Development/Architecture/KDE4/XMLGUI Technology
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Related information resources
- KAction tutorial
- Documentation for KDE 3 (still mostly valid)
- KParts - perhaps the most important use case for advanced KXMLGUI stuff
- kpartgui / KXMLGUI document type definition
- API documentation on KXMLGUI classes
- Expression error: Unrecognized word "x". - The base class for components that use and xml-gui
- Expression error: Unrecognized word "x". - The class responsible for managing one or many KXMLGUIClients in an application.
- Expression error: Unrecognized word "x".
Basics
For basic information, please start reading at Development/Tutorials/Using_KActions. For most simple cases you should be able to write a ui.rc for your application by simply expanding on the given examples.
Merging several KXMLGUI definitions
Once you have more than a single KXMLGUIClient/KPart in an application, it becomes important to control just how / just where menu entries and toolbar icons are merged.
How does merging happen
The first thing that happens is that the ui.rc file of you application is merged in the KDE global ui_standards.rc-file. This is to make sure that standard elements all end up in the KDE standard places.
Now, when you add further KXMLGUIClients (e.g. a KPart, or a plugin), in general the KXMLGUIFactory does the following:
- So called containers ("Menu", "ToolBar") are matched by their name. So if your application_ui.rc defines a menu with name="my_stuff", and the plugin_ui.rc of a plugin also has a menu by that name, the elements from that menu in the plugin get added to the elements of that menu in the application.
- All entries within a container are appended at the end, in the order they get added. This means, if you add KXMLGUIClient A after KXMLGUIClient B, the actions from A will generally end up after the actions from B, and vice versa.
Of course KXMLGUI allows for sophisticated ways to control this merging, and we'll deal with those in a minute, but first let us look at this basic scenario:
Bringing the clients together in C++:
MyMainWindow::MyMainWindow (...) : ... {
[...]
setXMLFile ("main_ui.rc");
insertChildClient (new MyComponentA ());
insertChildClient (new MyComponentB ());
[...]
}
MyComponentA () : public KXMLGUIClient () {
[...]
setXMLFile ("component_a.rc");
[...]
}
MyComponentB () : public KXMLGUIClient () {
[...]
setXMLFile ("component_b.rc");
[...]
}
main_ui.rc
<?xml version="1.0" encoding="UTF-8"?>
<gui [...]>
<MenuBar>
<Menu name="menu1" >
<Action name="main_first" />
<Action name="main_second" />
<Action name="main_third" />
</Menu>
<Menu name="menu2" >
</Menu>
</MenuBar>
</gui>
component_a.rc
<?xml version="1.0" encoding="UTF-8"?>
<gui [...]>
<MenuBar>
<Menu name="menu1" >
<Action name="a_first" />
</Menu>
<Menu name="menu3" >
<Action name="a_second" />
</Menu>
<Menu name="menu2" >
<Action name="a_third" />
</Menu>
</MenuBar>
</gui>
component_b.rc
<?xml version="1.0" encoding="UTF-8"?>
<gui [...]>
<MenuBar>
<Menu name="menu3" >
<Action name="b_first" />
</Menu>
<Menu name="menu2" >
<Action name="b_second" />
</Menu>
<Menu name="menu1" >
<Action name="b_third" />
</Menu>
</MenuBar>
</gui>
Now all of these together would look like this:
<gui>
<MenuBar>
<Menu name="menu1" >
<Action name="main_first" />
<Action name="main_second" />
<Action name="main_third" />
<Action name="a_first" />
<Action name="b_third" />
</Menu>
<Menu name="menu2" >
<Action name="a_third" />
<Action name="b_second" />
</Menu>
<Menu name="menu3" >
<Action name="a_second" />
<Action name="b_first" />
</Menu>
</MenuBar>
</gui>
Things to note:
- Actions from component_a.rc are placed below actions from main_ui.rc, because MyComponentA gets added after MyMainWindow. Similarily, actions from component_b.rc are placed below those from main_ui.rc and component_a.rc.
- When component_a.rc is read, a menu named "menu2" already exist, and is therefore merged with the existing one. Due to this, "menu3" gets appended at the end of the menubar, instead of between "menu1" and "menu2". Similarily the order of the definition of the menus in component_b.rc is effectively ignored, because those menus have already been defined, previously.
Elements to control merging
Often times the above principles of merging are not good enough. Fortunately, there are several ways to control the details of merging.
MergeLocal / Merge
<MergeLocal>
This can only be used in the KDE global ui_standards.rc-file. It defines points where other entries can be merged in. It can be used both with a name-attribute, or without (in the latter case it acts as a catch-all merge place).
<Merge>
<Merge> is the counterpart to <MergeLocal> and defines what is to be merged into a <MergeLocal>-point. TODO: Is this correct, examples, with/without names?
DefineGroup
While <MergeLocal> can only be used in the KDE global ui_standards.rc, <DefineGroup> allows you to achieve something very similar: In the main_ui.rc put this:
<Menu name="menu">
<Action name="main1"/>
<DefineGroup name="main_group1" append="main_group1"/>
<Action name="main2"/>
<DefineGroup name="main_group2" append="main_group2"/>
<Action name="main3"/>
</Menu>
and in a child clients component_a.rc:
<Menu name="menu">
<Action name="a1"/>
<Action name="a2" group="main_group2"/>
<Action name="a3"/>
<Action name="a4" group="main_group1"/>
<Action name="a5" group="main_group1"/>
<Action name="a6"/>
</Menu>
This effectively gets merged as:
<Menu name="menu">
<Action name="main1"/>
<Action name="a4"/>
<Action name="a5"/>
<Action name="main2"/>
<Action name="a2"/>
<Action name="a1"/>
<Action name="a3"/>
<Action name="a6"/>
</Menu>
Things to note:
- Actions a1, a3, and a6 are appended at the end of the menu, as this is the default behavior.
- Actions a4, and a5 are inserted at the point where "main_group1" is defined, and Action a2 is inserted at the place of "main_group2".
ActionList
Limitations of merging and workarounds
merging of grand-children
(e.g. a plugin inside a part inside a main window)
stripping down a KPart's GUI
(hack to (re-)move unwanted elements)