heavy Processor called multiple times

Hi,

I've developed a prompt that performs spellchecking by integrating the pyspellcheck library. However, I've noticed that underlining misspelled words causes a significant lag. I've optimized the spell-checking process by using caches, but the lag persists.

Upon further investigation, I added a print statement to the apply_transformation function and found that it is being called four times per keystroke. I attempted to create a ConditionalProcessor to address this, but there is no key_inserted event. Instead, I implemented hashing the buffer's text, but this approach breaks the underlining functionality entirely.

Any advice on how to resolve this issue would be greatly appreciated.

Thank you!

Sample: https://gist.github.com/planetis-m/ad078e0e184439e2712f3b853c192d01

Start with the sample gist and the prompt-toolkit code around the apply_transformation function to trace why it runs multiple times per keystroke. Review the attempted ConditionalProcessor and buffer-text hashing approach, then determine a way to avoid redundant spellchecking without breaking underlining. Done means the transformation no longer causes the reported lag while underlining remains functional.