How to Speed up CSS Development and Debugging

You may have already run the DITA Map PDF - based on HTML5 & CSS transformation scenario before using this procedure.

You can speed up your CSS development considerably by not invoking the entire pipeline of transforming your DITA maps to PDF. Instead, you can directly transform the merged map (.merged.html) into PDF using Oxygen PDF Chemistry.

Open the .merged.html located in the output directory in the editor.
Configure a new XML to PDF transformation with CSS scenario. There is no need to set the CSS URL in the resulting dialog box. The stylesheets are already declared in the file <head>. This scenario uses the Chemistry CSS processor.
Optional: Enable the console output of the CSS processor from: Options > Preferences > XML > PDF Output > CSS-based Processors.

Now you can make incremental changes to the CSS stylesheet and quickly see the results by transforming the merged file directly.

Fastpath: If your changes only involve element styling (with no specific paged media CSS rules and properties), you can simply open the merged file in a browser (such as Chrome or Firefox) and refresh at each CSS change, as shown in: Debugging the CSS.