Process Picture tags and multiple Images in a srcset

[tijmenbruggeman]

With the compression feature turned on, the plug-in will parse images on template_redirect. This parsed elements from the body to replace them with a picture element. One overlooked scenario was elements already wrapped by a element.

Additionally, it was not semantically correct to have multiple sources of one srcset in the picture element. This scenario is now covered as well.

Changes

• Added a unit test for the bug scenario
• Filtered out picture elements when searching for img tags.
• Improved documentation on various regexes as the regexes are getting quite complex
• Created two classes, one for handling tags and one for elements. Shared functionality comes from the base class.

Considerations

• Why not use DOMDocument to parse the html?
  DOMDocument is quite robust, it is not support or turned on for all servers/php runtimes. Therefor it is unsure wether we can use it or not.
• Why not use an existing package to read DOM nodes or attributes?
  Adding a package should not be taken lightly. It can increase vulnerability and complexity. Parsing the page for elements is a relatively small feature and adding a package for this might not be worth it.