Using Library Views
When your application design has been set up, you first should look for already existing code that will make your life a lot easier. A part of this search is to look for a widget that can be used as a view or at least as a part of it; either directly or by inheritance. The KDE and Qt libraries already contain a set of widgets that can be used for this purpose. To use them, you have two options:
Remove the new view class and create an instance of a library widget; then set this as the view,
Change the inheritance of the provided view class to the class of the library widget to use.
In either way, it is important to know that if the application framework is currently not linked against the library that contains the widget, the linker will fail. After you decided to use a certain widget, look for the library to link to; then open "Project"->"Options" from the KDevelop menubar. Switch to the "Linker Options" page and look for the checkmarks indicating the libraries that are currently used. If the library of your view widget is already checked, you can leave the project options untouched and start doing the necessary changes due to your choice. If not, and the linker options offer to add the library by a check box, check it and press "OK" to leave the project options dialog again. In any other case, add the library in the edit line below with the -l option. For libraries that your application has to search for before preparing the Makefiles by the configure script on the end-user machine, add the according search macro to the configure.in file located at the root directory of your project and add the macro to the edit line. Mind that you have to run "Build"->"Autoconf and automake" and "Build"->"Configure" before the Makefiles contain the correct expansion for the library macro.
Also, if the include files for the library to add are not in the current include path (which can be seen by the -I options in the output window on "Make"), you have to add the path to the Project Options dialog -"Compiler Options" page with the -I option or the according automake macro at the edit line for "Additional Options".
Looking at the first page of the Qt online documentation, you will find a link to "Widget Screenshots" where you can have a look at how the widgets Qt contains look like. These are ready to use and can be combined together to form complex widgets to create application views or dialogs. In the following, we'll discuss some of these which are very usable for creating application views, but keep in mind that the KDE libraries sometimes contain other widgets for the same purpose; those will be reviewed in the next section.
Here are a set of hints for what purpose you could use which Qt component:
If your view area isn't big enough to display all your data, the user must be enabled to scroll
over the document with bars on the left and bottom of the view. For this, Qt provides the class
QScrollView, which offers a scrollable child area. As explained, you could
inherit your own widget from QScrollView or use an instance to manage your
document's view widget.
to create a ScrollView yourself, inherit the View widget from QWidget
and add vertical and horizontal QScrollBars .
(This is done by KDE`s KHTMLView widget.)
For text processing, use QTextEdit. This class provides a complete
text editor widget that is already capable to cut, copy and paste text and is managed by a scrollview.
Use QTable to display data that is arranged in a table.
As QTable is managed by scrollbars as well, it offers a good solution for
table calculation applications.
To display two different widgets or two widget instances at the same time, use QSplitter
. This allows to tile views by horizontal or vertical dividers.
KMail is a good example what this would look like- the main view is separated by a
splitter vertically, the right window then is divided again horizontally.
QListView displays information in a list and tree.
This is useful for creating file trees or any other hierarchical information you want to interact with.
You see that Qt alone offers a whole set of widgets which are ready to use so you don't have to invent new solutions if these match your needs. The sideffect when using standard widgets is that users already know how to handle them and only have to concentrate on the displayed data.
The KDE libraries were invented to make designing applications for the K Desktop Environment easier and capable of more functionality than what Qt alone is offering. The kdeui library offers:
KListView: a more powerful version of QListView
KIconView: a graphical viewer of icon files
The khtml library, on the other hand, offers a complete HTML-interpreting widget that is ready to use. It is scrollable already, so you don't even have to take care for that. A possible use could be to integrate it as a preview widget for an HTML editor; used by applications such as Konqueror to display HTML files.
