Artificial Horizon GUI Control

void dglDrawBitmapRotated(TextureObject *texObject,
                        const RectI&   in_rStretch,
                        const RectI&   in_rSubRegion,
                        const U32      in_flip = GFlip_None,
                        const F32 spinAngle = 0.0f,
			const Point2F spinOffset = Point2F(0,0) );

void dglDrawBitmapRotated(TextureObject *texture,const RectI& dstRect,const RectI& srcRect,const U32 in_flip,F32 spinAngle, const Point2F spinOffset)
{
   AssertFatal(texture != NULL, "GSurface::drawBitmapStretchSR: NULL Handle");
   if(!dstRect.isValidRect())
      return;
   AssertFatal(srcRect.isValidRect() == true,
               "GSurface::drawBitmapRotated: routines assume normal rects");

   glEnable(GL_TEXTURE_2D);
   glBindTexture(GL_TEXTURE_2D, texture->texGLName);
   glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

   glEnable(GL_BLEND);
   glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

   glDisable(GL_LIGHTING);

   F32 texLeft   = F32(srcRect.point.x)                    / F32(texture->texWidth);
   F32 texRight  = F32(srcRect.point.x + srcRect.extent.x) / F32(texture->texWidth);
   F32 texTop    = F32(srcRect.point.y)                    / F32(texture->texHeight);
   F32 texBottom = F32(srcRect.point.y + srcRect.extent.y) / F32(texture->texHeight);

   F32 screenLeft   = dstRect.point.x;
   F32 screenRight  = dstRect.point.x + dstRect.extent.x;
   F32 screenTop    = dstRect.point.y;
   F32 screenBottom = dstRect.point.y + dstRect.extent.y;

   if(in_flip & GFlip_X)
   {
      F32 temp = texLeft;
      texLeft = texRight;
      texRight = temp;
   }
   if(in_flip & GFlip_Y)
   {
      F32 temp = texTop;
      texTop = texBottom;
      texBottom = temp;
   }
   
   glColor4ub(sg_bitmapModulation.red,
             sg_bitmapModulation.green,
             sg_bitmapModulation.blue,
             sg_bitmapModulation.alpha);
  
   F32 X = 0;

   // calculate the centroid of the rectangle (to use as rotation pivot)
   if (screenLeft < screenRight)
   {
        X = screenLeft + ((screenRight - screenLeft)*0.5f);
   }
   else
   {
        X = screenRight + ((screenLeft - screenRight)*0.5f);
   };

   F32 Y = 0;

   if (screenTop < screenBottom)
   {
        Y = screenTop + ((screenBottom - screenTop)*0.5f);
   }
   else
   {
        Y = screenBottom + ((screenTop - screenBottom)*0.5f);
   };
   
   // spin angle is in degree's so convert to radians..radians = degrees * pi /180
   spinAngle = spinAngle * 3.14 / 180.0f;

   Point2F screenPoint(X,Y); 

   F32 width = dstRect.extent.x;
   width *= 0.5;

   MatrixF rotMatrix( EulerF( 0.0, 0.0, spinAngle ) );

   Point3F offset( screenPoint.x, screenPoint.y, 0.0 );
   Point3F points[4];
   
   points[0] = Point3F(-width+spinOffset.x, -width+spinOffset.y, 0.0);
   points[1] = Point3F(-width+spinOffset.x,  width+spinOffset.y, 0.0);
   points[2] = Point3F( width+spinOffset.x,  width+spinOffset.y, 0.0);
   points[3] = Point3F( width+spinOffset.x, -width+spinOffset.y, 0.0);

   for( int i=0; i<4; i++ )
   {
      rotMatrix.mulP( points[i] );
      points[i] += offset;
   }

   glBegin(GL_TRIANGLE_FAN);
      glTexCoord2f(texLeft,texTop);
      glVertex2fv(points[0]);

      glTexCoord2f(texLeft, texBottom);
      glVertex2fv(points[1]);

      glTexCoord2f(texRight, texBottom);
      glVertex2fv(points[2]);

      glTexCoord2f(texRight, texTop);
      glVertex2fv(points[3]);
   glEnd();
   
   glDisable(GL_BLEND);
   glDisable(GL_TEXTURE_2D);
}