<!--  used for button positioning per context -->
<camera_contexts>
   <top2d>
      <button id="home"                marginleft="3" />
      <button id="ruler"               marginleft="2" />
      <button id="zoom_on_selection"   marginleft="91" />      
      <button id="zoom_in"             marginleft="0" />
      <button id="zoom_out"            marginleft="0" />
      <button id="pan_left"            marginleft="2" />
      <button id="pan_right"           marginleft="0" />
      <button id="pan_up"              marginleft="0" />
      <button id="pan_down"            marginleft="0" />
   </top2d>
   <front2d>
      <button id="home"                marginleft="3" />
      <button id="zoom_on_selection"   marginleft="125" />
      <button id="zoom_in"             marginleft="0" />
      <button id="zoom_out"            marginleft="0" />
      <button id="orbit_left_2d"       marginleft="3" />
      <button id="orbit_right_2d"      marginleft="0" />
      <button id="pan_left"            marginleft="3" />
      <button id="pan_right"           marginleft="0" />
      <button id="pan_up"              marginleft="0" />
      <button id="pan_down"            marginleft="0" />
   </front2d>
   <top3d>
      <button id="home"                marginleft="3" />
      <button id="enable_raytracing"   marginleft="2" />
      <!--<button id="increase_lighting"   marginleft="2" />
      <button id="decrease_lighting"   marginleft="0" />
      <button id="zoom_on_selection"   marginleft="22" />-->
      <button id="zoom_on_selection"   marginleft="77" />
      <button id="zoom_in"             marginleft="0" />
      <button id="zoom_out"            marginleft="0" />
      <button id="pan_left"            marginleft="2" />
      <button id="pan_right"           marginleft="0" />
      <button id="pan_up"              marginleft="0" />
      <button id="pan_down"            marginleft="0" />
   </top3d>
   <front3d>
      <button id="home"                marginleft="3" />
      <button id="enable_raytracing"   marginleft="2" />
      <!--<button id="increase_lighting"   marginleft="2" />
      <button id="decrease_lighting"   marginleft="0" />
      <button id="zoom_on_selection"   marginleft="22" />-->
      <button id="zoom_on_selection"   marginleft="77" />
      <button id="zoom_in"             marginleft="0" />
      <button id="zoom_out"            marginleft="0" />
      <button id="orbit_up"            marginleft="2" />
      <button id="orbit_down"          marginleft="0" />
      <button id="orbit_left"          marginleft="0" />
      <button id="orbit_right"         marginleft="0" />
      <button id="pan_left"            marginleft="2" />
      <button id="pan_right"           marginleft="0" />
      <button id="pan_up"              marginleft="0" />
      <button id="pan_down"            marginleft="0" />
   </front3d>
</camera_contexts>