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When do_paint breaks up a line of terminal text into contiguous runs of characters to treat the same, one of the criteria it uses is, 'Does this character even need redrawing? (or is it already displayed correctly from the previous redraw?)' When we encounter a character that matches its previous value, we end the previous run of characters, so that we can skip the one we've just encountered. That check was not taking account of the 'truecolour' field of the termchar it was checking. So it would sometimes falsely believe the character to be equivalent to its previously drawn value, even when in fact it was not, and hence insert a run break, anticipating that the previous character needed drawing and the current one did not. This didn't cause a _wrong_ redraw, because there's a separate loop further on which re-checks whether to actually draw things, which didn't make the same error. So the character that loop #1 thought didn't need a redraw, loop #2 knew _did_ need a redraw, and hence, everything did get redrawn. But by the time loop #2 is running, it's too late to change the run boundaries. So everything does get redrawn, but in much smaller chunks than it could have been. The net effect was that if the screen was filled with text displayed in true colour, and you changed it to the _same_ text in a different colour, then the whole terminal would be redrawn in one-character increments instead of the usual behaviour of folding together runs that can be drawn in one go. Thanks to Bradley Smith for debugging this very confusing issue!
This is the README for PuTTY, a free Windows and Unix Telnet and SSH
client.
PuTTY is built using CMake <https://cmake.org/>. To compile in the
simplest way (on any of Linux, Windows or Mac), run these commands in
the source directory:
cmake .
cmake --build .
Documentation (in various formats including Windows Help and Unix
`man' pages) is built from the Halibut (`.but') files in the `doc'
subdirectory using `doc/Makefile'. If you aren't using one of our
source snapshots, you'll need to do this yourself. Halibut can be
found at <https://www.chiark.greenend.org.uk/~sgtatham/halibut/>.
The PuTTY home web site is
https://www.chiark.greenend.org.uk/~sgtatham/putty/
If you want to send bug reports or feature requests, please read the
Feedback section of the web site before doing so. Sending one-line
reports saying `it doesn't work' will waste your time as much as
ours.
See the file LICENCE for the licence conditions.