highgui: allow specifying that a button should create a new buttonbar

modules/highgui/include/opencv2/highgui.hpp

@@ -239,9 +239,10 @@ enum QtFontStyles {
 
 //! Qt "button" type
 enum QtButtonTypes {
-       QT_PUSH_BUTTON = 0, //!< Push button.
-       QT_CHECKBOX    = 1, //!< Checkbox button.
-       QT_RADIOBOX    = 2  //!< Radiobox button.
+       QT_PUSH_BUTTON   = 0,    //!< Push button.
+       QT_CHECKBOX      = 1,    //!< Checkbox button.
+       QT_RADIOBOX      = 2,    //!< Radiobox button.
+       QT_NEW_BUTTONBAR = 1024  //!< Button should create a new buttonbar
      };
 
 /** @brief Callback function for mouse events. see cv::setMouseCallback
@@ -719,7 +720,8 @@ CV_EXPORTS  void stopLoop();
 
 The function createButton attaches a button to the control panel. Each button is added to a
 buttonbar to the right of the last button. A new buttonbar is created if nothing was attached to the
-control panel before, or if the last element attached to the control panel was a trackbar.
+control panel before, or if the last element attached to the control panel was a trackbar or if the
+QT_NEW_BUTTONBAR flag is added to the type.
 
 See below various examples of the cv::createButton function call: :
 @code
@@ -728,6 +730,7 @@ See below various examples of the cv::createButton function call: :
     createButton("button3",callbackButton,&value);
     createButton("button5",callbackButton1,NULL,QT_RADIOBOX);
     createButton("button6",callbackButton2,NULL,QT_PUSH_BUTTON,1);
+    createButton("button6",callbackButton2,NULL,QT_PUSH_BUTTON|QT_NEW_BUTTONBAR);// create a push button in a new row
 @endcode
 
 @param  bar_name Name of the button.

modules/highgui/src/window_QT.cpp

@@ -1139,13 +1139,18 @@ void GuiReceiver::addButton(QString button_name, int button_type, int initial_bu
     {
         CvBar* lastbar = (CvBar*) global_control_panel->myLayout->itemAt(global_control_panel->myLayout->count() - 1);
 
-        if (lastbar->type == type_CvTrackbar) //if last bar is a trackbar, create a new buttonbar, else, attach to the current bar
+        // if last bar is a trackbar or the user requests a new buttonbar, create a new buttonbar
+        // else, attach to the current bar
+        if (lastbar->type == type_CvTrackbar || cv::QT_NEW_BUTTONBAR & button_type)
             b = CvWindow::createButtonBar(button_name); //the bar has the name of the first button attached to it
         else
             b = (CvButtonbar*) lastbar;
 
     }
 
+    // unset buttonbar flag
+    button_type = button_type & ~cv::QT_NEW_BUTTONBAR;
+
     b->addButton(button_name, (CvButtonCallback) on_change, userdata, button_type, initial_button_state);
 }