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<TITLE>gentoo Documentation: Styles</TITLE>
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<H1>Styles</H1>
<IMG SRC="images/tone.gif" WIDTH=175 HEIGHT=18 BORDER="0">
<H2>Introduction</H2>
<P>
As was mentioned on the <A HREF="types.html">file types</A> page, each file type links to
something called a <EM>style</EM>. What is a style, you ask? Well, a style is a named
set of properties, where different properties control different aspects of how files
associated (through the typing system) with the style are handled.
</P>
<P>
Currently, the only type of property actually implemented is the <EM>visual</EM> ones,
which controls how files having the style are displayed in the pane lists. You can use a
style's visual properties to define the colors and icons used when rendering the files.
This allows for some serious niceness in the general look of <STRONG>gentoo</STRONG>, especially
when coupled with <A HREF="mailto:johan@tiq.com">Johan Hanson</A>'s wonderful icons.
Go ahead and play!
</P>
<H2>The Style Hierarchy</H2>
<P>
One thing is important to realize about styles: they form a <EM>hierarchy</EM>, namely
a singly-rooted N-tree. This means that no style exists by itself; all have a <EM>parent</EM>
style above them in the tree. The only style which actually doesn't have a parent is,
as could be expected from its name, the <EM>root</EM> one. The root style is special in
more ways; it is always available (you cannot delete it!) for example. If this sounds
horribly abstract and weird, perhaps this example picture can clear things up:
</P>
<DIV>
<TABLE WIDTH=90%>
<TR><TD><IMG SRC="images/style_tree.gif" WIDTH=112 HEIGHT=287 ALT="Style tree picture"></TD>
<TD>
<P>
This small tree, which is actually a cropped screenshot from the configuration window,
shows the general idea of a tree hierarchy. You can see the Root style on top. Notice
how all other styles sort of "hang" under the Root style; from any style you can trace
a way back up to Root.
</P>
<P>
Also note how the tree is sorted alphabetically on each level. This makes it easier
to locate a given subtree.
</P>
<P>
With a tree like this, generally only Root plus the "leaf" nodes (nodes without any
children, such as "DEB Archive", "RPM Archive", "Config", "Directory", and so on) are
actually bound to types. The other nodes, such as "Archive", "Image" and "Source",
are not. Then you might wonder if they're not just being wasted? No, they're not! See
below (on inheritance) for why.
</P>
</TD>
</TABLE>
</DIV>
<H2>Properties and the Use of Inheritance</H2>
<P>
So, what is the point of arranging the styles into a tree? Wouldn't it be just as
convenient to use a less structured model, such as the plain list used by types?
</P>
<P>
Funny you should ask that! The answer is no, and for a very good reason: inheritance.
Each style contains a number of named values, also called <EM>properties</EM>. Assigning
a specific value to a property is <EM>optional</EM>. If you don't assign a value to
a certain property in a style, that property copies the value from its parent! If the
parent doesn't assign a value either, then <EM>that</EM> style's parent is checked, and
so on. Eventually you'll reach the Root, and there the search will end, because Root
always gives a value to <EM>all</EM> its properties. If you go ahead and define a local
value, that value is said to <EM>override</EM> the one that would otherwise have been
copied from a parent.
</P>
<P>
This kind of operation, where a value is found by searching down a branch of a family
tree, is called <EM>inheritance</EM>. It is a very useful way of arranging things, and
is widely used, for example in object-oriented programming (languages such as Smalltalk,
C++ and Java all provide support for inheritance).
</P>
<P>
The point of inheritance in <STRONG>gentoo</STRONG> is that it reduces (or even removes completely) the
need to specify the same property value twice. It also naturally supports grouping; look how
all styles for various image formats have been grouped under the single parent style "Image",
for example. If you want all image files to be displayed with a common background color, you
can just assign that color once to the corresponding property in the "Image" style, and then
all specific image format styles ("JPEG", "GIF" etc) will inherit it!
</P>
<H2>Visual Properties</H2>
<P>
One big group of properties control how files belonging to a style are displayed in the
directory panes. These properties are (rather logically) called the <EM>visual properties</EM>.
They are:
</P>
<DIV>
<TABLE BORDER="0" CELLSPACING="0" CELLPADDING="8" WIDTH="85%">
<TR BGCOLOR="#E0E0F0"><TH WIDTH="15%">Name</TH><TH>Type</TH><TH WIDTH="75%">Explanation</TH></TR>
<TR BGCOLOR="#C0C0E0"><TD>Unselected Background</TD><TD ALIGN="center">Color</TD>
<TD>This is the color used as the background on unselected rows. It is normally
set once, in the Root style. Changing the unselected background color in child styles is
not recommended, since it can make it harder to distinguish between unselected and selected
rows. But then again, it's <EM>your</EM> configuration...
</TD></TR>
<TR BGCOLOR="#E0E0F0"><TD>Unselected Foreground</TD><TD ALIGN="center">Color</TD>
<TD>This is the foreground (text) color of unselected rows. Generally black.
</TD></TR>
<TR BGCOLOR="#C0C0E0"><TD>Unselected Icon</TD><TD ALIGN="center">Icon</TD>
<TD>This specifies the name of the icon to use (for the "Icon" column content) for
unselected rows of this style. The name is the filename of a small pixmap, sans
path. For more information about locating icons, see the <A HREF="misc.html#icons">misc page</A>.
</TD></TR>
<TR BGCOLOR="#E0E0F0"><TD>Selected Background</TD><TD ALIGN="center">Color</TD>
<TD>This is the background color used for selected rows. Generally the same as the unselected
<EM>foreground</EM>, to create an easily recognizable "inverse video" look.</TD></TR>
<TR BGCOLOR="#C0C0E0"><TD>Selected Foreground</TD><TD ALIGN="center">Color</TD>
<TD>As could be expected, this is the color used by the text of selected rows. Like
the unselected background, it is generally only set once; in Root.</TD></TR>
<TR BGCOLOR="#E0E0F0"><TD>Selected Icon</TD><TD ALIGN="center">Icon</TD>
<TD>Of course, this is the icon used on selected rows. If you forget to specify this,
the icon will disappear when the row is selected, which might look confusing.</TD></TR>
</TABLE>
</DIV>
<H2><A NAME="ap">Action Properties</A></H2>
<P>
Action properties allow you to control how <STRONG>gentoo</STRONG> should act upon files having
a particular style. For example, you could use action properties to inform <STRONG>gentoo</STRONG>
that is should use some external program to view images, and so on. These are the
action properties that are available:
</P>
<DIV>
<TABLE BORDER="0" CELLSPACING="0" CELLPADDING="8" WIDTH="85%">
<TR BGCOLOR="#E0E0F0"><TH WIDTH="15%">Name</TH><TH>Explanation</TH></TR>
<TR BGCOLOR="#C0C0E0"><TD>Doubleclick</TD><TD>This action is executed when a file having
this particular style is doubleclicked by the user. This action is key to <STRONG>gentoo</STRONG>'s
normal dirpane navigation: the style bound to directories generally has a doubleclick
action property of <B>DirEnter</B>.</TD></TR>
<TR BGCOLOR="#E0E0F0"><TD>View</TD><TD>This action is used by the built-in <B>FileView</B>
command: if a file being viewed specifies a view action, it is used in place of the
built-in (which is just a plain text reader for now).</TD></TR>
<TR BGCOLOR="#C0C0E0"><TD>Edit</TD><TD>This action is executed by the built-in <B>FileEdit</B>
command. There is currently no built-in default action.</TD></TR>
<TR BGCOLOR="#E0E0F0"><TD>Print</TD><TD>This action is inspected and executed by the
built-in <B>FilePrint</B> command. There is currently no built-in default.</TD></TR>
</TABLE>
</DIV>
<H2>Built-In Styles</H2>
<P>
There is a single style built into <STRONG>gentoo</STRONG>: it has been mentioned many times
above, and is generally called "Root". It defines standard values for <EM>all</EM>
properties, thereby guaranteeing that inheritance from any other style will find a
value sooner or later. You cannot delete the Root style, but you can (of course)
change its properties, thus causing non-overridden properties in the entire style
tree to change accordingly.
</P>
<H2>Tips on Naming Styles</H2>
<P>
Unlike <A HREF="types.html">types</A>, you don't need to pay any special attention
while naming styles to get a convenient grouping; it is already provided by the tree
hierarchy. I suggest using short names and not repeating the name of the parent in
the child's name (in the screenshot above, a little bit of both has been done...).
</P>
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