feat: Add bottom margin with the height of a page (Megaxela#14)

* feat: Add bottom margin with the height of a page

* fix: Fix crash when the document is empty

Author: ouuan

include/internal/QCodeEditor.hpp

@@ -234,6 +234,11 @@ class QCodeEditor : public QTextEdit
      */
     void resizeEvent(QResizeEvent *e) override;
 
+    /**
+     * @brief Method, update the bottom margin when the font changes.
+     */
+    void changeEvent(QEvent *e) override;
+
     /**
      * @brief Method, that's called on any key press, posted
      * into code editor widget. This method is overloaded for:
@@ -257,6 +262,12 @@ class QCodeEditor : public QTextEdit
      */
     bool event(QEvent *e) override;
 
+  private Q_SLOTS:
+    /**
+     * @brief Slot, that updates the bottom margin.
+     */
+    void updateBottomMargin();
+
   private:
     /**
      * @brief Method for initializing default

src/internal/QCodeEditor.cpp

@@ -50,6 +50,7 @@ void QCodeEditor::initFont()
 void QCodeEditor::performConnections()
 {
     connect(document(), &QTextDocument::blockCountChanged, this, &QCodeEditor::updateLineNumberAreaWidth);
+    connect(document(), &QTextDocument::blockCountChanged, this, &QCodeEditor::updateBottomMargin);
 
     connect(verticalScrollBar(), &QScrollBar::valueChanged, [this](int) { m_lineNumberArea->update(); });
 
@@ -119,6 +120,14 @@ void QCodeEditor::resizeEvent(QResizeEvent *e)
     QTextEdit::resizeEvent(e);
 
     updateLineGeometry();
+    updateBottomMargin();
+}
+
+void QCodeEditor::changeEvent(QEvent *e)
+{
+    QTextEdit::changeEvent(e);
+    if (e->type() == QEvent::FontChange)
+        updateBottomMargin();
 }
 
 void QCodeEditor::updateLineGeometry()
@@ -127,6 +136,20 @@ void QCodeEditor::updateLineGeometry()
     m_lineNumberArea->setGeometry(QRect(cr.left(), cr.top(), m_lineNumberArea->sizeHint().width(), cr.height()));
 }
 
+void QCodeEditor::updateBottomMargin()
+{
+    auto doc = document();
+    if (doc->blockCount() > 1)
+    {
+        // calling QTextFrame::setFrameFormat with an empty document makes the application crash
+        auto rf = doc->rootFrame();
+        auto format = rf->frameFormat();
+        int margin = doc->documentMargin();
+        format.setBottomMargin(qMax(margin, viewport()->height() - fontMetrics().height()) - margin);
+        rf->setFrameFormat(format);
+    }
+}
+
 void QCodeEditor::updateLineNumberAreaWidth(int)
 {
     setViewportMargins(m_lineNumberArea->sizeHint().width(), 0, 0, 0);
@@ -818,7 +841,7 @@ bool QCodeEditor::tabReplace() const
 void QCodeEditor::setTabReplaceSize(int val)
 {
     m_tabReplace.fill(' ', val);
-    setTabStopDistance(QFontMetrics(font()).horizontalAdvance(QString(val * 1000, ' ')) / 1000.0);
+    setTabStopDistance(fontMetrics().horizontalAdvance(QString(val * 1000, ' ')) / 1000.0);
 }
 
 int QCodeEditor::tabReplaceSize() const