From ca9ed9619f1c21ba0b3ef7687bbbad9eaf2bd39a Mon Sep 17 00:00:00 2001
From: Robin Burchell <robin.burchell@viroteck.net>
Date: Sat, 9 Jul 2016 12:53:53 +0200
Subject: Improve performance of Qt::mightBeRichText by using QStringRef

I noted this taking around 1% of QtQuick Text creation with a few simple bindings
which is quite considerable, so hopefully improvements here will add up gradually.

Also add a benchmark measuring changes:

                  Test                 |      From      |       To       |        Details
+--------------------------------------+----------------+----------------+-----------------------+
  mightBeRichText:br-invalidspace      | 14466.00 instr | 10563.00 instr | -26.98% FASTER! :)
  mightBeRichText:br-nospace           | 18581.00 instr | 14635.00 instr | -21.24% FASTER! :)
  mightBeRichText:br-space             | 18470.00 instr | 14377.00 instr | -22.16% FASTER! :)
  mightBeRichText:documentation-header | 16336.00 instr | 12992.00 instr | -20.47% FASTER! :)
  mightBeRichText:empty                | 2618.00 instr  | 2618.00 instr  | more or less the same
  mightBeRichText:invalid closing tag  | 11102.00 instr | 7159.00 instr  | -35.52% FASTER! :)
  mightBeRichText:no tags              | 12503.00 instr | 8581.00 instr  | -31.37% FASTER! :)
  mightBeRichText:simple               | 17316.00 instr | 14074.00 instr | -18.72% FASTER! :)
  mightBeRichText:simple2              | 14394.00 instr | 10745.00 instr | -25.35% FASTER! :)
+--------------------------------------+----------------+----------------+-----------------------+
             Overall result            |                                        -201.81% :)

Change-Id: I1817a69959d176b381bcbf27b72bb751885c3e9b
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
---
 src/gui/text/qtextdocument.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/gui/text/qtextdocument.cpp b/src/gui/text/qtextdocument.cpp
index a3dbf455cf..75899dec80 100644
--- a/src/gui/text/qtextdocument.cpp
+++ b/src/gui/text/qtextdocument.cpp
@@ -94,7 +94,7 @@ bool Qt::mightBeRichText(const QString& text)
         ++start;
 
     // skip a leading <?xml ... ?> as for example with xhtml
-    if (text.mid(start, 5) == QLatin1String("<?xml")) {
+    if (text.midRef(start, 5).compare(QLatin1String("<?xml")) == 0) {
         while (start < text.length()) {
             if (text.at(start) == QLatin1Char('?')
                 && start + 2 < text.length()
@@ -109,12 +109,12 @@ bool Qt::mightBeRichText(const QString& text)
             ++start;
     }
 
-    if (text.mid(start, 5).toLower() == QLatin1String("<!doc"))
+    if (text.midRef(start, 5).compare(QLatin1String("<!doc"), Qt::CaseInsensitive) == 0)
         return true;
     int open = start;
     while (open < text.length() && text.at(open) != QLatin1Char('<')
             && text.at(open) != QLatin1Char('\n')) {
-        if (text.at(open) == QLatin1Char('&') &&  text.mid(open+1,3) == QLatin1String("lt;"))
+        if (text.at(open) == QLatin1Char('&') &&  text.midRef(open + 1, 3) == QLatin1String("lt;"))
             return true; // support desperate attempt of user to see <...>
         ++open;
     }
-- 
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