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

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.
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?
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