[LyX/master] Improve implementation of TabWorkArea::posIsTab()

[Scott Kostyshak]

commit badb0bb96cc22c64210d140643fae521a78c6fdc
Author: Scott Kostyshak <skost...@lyx.org>
Date:   Fri Jul 29 13:06:49 2016 -0400

    Improve implementation of TabWorkArea::posIsTab()
    
    The Qt documentation states that tabAt() returns -1 if the position
    is not over a tab. This behavior has been consistent since Qt 4.3
    [1]. This commit's improvement likely makes the code faster in two
    ways:
    
    (1) we do not need to loop through potentially all tabs
    (2) we only need to look up the tab index corresponding with one
    position
    
    posIsTab() is not currently used intensively so no practical gain in
    speed is achieved, but it protects against future use.
    
    [1] https://doc.qt.io/archives/4.3/qtabbar.html#tabAt
---
 src/frontends/qt4/GuiWorkArea.cpp |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/frontends/qt4/GuiWorkArea.cpp 
b/src/frontends/qt4/GuiWorkArea.cpp
index b9e5e8e..9223964 100644
--- a/src/frontends/qt4/GuiWorkArea.cpp
+++ b/src/frontends/qt4/GuiWorkArea.cpp
@@ -1650,10 +1650,8 @@ void TabWorkArea::paintEvent(QPaintEvent * event)
 
 bool TabWorkArea::posIsTab(QPoint position)
 {
-       for (int i = 0; i < count(); ++i)
-               if (tabBar()->tabRect(i).contains(position))
-                       return true;
-       return false;
+       // tabAt returns -1 if tab does not covers position
+       return tabBar()->tabAt(position) > -1;
 }