Fullscreen QMainWindow, QGLWidget issue on OSX

[yk555]

I am using QT5.3 and using following code to add a QGLWidget to a layout of QMainWindow. (tried setCentralWidget as well)

In the QMainWindow("QtSystem_GameWindow" in the .ui file) init code:

QSizePolicy sizePolicy;
sizePolicy.setHorizontalPolicy(QSizePolicy::Expanding);
sizePolicy.setVerticalPolicy(QSizePolicy::Expanding);
m_pGLView->setSizePolicy(sizePolicy);
m_pGLView->resize(size());
 
QLayout* l = new QHBoxLayout(this);
l->setContentsMargins(0,0,0,0);
l->setSizeConstraint(QLayout::SizeConstraint::SetNoConstraint);
setLayout(l);
l->addWidget(m_pGLView);

QSizePolicy sizePolicy;
sizePolicy.setHorizontalPolicy(QSizePolicy::Expanding);
sizePolicy.setVerticalPolicy(QSizePolicy::Expanding);
m_pGLView->setSizePolicy(sizePolicy);
m_pGLView->resize(size());
        
QLayout* l = new QHBoxLayout(this);
l->setContentsMargins(0,0,0,0);
l->setSizeConstraint(QLayout::SizeConstraint::SetNoConstraint);
setLayout(l);
l->addWidget(m_pGLView);

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When I am using the native fullscreen button on OSX to make the window(1600x900) go fullscreen, QGLWidget stays 1600x900 and there is black border around the QGLWidget.

Could anyone tell me what should I do to make the QGLWidget to fill the whole screen space and stays at the old size (for example 1600x900)?

Thanks in advance.

Here is the .ui file for the QMainWindow.

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>QtSystem_GameWindow</class>
 <widget class="QMainWindow" name="QtSystem_GameWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="mouseTracking">
   <bool>true</bool>
  </property>
  <property name="windowTitle">
   <string>xxxxxx</string>
  </property>
  <property name="windowIcon">
   <iconset resource="xxxxxx.qrc">
    <normaloff>:/QtSystem_MainWindow/xxxxxx.ico</normaloff>:/QtSystem_MainWindow/xxxxxx.ico</iconset>
  </property>
  <widget class="QWidget" name="centralWidget"/>
  <widget class="QMenuBar" name="menuBar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>21</height>
    </rect>
   </property>
  </widget>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources>
  <include location="xxxxxx.qrc"/>
 </resources>
 <connections/>
</ui>

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>QtSystem_GameWindow</class>
 <widget class="QMainWindow" name="QtSystem_GameWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="mouseTracking">
   <bool>true</bool>
  </property>
  <property name="windowTitle">
   <string>xxxxxx</string>
  </property>
  <property name="windowIcon">
   <iconset resource="xxxxxx.qrc">
    <normaloff>:/QtSystem_MainWindow/xxxxxx.ico</normaloff>:/QtSystem_MainWindow/xxxxxx.ico</iconset>
  </property>
  <widget class="QWidget" name="centralWidget"/>
  <widget class="QMenuBar" name="menuBar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>21</height>
    </rect>
   </property>
  </widget>
 </widget>
 <layoutdefault spacing="6" margin="11"/>
 <resources>
  <include location="xxxxxx.qrc"/>
 </resources>
 <connections/>
</ui>

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[anda_skoa]

What is "this" in your code?
The widget taht you add as the central widget?

Cheers,
_

[yk555]

Sorry, forgot to mention "this" is the QMainWindow "QtSystem_GameWindow" in the .ui file.

[anda_skoa]

But a main window already has a layout.

Which of the main window elements do you currently need?
toolbars? statusbar?

Cheers,
_

[yk555]

But a main window already has a layout.

Which of the main window elements do you currently need?
toolbars? statusbar?

Cheers,
_

None, just a QGLWidget added to the main window.

[anda_skoa]

Then the question becomes: why use a QMainWindow at all?
Why not just have the GL widget as the window itself?

Cheers,
_

[yk555]

Then the question becomes: why use a QMainWindow at all?
Why not just have the GL widget as the window itself?

Cheers,
_

It's based on the Qt Widgets Application template in the Qt Creator.

[anda_skoa]

Ok, so if I understand you correctly, there is no reason to use the QMainWindow.

In which case just remove it and use your widget as the window.

Cheers,
_

[yk555]

Ok, so if I understand you correctly, there is no reason to use the QMainWindow.

In which case just remove it and use your widget as the window.

Cheers,
_

Thanks, just wonder if there is a way to make QGLWidget have a different framebuffer size from its actual size?

[anda_skoa]

No idea sorry.

Btw, I think the more current OpenGL widget is QOpenGLWidget, QGLWidget is deprecated

Cheers,
_

[yk555]

Thanks.

My final solution is to scale the offscreen buffer to fill the widget myself.