Editing WoW:UI XML tutorial (section)

== The Basics ==

An [[XML]] file is a collection of ''elements'' (with a start and end tag), of which the User Interface files are no exception. There are two main types of elements that appear in the UI XML files. The first type are those that declare user interface items or [[widget]]s, such as [[XML/Button|Button]]s, [[XML/Frame|Frames]], [[XML/CheckButton|Checkbox]]es. We will call these widget elements. The second type of element, which always occur inside the first type, define properties and behaviour of the widgets. We will call these property elements. Here is an example:

 <Button name="MyAddon_Button">
   <Anchors>
     <Anchor point="CENTER"/>
   </Anchors>
 </Button>

The [[XML/Button|Button]] element is of the first type, in other words a widget element. Its appearance in the XML file causes a Button with the name '''MyAddon_Button''' to be created. The elements inside it (such as [[Anchors]], Anchor) define its properties, hence are of the second type. The general structure is always the same, you have elements representing widgets, and other elements inside them representing their properties. It can also happen that a widget element is inside another one. For example:

 <Frame name="MyAddon_Frame">
   <Anchors>
     <Anchor point="CENTER"/>
   </Anchors>
   <Frames>
     <Button name="MyAddon_Button">
       <Anchors>
         <Anchor point="CENTER"/>
       </Anchors>
     </Button>
   </Frames>
 </Frame>

This example has two [[widget]] elements, [[XML/Frame|Frames]] and [[XML/Button|Button]], and several property elements ([[Anchors]], Anchor). This creates a Frame, with a Button inside it. Here, '''MyAddon_Button''' is a ''child'' of '''MyAddon_Frame''', and '''MyAddon_Frame''' is a ''parent'' of '''MyAddon_Button'''. Also note how the XML convention of abbreviating an empty element such as <Anchor point="CENTER"></Anchor> as <Anchor point="CENTER"/> is used.

Many of the elements (widget and property alike) can have ''attributes'', such as the '''name''' attribute in the above examples.

A complete and valid XML file must contain exactly one element named UI, with some rather long attributes (best use copy/paste for this). Hence a minimal example of a complete UI XML file would be something like:

 <Ui xmlns="<nowiki>http://www.blizzard.com/wow/ui/</nowiki>"
  xmlns:xsi="<nowiki>http://www.w3.org/2001/XMLSchema-instance</nowiki>"
  xsi:schemaLocation="<nowiki>http://www.blizzard.com/wow/ui/ ..\FrameXML\UI.xsd</nowiki>">
    <Frame name="MyAddon_Frame">
    </Frame>
 </Ui>

Such a file will create a single [[XML/Frame|Frames]], named '''MyAddon_Frame'''. However, that Frame wouldn't be visible and wouldn't have any content.