenderTarget(cmd, colorBuffer, depthBuffer, miplevel, cubemapFace, depthSlice);
-            SetViewport(cmd, camera, colorBuffer);
-            CoreUtils.ClearRenderTarget(cmd, clearFlag, clearColor);
+            SetViewportAndClear(cmd, camera, colorBuffer, clearFlag, clearColor);
         }
 
         public static void SetRenderTarget(CommandBuffer cmd, HDCamera camera, RenderTargetIdentifier[] colorBuffers, RTHandle depthBuffer)
         public static void SetRenderTarget(CommandBuffer cmd, HDCamera camera, RenderTargetIdentifier[] colorBuffers, RTHandle depthBuffer, ClearFlag clearFlag = ClearFlag.None)
         {
             CoreUtils.SetRenderTarget(cmd, colorBuffers, depthBuffer); // Don't clear here, viewport needs to be set before we do.
-            SetViewport(cmd, camera, depthBuffer);
-            CoreUtils.ClearRenderTarget(cmd, clearFlag, CoreUtils.clearColorAllBlack);
+            SetViewportAndClear(cmd, camera, depthBuffer, clearFlag, CoreUtils.clearColorAllBlack);
         }
 
         public static void SetRenderTarget(CommandBuffer cmd, HDCamera camera, RenderTargetIdentifier[] colorBuffers, RTHandle depthBuffer, ClearFlag clearFlag, Color clearColor)