Sounds like we'll need a new global hook and some helper functions (or coding guidelines/conventions) to avoid conflict between plugins accessing a custom parameter object.

What is the use case for this new hook?

• do you want to globally set a custom variable/parameter to all widgets?
• should it be persisted when clicks occuron widget (to sort, paginate, change view)?
• several plugins can persist variables
• several plugins can have different persisted variables

Yes, I hope it can be available to all widgets and it is persisted.

I think avoiding conflict is not difficult, for example, I use json format, and I can save array("myPlugin"=>array(param1=>'...',param2=>'...'),'otherPlugin1'=>...)
in it to avoid conflict.

I'm writng ECommerce plugin, and I need some parameters to use,such as dateRange and period 'hour'.If I add param myself without modify core code, many function can not work for my plugin such as export data as csv,php....

For me, I just need a parameter persisted in url, hook is not necessary, I can use some hook such as 'template_js_import' to add a js to modify this paramters, but it is better to have a hook.

If it need much time to add this hook, I hope piwik can add this parameter without hook first if it is possible.

Attachment: modify custom parameters by js added by hook 'template_js_import'
00.png

it should be possible using ViewDataTable::setCustomParameter ?