Spacers and Layouts

[saurabhsood]

I have just started out Qt from the book "C++ GUI programming with Qt4". I have some basic doubts 1.) What is the role/purpose of Spacers in designing the layouts? 2.) In the SortDialog prorgam, thelayout()->setSizeConstraint(QLayout::SetFixedSize); gives me a segmentation fault. I am not able to solve the problem. Without this line, the code works perfectly. 3.) What is a Top Level Layout? pls help...thnx

[goetz]

1. Spacers
   In short words: These keep things apart that would otherwise be glued together by the layout. I'd suggest you play around with Qt Designer - you will have immediate visual feedback. It's very easy to understand then.

2. Segfault
   Hard to comment without the source code. But a segfault is almost always on a null pointer, so it is very likely that you forgot to set the layout. Also, is "thelayout()" really a method?

3. Toplevel Layouts
   This is the layout that is applied to the widget. You will almost always have some further layouts, that are included in the toplevel layout.

[saurabhsood]

thnx for the reply...
thelayout was a typo. it should be layout()->.....
does setting the layout in Qt Designer mean i just have to lay out the widgets in a specified order, like Lay out Horizontally / Vertically ? . Does setting this mean setting a Top Level Layout.

[mohsen]

Layout are designed to automatically forming objects positions when resizing the form or its parent.

[quote author="saurabhsood" date="1294852671"]thnx for the reply...
thelayout was a typo. it should be layout()->.....
does setting the layout in Qt Designer mean i just have to lay out the widgets in a specified order, like Lay out Horizontally / Vertically ? . Does setting this mean setting a Top Level Layout. [/quote]

[goetz]

[quote author="saurabhsood" date="1294852671"]thnx for the reply...
thelayout was a typo. it should be layout()->.....
does setting the layout in Qt Designer mean i just have to lay out the widgets in a specified order, like Lay out Horizontally / Vertically ? . Does setting this mean setting a Top Level Layout. [/quote]

Did you read the Qt docs on layouts already?

• "Layout Management":http://doc.qt.nokia.com/4.7-snapshot/layout.html
• "Widgets and Layouts":http://doc.qt.nokia.com/4.7-snapshot/widgets-and-layouts.html#layouts
• "Widgets Tutorial - Using Layouts":http://doc.qt.nokia.com/4.7-snapshot/tutorials-widgets-windowlayout.html
• "Widgets Tutorial - Nested Layouts":http://doc.qt.nokia.com/4.7-snapshot/tutorials-widgets-nestedlayouts.html
• "A Quick Start to Qt Designer":http://doc.qt.nokia.com/4.7-snapshot/designer-quick-start.html
• "Layout Examples":http://doc.qt.nokia.com/4.7-snapshot/examples-layouts.html