tdf#122459 Qt5 IM underline pre-edit

This simply always underlines the pre-edit text, so it'S easier to
see what text block is currently IM edited.

Change-Id: I45145e4faa872c44eb6583ac6f335dd40fe3e53e
Reviewed-on: https://gerrit.libreoffice.org/65856
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>

vcl/qt5/Qt5Widget.cxx

@@ -41,6 +41,7 @@
 
 #include <cairo.h>
 #include <headless/svpgdi.hxx>
+#include <vcl/commandevent.hxx>
 
 void Qt5Widget::paintEvent(QPaintEvent* pEvent)
 {
@@ -449,6 +450,10 @@ void Qt5Widget::inputMethodEvent(QInputMethodEvent* pEvent)
     {
         aInputEvent.maText = toOUString(pEvent->preeditString());
         aInputEvent.mnCursorPos = 0;
+        sal_Int32 nLength = aInputEvent.maText.getLength();
+        std::vector<ExtTextInputAttr> aTextAttrs(nLength, ExtTextInputAttr::Underline);
+        if (nLength)
+            aInputEvent.mpTextAttr = &aTextAttrs[0];
         m_pFrame->CallCallback(SalEvent::ExtTextInput, &aInputEvent);
         pEvent->accept();
     }