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cb43c58150
When moving the viewport in the scrollback (i.e. “scrolling”), we need to ensure the viewport is not moved past the beginning, or end, of the scrollback. This was previously accomplish by first limiting the number of lines to scroll to the number of visible rows (i.e the viewport _size_), and by adjusting the viewport after moving it, to ensure it doesn’t point into an uninitialized scrollback area etc. I.e. the implementation was _reactive_. This patch rewrites the logic to be _proactive_; we now calculate _where_ the beginning (or end) of the scrollback is, and then how many lines there is from there, to the viewport. This is our _maximum_ number of lines to scroll. When done correctly (which I hope this patch does), this allows us to remove _all_ checks after moving the viewport - we already _know_ it’s correct, and valid. As a bonus, we can remove the old limit, where scrolling was only allowed to be at most a single page.
132 lines
3.6 KiB
C
132 lines
3.6 KiB
C
#include "commands.h"
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#define LOG_MODULE "commands"
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#define LOG_ENABLE_DBG 0
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#include "log.h"
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#include "grid.h"
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#include "render.h"
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#include "selection.h"
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#include "terminal.h"
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#include "url-mode.h"
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#include "util.h"
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void
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cmd_scrollback_up(struct terminal *term, int rows)
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{
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if (term->grid == &term->alt)
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return;
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if (urls_mode_is_active(term))
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return;
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const struct grid *grid = term->grid;
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const int offset = grid->offset;
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const int view = grid->view;
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const int grid_rows = grid->num_rows;
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const int screen_rows = term->rows;
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int scrollback_start = (offset + screen_rows) & (grid_rows - 1);
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/* Part of the scrollback may be uninitialized */
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while (grid->rows[scrollback_start] == NULL) {
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scrollback_start++;
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scrollback_start &= grid_rows - 1;
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}
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/* Number of rows to scroll, without going past the scrollback start */
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int max_rows = 0;
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if (view + screen_rows >= grid_rows) {
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/* View crosses scrollback wrap-around */
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xassert(scrollback_start <= view);
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max_rows = view - scrollback_start;
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} else {
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if (scrollback_start <= view)
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max_rows = view - scrollback_start;
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else
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max_rows = view + (grid_rows - scrollback_start);
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}
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rows = min(rows, max_rows);
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if (rows == 0)
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return;
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int new_view = (view + grid_rows) - rows;
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new_view &= grid_rows - 1;
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xassert(new_view != view);
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xassert(grid->rows[new_view] != NULL);
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#if defined(_DEBUG)
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for (int r = 0; r < term->rows; r++)
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xassert(grid->rows[(new_view + r) & (grid->num_rows - 1)] != NULL);
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#endif
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LOG_DBG("scrollback UP: %d -> %d (offset = %d, end = %d, rows = %d)",
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view, new_view, offset, end, grid_rows);
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selection_view_up(term, new_view);
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term->grid->view = new_view;
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if (rows < term->rows) {
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term_damage_scroll(
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term, DAMAGE_SCROLL_REVERSE_IN_VIEW,
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(struct scroll_region){0, term->rows}, rows);
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term_damage_rows_in_view(term, 0, rows - 1);
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} else
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term_damage_view(term);
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render_refresh_urls(term);
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render_refresh(term);
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}
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void
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cmd_scrollback_down(struct terminal *term, int rows)
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{
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if (term->grid == &term->alt)
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return;
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if (urls_mode_is_active(term))
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return;
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const struct grid *grid = term->grid;
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const int offset = grid->offset;
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const int view = grid->view;
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const int grid_rows = grid->num_rows;
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const int screen_rows = term->rows;
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const int scrollback_end = offset;
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/* Number of rows to scroll, without going past the scrollback end */
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int max_rows = 0;
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if (view <= scrollback_end)
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max_rows = scrollback_end - view;
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else
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max_rows = offset + (grid_rows - view);
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rows = min(rows, max_rows);
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if (rows == 0)
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return;
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int new_view = (view + rows) & (grid_rows - 1);
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xassert(new_view != view);
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xassert(grid->rows[new_view] != NULL);
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#if defined(_DEBUG)
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for (int r = 0; r < term->rows; r++)
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xassert(grid->rows[(new_view + r) & (grid_rows - 1)] != NULL);
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#endif
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LOG_DBG("scrollback DOWN: %d -> %d (offset = %d, end = %d, rows = %d)",
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view, new_view, offset, end, grid_rows);
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selection_view_down(term, new_view);
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term->grid->view = new_view;
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if (rows < term->rows) {
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term_damage_scroll(
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term, DAMAGE_SCROLL_IN_VIEW,
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(struct scroll_region){0, term->rows}, rows);
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term_damage_rows_in_view(term, term->rows - rows, screen_rows - 1);
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} else
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term_damage_view(term);
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render_refresh_urls(term);
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render_refresh(term);
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}
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