[LyX/2.3.x] Fix bad refresh when changing zoom level

[Jean-Marc Lasgouttes]

commit f6cbc08a7db3c2185b6eae768c026c58f577b0bc
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Wed Sep 27 17:52:06 2017 +0200

    Fix bad refresh when changing zoom level
    
    Replace the tricky code in LFUN_SCREEN_FONT_UPDATE and replace it with
    proper use of DispatchResult flags.
    
    LFUN_BUFFER_ZOOM* does not need to call LFUN_SCREEN_FONT_UPDATE, since
    it already does everything that is required.
    
    (cherry picked from commit 9df59aac63bbb56d9d5f5ddcccfaa3ebace2f03d)
---
 src/frontends/qt4/GuiApplication.cpp |    9 +--------
 src/frontends/qt4/GuiView.cpp        |    2 +-
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/src/frontends/qt4/GuiApplication.cpp 
b/src/frontends/qt4/GuiApplication.cpp
index ee379ff..110b63e 100644
--- a/src/frontends/qt4/GuiApplication.cpp
+++ b/src/frontends/qt4/GuiApplication.cpp
@@ -1628,14 +1628,7 @@ void GuiApplication::dispatch(FuncRequest const & cmd, 
DispatchResult & dr)
        case LFUN_SCREEN_FONT_UPDATE: {
                // handle the screen font changes.
                d->font_loader_.update();
-               // Backup current_view_
-               GuiView * view = current_view_;
-               // Set current_view_ to zero to forbid GuiWorkArea::redraw()
-               // to skip the refresh.
-               current_view_ = 0;
-               theBufferList().changed(false);
-               // Restore current_view_
-               current_view_ = view;
+               dr.screenUpdate(Update::Force | Update::FitCursor);
                break;
        }
 
diff --git a/src/frontends/qt4/GuiView.cpp b/src/frontends/qt4/GuiView.cpp
index 785abfd..2aee273 100644
--- a/src/frontends/qt4/GuiView.cpp
+++ b/src/frontends/qt4/GuiView.cpp
@@ -4152,7 +4152,7 @@ void GuiView::dispatch(FuncRequest const & cmd, 
DispatchResult & dr)
                        // painting so we must reset it.
                        QPixmapCache::clear();
                        guiApp->fontLoader().update();
-                       lyx::dispatch(FuncRequest(LFUN_SCREEN_FONT_UPDATE));
+                       dr.screenUpdate(Update::Force | Update::FitCursor);
                        break;
                }