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<div id="projectname">edelib
 <span id="projectnumber">2.0.0</span>
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<li class="navelem"><a class="el" href="themedoc.html">Themes and theming details</a> </li>
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<div class="title">Introduction and concepts </div> </div>
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<div class="textblock"><h2><a class="anchor" id="themeintro_intro"></a>
Introduction</h2>
<p>edelib theming facility allows theming widgets, their behavior and theming full applications. It also can behave as container for other themes, like sound theme or icon theme.</p>
<p>At first this sounds pretty abstract and that is true: theming facility is abstracted as much as possible.</p>
<p>Today, themed can be everything: widget look, behavior, sound events, icons and wallpapers, fonts and etc. Some toolkits and environments provides something so called <em>metatheme</em>, a theme that has a bunch of other, unrelated themes like themes for icons or GUI look. edelib theming implementation behaves (at some point) as metatheme too.</p>
<p>To allow this, <a class="el" href="classedelib_1_1Theme.html" title="Theming engine for widgets.">edelib::Theme</a> implements a Scheme-like language to load, parse and eventually transform theme code. Actually, <a class="el" href="classedelib_1_1Theme.html" title="Theming engine for widgets.">edelib::Theme</a> provides a full Scheme language (based on <a href="http://tinyscheme.sourceforge.net">TinyScheme</a> engine), but you will often see only the small parts of it.</p>
<h2><a class="anchor" id="themeintro_concepts"></a>
Concepts</h2>
<p>Theme is introducing a few terms known from other toolkits and environments, where some have pretty the same meaning and some have a different one.</p>
<h3><a class="anchor" id="themeintro_style"></a>
Style</h3>
<p>Theme style is a set of elements with values. Elements can be anything, like font size or background color. When application is querying certain preferences (e.g. font size), it do that from certain style.</p>
<p>Each styles in the same theme must have a unique name. In the case of duplicate names, first found style will be used.</p>
<h3><a class="anchor" id="themeintro_scheme"></a>
Scheme</h3>
<p>Scheme is engine for painting widgets. Scheme is term from FLTK (see Fl::scheme() in FLTK documentation) and should not be confused with Scheme language; you can see schemes for FLTK as <em>engines</em> for GTK+. Schemes are implemented in C++ and uses FLTK low level drawing facility to paint widget elements.</p>
<p>Currently schemes can't be extended and theme loader uses a few of them already built in FLTK code.</p>
<h3><a class="anchor" id="themeintro_item"></a>
Style item</h3>
<p>Style item is entry in one style. Style item can be e.g. font color or anything that some application see as value for theming.</p>
<h3><a class="anchor" id="themeintro_themefile"></a>
Theme file</h3>
<p>Theme file is the file with one or bunch of styles. First file loaded from every theme is <em>main.ewt</em> (ewt here means Ede Widget Theme). Here is an example how <em>main.ewt</em> can look like: </p>
<div class="fragment"><pre class="fragment">;; <span class="keyword">this</span> is a comment
(theme.name <span class="stringliteral">"Sample Theme"</span>)
(theme.author <span class="stringliteral">"John Foo <john@foo.com>"</span>)
(theme.sample <span class="stringliteral">"img.jpg"</span>)
(theme.style <span class="stringliteral">"ede"</span> [
scheme <span class="stringliteral">"gtk+"</span>
background_color <span class="stringliteral">"dark slate gray"</span>
background_color2 <span class="stringliteral">"#043456"</span>
foreground_color <span class="stringliteral">"red"</span>
font <span class="stringliteral">"sans 12"</span>
icon_theme <span class="stringliteral">"edeneu"</span>
])
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