From Terry Welsh, "Okay, here are the mods I wrote for drawing a filled bounding box

behind osgText::Text.  I made it so the box would get drawn using
whichever BackdropImplementation was selected.  However, I did not
implement STENCIL_BUFFER.  In that case it defaults to drawing the
bounding box using POLYGON_OFFSET instead.

Also made it so the BOUNDINGBOX and FILLEDBOUNDINGBOX are drawn with a
settable color and margin size.

While I was at it I tightened up the values applied with DEPTH_RANGE
and POLYGON_OFFSET, not just for drawing the bounding box but also for
drawing backdrop text (these values must be coupled since the bounding
box has to be drawn deeper in Z than the backdrop text).  The values
in use before seemed like overkill and I was seeing some z-clipping
with my background scenery in the case of DEPTH_RANGE.  If there was a
good reason for the large values please let me know...."

src/osgText/TextBase.cpp

@@ -44,6 +44,8 @@ TextBase::TextBase():
     _autoRotateToScreen(false),
     _layout(LEFT_TO_RIGHT),
     _drawMode(TEXT),
+    _textBBMargin(0.0f),
+    _textBBColor(0.0, 0.0, 0.0, 0.5),
     _kerningType(KERNING_DEFAULT),
     _lineCount(0)
 {
@@ -69,6 +71,8 @@ TextBase::TextBase(const TextBase& textBase,const osg::CopyOp& copyop):
     _autoRotateToScreen(textBase._autoRotateToScreen),
     _layout(textBase._layout),
     _drawMode(textBase._drawMode),
+    _textBBMargin(textBase._textBBMargin),
+    _textBBColor(textBase._textBBColor),
     _kerningType(textBase._kerningType),
     _lineCount(textBase._lineCount)
 {
@@ -225,6 +229,16 @@ void TextBase::setDrawMode(unsigned int mode)
 }
 
 
+void TextBase::setBoundingBoxMargin(float margin)
+{
+    if (_textBBMargin == margin)
+        return;
+
+    _textBBMargin = margin;
+    computeGlyphRepresentation();
+}
+
+
 osg::BoundingBox TextBase::computeBound() const
 {
     osg::BoundingBox  bbox;