We are trying to use a grid design on a master page in SharePoint 2013 / Office 365. This will imitate the default title bar + side nav bar but with a third party framework. The reason I am asking here is because it seems to be framework independent for our issue. Basically we only want the ContentPlaceHolderMain to show in a dialog as per normal. But, with a grid framework we have a column for the side nav bar and a column for the content placeholder within the same row. When we add the ns-dialogHidden to the side nav it hides all the data but the page width is still taken up in the dialog.
Any ideas of how to get around this? A simple way would be to test if the "page" is within a dialog box and write Sass code to modify the columns. I did not see a way to do this though.