A collection of proposed enhancements #28
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The trailing whitespace gets removed by editing steps I have done for other changes, so I wanted to commit this change by itself first to avoid making the other changes less clear.
Instead of separate memset calls and assignments to initialize various members of the microrl_t struct to zero, just clear the entire struct first and then set the nonzero values.
1. Add a 'void* userdata' member to microrl_t that can be used by applications to store a C++ object pointer or other context info. 2. Pass the pointer to microrl_t in all callbacks so that the operations can be specific to a particular instance of microrl. 3. Enclose the definitions in microrl.h in a conditional 'extern "C"' block to allow those definitions to be referenced from C++ files.
This is a change that was missed in copying over to this repository in the previous commit 7334fbd.
Change the example code to include the microrl_t pointer as the first argument of all the callbacks as was added to the microrl library in commit 7334fbd. Note: The changes in avr_misc have not been tested since I don't have a build environment.
Typing multiple Ctrl-D while on an empty command line would crash. This was missed in merging changes from another repository.
When used over a network connection, each print() call in microrl may be transmitted as a separate packet, so the many small print operations make output slow. This commit optimizes some common cases to avoid unnecessary prints and combines others into a buffer to be printed together. - When adding characters to the end of a command, now just the single character is output. This avoids cursor jumping. Similarly, when backspacing at the end of the line, just the simple sequence back-one, space, back-one is sufficient. - The biggest number of back-to-back print operations occurred in terminal_print_line() where each character was printed separately. Now the characters are packed into a temporary buffer first so they can be printed in one or a few operations, depending upon the command length and buffer size. Positioning sequences are also consolidated into the buffer. - Some calls to terminal_reset_cursor() that were changed to call terminal_move_cursor() instead since the latter outputs fewer characters and avoids extra jumping of the cursor on slow lines. The code to reset the cursor position was then incorporated into terminal_print_line() where those positioning operations can be consolidated into a print buffer. Since the reset is not always necessary, an argument controls whether it is done. - A new define _USE_CARRIAGE_RETURN controls using a carriate return to reposition the cursor to the left margin rather than moving left by a large number. This takes fewer characters. This optimization can be turned off if the terminal simulates receiving a linefeed when it receives the carriage return. - In terminal_print_line(), the delete-to-end-of-line escape sequence is moved to be output after all of the command text. This avoids a flash of the text going away and then being repainted. - The code to create repositioning sequences was extracted into a separate function generate_move_cursor() so it can be shared between terminal_move_cursor() and terminal_print_line(). - After reorganizing the code to generate repositioning strings there was only one call to u16bit_to_str(), so it was merged inline. - strcpy() calls of just a few characters are replaced by depositing the characters individually. This removes a dependency and may use fewer instructions. - To allow ^U to backspace across all of the characters to the left of the curso in one motion, microrl_backspace() now takes a parameter for the number of spaces to move rather than always moving one.
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I have added several enhancements to microrl as we are using it in the Open Vehicle Monitoring System project. I have separated those enhancements into separate commits in my repository here and arranged them with the ones least likely to raise objections applied first.