# HTML Gallery Themes HOWTO
---------------------------

The HTML Gallery tool can easily be themed to produce very different sites.
This document explains how to create themes.

## Getting started

A theme is a folder which contains at least two files:
- a desktop file describing the theme.
- a template.xsl file to generate the HTML files.

When the tool is run it does the following:

- Create an output folder
- For each image collection:

  - Create a folder
  - Generate thumbnails (square by default)
  - Generate full images
  - Optionally copy original images

- Copy the theme folder to the output folder
- Generate an XML file describing the image collections: gallery.xml
- Generate the HTML files by applying template.xsl to gallery.xml

## Presentation of the desktop file

The desktop file describes the theme. The information it contains is used in the
theme selection page of the tool.

It's a .ini-style file and looks like this:

    [Desktop Entry]
    Type=Theme
    Name=Hello World
    Comment=A demonstration theme

    [X-HTMLGallery Author]
    Name=The Author
    Url=http://example.com/themes/helloworld

    [X-HTMLGallery Preview]
    Name=Preview's Caption
    Url=preview.png

We use a desktop file format so that entries can be translated. If you look at
the desktop file for one of the themes shipped with the tool, you will find
something like this:

    [Desktop Entry]
    Name=Simple
    Name[br]=Eeun
    Name[cs]=Jednoduchý
    Name[cy]=Syml
    Name[da]=Simpel
    ...

The nice thing is that when your theme get integrated into HTML Gallery default
themes, translators will intertionalize the desktop file for you.

Image preview file will be placed in the root theme folder.

## Getting started: creating one theme from another

The easiest way to get started is to copy one theme and modify it.
Theme folders can be found in ${DATA_INSTALL_DIR}/digikam/themes/,
where ${DATA_INSTALL_DIR} is the install folder of digiKam on your machine
(usually /usr under Linux).

Writing in this folder requires root access, so we will not create our theme
there, instead do the following:

Create a theme folder in your home:

    mkdir -p ~/.local/share/digikam/themes/

Cd to it:

    cd ~/.local/share/digikam/themes/

Copy the "snow" theme to this folder, under a new name: "snow2":

    cp -r ${DATA_INSTALL_DIR}/digikam/themes/snow snow2

Rename the desktop file accordingly:

    cd snow2
    mv snow.desktop snow2.desktop

Edit "snow2.desktop": Remove all the `Name[...]` entries and replace `Name=Snow`
with `Name=Snow 2`.

You are done, you can now open digiKam and start the HTML Gallery tool,
the "Snow 2" theme should appear in the theme list.

## Generating HTML files, template.xsl

The template.xsl file is responsible for generating the HTML files from the
gallery.xml file.

gallery.xml looks like this:

     <?xml version="1.0" encoding="UTF-8"?>
     <collections>
      <collection>
       <name>Name of first collection</name>
       <fileName>collection_folder</fileName>
       <comment>Collection comment</comment>
       <image>
        <title>Image Title</title>
        <description>Image Description</description>
        <date>2009-08-27T09:53:26</date>
        <full fileName="pict1279.jpeg" height="450" width="600"/>
        <thumbnail fileName="thumb_pict1279.jpeg" height="80" width="80"/>
        <!-- If there is an original image, you will get the 'original' tag -->
        <original fileName="original_pict1279.jpeg" height="3000" width="4000"/>

       </image>
       <image>
        <title>Image Title</title>
        <date>2009-08-27T09:55:33</date>
        <description>Image Description</description>
        <full fileName="pict1280.jpeg" height="450" width="600"/>
        <thumbnail fileName="thumb_pict1280.jpeg" height="80" width="80"/>
        <original fileName="original_pict1279.jpeg" height="3000" width="4000"/>
       </image>
       ...
      </collection>

      <collection>
       <name>Name of second collection</name>
       ...
      </collection>
     </collections>

We won't explain XSLT here, you should be able to find the documentation you
need on the web. We recommend to learn XSLT with the [XSLT tutorial from
w3schools.com][1].

It's worth nothing nevertheless that you can make use of [EXSLT][2], a set of
extensions to XSLT. In particular, the [`exslt:document` element][3] is
extremely useful because it allows you to generate multiple documents from the
same file.

HTML Gallery tool imposes no constraint on the organisation of HTML files: you
can generate one file per image, or only one per collection. One could imagine
a theme which would only contains one HTML file and uses Javascript to show the
different images, there is already one theme using frames, you can even
generate CSS files on the fly if you want to.

[1]: http://www.w3schools.com/xsl
[2]: http://www.exslt.org
[3]: http://www.exslt.org/exsl/elements/document

### About translations

You should not "hardcode" any text in the template, instead you should use the
"i18n parameters". For example instead of using this:

    <a href="previous">Previous</a>
    | <a href="next">Next</a>

Do this:

    <a href="previous"><xsl:value-of select="$i18nPrevious"/></a>
    | <a href="next"><xsl:value-of select="$i18nNext"/></a>

It's quite a lot more verbose, but this way your user will get localized HTML
output.

If you want to use "i18n parameters" in attributes, do it like this:

    <a href="previous" title="{$i18nPrevious}"><img src="previous.png"/></a>
    | <a href="next" title="{$i18nNext}"><img src="next.png"/></a>

For now, the available general "i18n parameters" are:

- i18nPrevious
- i18nNext
- i18nCollectionList
- i18nOriginalImage
- i18nUp

and for the image details are:

- i18nexifimagemake ("Make")
- i18nexifimagemodel ("Model")
- i18nexifimageorientation ("Image Orientation")
- i18nexifimagexresolution ("Image X Resolution")
- i18nexifimageyresolution ("Image Y Resolution")
- i18nexifimageresolutionunit ("Image Resolution Unit")
- i18nexifimagedatetime ("Image Date Time")
- i18nexifimageycbcrpositioning ("YCBCR Positioning")
- i18nexifphotoexposuretime ("Exposure Time")
- i18nexifphotofnumber ("F Number")
- i18nexifphotoexposureprogram ("Exposure Index")
- i18nexifphotoisospeedratings ("ISO Speed Ratings")
- i18nexifphotoshutterspeedvalue ("Shutter Speed Value")
- i18nexifphotoaperturevalue ("Aperture Value")
- i18nexifphotofocallength ("Focal Length")

*generated by i18n entries from core/utilities/assistants/htmlgallery/generator/gallerygenerator.cpp*

If you need other i18n parameters, let us know.

## Images, CSS files and others

You are free to use images, CSS files or other files in your theme: just put
them in the theme folder and the tool will copy them in the output folder.

## Original images

As explained before, if the user selects the option "include original images",
the gallery.xml file will contain `<original />` tags. If this tag is present,
the image page should contain a link to download the original image.

Here is an example:

     <xsl:if test="original/@fileName != ''">
          <p>
               <a href="{original/@fileName}"><xsl:value-of select="$i18nOriginalImage"/></a>
          </p>
     </xsl:if>

## Non-square thumbnails

By default, thumbnails are cropped so that they are square-shaped and all have
an identical size. This makes it easier to create the HTML/CSS style.

However, if your theme is ready to cope with thumbnails of different sizes,
add this snippet to your desktop file:

    [X-HTMLGallery Options]
    Allow-non-square-thumbnails=true

The user will then be able to select whether squares should or should not be
square. For non-square thumbnails, the specified thumbnail size becomes the
size of the larger side of the thumbnail.


## Going further, theme parameters

You might want to provide a way for your user to customize your theme, for
example you could provide a few alternative CSS files, or let the user
customize the background color. This is easy to do.

### Declaring a parameter

First, you need to declare your parameter. Edit your desktop file and add
something like this:

    [X-HTMLGallery Parameter bgColor]
    Name=Background Color
    Type=color
    Default=#123456

Now start the tool and select your theme, after pressing next, you should
see an option page with a color button initialized to the #123456 color.

### Using the value of a parameter

In template.xsl, you can get the value of your parameter like this:

    <xsl:value-of select="$bgColor"/>

To change the background color of the "body" tag, you would write something
like this:

    <body bgcolor="{$bgColor}">
    ...
    </body>

### Parameter reference

Here is a more complete description of the way to declare parameters:

A parameter is declared by a section named "X-HTMLGallery Parameter someName".
`someName` should be replaced with the name you want to use in template.xsl.

- The `Name` key defines the text which will be shown in the option page. Since
this is a desktop file, it can be translated like the other keys.

- The `Type` key defines the type of the parameter. At the time
of this writing it can be one of:

 - string
 - color
 - list
 - int

- The `Default` key defines the default value of the parameter.

#### List parameter keys

A list parameter lets the user select an item from a list. To declare the
available items, you must use two sets of keys: `Value-N` and `Caption-N`,
where N is the position of the item, starting from 0.

`Value-N` is the internal value of the item. This is the value which will be
set to the parameter.

`Caption-N` is the displayed value of the item. This is the text which will
be shown in the list.

Here is an example: the "style" parameter from the "Simple" theme:

     [X-HTMLGallery Parameter style]
     Name=Style
     Type=list
     Default=natural.css
     Value-0=natural.css
     Caption-0=Natural
     Value-1=dark.css
     Caption-1=Dark

As you can see, the user will be able to choose either "Natural" or "Dark".
Depending on the user choice, `<xsl:value-of select='$style'/>` will expand to
either "natural.css" or "dark.css".

#### Int parameter keys

An int parameter lets the user select an integer using a spinbox. In addition
to the default value, you can define the minimum and maximum values, using the
`Min` and `Max` keys.

Here is an example:

     [X-HTMLGallery Parameter size]
     Name=Size
     Type=int
     Default=12
     Min=4
     Max=28

## Final words

This is the end of this howto, now is the time for you to get creative and
design awesome themes.

When you are done, do not hesitate to contact the digiKam users mailing
list (<digikam-users@kde.org>). If you want to get your theme included in the
official theme list, we need more themes.
