Fix performance of QTextDocumentPrivate::adjustDocumentChangesAndCursors

As the changedCursors list grew large, the function used to spend an
extraordinate amount of time in QList::contains.

The fix removes the changedCursors list outright and replaces it with a
flag in QTextCursorPrivate.

Done-with: mae

4 files changed, 22 insertions, 21 deletions

diff --git a/src/gui/text/qtextcursor.cpp b/src/gui/text/qtextcursor.cpp
index a9caa6b..63aa946 100644
--- a/src/gui/text/qtextcursor.cpp
+++ b/src/gui/text/qtextcursor.cpp
@@ -64,7 +64,8 @@ enum {
 
 QTextCursorPrivate::QTextCursorPrivate(QTextDocumentPrivate *p)
     : priv(p), x(0), position(0), anchor(0), adjusted_anchor(0),
-      currentCharFormat(-1), visualNavigation(false), keepPositionOnInsert(false)
+      currentCharFormat(-1), visualNavigation(false), keepPositionOnInsert(false),
+      changed(false)
 {
     priv->addCursor(this);
 }
diff --git a/src/gui/text/qtextcursor_p.h b/src/gui/text/qtextcursor_p.h
index 4e36b95..4b3262f 100644
--- a/src/gui/text/qtextcursor_p.h
+++ b/src/gui/text/qtextcursor_p.h
@@ -114,6 +114,7 @@ public:
     int currentCharFormat;
     uint visualNavigation : 1;
     uint keepPositionOnInsert : 1;
+    uint changed : 1;
 };
 
 QT_END_NAMESPACE
diff --git a/src/gui/text/qtextdocument_p.cpp b/src/gui/text/qtextdocument_p.cpp
index a55e5f3..9849317 100644
--- a/src/gui/text/qtextdocument_p.cpp
+++ b/src/gui/text/qtextdocument_p.cpp
@@ -235,17 +235,17 @@ void QTextDocumentPrivate::init()
 void QTextDocumentPrivate::clear()
 {
     Q_Q(QTextDocument);
-    for (int i = 0; i < cursors.count(); ++i) {
-        cursors.at(i)->setPosition(0);
-        cursors.at(i)->currentCharFormat = -1;
-        cursors.at(i)->anchor = 0;
-        cursors.at(i)->adjusted_anchor = 0;
+
+    foreach (QTextCursorPrivate *curs, cursors) {
+        curs->setPosition(0);
+        curs->currentCharFormat = -1;
+        curs->anchor = 0;
+        curs->adjusted_anchor = 0;
     }
 
     QList<QTextCursorPrivate *>oldCursors = cursors;
     QT_TRY{
         cursors.clear();
-        changedCursors.clear();
 
         QMap<int, QTextObject *>::Iterator objectIt = objects.begin();
         while (objectIt != objects.end()) {
@@ -288,8 +288,8 @@ void QTextDocumentPrivate::clear()
 
 QTextDocumentPrivate::~QTextDocumentPrivate()
 {
-    for (int i = 0; i < cursors.count(); ++i)
-        cursors.at(i)->priv = 0;
+    foreach (QTextCursorPrivate *curs, cursors)
+        curs->priv = 0;
     cursors.clear();
     undoState = 0;
     undoEnabled = true;
@@ -1225,9 +1225,11 @@ void QTextDocumentPrivate::finishEdit()
         }
     }
 
-    while (!changedCursors.isEmpty()) {
-        QTextCursorPrivate *curs = changedCursors.takeFirst();
-        emit q->cursorPositionChanged(QTextCursor(curs));
+    foreach (QTextCursorPrivate *curs, cursors) {
+        if (curs->changed) {
+            curs->changed = false;
+            emit q->cursorPositionChanged(QTextCursor(curs));
+        }
     }
 
     contentsChanged();
@@ -1273,11 +1275,9 @@ void QTextDocumentPrivate::adjustDocumentChangesAndCursors(int from, int addedOr
     if (!editBlock)
         ++revision;
 
-    for (int i = 0; i < cursors.size(); ++i) {
-        QTextCursorPrivate *curs = cursors.at(i);
+    foreach (QTextCursorPrivate *curs, cursors) {
         if (curs->adjustPosition(from, addedOrRemoved, op) == QTextCursorPrivate::CursorMoved) {
-            if (!changedCursors.contains(curs))
-                changedCursors.append(curs);
+            curs->changed = true;
         }
     }
 
@@ -1700,8 +1700,8 @@ bool QTextDocumentPrivate::ensureMaximumBlockCount()
 void QTextDocumentPrivate::aboutToRemoveCell(int from, int to)
 {
     Q_ASSERT(from <= to);
-    for (int i = 0; i < cursors.size(); ++i)
-        cursors.at(i)->aboutToRemoveCell(from, to);
+    foreach (QTextCursorPrivate *curs, cursors)
+        curs->aboutToRemoveCell(from, to);
 }
 
 QT_END_NAMESPACE
diff --git a/src/gui/text/qtextdocument_p.h b/src/gui/text/qtextdocument_p.h
index 06e0753..dcac99d 100644
--- a/src/gui/text/qtextdocument_p.h
+++ b/src/gui/text/qtextdocument_p.h
@@ -277,7 +277,7 @@ public:
     void documentChange(int from, int length);
 
     inline void addCursor(QTextCursorPrivate *c) { cursors.append(c); }
-    inline void removeCursor(QTextCursorPrivate *c) { cursors.removeAll(c); changedCursors.removeAll(c); }
+    inline void removeCursor(QTextCursorPrivate *c) { cursors.removeAll(c); }
 
     QTextFrame *frameAt(int pos) const;
     QTextFrame *rootFrame() const;
@@ -329,8 +329,7 @@ private:
     BlockMap blocks;
     int initialBlockCharFormatIndex;
 
-    QList<QTextCursorPrivate*> cursors;
-    QList<QTextCursorPrivate*> changedCursors;
+    QList<QTextCursorPrivate *> cursors;
     QMap<int, QTextObject *> objects;
     QMap<QUrl, QVariant> resources;
     QMap<QUrl, QVariant> cachedResources;