Examples: remove OpenGL code paths from painting examples

The extra code for using the OpenGL paint engine is significant enough
to be distracting from what the examples are supposed to show. If we
want to show how to use QPainter on an OpenGL widget, then we can make
dedicated and documented examples for that, in the OpenGL category. And
we have such examples in the Qt OpenGL module anyway.

As is, the examples feel more like manual tests of the OpenGL paint
engine; if we need more coverage there, then we can add it there.

Change-Id: I7b56ea6d08c02cd0a1050ab03991656a0538498d
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

15 files changed, 22 insertions, 489 deletions

diff --git a/examples/widgets/painting/CMakeLists.txt b/examples/widgets/painting/CMakeLists.txt
index 38ff34c540..055ae44c45 100644
--- a/examples/widgets/painting/CMakeLists.txt
+++ b/examples/widgets/painting/CMakeLists.txt
@@ -4,7 +4,7 @@
 qt_internal_add_example(basicdrawing)
 qt_internal_add_example(concentriccircles)
 qt_internal_add_example(affine)
-# qt_internal_add_example(composition) # FIXME: Seems buggy wrt. usesOpenGL function
+qt_internal_add_example(composition)
 qt_internal_add_example(deform)
 qt_internal_add_example(gradients)
 qt_internal_add_example(pathstroke)
diff --git a/examples/widgets/painting/affine/xform.cpp b/examples/widgets/painting/affine/xform.cpp
index 87d653acd3..5754490eed 100644
--- a/examples/widgets/painting/affine/xform.cpp
+++ b/examples/widgets/painting/affine/xform.cpp
@@ -777,12 +777,6 @@ XFormWidget::XFormWidget(QWidget *parent)
 
     QPushButton *showSourceButton = new QPushButton(mainGroup);
     showSourceButton->setText(tr("Show Source"));
-#if QT_CONFIG(opengl)
-    QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
-    enableOpenGLButton->setText(tr("Use OpenGL"));
-    enableOpenGLButton->setCheckable(true);
-    enableOpenGLButton->setChecked(view->usesOpenGL());
-#endif
     QPushButton *whatsThisButton = new QPushButton(mainGroup);
     whatsThisButton->setText(tr("What's This?"));
     whatsThisButton->setCheckable(true);
@@ -812,9 +806,6 @@ XFormWidget::XFormWidget(QWidget *parent)
     mainGroupLayout->addWidget(resetButton);
     mainGroupLayout->addWidget(animateButton);
     mainGroupLayout->addWidget(showSourceButton);
-#if QT_CONFIG(opengl)
-    mainGroupLayout->addWidget(enableOpenGLButton);
-#endif
     mainGroupLayout->addWidget(whatsThisButton);
 
     mainGroup->setLayout(mainGroupLayout);
@@ -852,9 +843,6 @@ XFormWidget::XFormWidget(QWidget *parent)
     connect(view, &XFormView::descriptionEnabledChanged, view->hoverPoints(), &HoverPoints::setDisabled);
     connect(view, &XFormView::descriptionEnabledChanged, whatsThisButton, &QPushButton::setChecked);
     connect(showSourceButton, &QPushButton::clicked, view, &XFormView::showSource);
-#if QT_CONFIG(opengl)
-    connect(enableOpenGLButton, &QPushButton::clicked, view, &XFormView::enableOpenGL);
-#endif
     view->loadSourceFile(":res/affine/xform.cpp");
     view->loadDescription(":res/affine/xform.html");
 
diff --git a/examples/widgets/painting/composition/composition.cpp b/examples/widgets/painting/composition/composition.cpp
index b902498b2d..b4fb4fa3f7 100644
--- a/examples/widgets/painting/composition/composition.cpp
+++ b/examples/widgets/painting/composition/composition.cpp
@@ -10,11 +10,6 @@
 #include <QMouseEvent>
 #include <qmath.h>
 
-#if QT_CONFIG(opengl)
-#include <QOpenGLFunctions>
-#include <QOpenGLWindow>
-#endif
-
 const int animationInterval = 15; // update every 16 ms = ~60FPS
 
 CompositionWidget::CompositionWidget(QWidget *parent)
@@ -94,12 +89,6 @@ CompositionWidget::CompositionWidget(QWidget *parent)
 
     QPushButton *showSourceButton = new QPushButton(mainGroup);
     showSourceButton->setText(tr("Show Source"));
-#if QT_CONFIG(opengl)
-    QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
-    enableOpenGLButton->setText(tr("Use OpenGL"));
-    enableOpenGLButton->setCheckable(true);
-    enableOpenGLButton->setChecked(view->usesOpenGL());
-#endif
     QPushButton *whatsThisButton = new QPushButton(mainGroup);
     whatsThisButton->setText(tr("What's This?"));
     whatsThisButton->setCheckable(true);
@@ -121,9 +110,6 @@ CompositionWidget::CompositionWidget(QWidget *parent)
     mainGroupLayout->addWidget(animateButton);
     mainGroupLayout->addWidget(whatsThisButton);
     mainGroupLayout->addWidget(showSourceButton);
-#if QT_CONFIG(opengl)
-    mainGroupLayout->addWidget(enableOpenGLButton);
-#endif
 
     QGridLayout *modesLayout = new QGridLayout(modesGroup);
     modesLayout->addWidget(rbClear, 0, 0);
@@ -165,9 +151,6 @@ CompositionWidget::CompositionWidget(QWidget *parent)
     connect(whatsThisButton, &QAbstractButton::clicked, view, &ArthurFrame::setDescriptionEnabled);
     connect(view, &ArthurFrame::descriptionEnabledChanged, whatsThisButton, &QAbstractButton::setChecked);
     connect(showSourceButton, &QAbstractButton::clicked, view, &ArthurFrame::showSource);
-#if QT_CONFIG(opengl)
-    connect(enableOpenGLButton, &QAbstractButton::clicked, view, &ArthurFrame::enableOpenGL);
-#endif
     connect(animateButton, &QAbstractButton::toggled, view, &CompositionRenderer::setAnimationEnabled);
 
     circleColorSlider->setValue(270);
@@ -217,10 +200,6 @@ CompositionRenderer::CompositionRenderer(QWidget *parent)
     m_circle_pos = QPoint(200, 100);
 
     setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
-#if QT_CONFIG(opengl)
-    m_pbuffer_size = 1024;
-    m_base_tex = 0;
-#endif
 }
 
 CompositionRenderer::~CompositionRenderer()
@@ -313,89 +292,25 @@ void CompositionRenderer::drawSource(QPainter &p)
 
 void CompositionRenderer::paint(QPainter *painter)
 {
-#if QT_CONFIG(opengl)
-    if (usesOpenGL() && glWindow()->isValid()) {
-        auto *funcs = QOpenGLContext::currentContext()->functions();
-
-        if (!m_blitter.isCreated())
-            m_blitter.create();
-
-        int new_pbuf_size = m_pbuffer_size;
-        while (size().width() > new_pbuf_size || size().height() > new_pbuf_size)
-            new_pbuf_size *= 2;
-
-        while (size().width() < new_pbuf_size/2 && size().height() < new_pbuf_size/2)
-            new_pbuf_size /= 2;
-
-        if (!m_fbo || new_pbuf_size != m_pbuffer_size) {
-            m_fbo.reset(new QFboPaintDevice(QSize(new_pbuf_size, new_pbuf_size), false, false));
-            m_pbuffer_size = new_pbuf_size;
-        }
-
-        if (size() != m_previous_size) {
-            m_previous_size = size();
-            QPainter p(m_fbo.get());
-            p.setCompositionMode(QPainter::CompositionMode_Source);
-            p.fillRect(QRect(QPoint(0, 0), size()), Qt::transparent);
-            p.setCompositionMode(QPainter::CompositionMode_SourceOver);
-            drawBase(p);
-            p.end();
-            if (m_base_tex)
-                funcs->glDeleteTextures(1, &m_base_tex);
-            m_base_tex = m_fbo->takeTexture();
-        }
-
-        painter->beginNativePainting();
-        uint compositingTex;
-        {
-            QPainter p(m_fbo.get());
-            p.beginNativePainting();
-            m_blitter.bind();
-            const QRect targetRect(QPoint(0, 0), m_fbo->size());
-            const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(targetRect, QRect(QPoint(0, 0), m_fbo->size()));
-            m_blitter.blit(m_base_tex, target, QOpenGLTextureBlitter::OriginBottomLeft);
-            m_blitter.release();
-            p.endNativePainting();
-            drawSource(p);
-            p.end();
-            compositingTex = m_fbo->texture();
-        }
-        painter->endNativePainting();
-
-        painter->beginNativePainting();
-        funcs->glEnable(GL_BLEND);
-        funcs->glBlendEquation(GL_FUNC_ADD);
-        funcs->glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
-        m_blitter.bind();
-        const QRect targetRect(QPoint(0, 0), m_fbo->size());
-        const QMatrix4x4 target = QOpenGLTextureBlitter::targetTransform(targetRect, QRect(QPoint(0, 0), size()));
-        m_blitter.blit(compositingTex, target, QOpenGLTextureBlitter::OriginBottomLeft);
-        m_blitter.release();
-        painter->endNativePainting();
-    } else
-#endif
-    {
-        // using a QImage
-        if (m_buffer.size() != size()) {
-            m_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);
-            m_base_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);
+    if (m_buffer.size() != size()) {
+        m_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);
+        m_base_buffer = QImage(size(), QImage::Format_ARGB32_Premultiplied);
 
-            m_base_buffer.fill(0);
+        m_base_buffer.fill(0);
 
-            QPainter p(&m_base_buffer);
+        QPainter p(&m_base_buffer);
 
-            drawBase(p);
-        }
-
-        memcpy(m_buffer.bits(), m_base_buffer.bits(), m_buffer.sizeInBytes());
+        drawBase(p);
+    }
 
-        {
-            QPainter p(&m_buffer);
-            drawSource(p);
-        }
+    memcpy(m_buffer.bits(), m_base_buffer.bits(), m_buffer.sizeInBytes());
 
-        painter->drawImage(0, 0, m_buffer);
+    {
+        QPainter p(&m_buffer);
+        drawSource(p);
     }
+
+    painter->drawImage(0, 0, m_buffer);
 }
 
 void CompositionRenderer::mousePressEvent(QMouseEvent *e)
@@ -443,12 +358,6 @@ void CompositionRenderer::setCirclePos(const QPointF &pos)
     const QRect oldRect = rectangle_around(m_circle_pos).toAlignedRect();
     m_circle_pos = pos;
     const QRect newRect = rectangle_around(m_circle_pos).toAlignedRect();
-#if QT_CONFIG(opengl)
-    if (usesOpenGL()) {
-        update();
-        return;
-    }
-#endif
     update(oldRect | newRect);
 }
 
diff --git a/examples/widgets/painting/composition/composition.h b/examples/widgets/painting/composition/composition.h
index 0745eb41b9..6a5206da08 100644
--- a/examples/widgets/painting/composition/composition.h
+++ b/examples/widgets/painting/composition/composition.h
@@ -6,11 +6,6 @@
 
 #include "arthurwidgets.h"
 
-#if QT_CONFIG(opengl)
-#include "fbopaintdevice.h"
-#include <QOpenGLTextureBlitter>
-#endif
-
 #include <QPainter>
 #include <QEvent>
 
@@ -143,14 +138,6 @@ private:
     ObjectType m_current_object;
     bool m_animation_enabled;
     int m_animationTimer;
-
-#if QT_CONFIG(opengl)
-    std::unique_ptr<QFboPaintDevice> m_fbo;
-    int m_pbuffer_size; // width==height==size of pbuffer
-    uint m_base_tex;
-    QSize m_previous_size;
-    QOpenGLTextureBlitter m_blitter;
-#endif
 };
 
 #endif // COMPOSITION_H
diff --git a/examples/widgets/painting/deform/pathdeform.cpp b/examples/widgets/painting/deform/pathdeform.cpp
index fead0e3c13..f2c67c1587 100644
--- a/examples/widgets/painting/deform/pathdeform.cpp
+++ b/examples/widgets/painting/deform/pathdeform.cpp
@@ -61,13 +61,6 @@ void PathDeformControls::layoutForDesktop()
     QPushButton *showSourceButton = new QPushButton(mainGroup);
     showSourceButton->setText(tr("Show Source"));
 
-#if QT_CONFIG(opengl)
-    QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
-    enableOpenGLButton->setText(tr("Use OpenGL"));
-    enableOpenGLButton->setCheckable(true);
-    enableOpenGLButton->setChecked(m_renderer->usesOpenGL());
-#endif
-
     QPushButton *whatsThisButton = new QPushButton(mainGroup);
     whatsThisButton->setText(tr("What's This?"));
     whatsThisButton->setCheckable(true);
@@ -82,9 +75,6 @@ void PathDeformControls::layoutForDesktop()
     mainGroupLayout->addWidget(textGroup);
     mainGroupLayout->addWidget(animateButton);
     mainGroupLayout->addStretch(1);
-#if QT_CONFIG(opengl)
-    mainGroupLayout->addWidget(enableOpenGLButton);
-#endif
     mainGroupLayout->addWidget(showSourceButton);
     mainGroupLayout->addWidget(whatsThisButton);
 
@@ -108,9 +98,6 @@ void PathDeformControls::layoutForDesktop()
     connect(deformSlider, &QAbstractSlider::valueChanged, m_renderer, &PathDeformRenderer::setIntensity);
     connect(fontSizeSlider, &QAbstractSlider::valueChanged, m_renderer, &PathDeformRenderer::setFontSize);
     connect(animateButton, &QAbstractButton::clicked, m_renderer, &PathDeformRenderer::setAnimated);
-#if QT_CONFIG(opengl)
-    connect(enableOpenGLButton, &QAbstractButton::clicked, m_renderer, &ArthurFrame::enableOpenGL);
-#endif
 
     connect(textInput, &QLineEdit::textChanged, m_renderer, &PathDeformRenderer::setText);
     connect(m_renderer, &ArthurFrame::descriptionEnabledChanged,
@@ -151,13 +138,6 @@ void PathDeformControls::layoutForSmallScreen()
     QPushButton *animateButton = new QPushButton(tr("Animated"), mainGroup);
     animateButton->setCheckable(true);
 
-#if QT_CONFIG(opengl)
-    QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
-    enableOpenGLButton->setText(tr("Use OpenGL"));
-    enableOpenGLButton->setCheckable(mainGroup);
-    enableOpenGLButton->setChecked(m_renderer->usesOpenGL());
-#endif
-
     QPushButton *quitButton = new QPushButton(tr("Quit"), mainGroup);
     QPushButton *okButton = new QPushButton(tr("OK"), mainGroup);
 
@@ -171,9 +151,6 @@ void PathDeformControls::layoutForSmallScreen()
     mainGroupLayout->addWidget(fontSizeLabel, 2, 0, Qt::AlignRight);
     mainGroupLayout->addWidget(fontSizeSlider, 2, 1);
     mainGroupLayout->addWidget(animateButton, 3,0, 1,2);
-#if QT_CONFIG(opengl)
-    mainGroupLayout->addWidget(enableOpenGLButton, 4,0, 1,2);
-#endif
 
     QVBoxLayout *mainLayout = new QVBoxLayout(this);
     mainLayout->addWidget(mainGroup);
@@ -187,10 +164,6 @@ void PathDeformControls::layoutForSmallScreen()
     connect(deformSlider, &QAbstractSlider::valueChanged, m_renderer, &PathDeformRenderer::setIntensity);
     connect(fontSizeSlider, &QAbstractSlider::valueChanged, m_renderer, &PathDeformRenderer::setFontSize);
     connect(animateButton, &QAbstractButton::clicked, m_renderer, &PathDeformRenderer::setAnimated);
-#if QT_CONFIG(opengl)
-    connect(enableOpenGLButton, &QAbstractButton::clicked, m_renderer, &ArthurFrame::enableOpenGL);
-#endif
-
 
     animateButton->animateClick();
     deformSlider->setValue(80);
@@ -380,7 +353,6 @@ void PathDeformRenderer::setAnimated(bool animated)
 
 void PathDeformRenderer::timerEvent(QTimerEvent *e)
 {
-
     if (e->timerId() == m_repaintTimer.timerId()) {
 
         if (QLineF(QPointF(0,0), m_direction).length() > 1)
@@ -414,22 +386,9 @@ void PathDeformRenderer::timerEvent(QTimerEvent *e)
             m_pos.setY(height() - m_radius);
         }
 
-#if QT_CONFIG(opengl)
-        if (usesOpenGL()) {
-            update();
-        } else
-#endif
-        {
-            QRect rectAfter = circle_bounds(m_pos, m_radius, m_fontSize);
-            update(rectAfter | rectBefore);
-        }
+        QRect rectAfter = circle_bounds(m_pos, m_radius, m_fontSize);
+        update(rectAfter | rectBefore);
     }
-//     else if (e->timerId() == m_fpsTimer.timerId()) {
-//         printf("fps: %d\n", m_fpsCounter);
-//         emit frameRate(m_fpsCounter);
-//         m_fpsCounter = 0;
-
-//     }
 }
 
 void PathDeformRenderer::mousePressEvent(QMouseEvent *e)
@@ -478,15 +437,8 @@ void PathDeformRenderer::mouseMoveEvent(QMouseEvent *e)
             m_direction = (m_direction + dir) / 2;
         }
         m_pos = e->position().toPoint() + m_offset;
-#if QT_CONFIG(opengl)
-        if (usesOpenGL()) {
-            update();
-        } else
-#endif
-        {
-            QRect rectAfter = circle_bounds(m_pos, m_radius, m_fontSize);
-            update(rectBefore | rectAfter);
-        }
+        QRect rectAfter = circle_bounds(m_pos, m_radius, m_fontSize);
+        update(rectBefore | rectAfter);
     }
 }
 
@@ -570,27 +522,13 @@ void PathDeformRenderer::setRadius(int radius)
     qreal max = qMax(m_radius, (qreal)radius);
     m_radius = radius;
     generateLensPixmap();
-    if (!m_animated || m_radius < max) {
-#if QT_CONFIG(opengl)
-        if (usesOpenGL()){
-            update();
-            return;
-        }
-#endif
+    if (!m_animated || m_radius < max)
         update(circle_bounds(m_pos, max, m_fontSize));
-    }
 }
 
 void PathDeformRenderer::setIntensity(int intensity)
 {
     m_intensity = intensity;
-    if (!m_animated) {
-#if QT_CONFIG(opengl)
-        if (usesOpenGL()) {
-            update();
-            return;
-        }
-#endif
+    if (!m_animated)
         update(circle_bounds(m_pos, m_radius, m_fontSize));
-    }
 }
diff --git a/examples/widgets/painting/gradients/gradients.cpp b/examples/widgets/painting/gradients/gradients.cpp
index 538d851eb8..5ed3d764d1 100644
--- a/examples/widgets/painting/gradients/gradients.cpp
+++ b/examples/widgets/painting/gradients/gradients.cpp
@@ -273,12 +273,6 @@ GradientWidget::GradientWidget(QWidget *parent)
 
     QPushButton *showSourceButton = new QPushButton(mainGroup);
     showSourceButton->setText(tr("Show Source"));
-#if QT_CONFIG(opengl)
-    QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
-    enableOpenGLButton->setText(tr("Use OpenGL"));
-    enableOpenGLButton->setCheckable(true);
-    enableOpenGLButton->setChecked(m_renderer->usesOpenGL());
-#endif
     QPushButton *whatsThisButton = new QPushButton(mainGroup);
     whatsThisButton->setText(tr("What's This?"));
     whatsThisButton->setCheckable(true);
@@ -292,9 +286,6 @@ GradientWidget::GradientWidget(QWidget *parent)
     mainGroupLayout->addWidget(defaultsGroup);
     mainGroupLayout->addStretch(1);
     mainGroupLayout->addWidget(showSourceButton);
-#if QT_CONFIG(opengl)
-    mainGroupLayout->addWidget(enableOpenGLButton);
-#endif
     mainGroupLayout->addWidget(whatsThisButton);
 
     QVBoxLayout *editorGroupLayout = new QVBoxLayout(editorGroup);
@@ -370,11 +361,6 @@ GradientWidget::GradientWidget(QWidget *parent)
 
     connect(showSourceButton, &QPushButton::clicked,
             m_renderer, &GradientRenderer::showSource);
-#if QT_CONFIG(opengl)
-    connect(enableOpenGLButton, QOverload<bool>::of(&QPushButton::clicked),
-            m_renderer, &ArthurFrame::enableOpenGL);
-#endif
-
     connect(whatsThisButton, QOverload<bool>::of(&QPushButton::clicked),
             m_renderer, &ArthurFrame::setDescriptionEnabled);
     connect(whatsThisButton, QOverload<bool>::of(&QPushButton::clicked),
diff --git a/examples/widgets/painting/pathstroke/pathstroke.cpp b/examples/widgets/painting/pathstroke/pathstroke.cpp
index 8c0548bdf0..cd54a7a8aa 100644
--- a/examples/widgets/painting/pathstroke/pathstroke.cpp
+++ b/examples/widgets/painting/pathstroke/pathstroke.cpp
@@ -177,12 +177,6 @@ void PathStrokeControls::layoutForDesktop()
 
     QPushButton *showSourceButton = new QPushButton(mainGroup);
     showSourceButton->setText(tr("Show Source"));
-#if QT_CONFIG(opengl)
-    QPushButton *enableOpenGLButton = new QPushButton(mainGroup);
-    enableOpenGLButton->setText(tr("Use OpenGL"));
-    enableOpenGLButton->setCheckable(true);
-    enableOpenGLButton->setChecked(m_renderer->usesOpenGL());
-#endif
     QPushButton *whatsThisButton = new QPushButton(mainGroup);
     whatsThisButton->setText(tr("What's This?"));
     whatsThisButton->setCheckable(true);
@@ -206,9 +200,6 @@ void PathStrokeControls::layoutForDesktop()
     mainGroupLayout->addWidget(animated);
     mainGroupLayout->addStretch(1);
     mainGroupLayout->addWidget(showSourceButton);
-#if QT_CONFIG(opengl)
-    mainGroupLayout->addWidget(enableOpenGLButton);
-#endif
     mainGroupLayout->addWidget(whatsThisButton);
 
 
@@ -221,10 +212,6 @@ void PathStrokeControls::layoutForDesktop()
 
     connect(showSourceButton, &QAbstractButton::clicked,
             m_renderer, &ArthurFrame::showSource);
-#if QT_CONFIG(opengl)
-    connect(enableOpenGLButton, &QAbstractButton::clicked,
-            m_renderer, &ArthurFrame::enableOpenGL);
-#endif
     connect(whatsThisButton, &QAbstractButton::clicked,
             m_renderer, &ArthurFrame::setDescriptionEnabled);
     connect(m_renderer, &ArthurFrame::descriptionEnabledChanged,
@@ -259,13 +246,6 @@ void PathStrokeControls::layoutForSmallScreens()
     penWidth->setSizePolicy(QSizePolicy::Preferred, QSizePolicy::Fixed);
     penWidth->setRange(0, 500);
 
-#if QT_CONFIG(opengl)
-    QPushButton *enableOpenGLButton = new QPushButton(this);
-    enableOpenGLButton->setText(tr("Use OpenGL"));
-    enableOpenGLButton->setCheckable(true);
-    enableOpenGLButton->setChecked(m_renderer->usesOpenGL());
-#endif
-
     // Layouts:
     QHBoxLayout *penWidthLayout = new QHBoxLayout;
     penWidthLayout->addWidget(penWidthLabel, 0, Qt::AlignRight);
@@ -274,9 +254,6 @@ void PathStrokeControls::layoutForSmallScreens()
     QVBoxLayout *leftLayout = new QVBoxLayout;
     leftLayout->addWidget(m_capGroup);
     leftLayout->addWidget(m_joinGroup);
-#if QT_CONFIG(opengl)
-    leftLayout->addWidget(enableOpenGLButton);
-#endif
     leftLayout->addLayout(penWidthLayout);
 
     QVBoxLayout *rightLayout = new QVBoxLayout;
@@ -297,10 +274,6 @@ void PathStrokeControls::layoutForSmallScreens()
     mainLayout->addWidget(quitBtn, 2, 1, Qt::AlignHCenter | Qt::AlignTop);
     mainLayout->addWidget(okBtn, 2, 2, Qt::AlignHCenter | Qt::AlignTop);
 
-#if QT_CONFIG(opengl)
-    connect(enableOpenGLButton, &QAbstractButton::clicked, m_renderer, &ArthurFrame::enableOpenGL);
-#endif
-
     connect(penWidth, &QAbstractSlider::valueChanged, m_renderer, &PathStrokeRenderer::setPenWidth);
     connect(quitBtn, &QAbstractButton::clicked, this, &PathStrokeControls::emitQuitSignal);
     connect(okBtn, &QAbstractButton::clicked, this, &PathStrokeControls::emitOkSignal);
diff --git a/examples/widgets/painting/shared/CMakeLists.txt b/examples/widgets/painting/shared/CMakeLists.txt
index fbd356e162..5e5b0ec12d 100644
--- a/examples/widgets/painting/shared/CMakeLists.txt
+++ b/examples/widgets/painting/shared/CMakeLists.txt
@@ -15,15 +15,3 @@ set_target_properties(painting_shared PROPERTIES UNITY_BUILD OFF)
 
 target_link_libraries(painting_shared PUBLIC Qt6::Widgets)
 target_include_directories(painting_shared PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}")
-
-## Scopes:
-#####################################################################
-
-if (TARGET Qt6::OpenGL OR QT_FEATURE_opengles2)
-    target_compile_definitions(painting_shared PRIVATE QT_OPENGL_SUPPORT)
-    target_link_libraries(painting_shared PUBLIC
-        Qt6::OpenGL
-    )
-    qt6_wrap_cpp(moc_files_gl fbopaintdevice.h) # no automoc for OBJECT libs
-    target_sources(painting_shared PRIVATE fbopaintdevice.cpp fbopaintdevice.h ${moc_files_gl})
-endif()
diff --git a/examples/widgets/painting/shared/arthurwidgets.cpp b/examples/widgets/painting/shared/arthurwidgets.cpp
index 7f3e50f5e6..4ff435783b 100644
--- a/examples/widgets/painting/shared/arthurwidgets.cpp
+++ b/examples/widgets/painting/shared/arthurwidgets.cpp
@@ -14,11 +14,6 @@
 #include <QBoxLayout>
 #include <QRegularExpression>
 #include <QOffscreenSurface>
-#include <QOpenGLContext>
-#if QT_CONFIG(opengl)
-#include <QtOpenGL/QOpenGLPaintDevice>
-#include <QtOpenGL/QOpenGLWindow>
-#endif
 
 extern QPixmap cached(const QString &img);
 
@@ -34,61 +29,13 @@ ArthurFrame::ArthurFrame(QWidget *parent)
     pt.end();
 }
 
-
-#if QT_CONFIG(opengl)
-void ArthurFrame::enableOpenGL(bool use_opengl)
-{
-    if (m_use_opengl == use_opengl)
-        return;
-
-    m_use_opengl = use_opengl;
-
-    if (!m_glWindow && use_opengl) {
-        createGlWindow();
-        QApplication::postEvent(this, new QResizeEvent(size(), size()));
-    }
-
-    if (use_opengl) {
-        m_glWidget->show();
-    } else {
-        if (m_glWidget)
-            m_glWidget->hide();
-    }
-
-    update();
-}
-
-void ArthurFrame::createGlWindow()
-{
-    Q_ASSERT(m_use_opengl);
-
-    m_glWindow = new QOpenGLWindow();
-    QSurfaceFormat f = QSurfaceFormat::defaultFormat();
-    f.setSamples(4);
-    f.setAlphaBufferSize(8);
-    f.setStencilBufferSize(8);
-    m_glWindow->setFormat(f);
-    m_glWindow->setFlags(Qt::WindowTransparentForInput);
-    m_glWindow->resize(width(), height());
-    m_glWidget = QWidget::createWindowContainer(m_glWindow, this);
-    // create() must be called after createWindowContainer() otherwise
-    // an incorrect offsetting of the position will occur.
-    m_glWindow->create();
-}
-#endif
-
-
 void ArthurFrame::paintEvent(QPaintEvent *e)
 {
     static QImage *static_image = nullptr;
 
     QPainter painter;
 
-    if (preferImage()
-#if QT_CONFIG(opengl)
-        && !m_use_opengl
-#endif
-        ) {
+    if (preferImage()) {
         if (!static_image || static_image->size() != size()) {
             delete static_image;
             static_image = new QImage(size(), QImage::Format_RGB32);
@@ -103,18 +50,7 @@ void ArthurFrame::paintEvent(QPaintEvent *e)
         painter.fillRect(0, height() - o, o, o, bg);
         painter.fillRect(width() - o, height() - o, o, o, bg);
     } else {
-#if QT_CONFIG(opengl)
-        if (m_use_opengl && m_glWindow->isValid()) {
-            m_glWindow->makeCurrent();
-
-            painter.begin(m_glWindow);
-            painter.fillRect(QRectF(0, 0, m_glWindow->width(), m_glWindow->height()), palette().color(backgroundRole()));
-        } else {
-            painter.begin(this);
-        }
-#else
         painter.begin(this);
-#endif
     }
 
     painter.setClipRect(e->rect());
@@ -158,27 +94,15 @@ void ArthurFrame::paintEvent(QPaintEvent *e)
     painter.setBrush(Qt::NoBrush);
     painter.drawPath(clipPath);
 
-    if (preferImage()
-#if QT_CONFIG(opengl)
-        && !m_use_opengl
-#endif
-        ) {
+    if (preferImage()) {
         painter.end();
         painter.begin(this);
         painter.drawImage(e->rect(), *static_image, e->rect());
     }
-#if QT_CONFIG(opengl)
-    if (m_use_opengl)
-        m_glWindow->update();
-#endif
 }
 
 void ArthurFrame::resizeEvent(QResizeEvent *e)
 {
-#if QT_CONFIG(opengl)
-    if (m_glWidget)
-        m_glWidget->setGeometry(0, 0, e->size().width(), e->size().height());
-#endif
     QWidget::resizeEvent(e);
 }
 
diff --git a/examples/widgets/painting/shared/arthurwidgets.h b/examples/widgets/painting/shared/arthurwidgets.h
index bf50b24346..79d4090c67 100644
--- a/examples/widgets/painting/shared/arthurwidgets.h
+++ b/examples/widgets/painting/shared/arthurwidgets.h
@@ -9,7 +9,6 @@
 #include <QPushButton>
 #include <QGroupBox>
 
-QT_FORWARD_DECLARE_CLASS(QOpenGLWindow)
 QT_FORWARD_DECLARE_CLASS(QTextDocument)
 QT_FORWARD_DECLARE_CLASS(QTextEdit)
 QT_FORWARD_DECLARE_CLASS(QVBoxLayout)
@@ -30,20 +29,12 @@ public:
     void loadSourceFile(const QString &fileName);
 
     bool preferImage() const { return m_preferImage; }
-#if QT_CONFIG(opengl)
-    QOpenGLWindow *glWindow() const { return m_glWindow; }
-#endif
 
 public slots:
     void setPreferImage(bool pi) { m_preferImage = pi; }
     void setDescriptionEnabled(bool enabled);
     void showSource();
 
-#if QT_CONFIG(opengl)
-    void enableOpenGL(bool use_opengl);
-    bool usesOpenGL() { return m_use_opengl; }
-#endif
-
 signals:
     void descriptionEnabledChanged(bool);
 
@@ -51,12 +42,6 @@ protected:
     void paintEvent(QPaintEvent *) override;
     void resizeEvent(QResizeEvent *) override;
 
-#if QT_CONFIG(opengl)
-    virtual void createGlWindow();
-    QOpenGLWindow *m_glWindow = nullptr;
-    QWidget *m_glWidget = nullptr;
-    bool m_use_opengl = false;
-#endif
     QPixmap m_tile;
 
     bool m_showDoc = false;
diff --git a/examples/widgets/painting/shared/fbopaintdevice.cpp b/examples/widgets/painting/shared/fbopaintdevice.cpp
deleted file mode 100644
index 5875e6574b..0000000000
--- a/examples/widgets/painting/shared/fbopaintdevice.cpp
+++ /dev/null
@@ -1,75 +0,0 @@
-// Copyright (C) 2018 The Qt Company Ltd.
-// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
-
-#include "fbopaintdevice.h"
-
-#include <QOffscreenSurface>
-#include <QOpenGLFunctions>
-
-QFboPaintDevice::QFboPaintDevice(const QSize &size, bool flipped, bool clearOnInit,
-                                 QOpenGLFramebufferObject::Attachment attachment)
-        : QOpenGLPaintDevice(size)
-{
-    QOpenGLFramebufferObjectFormat format;
-    format.setAttachment(attachment);
-    format.setSamples(4);
-    m_framebufferObject = new QOpenGLFramebufferObject(size, format);
-    QOffscreenSurface *surface = new QOffscreenSurface();
-    surface->create();
-    m_surface = surface;
-    setPaintFlipped(flipped);
-    if (clearOnInit) {
-        m_framebufferObject->bind();
-
-        context()->functions()->glClearColor(0, 0, 0, 0);
-        context()->functions()->glClear(GL_COLOR_BUFFER_BIT);
-    }
-    m_resolvedFbo = new QOpenGLFramebufferObject(m_framebufferObject->size(), m_framebufferObject->attachment());
-}
-
-QFboPaintDevice::~QFboPaintDevice()
-{
-    delete m_framebufferObject;
-    delete m_resolvedFbo;
-    delete m_surface;
-}
-
-void QFboPaintDevice::ensureActiveTarget()
-{
-    if (QOpenGLContext::currentContext() != context())
-        context()->makeCurrent(m_surface);
-
-    m_framebufferObject->bind();
-}
-
-GLuint QFboPaintDevice::texture()
-{
-    m_resolvedFbo->bind(); // to get the backing texture recreated if it was taken (in takeTexture) previously
-    QOpenGLFramebufferObject::blitFramebuffer(m_resolvedFbo, m_framebufferObject);
-    return m_resolvedFbo->texture();
-}
-
-GLuint QFboPaintDevice::takeTexture()
-{
-    m_resolvedFbo->bind(); // to get the backing texture recreated if it was taken (in takeTexture) previously
-    // We have multisamples so we can't just forward takeTexture(), have to resolve first.
-    QOpenGLFramebufferObject::blitFramebuffer(m_resolvedFbo, m_framebufferObject);
-    return m_resolvedFbo->takeTexture();
-}
-
-QImage QFboPaintDevice::toImage() const
-{
-    QOpenGLContext *currentContext = QOpenGLContext::currentContext();
-    QSurface *currentSurface = currentContext ? currentContext->surface() : nullptr;
-
-    context()->makeCurrent(m_surface);
-
-    QImage image = m_framebufferObject->toImage(!paintFlipped());
-
-    if (currentContext)
-        currentContext->makeCurrent(currentSurface);
-    else
-        context()->doneCurrent();
-
-    return image;
-}
diff --git a/examples/widgets/painting/shared/fbopaintdevice.h b/examples/widgets/painting/shared/fbopaintdevice.h
deleted file mode 100644
index b2e77a228a..0000000000
--- a/examples/widgets/painting/shared/fbopaintdevice.h
+++ /dev/null
@@ -1,46 +0,0 @@
-// Copyright (C) 2018 The Qt Company Ltd.
-// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
-
-#ifndef QFBOPAINTDEVICE_H
-#define QFBOPAINTDEVICE_H
-
-#ifndef QT_NO_OPENGL
-
-#include <QImage>
-#include <QOpenGLFramebufferObject>
-#include <QOpenGLPaintDevice>
-#include <QSurface>
-
-class QFboPaintDevice : public QOpenGLPaintDevice {
-public:
-    QFboPaintDevice(const QSize &size, bool flipped = false, bool clearOnInit = true,
-        QOpenGLFramebufferObject::Attachment = QOpenGLFramebufferObject::CombinedDepthStencil);
-    ~QFboPaintDevice();
-
-    // QOpenGLPaintDevice:
-    void ensureActiveTarget() override;
-
-    bool isValid() const { return m_framebufferObject->isValid(); }
-    GLuint handle() const { return m_framebufferObject->handle(); }
-    GLuint texture();
-    GLuint takeTexture();
-    QImage toImage() const;
-
-    bool bind() { return m_framebufferObject->bind(); }
-    bool release() { return m_framebufferObject->release(); }
-    QSize size() const { return m_framebufferObject->size(); }
-
-    QOpenGLFramebufferObject* framebufferObject() { return m_framebufferObject; }
-    const QOpenGLFramebufferObject* framebufferObject() const { return m_framebufferObject; }
-
-    static bool isSupported() { return QOpenGLFramebufferObject::hasOpenGLFramebufferObjects(); }
-
-private:
-    QOpenGLFramebufferObject *m_framebufferObject;
-    QOpenGLFramebufferObject *m_resolvedFbo;
-    QSurface *m_surface;
-};
-
-#endif // QT_NO_OPENGL
-
-#endif // QFBOPAINTDEVICE_H
diff --git a/examples/widgets/painting/shared/hoverpoints.cpp b/examples/widgets/painting/shared/hoverpoints.cpp
index a9f76084e1..1df6f214ae 100644
--- a/examples/widgets/painting/shared/hoverpoints.cpp
+++ b/examples/widgets/painting/shared/hoverpoints.cpp
@@ -6,10 +6,6 @@
 
 #include <algorithm>
 
-#if QT_CONFIG(opengl)
-#include <QtOpenGL/QOpenGLWindow>
-#endif
-
 HoverPoints::HoverPoints(QWidget *widget, PointShape shape)
     : QObject(widget),
       m_widget(widget),
@@ -230,17 +226,7 @@ bool HoverPoints::eventFilter(QObject *object, QEvent *event)
 void HoverPoints::paintPoints()
 {
     QPainter p;
-#if QT_CONFIG(opengl)
-    ArthurFrame *af = qobject_cast<ArthurFrame *>(m_widget);
-    if (af && af->usesOpenGL() && af->glWindow()->isValid()) {
-        af->glWindow()->makeCurrent();
-        p.begin(af->glWindow());
-    } else {
-        p.begin(m_widget);
-    }
-#else
     p.begin(m_widget);
-#endif
 
     p.setRenderHint(QPainter::Antialiasing);
 
diff --git a/examples/widgets/painting/shared/shared.pri b/examples/widgets/painting/shared/shared.pri
index 7e2b4df8cb..77881b03cc 100644
--- a/examples/widgets/painting/shared/shared.pri
+++ b/examples/widgets/painting/shared/shared.pri
@@ -1,11 +1,5 @@
 INCLUDEPATH += $$PWD
 
-qtConfig(opengl) {
-    QT += opengl
-    SOURCES += $$PWD/fbopaintdevice.cpp
-    HEADERS += $$PWD/fbopaintdevice.h
-}
-
 SOURCES += \
     $$PWD/arthurstyle.cpp\
     $$PWD/arthurwidgets.cpp \
diff --git a/examples/widgets/painting/shared/use_lib.cmake b/examples/widgets/painting/shared/use_lib.cmake
index dc17fff3c0..6f1668dc5e 100644
--- a/examples/widgets/painting/shared/use_lib.cmake
+++ b/examples/widgets/painting/shared/use_lib.cmake
@@ -9,8 +9,4 @@ if(NOT TARGET Qt::Widgets)
     find_package(Qt6 REQUIRED COMPONENTS Widgets)
 endif()
 
-if(NOT TARGET Qt::OpenGL)
-    find_package(Qt6 OPTIONAL_COMPONENTS OpenGL)
-endif()
-
 add_subdirectory("${CMAKE_CURRENT_LIST_DIR}" painting_shared)