Clip QOpenGLWidget and QQuickWidget correctly

Introduce support for the widgets' clipRect(). Right now render-to-texture widgets
in scroll areas placed close to each other result in broken (non-existent) clipping.
Similarly, stack-on-top widgets fail to clip when placed inside a scroll area.

This is now corrected and the qopenglwidget example is enhanced to utilize a scroll
area.

Task-number: QTBUG-45860
Change-Id: I859a63d61a50d64ba9e87244f83c5969dce12337
Reviewed-by: Jørgen Lind <jorgen.lind@theqtcompany.com>

3 files changed, 21 insertions, 7 deletions

diff --git a/examples/opengl/qopenglwidget/glwidget.cpp b/examples/opengl/qopenglwidget/glwidget.cpp
index f93e667615..df52e3efbf 100644
--- a/examples/opengl/qopenglwidget/glwidget.cpp
+++ b/examples/opengl/qopenglwidget/glwidget.cpp
@@ -537,14 +537,14 @@ void GLWidget::setTransparent(bool transparent)
     window()->update();
 }
 
-void GLWidget::resizeGL(int w, int h)
+void GLWidget::resizeGL(int, int)
 {
     if (m_hasButton) {
         if (!m_btn) {
-            m_btn = new QPushButton("A widget on top.\nPress me!", this);
+            m_btn = new QPushButton("A widget on top.\nPress for more widgets.", this);
             connect(m_btn, &QPushButton::clicked, this, &GLWidget::handleButtonPress);
         }
-        m_btn->move(w / 2, h / 2);
+        m_btn->move(20, 80);
     }
 }
 
diff --git a/examples/opengl/qopenglwidget/mainwindow.cpp b/examples/opengl/qopenglwidget/mainwindow.cpp
index 6cf1d5d6e2..22111afdcb 100644
--- a/examples/opengl/qopenglwidget/mainwindow.cpp
+++ b/examples/opengl/qopenglwidget/mainwindow.cpp
@@ -47,6 +47,7 @@
 #include <QLabel>
 #include <QCheckBox>
 #include <QSpinBox>
+#include <QScrollArea>
 
 #include "glwidget.h"
 
@@ -69,7 +70,7 @@ MainWindow::MainWindow()
                                "and therefore an interval < 16 ms will likely lead to a 60 FPS update rate.");
     QGroupBox *updateGroupBox = new QGroupBox(this);
     QCheckBox *timerBased = new QCheckBox("Use timer", this);
-    timerBased->setChecked(true);
+    timerBased->setChecked(false);
     timerBased->setToolTip("Toggles using a timer to trigger update().\n"
                            "When not set, each paintGL() schedules the next update immediately,\n"
                            "expecting the blocking swap to throttle the thread.\n"
@@ -87,7 +88,7 @@ MainWindow::MainWindow()
     slider->setRange(0, 50);
     slider->setSliderPosition(30);
     m_timer->setInterval(10);
-    label->setText("A QOpenGLWidget");
+    label->setText("A scrollable QOpenGLWidget");
     label->setAlignment(Qt::AlignHCenter);
 
     QGroupBox * groupBox = new QGroupBox(this);
@@ -96,7 +97,10 @@ MainWindow::MainWindow()
 
     m_layout = new QGridLayout(groupBox);
 
-    m_layout->addWidget(glwidget,1,0,8,1);
+    QScrollArea *scrollArea = new QScrollArea;
+    scrollArea->setWidget(glwidget);
+
+    m_layout->addWidget(scrollArea,1,0,8,1);
     m_layout->addWidget(label,9,0,1,1);
     m_layout->addWidget(updateGroupBox, 10, 0, 1, 1);
     m_layout->addWidget(slider, 11,0,1,1);
@@ -134,7 +138,10 @@ MainWindow::MainWindow()
     connect(timerBased, &QCheckBox::toggled, this, &MainWindow::timerUsageChanged);
     connect(timerBased, &QCheckBox::toggled, updateInterval, &QWidget::setEnabled);
 
-    m_timer->start();
+    if (timerBased->isChecked())
+        m_timer->start();
+    else
+        updateInterval->setEnabled(false);
 }
 
 void MainWindow::updateIntervalChanged(int value)
@@ -170,3 +177,8 @@ void MainWindow::timerUsageChanged(bool enabled)
             w->update();
     }
 }
+
+void MainWindow::resizeEvent(QResizeEvent *)
+{
+     m_glWidgets[0]->setMinimumSize(size() + QSize(128, 128));
+}
diff --git a/examples/opengl/qopenglwidget/mainwindow.h b/examples/opengl/qopenglwidget/mainwindow.h
index f1b2c51e53..9ad8a01339 100644
--- a/examples/opengl/qopenglwidget/mainwindow.h
+++ b/examples/opengl/qopenglwidget/mainwindow.h
@@ -56,6 +56,8 @@ public:
     void addNew();
     bool timerEnabled() const { return m_timer->isActive(); }
 
+    void resizeEvent(QResizeEvent *);
+
 private slots:
     void updateIntervalChanged(int value);
     void timerUsageChanged(bool enabled);