Merge branch '18189-progdlg-modality'

See https://github.com/wxWidgets/wxWidgets/pull/886

interface/wx/progdlg.h

@@ -55,8 +55,9 @@
 
     @beginStyleTable
     @style{wxPD_APP_MODAL}
-           Make the progress dialog modal. If this flag is not given, it is
-           only "locally" modal - that is the input to the parent window is
+           Make the progress dialog application-modal, i.e. disable all
+           application windows while it is shown. If this flag is not given, it
+           is only "locally" modal -- that is the input to the parent window is
            disabled, but not to the other ones.
     @style{wxPD_AUTO_HIDE}
            Causes the progress dialog to disappear from screen as soon as the
@@ -104,7 +105,11 @@ public:
             In the generic implementation the progress bar is constructed
             only if this value is greater than zero.
         @param parent
-            Parent window.
+            Parent window. It will be disabled while this dialog is shown if
+            non-null (whether @c wxPD_APP_MODAL is specified or not). Note that
+            if you specify null parent and don't use @c wxPD_APP_MODAL, you
+            need to take care to avoid reentrancies, i.e. avoiding showing the
+            progress dialog again while this one is shown.
         @param style
             The dialog style. See wxProgressDialog.
     */