How were RPA tools such as UiPath originally developed? From which Windows libraries did they extract the text (e.g. based on Win32 API or MS UI automation or pure OCR).
Well it abination of different Microsoft libraries. For instance Blue Prism can automate Browser Java Windows and Mainframe applications. A browser application can be automated using Active Accessibility UIA (UI Automation) HTML Window and Region modes. To be able to use these modes Blue Prism product has the packaged dll files in it Blue Prism automate folder. Similarly Blue Prism uses ehllapi hllapi dll to automate IBM mainframes. The list goes on and on. If your question is pertaining to the underlying technology of either Blue Prism or UIPath they were originally built using either WPF or Winform. The queue system most likely message queues and themunications managed using WCF. I hope this helps.