tune auto-indentation of pasted text

auto-indentation of pasted text now only happens when complete
lines including a trailing paragraph separator are copied and pasted.

In addition, the reindent() functions ensures that the relative indentation
within the pasted block is preserved. This mechanism is now also used for
moving lines up/down.

Done with thorbjorn

src/plugins/texteditor/tabsettings.cpp

@@ -87,6 +87,14 @@ void TabSettings::fromSettings(const QString &category, const QSettings *s)
     m_tabKeyBehavior  = (TabKeyBehavior)s->value(group + QLatin1String(tabKeyBehaviorKey), m_tabKeyBehavior).toInt();
 }
 
+
+bool TabSettings::cursorIsAtBeginningOfLine(const QTextCursor &cursor) const
+{
+    QString text = cursor.block().text();
+    int fns = firstNonSpace(text);
+    return (cursor.position() - cursor.block().position() <= fns);
+}
+
 int TabSettings::lineIndentPosition(const QString &text) const
 {
     int i = 0;
@@ -255,6 +263,32 @@ void TabSettings::indentLine(QTextBlock block, int newIndent) const
     cursor.endEditBlock();
 }
 
+void TabSettings::reindentLine(QTextBlock block, int delta) const
+{
+    const QString text = block.text();
+    const int oldBlockLength = text.size();
+
+    int oldIndent = indentationColumn(text);
+    int newIndent = qMax(oldIndent + delta, 0);
+
+    if (oldIndent == newIndent)
+        return;
+
+    const QString indentString = indentationString(0, newIndent);
+    newIndent = indentString.length();
+
+    if (oldBlockLength == indentString.length() && text == indentString)
+        return;
+
+    QTextCursor cursor(block);
+    cursor.beginEditBlock();
+    cursor.movePosition(QTextCursor::StartOfBlock);
+    cursor.movePosition(QTextCursor::NextCharacter, QTextCursor::KeepAnchor, firstNonSpace(text));
+    cursor.removeSelectedText();
+    cursor.insertText(indentString);
+    cursor.endEditBlock();
+}
+
 bool TabSettings::equals(const TabSettings &ts) const
 {
     return m_spacesForTabs == ts.m_spacesForTabs