fix #345

[liquidaty]

No description provided.

[liquidaty]

@richiejp spent a LOT of time debugging. Think I found the issue. Hope this resolves properly, but pls take a look to see:

On macos-14, upon pressing T:

1. get_data_index_async() never fires, and there is a very brief "Unexpected error!" flash in the status bar because it tries to seek to a newline, but there is no index data so it seeks to the start of the file and does not encounter a newline

2. This line of code only executes once, and sets need_index to false, because uibuff->write_in_progress is set to 1 via uibopts.write_after_open in transformation.c:247. Perhaps on other platforms the write_in_progress is actually not 1 due to it being a bit and uibopts.write_after_open being a char?

• char need_index = !uibuff->index_started && !uibuff->write_in_progress;

3. There might be a race condition from the time between need_index = uibuff->index_started and writing uibuff->index_started = 1

4. Changing need_index to not check write_in_progress, and changing transformation.c to not explicitly call the worker. This also makes various functions in transformation.c unnecessary; they seem to be redundant with what is in index.c anyway and probably would have been best consolidated from the get-go

[liquidaty]

Looking more closely this definitely does not fix the issue without causing others but adding zsvsheet_run_buffer_transformation() back in causes an assertion to fail.

If it is kept, zsvsheet_run_buffer_transformation() should be consolidated with the similar code in index.c, and the mechanism for starting an index run should also be consolidated, probably triggered in read-data.c so that it does not need to come via a push_transformation call. That sound good?

[richiejp]

get_data_index_async() never fires, and there is a very brief "Unexpected error!" flash in the status bar

Just on a partially related note, I added something which makes the status messages last longer here @liquidaty

2ed256f