MultiProgressBar now buffers the output text to a single write #1825
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This is to avoid multiple small writes to the terminal, which can cause flickering.
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I was just looking at the same problem and want to suggest also simplifying the command sequences (around line 102). Currently it repeats the cursor-up-one, clear-line control sequences for as many lines as need to be cleared. But the control sequences can tell the terminal how much to move/clear in a single command. No loop required; just fill in n:
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@psimonyi thanks for your feedback! I've implemented your suggestions. In fact, I was able to remove the clear line tty commands altogether! I figured that it was enough to move the cursor up, and simply let the next progress update write over the previous terminal contents. I've tested this with multiple terminals while resizing them during download and it all works beautifully 😄 |
| for (std::size_t i = 1; i < mbar.num_of_lines_to_clear; i++) { | ||
| text_buffer << tty::cursor_up << tty::clear_line; | ||
| if (mbar.num_of_lines_to_clear > 1) { | ||
| text_buffer << tty::cursor_up_multiple_lines(mbar.num_of_lines_to_clear - 1); |
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I like the approach, but please don't do it like this via a new public class.
Perhaps just inline it with a comment what the sequences mean.
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Done! Let me know if you are happy with how it looks now :)
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It is much better and simpler, thank you.
Instead of sending multiple cursor_up and clear_line sequences, send a single command to move the cursor up multiple lines. This makes the tty::clear_line redundant, because the next update will overwrite the previous lines anyway.
8fbbeb2
This is to avoid multiple small writes to the terminal, which can cause flickering.
On my machine (Fedora 41 GNOME) I can see that the new concurrent download status bar flickers quite a bit. I've tested this on gnome-terminal/xfce4-terminal/uterm and kitty. Only Kitty does not flicker. The flickering happens regardless if Wayland/X11 is used.
The old behaviour would issue multiple clear_line writes, followed by multiple writes to "draw" the new status bars.
The new behaviour buffers all of the screen updates for a single "frame" and then writes all of that out with a single syscall.
I've tested the code changes using gnome-terminal/xfce4-terminal/uterm and kitty. Wayland and X11 sessions. It works flawlessly for me now.
I've also tested resizing the terminal window during download, and that works as before (w/o flickering now)
I believe this also fixes #1263