improve text positioning

Change-Id: I9a6d99105ae32a2e03e4756983a87cb4ad174ea2

chart2/source/view/main/OpenGLRender.cxx

@@ -1290,6 +1290,9 @@ int OpenGLRender::CreateTextTexture(const BitmapEx& rBitmapEx, const awt::Point&
     aTextInfo.vertex[10] = (rTrans.Line2.Column3 + aSize.Height) / OPENGL_SCALE_VALUE;
     aTextInfo.vertex[11] = m_fZStep;
 
+    aTextInfo.bmpWidth = bmpWidth;
+    aTextInfo.bmpHeight = bmpHeight;
+
     //if has ratotion, we must re caculate the central pos
     if (!rtl::math::approxEqual(0, rotation))
     {
@@ -1324,7 +1327,7 @@ int OpenGLRender::RenderTextShape()
     for (size_t i = 0; i < listNum; i++)
     {
         TextInfo &textInfo = m_TextInfoList.front();
-        PosVecf3 trans = {0, 0, 0};
+        PosVecf3 trans = { (float)-textInfo.bmpWidth/2.0f, (float)-textInfo.bmpHeight/2.0f, 0};
         PosVecf3 angle = {0.0f, 0.0f, float(textInfo.rotation)};
         PosVecf3 scale = {1.0, 1.0, 1.0f};
         MoveModelf(trans, angle, scale);

chart2/source/view/main/OpenGLRender.hxx

@@ -81,6 +81,8 @@ struct TextInfo
     GLuint texture;
     double rotation;
     float vertex[12];
+    long bmpWidth;
+    long bmpHeight;
 };
 
 typedef std::vector<GLfloat> Area2DPointList;