Enable mouse middle and right buttons for ImGui

CHANGELOG.md

@@ -39,6 +39,7 @@
   * Fixed OSG transparent object sorting: [#1414](https://github.com/dartsim/dart/pull/1414)
   * Added modifier key support to ImGuiHandler: [#1436](https://github.com/dartsim/dart/pull/1436)
   * Fixed mixed intrinsic and extrinsic camera parameters in OpenGL projection matrix: [#1485](https://github.com/dartsim/dart/pull/1485)
+  * Enabled mouse middle and right buttons in ImGuiHandler: [#1500](https://github.com/dartsim/dart/pull/1500)
 
 * Parser
 

dart/gui/osg/ImGuiHandler.cpp

@@ -349,7 +349,29 @@ bool ImGuiHandler::handle(
     {
       io.MousePos
           = ImVec2(eventAdapter.getX(), io.DisplaySize.y - eventAdapter.getY());
-      mMousePressed[0] = true;
+
+      if (eventAdapter.getButtonMask()
+          == osgGA::GUIEventAdapter::LEFT_MOUSE_BUTTON)
+      {
+        mMousePressed[0] = true;
+      }
+      else if (
+          eventAdapter.getButtonMask()
+          == osgGA::GUIEventAdapter::RIGHT_MOUSE_BUTTON)
+      {
+        mMousePressed[1] = true;
+      }
+      else if (
+          eventAdapter.getButtonMask()
+          == osgGA::GUIEventAdapter::MIDDLE_MOUSE_BUTTON)
+      {
+        mMousePressed[2] = true;
+      }
+      else
+      {
+        // Shouldn't be reached to here. Mark left button by default.
+        mMousePressed[0] = true;
+      }
 
       return wantCapureMouse;
     }
@@ -363,7 +385,11 @@ bool ImGuiHandler::handle(
     }
     case osgGA::GUIEventAdapter::RELEASE:
     {
+      // When a mouse button is released no button mask is set. So we mark all
+      // the buttons are released.
       mMousePressed[0] = false;
+      mMousePressed[1] = false;
+      mMousePressed[2] = false;
 
       return wantCapureMouse;
     }