don't use constructors for C API structures

modules/highgui/src/window.cpp

@@ -356,7 +356,7 @@ void cv::imshow( const String& winname, InputArray _img )
     CV_Assert(size.width>0 && size.height>0);
     {
         Mat img = _img.getMat();
-        CvMat c_img = img;
+        CvMat c_img = cvMat(img);
         cvShowImage(winname.c_str(), &c_img);
     }
 #else

modules/highgui/src/window_gtk.cpp

@@ -1755,8 +1755,8 @@ static gboolean icvOnMouse( GtkWidget *widget, GdkEvent *event, gpointer user_da
 {
     // TODO move this logic to CvImageWidget
     CvWindow* window = (CvWindow*)user_data;
-    CvPoint2D32f pt32f(-1., -1.);
-    CvPoint pt(-1,-1);
+    CvPoint2D32f pt32f = {-1., -1.};
+    CvPoint pt = {-1,-1};
     int cv_event = -1, state = 0, flags = 0;
     CvImageWidget * image_widget = CV_IMAGE_WIDGET( widget );