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Archived:Handle change in screen orientation in Qt

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|creationdate=June 26, 2009
 
|creationdate=June 26, 2009
 
|keywords=QWidget::resizeEvent()
 
|keywords=QWidget::resizeEvent()
 
 
|sourcecode= <!-- Link to example source code (e.g. [[Media:The Code Example ZIP.zip]]) -->
 
|sourcecode= <!-- Link to example source code (e.g. [[Media:The Code Example ZIP.zip]]) -->
 
|installfile= <!-- Link to installation file (e.g. [[Media:The Installation File.sis]]) -->
 
|installfile= <!-- Link to installation file (e.g. [[Media:The Installation File.sis]]) -->
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}}
  
==Note: This article is error prone, and needs code change in the example to work properly in Qt 4.7 in Symbian==
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{{Warning|'''This article does not work properly in Qt 4.7 in Symbian'''. It can be rectified with the change described below.<br />
  
'''PLEASE NOTE that the code in the arcticle doesn't work properly in Qt 4.7 on Symbian.''' The issue is in the example code's ResizeEvent::GetScreenCoordinates() method. The GetScreenCoordinates uses QDesktopWidget::availableGeometry and QDesktopWidget::screenGeometry methods. In all cases these methods do not reflect ''current'' screen geometry values during QWidget::resizeEvent call as the respective values are only changed ''after'' the resizeEvent has occured. This means that e.g. during the startup of the application these may return wrong values as the values are not yet set properly.
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The issue is in the example code's {{Icode|ResizeEvent::GetScreenCoordinates()}} method. The {{Icode|GetScreenCoordinates}} uses {{Icode|QDesktopWidget::availableGeometry}} and {{Icode|QDesktopWidget::screenGeometry}} methods. In all cases these methods do not reflect ''current'' screen geometry values during {{Icode|QWidget::resizeEvent}} call as the respective values are only changed ''after'' the resizeEvent has occured. This means that e.g. during the startup of the application these may return wrong values as the values are not yet set properly.
  
If the whole screen geometry information is needed from QDesktopWidget it's advised to connect to QApplication::desktop()'s workAreaResized(int) signal and call QApplication::desktop()->availableGeometry() in the connected slot function. This works in Qt 4.7.3 in Symbian but not (due to bug) in Qt 4.6.
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If the whole screen geometry information is needed from QDesktopWidget it's advised to connect to QApplication::desktop()'s workAreaResized(int) signal and call {{Icode|QApplication::desktop()->availableGeometry()}} in the connected slot function. This works in Qt 4.7.3 in Symbian but not (due to bug) in Qt 4.6.
  
 
See following bug report for more details. The [http://bugreports.qt.nokia.com/browse/QTBUG-14058 QTBUG-14058]'s fix introduces documentation for QDesktopWidget on this issue.
 
See following bug report for more details. The [http://bugreports.qt.nokia.com/browse/QTBUG-14058 QTBUG-14058]'s fix introduces documentation for QDesktopWidget on this issue.
  
 
In many cases application should however get simply the geometry of the main window using simply  
 
In many cases application should however get simply the geometry of the main window using simply  
QMainWindow::width() and ::height() methods during QMainWindow's resizeEvent.
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{{Icode|QMainWindow::width()}} and {{Icode|::height()}} methods during {{Icode|QMainWindow}}'s {{Icode|resizeEvent}}.}}
  
 
==Overview==
 
==Overview==

Revision as of 02:37, 30 June 2011

{{{width}}}
16 Sep
2009
Article Metadata
Tested with
Devices(s): Nokia 5800 XpressMusic
Compatibility
Platform(s): S60 3rd Edition, FP1, FP2
S60 5th Edition
Symbian
Article
Keywords: QWidget::resizeEvent()
Created: savaj (26 Jun 2009)
Last edited: hamishwillee (30 Jun 2011)

Warning.pngWarning: This article does not work properly in Qt 4.7 in Symbian. It can be rectified with the change described below.

The issue is in the example code's ResizeEvent::GetScreenCoordinates() method. The GetScreenCoordinates uses QDesktopWidget::availableGeometry and QDesktopWidget::screenGeometry methods. In all cases these methods do not reflect current screen geometry values during QWidget::resizeEvent call as the respective values are only changed after the resizeEvent has occured. This means that e.g. during the startup of the application these may return wrong values as the values are not yet set properly.

If the whole screen geometry information is needed from QDesktopWidget it's advised to connect to QApplication::desktop()'s workAreaResized(int) signal and call QApplication::desktop()->availableGeometry() in the connected slot function. This works in Qt 4.7.3 in Symbian but not (due to bug) in Qt 4.6.

See following bug report for more details. The QTBUG-14058's fix introduces documentation for QDesktopWidget on this issue.

In many cases application should however get simply the geometry of the main window using simply

QMainWindow::width() and ::height() methods during QMainWindow's resizeEvent.

Contents

Overview

This code example shows how to get notification when the screen mode changes using QWidget::resizeEvent(). This method gets called when the screen mode changes, so you have to implement that virtual method in your class.

This snippet can be self-signed.

Preconditions

  • Download and install the Qt SDK

Source

//resizeEvent() method get called when user change screen mode.
void ResizeEvent::resizeEvent (QResizeEvent* event)
{
QSize widgetSize = event->size();
//Resize your custom control according to new size.
QMainWindow::resizeEvent(event);
}

Postconditions

The code snippet is expected to notify change in screen mode.

Normal screen

ResizeEvent2.JPG

Screen after changing mode to portrait

ResizeEvent1.JPG

Related link

Download Code Example

  • File:QtResizeEvent.zip shows new screen size when user change screen mode. This example is tested on Nokia 5800 XpressMusic.


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