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Merge pull request #7122 from friendica/MrPetovan-addon-doc 

Improve addon documentation
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@ -7,48 +7,65 @@ Please see the sample addon 'randplace' for a working example of using some of t
Addons work by intercepting event hooks - which must be registered.
Modules work by intercepting specific page requests (by URL path).
Addon names cannot contain spaces or other punctuation and are used as filenames and function names.
You may supply a "friendly" name within the comment block.
Each addon must contain both an install and an uninstall function based on the addon name.
For instance "addon1name_install()".
These two functions take no arguments and are usually responsible for registering (and unregistering) event hooks that your addon will require.
The install and uninstall functions will also be called (i.e. re-installed) if the addon changes after installation.
## Naming
Addon names are used in file paths and functions names, and as such:
- Can't contain spaces or punctuation.
- Can't start with a number.
## Metadata
You can provide human-readable information about your addon in the first multi-line comment of your addon file.
Here's the structure:
```php
/**
* Name: {Human-readable name}
* Description: {Short description}
* Version: 1.0
* Author: {Author1 Name}
* Author: {Author2 Name} <{Author profile link}>
* Maintainer: {Maintainer1 Name}
* Maintainer: {Maintainer2 Name} <{Maintainer profile link}>
* Status: {Unsupported|Arbitrary status}
*/
```
You can also provide a longer documentation in a `README` or `README.md` file.
The latter will be converted from Markdown to HTML in the addon detail page.
## Install/Uninstall
If your addon uses hooks, they have to be registered in a `<addon>_install()` function.
This function also allows to perform arbitrary actions your addon needs to function properly.
Uninstalling an addon automatically unregisters any hook it registered, but if you need to provide specific uninstallation steps, you can add them in a `<addon>_uninstall()` function.
The install and uninstall functions will be called (i.e. re-installed) if the addon changes after installation.
Therefore your uninstall should not destroy data and install should consider that data may already exist.
Future extensions may provide for "setup" amd "remove".
Addons should contain a comment block with the four following parameters:
/*
* Name: My Great Addon
* Description: This is what my addon does. It's really cool.
* Version: 1.0
* Author: John Q. Public <john@myfriendicasite.com>
*/
Please also add a README or README.md file to the addon directory.
It will be displayed in the admin panel and should include some further information in addition to the header information.
## PHP addon hooks
Register your addon hooks during installation.
\Friendica\Core\Hook::register($hookname, $file, $function);
$hookname is a string and corresponds to a known Friendica PHP hook.
`$hookname` is a string and corresponds to a known Friendica PHP hook.
$file is a pathname relative to the top-level Friendica directory.
This *should* be 'addon/*addon_name*/*addon_name*.php' in most cases.
`$file` is a pathname relative to the top-level Friendica directory.
This *should* be 'addon/*addon_name*/*addon_name*.php' in most cases and can be shortened to `__FILE__`.
$function is a string and is the name of the function which will be executed when the hook is called.
`$function` is a string and is the name of the function which will be executed when the hook is called.
### Arguments
Your hook callback functions will be called with at least one and possibly two arguments
function myhook_function(App $a, &$b) {
function <addon>_<hookname>(App $a, &$b) {
}
If you wish to make changes to the calling data, you must declare them as reference variables (with `&`) during function declaration.
#### $a
@ -67,6 +84,12 @@ $b can be called anything you like.
This is information specific to the hook currently being processed, and generally contains information that is being immediately processed or acted on that you can use, display, or alter.
Remember to declare it with `&` if you wish to alter it.
## Admin settings
Your addon can provide user-specific settings via the `addon_settings` PHP hook, but it can also provide node-wide settings in the administration page of your addon.
Simply declare a `<addon>_addon_admin(App $a)` function to display the form and a `<addon>_addon_admin_post(App $a)` function to process the data from the form.
## Global stylesheets
If your addon requires adding a stylesheet on all pages of Friendica, add the following hook:
@ -132,11 +155,11 @@ No additional data is provided.
## Modules
Addons may also act as "modules" and intercept all page requests for a given URL path.
In order for a addon to act as a module it needs to define a function "addon_name_module()" which takes no arguments and needs not do anything.
In order for a addon to act as a module it needs to declare an empty function `<addon>_module()`.
If this function exists, you will now receive all page requests for "http://my.web.site/addon_name" - with any number of URL components as additional arguments.
If this function exists, you will now receive all page requests for `https://my.web.site/<addon>` - with any number of URL components as additional arguments.
These are parsed into an array $a->argv, with a corresponding $a->argc indicating the number of URL components.
So http://my.web.site/addon/arg1/arg2 would look for a module named "addon" and pass its module functions the $a App structure (which is available to many components).
So `https://my.web.site/addon/arg1/arg2` would look for a module named "addon" and pass its module functions the $a App structure (which is available to many components).
This will include:
```php
@ -144,9 +167,9 @@ $a->argc = 3
$a->argv = array(0 => 'addon', 1 => 'arg1', 2 => 'arg2');
```
Your module functions will often contain the function addon_name_content(App $a), which defines and returns the page body content.
They may also contain addon_name_post(App $a) which is called before the _content function and typically handles the results of POST forms.
You may also have addon_name_init(App $a) which is called very early on and often does module initialisation.
To display a module page, you need to declare the function `<addon>_content(App $a)`, which defines and returns the page body content.
They may also contain `<addon>_post(App $a)` which is called before the `<addon>_content` function and typically handles the results of POST forms.
You may also have `<addon>_init(App $a)` which is called before `<addon>_content` and should include common logic to your module.
## Templates
@ -160,7 +183,7 @@ In your code, like in the function addon_name_content(), load the template file
```php
# load template file. first argument is the template name,
# second is the addon path relative to friendica top folder
$tpl = Renderer::getMarkupTemplate('mytemplate.tpl', 'addon/addon_name/');
$tpl = Renderer::getMarkupTemplate('mytemplate.tpl', __DIR__);
# apply template. first argument is the loaded template,
# second an array of 'name' => 'values' to pass to template