Hi! Should/must/may a frontend call sane_read after sane_cancel?
Case I: sane_cancel was called in a signal handler or in other thread. The reader thread still keeps calling sane_read until it returns an error or EOF. That's clear for me. Case II: The frontend has read a block of image data from a backend and it is writing the data to a file but a IO error occurs. The frontend probably calls sane_cancel. What will/must the frontend do next? Will it call sane_read until an error or EOF occurs? This is important to my backend (pixma). It would be much more complex if frontends are not required to call sane_read after sane_cancel because I have to check whether sane_cancel was called synchronously or asynchronously. If it's called synchronously (case II), an outstanding scan operation must be completely canceled before sane_cancel returns. If it's call asynchronously (case I), the request must be postponed by setting a flag for example. The request will be carried out when we return to the reader thread. Regards -- Wittawat Yamwong Hannover, Germany
