Fix QPlainTextEdit corruption/crash with scrolling

There was an off-by-one error when QPlainTextEdit
calculated the number of visible lines (not blocks)
on the screne. When running into the error case,
the number of visible lines was falsely 0 (not 1),
which resulted in all softs of negative side effects
as the scrollbar permitted the user to scroll
behind the last paragraph.

Task-number: QTBUG-17230
Reviewed-by: con

1 files changed, 1 insertions, 1 deletions

diff --git a/src/gui/widgets/qplaintextedit.cpp b/src/gui/widgets/qplaintextedit.cpp
index d3af9e197f..7435691bf0 100644
--- a/src/gui/widgets/qplaintextedit.cpp
+++ b/src/gui/widgets/qplaintextedit.cpp
@@ -967,7 +967,7 @@ void QPlainTextEditPrivate::_q_adjustScrollbars()
                     ++lineNumber;
                 }
                 if (lineNumber < layoutLineCount)
-                    visibleFromBottom += (layoutLineCount - lineNumber - 1);
+                    visibleFromBottom += (layoutLineCount - lineNumber);
                 break;
 
             }