linenoiseRemoteRefereshLine() #140
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When other processes call printf and linenoise had a prompt displayed, the text gets printed after the prompt and looks horrible. This function allows other threads or processes to refresh the linenoise line. Thereby they can print their string on its own line, then reshesh the prompt so everything looks nice. This is accomplished by replacing read in several places with a function that uses select to wait on two file descriptors, stdin and a control pipe that we create. linenoiseRemoteRefreshLine() pushes a new control character (ctrl-r) into our control pipe; when that is received, a flag is set that calls for refresh line to be called.
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This patch has a high level of complexity and while it implements a feature that's valuable to your specific application I feel that there may be alternative solutions in other cases. This patch doesn't need to be merged. |
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Hello, I agree with @rain-1. Specifically the way I think linenoise should evolve to support this use case, is to make it internally able to be used in a stateless way. So instead of reading in a direct way, we should have an interface that feeds linenoise with characters. This way the normal blocking behavior can be easily provided by using, internally, the non-blocking API. However for advanced uses, it is possible to instead use linenoise by creating a context and feeding it with bytes and so forth. I have plans to make such changes, because in the future those features will be needed for redis-cli... Note how this also makes linenoise able to be used easily in order to, for example, create an IRC client or any more complex system doing multiplexing on multiple I/O devices: the console, sockets, and so forth. |
We've been using linenoise in a larger multi-threaded project. When another thread uses printf to display some message and a linenoise prompt is on the screen, the message prints at the end of our current prompt, and no new prompt is displayed resulting in ugly output.
Our new function allows other processes to remotely refresh the linenoise line. Thereby they can print their string on its own line, then reshesh the prompt so everything looks nice.
This is accomplished by replacing read in several places with a function that uses select to wait on two file descriptors, stdin and a control pipe that we create. linenoiseRemoteRefreshLine() pushes a new control
character (ctrl-r) into our control pipe; when that is received, a flag is set that calls for refresh line to be called.