message: Support for mouse wheel zooming in / out graph
diff: #include "GL/gl3w.h"
  #include "gpuvis.h"
  -//$ TODO: Add --fullscreen option to start the trace file window maximized
  -// and resize with the main window.
  -
  //$ TODO: option to start "Events List" closed.
  //$ TODO: Sort graphs by process with most # of events.
  //$ TODO: do a pan with just a single click, not ctrl+click.
  -//$ TODO: mouse wheel should zoom graph in and out.
  -
  //$ TODO: Show drm_vblank_event crtc:0 (blue) or crtc1:1 (red)
  //$ TODO: Make colors configurable so they're easy to distinguish.
  //$ TODO: Add ability to show row for an event with a parameter?
  -//$ TODO: Need to handle lots of rows, ie ~100
  +//$ TODO: Need to handle lots of graph rows, ie ~100
  // popup graph tooltip shows events around location you're at?
  @@ -964,6 +959,10 @@ bool TraceWin::render( class TraceLoader *loader )
  bool zoom_in = ImGui::SmallButton( "Zoom In" );
  ImGui::SameLine();
  bool zoom_out = ImGui::SmallButton( "Zoom Out" );
  +
  + zoom_in |= ( ImGui::GetIO().MouseWheel > 0 );
  + zoom_out |= ( ImGui::GetIO().MouseWheel < 0 );
  +
  if ( zoom_in || zoom_out )
  {
  int64_t sign = zoom_in ? -1 : +1;
  @@ -1852,14 +1851,6 @@ void TraceWin::render_mouse_graph( class graph_info_t *pgi )
  }
  #endif
  }
  - else if ( ImGui::IsMouseDoubleClicked( 0 ) &&
  - !gi.hovered_items.empty() )
  - {
  - // Double click: move event log to clicked time.
  - m_goto_eventid = gi.hovered_items[ 0 ].eventid;
  - m_selected_eventid = gi.hovered_items[ 0 ].eventid;
  - m_do_gotoevent = true;
  - }
  }
  }
  