TextEdit example: add indent/unindent feature

It was not possible to interactively create the example text without
this feature; and in general it's necessary to work with nested lists.
But currently it does not deal with all possible changes of list nesting,
because the API seems incomplete for that purpose.

Task-number: QTBUG-75589
Change-Id: I3e29ca15a2e7c37300a0103ceb90670716472ffb
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

examples/widgets/richtext/textedit/textedit.cpp

@@ -317,6 +317,14 @@ void TextEdit::setupTextActions()
     actionAlignJustify->setShortcut(Qt::CTRL + Qt::Key_J);
     actionAlignJustify->setCheckable(true);
     actionAlignJustify->setPriority(QAction::LowPriority);
+    const QIcon indentMoreIcon = QIcon::fromTheme("format-indent-more", QIcon(rsrcPath + "/format-indent-more.png"));
+    actionIndentMore = menu->addAction(indentMoreIcon, tr("&Indent"), this, &TextEdit::indent);
+    actionIndentMore->setShortcut(Qt::CTRL + Qt::Key_BracketRight);
+    actionIndentMore->setPriority(QAction::LowPriority);
+    const QIcon indentLessIcon = QIcon::fromTheme("format-indent-less", QIcon(rsrcPath + "/format-indent-less.png"));
+    actionIndentLess = menu->addAction(indentLessIcon, tr("&Unindent"), this, &TextEdit::unindent);
+    actionIndentLess->setShortcut(Qt::CTRL + Qt::Key_BracketLeft);
+    actionIndentLess->setPriority(QAction::LowPriority);
 
     // Make sure the alignLeft  is always left of the alignRight
     QActionGroup *alignGroup = new QActionGroup(this);
@@ -335,6 +343,10 @@ void TextEdit::setupTextActions()
 
     tb->addActions(alignGroup->actions());
     menu->addActions(alignGroup->actions());
+    tb->addAction(actionIndentMore);
+    tb->addAction(actionIndentLess);
+    menu->addAction(actionIndentMore);
+    menu->addAction(actionIndentLess);
 
     menu->addSeparator();
 
@@ -736,6 +748,40 @@ void TextEdit::setChecked(bool checked)
     textStyle(checked ? 5 : 4);
 }
 
+void TextEdit::indent()
+{
+    modifyIndentation(1);
+}
+
+void TextEdit::unindent()
+{
+    modifyIndentation(-1);
+}
+
+void TextEdit::modifyIndentation(int amount)
+{
+    QTextCursor cursor = textEdit->textCursor();
+    cursor.beginEditBlock();
+    if (cursor.currentList()) {
+        QTextListFormat listFmt = cursor.currentList()->format();
+        // See whether the line above is the list we want to move this item into,
+        // or whether we need a new list.
+        QTextCursor above(cursor);
+        above.movePosition(QTextCursor::Up);
+        if (above.currentList() && listFmt.indent() + amount == above.currentList()->format().indent()) {
+            above.currentList()->add(cursor.block());
+        } else {
+            listFmt.setIndent(listFmt.indent() + amount);
+            cursor.createList(listFmt);
+        }
+    } else {
+        QTextBlockFormat blockFmt = cursor.blockFormat();
+        blockFmt.setIndent(blockFmt.indent() + amount);
+        cursor.setBlockFormat(blockFmt);
+    }
+    cursor.endEditBlock();
+}
+
 void TextEdit::currentCharFormatChanged(const QTextCharFormat &format)
 {
     fontChanged(format.font());

examples/widgets/richtext/textedit/textedit.h

@@ -97,6 +97,8 @@ private slots:
     void textColor();
     void textAlign(QAction *a);
     void setChecked(bool checked);
+    void indent();
+    void unindent();
 
     void currentCharFormatChanged(const QTextCharFormat &format);
     void cursorPositionChanged();
@@ -111,6 +113,7 @@ private:
     void setupTextActions();
     bool maybeSave();
     void setCurrentFileName(const QString &fileName);
+    void modifyIndentation(int amount);
 
     void mergeFormatOnWordOrSelection(const QTextCharFormat &format);
     void fontChanged(const QFont &f);
@@ -126,6 +129,8 @@ private:
     QAction *actionAlignCenter;
     QAction *actionAlignRight;
     QAction *actionAlignJustify;
+    QAction *actionIndentLess;
+    QAction *actionIndentMore;
     QAction *actionToggleCheckState;
     QAction *actionUndo;
     QAction *actionRedo;

examples/widgets/richtext/textedit/textedit.qrc

@@ -13,6 +13,8 @@
   <file>images/mac/fileopen.png</file>
   <file>images/mac/fileprint.png</file>
   <file>images/mac/filesave.png</file>
+  <file>images/mac/format-indent-less.png</file>
+  <file>images/mac/format-indent-more.png</file>
   <file>images/mac/textbold.png</file>
   <file>images/mac/textcenter.png</file>
   <file>images/mac/textitalic.png</file>
@@ -34,6 +36,8 @@
   <file>images/win/fileopen.png</file>
   <file>images/win/fileprint.png</file>
   <file>images/win/filesave.png</file>
+  <file>images/win/format-indent-less.png</file>
+  <file>images/win/format-indent-more.png</file>
   <file>images/win/textbold.png</file>
   <file>images/win/textcenter.png</file>
   <file>images/win/textitalic.png</file>