qt 6.5.1 original

tests/manual/textrendering/codeeditor/CMakeLists.txt

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+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+cmake_minimum_required(VERSION 3.16)
+project(codeeditor LANGUAGES CXX)
+
+if(NOT DEFINED INSTALL_EXAMPLESDIR)
+    set(INSTALL_EXAMPLESDIR "examples")
+endif()
+
+set(INSTALL_EXAMPLEDIR "${INSTALL_EXAMPLESDIR}/widgets/widgets/codeeditor")
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)
+
+qt_standard_project_setup()
+
+qt_add_executable(codeeditor
+    codeeditor.cpp codeeditor.h
+    main.cpp
+)
+
+set_target_properties(codeeditor PROPERTIES
+    WIN32_EXECUTABLE TRUE
+    MACOSX_BUNDLE TRUE
+)
+
+target_link_libraries(codeeditor PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+)
+
+install(TARGETS codeeditor
+    RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
+)

tests/manual/textrendering/codeeditor/codeeditor.cpp

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+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "codeeditor.h"
+
+#include <QPainter>
+#include <QTextBlock>
+
+//![constructor]
+
+CodeEditor::CodeEditor(QWidget *parent) : QPlainTextEdit(parent)
+{
+    lineNumberArea = new LineNumberArea(this);
+
+    connect(this, &CodeEditor::blockCountChanged, this, &CodeEditor::updateLineNumberAreaWidth);
+    connect(this, &CodeEditor::updateRequest, this, &CodeEditor::updateLineNumberArea);
+    connect(this, &CodeEditor::cursorPositionChanged, this, &CodeEditor::highlightCurrentLine);
+
+    updateLineNumberAreaWidth(0);
+    highlightCurrentLine();
+}
+
+//![constructor]
+
+//![extraAreaWidth]
+
+int CodeEditor::lineNumberAreaWidth()
+{
+    int digits = 1;
+    int max = qMax(1, blockCount());
+    while (max >= 10) {
+        max /= 10;
+        ++digits;
+    }
+
+    int space = 3 + fontMetrics().horizontalAdvance(QLatin1Char('9')) * digits;
+
+    return space;
+}
+
+//![extraAreaWidth]
+
+//![slotUpdateExtraAreaWidth]
+
+void CodeEditor::updateLineNumberAreaWidth(int /* newBlockCount */)
+{
+    setViewportMargins(lineNumberAreaWidth(), 0, 0, 0);
+}
+
+//![slotUpdateExtraAreaWidth]
+
+//![slotUpdateRequest]
+
+void CodeEditor::updateLineNumberArea(const QRect &rect, int dy)
+{
+    if (dy)
+        lineNumberArea->scroll(0, dy);
+    else
+        lineNumberArea->update(0, rect.y(), lineNumberArea->width(), rect.height());
+
+    if (rect.contains(viewport()->rect()))
+        updateLineNumberAreaWidth(0);
+}
+
+//![slotUpdateRequest]
+
+//![resizeEvent]
+
+void CodeEditor::resizeEvent(QResizeEvent *e)
+{
+    QPlainTextEdit::resizeEvent(e);
+
+    QRect cr = contentsRect();
+    lineNumberArea->setGeometry(QRect(cr.left(), cr.top(), lineNumberAreaWidth(), cr.height()));
+}
+
+//![resizeEvent]
+
+//![cursorPositionChanged]
+
+void CodeEditor::highlightCurrentLine()
+{
+    QList<QTextEdit::ExtraSelection> extraSelections;
+
+    if (!isReadOnly()) {
+        QTextEdit::ExtraSelection selection;
+
+        QColor lineColor = QColor(Qt::yellow).lighter(160);
+
+        selection.format.setBackground(lineColor);
+        selection.format.setProperty(QTextFormat::FullWidthSelection, true);
+        selection.cursor = textCursor();
+        selection.cursor.clearSelection();
+        extraSelections.append(selection);
+    }
+
+    setExtraSelections(extraSelections);
+}
+
+//![cursorPositionChanged]
+
+//![extraAreaPaintEvent_0]
+
+void CodeEditor::lineNumberAreaPaintEvent(QPaintEvent *event)
+{
+    QPainter painter(lineNumberArea);
+    painter.fillRect(event->rect(), Qt::lightGray);
+
+//![extraAreaPaintEvent_0]
+
+//![extraAreaPaintEvent_1]
+    QTextBlock block = firstVisibleBlock();
+    int blockNumber = block.blockNumber();
+    int top = qRound(blockBoundingGeometry(block).translated(contentOffset()).top());
+    int bottom = top + qRound(blockBoundingRect(block).height());
+//![extraAreaPaintEvent_1]
+
+//![extraAreaPaintEvent_2]
+    while (block.isValid() && top <= event->rect().bottom()) {
+        if (block.isVisible() && bottom >= event->rect().top()) {
+            QString number = QString::number(blockNumber + 1);
+            painter.setPen(Qt::black);
+            painter.drawText(0, top, lineNumberArea->width(), fontMetrics().height(),
+                             Qt::AlignRight, number);
+        }
+
+        block = block.next();
+        top = bottom;
+        bottom = top + qRound(blockBoundingRect(block).height());
+        ++blockNumber;
+    }
+}
+//![extraAreaPaintEvent_2]
+

tests/manual/textrendering/codeeditor/codeeditor.h

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+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#ifndef CODEEDITOR_H
+#define CODEEDITOR_H
+
+#include <QPlainTextEdit>
+
+QT_BEGIN_NAMESPACE
+class QPaintEvent;
+class QResizeEvent;
+class QSize;
+class QWidget;
+QT_END_NAMESPACE
+
+class LineNumberArea;
+
+//![codeeditordefinition]
+
+class CodeEditor : public QPlainTextEdit
+{
+    Q_OBJECT
+
+public:
+    CodeEditor(QWidget *parent = nullptr);
+
+    void lineNumberAreaPaintEvent(QPaintEvent *event);
+    int lineNumberAreaWidth();
+
+protected:
+    void resizeEvent(QResizeEvent *event) override;
+
+private slots:
+    void updateLineNumberAreaWidth(int newBlockCount);
+    void highlightCurrentLine();
+    void updateLineNumberArea(const QRect &rect, int dy);
+
+private:
+    QWidget *lineNumberArea;
+};
+
+//![codeeditordefinition]
+//![extraarea]
+
+class LineNumberArea : public QWidget
+{
+public:
+    LineNumberArea(CodeEditor *editor) : QWidget(editor), codeEditor(editor)
+    {}
+
+    QSize sizeHint() const override
+    {
+        return QSize(codeEditor->lineNumberAreaWidth(), 0);
+    }
+
+protected:
+    void paintEvent(QPaintEvent *event) override
+    {
+        codeEditor->lineNumberAreaPaintEvent(event);
+    }
+
+private:
+    CodeEditor *codeEditor;
+};
+
+//![extraarea]
+
+#endif

tests/manual/textrendering/codeeditor/codeeditor.pro

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+QT += widgets
+
+HEADERS     = codeeditor.h
+SOURCES     = main.cpp \
+              codeeditor.cpp
+# install
+target.path = $$[QT_INSTALL_EXAMPLES]/widgets/widgets/codeeditor
+INSTALLS += target

tests/manual/textrendering/codeeditor/codeeditor.qdoc

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+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+    \example widgets/codeeditor
+    \title Code Editor Example
+    \ingroup examples-widgets
+    \brief The Code Editor example shows how to create a simple editor that
+    has line numbers and that highlights the current line.
+
+    \borderedimage codeeditor-example.png
+
+    As can be seen from the image, the editor displays the line
+    numbers in an area to the left of the area for editing. The editor
+    will highlight the line containing the cursor.
+
+    We implement the editor in \c CodeEditor, which is a widget that
+    inherits QPlainTextEdit. We keep a separate widget in \c
+    CodeEditor (\c LineNumberArea) onto which we draw the line
+    numbers.
+
+    QPlainTextEdit inherits from QAbstractScrollArea, and editing
+    takes place within its \l{QAbstractScrollArea::}{viewport()}'s
+    margins. We make room for our line number area by setting the left
+    margin of the viewport to the size we need to draw the line
+    numbers.
+
+    When it comes to editing code, we prefer QPlainTextEdit over
+    QTextEdit because it is optimized for handling plain text. See
+    the QPlainTextEdit class description for details.
+
+    QPlainTextEdit lets us add selections in addition to the
+    selection the user can make with the mouse or keyboard. We use
+    this functionality to highlight the current line. More on this
+    later.
+
+    We will now move on to the definitions and implementations of \c
+    CodeEditor and \c LineNumberArea. Let's start with the \c
+    LineNumberArea class.
+
+    \section1 The LineNumberArea Class
+
+    We paint the line numbers on this widget, and place it over the \c
+    CodeEditor's \l{QAbstractScrollArea::}{viewport()}'s left margin
+    area.
+
+    We need to use protected functions in QPlainTextEdit while
+    painting the area. So to keep things simple, we  paint the area in
+    the \c CodeEditor class. The area also asks the editor to
+    calculate its size hint.
+
+    Note that we could simply paint the line numbers directly on the
+    code editor, and drop the LineNumberArea class. However, the
+    QWidget class helps us to \l{QWidget::}{scroll()} its contents.
+    Also, having a separate widget is the right choice if we wish to
+    extend the editor with breakpoints or other code editor features.
+    The widget would then help in the handling of mouse events.
+
+    \snippet widgets/codeeditor/codeeditor.h extraarea
+
+    \section1 CodeEditor Class Definition
+
+    Here is the code editor's class definition:
+
+    \snippet widgets/codeeditor/codeeditor.h codeeditordefinition
+
+    In the editor we resize and draw the line numbers on the \c
+    LineNumberArea. We need to do this when the number of lines in the
+    editor changes, and when the editor's viewport() is scrolled. Of
+    course, it is also done when the editor's size changes. We do
+    this in \c updateLineNumberWidth() and \c updateLineNumberArea().
+
+    Whenever, the cursor's position changes, we highlight the current
+    line in \c highlightCurrentLine().
+
+    \section1 CodeEditor Class Implementation
+
+    We will now go through the code editors implementation, starting
+    off with the constructor.
+
+    \snippet widgets/codeeditor/codeeditor.cpp constructor
+
+    In the constructor we connect our slots to signals in
+    QPlainTextEdit. It is necessary to calculate the line number area
+    width and highlight the first line when the editor is created.
+
+    \snippet widgets/codeeditor/codeeditor.cpp extraAreaWidth
+
+    The \c lineNumberAreaWidth() function calculates the width of the
+    \c LineNumberArea widget. We take the number of digits in the last
+    line of the editor and multiply that with the maximum width of a
+    digit.
+
+    \snippet widgets/codeeditor/codeeditor.cpp slotUpdateExtraAreaWidth
+
+    When we update the width of the line number area, we simply call
+    QAbstractScrollArea::setViewportMargins().
+
+    \snippet widgets/codeeditor/codeeditor.cpp slotUpdateRequest
+
+    This slot is invoked when the editors viewport has been scrolled.
+    The QRect given as argument is the part of the editing area that
+    is do be updated (redrawn). \c dy holds the number of pixels the
+    view has been scrolled vertically.
+
+    \snippet widgets/codeeditor/codeeditor.cpp resizeEvent
+
+    When the size of the editor changes, we also need to resize the
+    line number area.
+
+    \snippet widgets/codeeditor/codeeditor.cpp cursorPositionChanged
+
+    When the cursor position changes, we highlight the current line,
+    i.e., the line containing the cursor.
+
+    QPlainTextEdit gives the possibility to have more than one
+    selection at the same time. we can set the character format
+    (QTextCharFormat) of these selections. We clear the cursors
+    selection before setting the new new
+    QPlainTextEdit::ExtraSelection, else several lines would get
+    highlighted when the user selects multiple lines with the mouse.
+    \omit ask someone how this works \endomit
+
+    One sets the selection with a text cursor. When using the
+    FullWidthSelection property, the current cursor text block (line)
+    will be selected. If you want to select just a portion of the text
+    block, the cursor should be moved with QTextCursor::movePosition()
+    from a position set with \l{QTextCursor::}{setPosition()}.
+
+    \snippet widgets/codeeditor/codeeditor.cpp extraAreaPaintEvent_0
+
+    The \c lineNumberAreaPaintEvent() is called from \c LineNumberArea
+    whenever it receives a paint event. We start off by painting the
+    widget's background.
+
+    \snippet widgets/codeeditor/codeeditor.cpp extraAreaPaintEvent_1
+
+    We will now loop through all visible lines and paint the line
+    numbers in the extra area for each line. Notice that in a plain
+    text edit each line will consist of one QTextBlock; though, if
+    line wrapping is enabled, a line may span several rows in the text
+    edit's viewport.
+
+    We get the top and bottom y-coordinate of the first text block,
+    and adjust these values by the height of the current text block in
+    each iteration in the loop.
+
+    \snippet widgets/codeeditor/codeeditor.cpp extraAreaPaintEvent_2
+
+    Notice that we check if the block is visible in addition to check
+    if it is in the areas viewport - a block can, for example, be
+    hidden by a window placed over the text edit.
+
+    \section1 Suggestions for Extending the Code Editor
+
+    No self-respecting code editor is without a syntax
+    highligther; the \l{Syntax Highlighter Example} shows how to
+    create one.
+
+    In addition to line numbers, you can add more to the extra area,
+    for instance, break points.
+
+    QSyntaxHighlighter gives the possibility to add user data to each
+    text block with
+    \l{QSyntaxHighlighter::}{setCurrentBlockUserData()}. This can be
+    used to implement parenthesis matching. In the \c
+    highlightCurrentLine(), the data of the currentBlock() can be
+    fetched with QTextBlock::userData(). Matching parentheses can be
+    highlighted with an extra selection. The "Matching Parentheses
+    with QSyntaxHighlighter" article in Qt Quarterly 31 implements
+    this. You find it here: \l{http://doc.qt.io/archives/qq/}.
+
+*/

tests/manual/textrendering/codeeditor/main.cpp

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+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include <QApplication>
+
+#include "codeeditor.h"
+
+int main(int argv, char **args)
+{
+    QApplication app(argv, args);
+
+    CodeEditor editor;
+    editor.setWindowTitle(QObject::tr("Code Editor Example"));
+    editor.show();
+
+    return app.exec();
+}
+