[LyX/2.3.x] Avoid crash when trying to handle FitCursor

[Jean-Marc Lasgouttes]

commit 45fba1ce1b5b447a047071f62d6dd73aaceae11e
Author: Jean-Marc Lasgouttes <lasgout...@lyx.org>
Date:   Fri May 11 11:27:26 2018 +0200

    Avoid crash when trying to handle FitCursor
    
    It is better to handle SinglePar before FitCursor, since the later
    requires correct metrics at cursor position.
    
    Fixes bug #11139 and probably #11125.
    
    (cherry picked from commit 7f83d26934e50e3d83e254b0f9ab847d957053f7)
---
 src/BufferView.cpp |   21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/src/BufferView.cpp b/src/BufferView.cpp
index da09fcd..588dea7 100644
--- a/src/BufferView.cpp
+++ b/src/BufferView.cpp
@@ -461,7 +461,8 @@ string flagsAsString(Update::flags flags)
        return string((flags & Update::FitCursor) ? "FitCursor " : "")
                + ((flags & Update::Force) ? "Force " : "")
                + ((flags & Update::ForceDraw) ? "ForceDraw " : "")
-               + ((flags & Update::SinglePar) ? "SinglePar " : "");
+               + ((flags & Update::SinglePar) ? "SinglePar " : "")
+               + ((flags & Update::Decoration) ? "Decoration " : "");
 }
 
 }
@@ -487,6 +488,16 @@ void BufferView::processUpdateFlags(Update::flags flags)
                updateMetrics(flags);
        }
 
+       // Detect whether we can only repaint a single paragraph.
+       // We handle this before FitCursor because the later will require
+       // correct metrics at cursor position.
+       if (!(flags & Update::ForceDraw)) {
+               if (singleParUpdate())
+                       flags = flags | Update::SinglePar;
+               else
+                       updateMetrics(flags);
+       }
+
        // Then make sure that the screen contains the cursor if needed
        if (flags & Update::FitCursor) {
                if (needsFitCursor()) {
@@ -497,14 +508,6 @@ void BufferView::processUpdateFlags(Update::flags flags)
                flags = flags & ~Update::FitCursor;
        }
 
-       // Finally detect whether we can only repaint a single paragraph
-       if (!(flags & Update::ForceDraw)) {
-               if (singleParUpdate())
-                       flags = flags | Update::SinglePar;
-               else
-                       updateMetrics(flags);
-       }
-
        // Add flags to the the update flags. These will be reset to None
        // after the redraw is actually done
        d->update_flags_ = d->update_flags_ | flags;