When you want to use Silex it is important to understand that there is a layer hierarchy. Some layers are called “parent layers” and some are called “children layers”.
We call parent layer, a layer from which one another layer had been created (its children layer).
If you want more details about layers you can look at the article “page creation”.
3 basics things:
* a parent layer can have several children layers
* a layer can be both parent and children layer
* all the components that are on a parent layer will be visible on stage from its children layer(s)
Here <start> is the parent layer of <template_import_pdf_first_page> and consequently, <template_import_pdf_first_page> is the children layer of <start>.
To know if a layer is parent or children layer or both, help you of layers order in the layers toolbox.
Example : in the illustration above, <start> is on top and has a layer under it, so it’s the parent layer of this layer.
The layer under <start> has no layer under it so it’s only a children-layer.
Look at this example :
Here <start> is the parent layer of <template_import_pdf_first_page>.
<template_import_pdf_first_page> is the children layer of <start> and it’s also the parent layer of <detail>.
<detail> is only the children layer of <template_import_pdf_first_page>.
In that example we have what we call different level of depth. <Start> corresponds to the level 0, <template_import_pdf_first_page” to the level 1 and <detail> to the level 2.
Note : you can have as many levels as you want
It implies this :
▪ <start> corresponds to the level 0 = all the elements that are on this layer would be find on all the pages and sub-pages of your publication.
▪ <template_import_pdf_first_page> corresponds to the level 1 = the elements that you will find here are those that you would put on this layer + those that are on the <start> layer
▪ <detail> corresponds to the level 2 : the elements that you will find here are those that you would put on this layer + those that are on the <start> layer + those that are on the <template_import_pdf_first_page> layer.
Note 1 : to resume, a children layer inherit of its parent layer’s content.
Note 2 : if a layer has several children layers, you won’t see them at the same time in the layers toolbox.