eugen-keeper commented on code in PR #597:
URL: https://github.com/apache/guacamole-server/pull/597#discussion_r2124884051
##########
src/terminal/terminal.c:
##########
@@ -868,6 +868,14 @@ void guac_terminal_scroll_up(guac_terminal* term,
void guac_terminal_scroll_down(guac_terminal* term,
int start_row, int end_row, int amount) {
+ /*
+ * This is necessary because guac_terminal_copy_rows will set new
GUAC_CHAR_COPY
+ * for cells of shifted rows meanwhile preceding GUAC_CHAR_SET for these
cells
+ * are not actually done yet. The GUAC_CHAR_COPY operation has the highest
priority,
+ * so if we do not 'flush' here, wrong content will be copied.
+ */
+ guac_terminal_display_flush(term->display);
Review Comment:
I performed the research sometime ago. Even after I did it, I was confused a
little about the behavior because we have mix of numbers and images there. It
was difficult to simply sample frames or dump rows to understand every details.
Anyway, I remember the following things.
1. `guac_common_surface_flush` is actually not necessary, the following
calls are necessary:
- `__guac_terminal_display_flush_copy`
- `__guac_terminal_display_flush_clear`
- `__guac_terminal_display_flush_set`
2. Based on my research the solution could be `set` before
`guac_terminal_copy_rows` and copy/clear at the end of
`guac_terminal_scroll_down`. Although performing all the operations
`guac_terminal_copy_rows` also helps 100%. Tested!
3. I would prefer to avoid making changes inside `guac_terminal_copy_rows`
because the issue happens only during `scrolling down` because the first line
is set with new characters and then we have to copy them to one of the next
lines.
4. Overall, no matter how I tried to fix it a different way, as far as
remember I found that the best solution is to flush between preceding `set`
operations and guac_terminal_display_copy_rows.
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