Fix part of http://bugzilla.lyx.org/show_bug.cgi?id=5347

Use crc checking in order to decide if the widget needs to be updated or not. This speed up a lot the cursor moving use case.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@26946 a592a061-630c-0410-9148-cb99ea01b6c8

diff --git a/src/frontends/qt4/GuiViewSource.cpp b/src/frontends/qt4/GuiViewSource.cpp
index b83082336fdaeddf0aa763069180fe2338ad86d6..ae5d9ff4b9bddf80fe6c3588dd074d2932a6245f 100644 (file)
--- a/src/frontends/qt4/GuiViewSource.cpp
+++ b/src/frontends/qt4/GuiViewSource.cpp
@@ -28,6 +28,8 @@
 #include "support/docstream.h"
 #include "support/gettext.h"
 
+#include <boost/crc.hpp>
+
 #include <QSettings>
 #include <QTextCursor>
 #include <QTextDocument>
@@ -69,10 +71,19 @@ ViewSourceWidget::ViewSourceWidget()
 }
 
 
+static size_t crcCheck(docstring const & s)
+{
+       boost::crc_32_type crc;
+       crc.process_bytes(&s[0], sizeof(char_type) * s.size());
+       return crc.checksum();
+}
+
+
 /** get the source code of selected paragraphs, or the whole document
        \param fullSource get full source code
+       \return true if the content has changed since last call.
  */
-static QString getContent(BufferView const * view, bool fullSource)
+static bool getContent(BufferView const * view, bool fullSource, QString & qstr)
 {
        // get the *top* level paragraphs that contain the cursor,
        // or the selected text
@@ -90,7 +101,14 @@ static QString getContent(BufferView const * view, bool fullSource)
                swap(par_begin, par_end);
        odocstringstream ostr;
        view->buffer().getSourceCode(ostr, par_begin, par_end + 1, fullSource);
-       return toqstr(ostr.str());
+       docstring s = ostr.str();
+       static size_t crc = 0;
+       size_t newcrc = crcCheck(s);
+       if (newcrc == crc)
+               return false;
+       crc = newcrc;
+       qstr = toqstr(s);
+       return true;
 }
 
 
@@ -108,7 +126,9 @@ void ViewSourceWidget::updateView()
                return;
        }
 
-       document_->setPlainText(getContent(bv_, viewFullSourceCB->isChecked()));
+       QString content;
+       if (getContent(bv_, viewFullSourceCB->isChecked(), content))
+               document_->setPlainText(content);
 
        CursorSlice beg = bv_->cursor().selectionBegin().bottom();
        CursorSlice end = bv_->cursor().selectionEnd().bottom();