use FBO for the picking

Change-Id: Ibab6daa1f76300d159ccd4cfbca061c8d8c1951f

chart2/source/view/charttypes/GL3DBarChart.cxx

@@ -217,14 +217,16 @@ public:
 
 }
 
-void GL3DBarChart::clickedAt(const Point& )
+void GL3DBarChart::clickedAt(const Point& rPos)
 {
+    sal_uInt32 nId = 1;
     {
         PickingModeSetter(mpRenderer.get());
         render();
+        nId = mpRenderer->GetPixelColorFromPoint(rPos.X(), rPos.Y());
     }
     if (mpCamera)
-        mpCamera->zoom(1);
+        mpCamera->zoom(nId);
 }
 
 }

chart2/source/view/inc/GL3DRenderer.hxx

@@ -179,6 +179,8 @@ public:
     void ProcessUnrenderedShape();
 
     void SetPickingMode(bool bPickingMode);
+
+    sal_uInt32 GetPixelColorFromPoint(long nX, long nY);
 private:
     void MoveModelf(PosVecf3& trans,PosVecf3& angle,PosVecf3& scale);
 
@@ -362,6 +364,10 @@ private:
 
     bool mbPickingMode;
     SceneBox m_SenceBox;
+
+    GLuint mnPickingFbo;
+    GLuint mnPickingRbo;
+    GLuint mnPickingTexture;
 };
 
 }

chart2/source/view/main/GL3DRenderer.cxx

@@ -249,6 +249,8 @@ void OpenGL3DRenderer::init()
     glBufferData(GL_ARRAY_BUFFER, sizeof(squareVertices), squareVertices, GL_STATIC_DRAW);
     glBindBuffer(GL_ARRAY_BUFFER, 0);
 
+    OpenGLHelper::createFramebuffer(m_iWidth, m_iHeight, mnPickingFbo, mnPickingRbo, mnPickingTexture);
+
     CHECK_GL_ERROR();
     Init3DUniformBlock();
 
@@ -1580,6 +1582,22 @@ void OpenGL3DRenderer::MoveModelf(PosVecf3& trans,PosVecf3& angle,PosVecf3& scal
 void OpenGL3DRenderer::SetPickingMode(bool bPickingMode)
 {
     mbPickingMode = bPickingMode;
+    if(mbPickingMode)
+    {
+        glBindFramebuffer(GL_FRAMEBUFFER, mnPickingFbo);
+    }
+    else
+    {
+        glBindFramebuffer(GL_FRAMEBUFFER, 0);
+    }
+}
+
+sal_uInt32 OpenGL3DRenderer::GetPixelColorFromPoint(long nX, long nY)
+{
+    boost::scoped_array<sal_uInt8> buf(new sal_uInt8[4]);
+    glReadPixels(nX, nY, 1, 1, GL_BGRA, GL_UNSIGNED_BYTE, buf.get());
+    Color aColor(buf[3], buf[2], buf[1], buf[0]);
+    return aColor.GetColor();
 }
 
 }