From 053ba0c543f95ed3fecf5dd3e3fe0cd36e23e8c5 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Fri, 1 Jun 2007 19:45:24 +0000
Subject: [PATCH] From Wojciech Lewandowski, "I did few tests to see whether
 adding PreDraw callback would help us with SPI problems when using Viewer.
 Results were positive so I decided to give it a try and ask you to verify and
 maybe merge with existing codebase.

I added _preDrawCallback member and neccessary access methods plus modified osgUtil RenderStage.cpp to invoke it before all drawInner calls are made. I tried to maintain symmetry with postDrawCallback but you know better where is a proper place for this call ;-)
"
---
 include/osg/Camera          | 13 ++++++++++++-
 src/osg/Camera.cpp          |  1 +
 src/osgUtil/RenderStage.cpp |  6 ++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/include/osg/Camera b/include/osg/Camera
index a6592775b..596dc0623 100644
--- a/include/osg/Camera
+++ b/include/osg/Camera
@@ -384,7 +384,17 @@ class OSG_EXPORT Camera : public Transform, public CullSettings
             virtual void operator () (const osg::Camera& /*camera*/) const {}
         };
         
-        /** Set the post draw callback for custom operations to do done after the drawing of the camera's subgraph has been completed.*/
+       /** Set the pre draw callback for custom operations to be done before the drawing of the camera's subgraph has been completed.*/
+        void setPreDrawCallback(DrawCallback* cb) { _preDrawCallback = cb; }
+
+        /** Get the pre draw callback.*/
+        DrawCallback* getPreDrawCallback() { return _preDrawCallback.get(); }
+
+        /** Get the const pre draw callback.*/
+        const DrawCallback* getPreDrawCallback() const { return _preDrawCallback.get(); }
+ 
+
+        /** Set the post draw callback for custom operations to be done after the drawing of the camera's subgraph has been completed.*/
         void setPostDrawCallback(DrawCallback* cb) { _postDrawCallback = cb; }
 
         /** Get the post draw callback.*/
@@ -451,6 +461,7 @@ class OSG_EXPORT Camera : public Transform, public CullSettings
         
         buffered_object< ref_ptr<Object> >  _renderingCache;
         
+        ref_ptr<DrawCallback>               _preDrawCallback;
         ref_ptr<DrawCallback>               _postDrawCallback;
 };
 
diff --git a/src/osg/Camera.cpp b/src/osg/Camera.cpp
index c247020bf..4f8f1d062 100644
--- a/src/osg/Camera.cpp
+++ b/src/osg/Camera.cpp
@@ -52,6 +52,7 @@ Camera::Camera(const Camera& camera,const CopyOp& copyop):
     _renderTargetImplementation(camera._renderTargetImplementation),
     _renderTargetFallback(camera._renderTargetFallback),
     _bufferAttachmentMap(camera._bufferAttachmentMap),
+    _preDrawCallback(camera._preDrawCallback),
     _postDrawCallback(camera._postDrawCallback)
 {
     // need to copy/share graphics context?
diff --git a/src/osgUtil/RenderStage.cpp b/src/osgUtil/RenderStage.cpp
index ec959ded1..80dbc744f 100644
--- a/src/osgUtil/RenderStage.cpp
+++ b/src/osgUtil/RenderStage.cpp
@@ -864,6 +864,12 @@ void RenderStage::draw(osg::RenderInfo& renderInfo,RenderLeaf*& previous)
         
         if (!useThread) useContext->makeCurrent();
     }
+
+    if (_camera && _camera->getPreDrawCallback())
+    {
+        // if we have a camera with a post draw callback invoke it.
+        (*(_camera->getPreDrawCallback()))(*_camera);
+    }
     
     bool doCopyTexture = _texture.valid() ? 
                         (callingContext != useContext) :