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Use a common algorithm for scrollbars

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Let's have reasonable behaviour with Unicode one as well.
This commit is contained in:
Přemysl Eric Janouch 2018-10-20 04:27:35 +02:00
parent 3fd88d593c
commit e957bba771
Signed by: p
GPG Key ID: A0420B94F92B9493
1 changed files with 19 additions and 23 deletions
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42
nncmpp.c
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@ -1172,25 +1172,30 @@ app_visible_items (void)
return MAX (0, app_fitting_items ());
}
/// Figure out scrollbar appearance. @a s is the minimal slider length as well
/// as the scrollbar resolution per @a visible item.
struct scrollbar { long length, start; }
app_compute_scrollbar (long top, long total, long visible)
app_compute_scrollbar (struct tab *tab, long visible, long s)
{
long top = tab->item_top, total = tab->item_count;
if (total < visible)
return (struct scrollbar) { 0, 0 };
if (visible == 1)
return (struct scrollbar) { 1, 0 };
return (struct scrollbar) { s, 0 };
if (visible == 2)
return (struct scrollbar) { 1, top >= total / 2 };
return (struct scrollbar) { s, top >= total / 2 ? s : 0 };
// Only be at the top or bottom when the top or bottom item can be seen.
// The algorithm isn't optimal but it's a bitch to get right.
double lenf = 1. + (visible - 2.) * visible / total, length = 0.;
long offset = 1. + (visible - 2.) * top / total + modf (lenf, &length);
double available_length = s * visible - 2 - s + 1;
double lenf = s + available_length * visible / total, length = 0.;
long offset = 1 + available_length * top / total + modf (lenf, &length);
if (top == 0)
return (struct scrollbar) { length, 0 };
if (top + visible >= total)
return (struct scrollbar) { length, visible - length };
return (struct scrollbar) { length, s * visible - length };
return (struct scrollbar) { length, offset };
}
@ -1210,8 +1215,7 @@ app_draw_scrollbar (void)
hard_assert (tab->item_count != 0);
if (!g.use_partial_boxes)
{
struct scrollbar bar = app_compute_scrollbar
(tab->item_top, tab->item_count, visible_items);
struct scrollbar bar = app_compute_scrollbar (tab, visible_items, 1);
for (int row = 0; row < visible_items; row++)
{
move (g.header_height + row, COLS - 1);
@ -1223,19 +1227,11 @@ app_draw_scrollbar (void)
return;
}
// TODO: clamp the values, make sure they follow the right order
// We subtract half a character from both the top and the bottom, hence -1
// XXX: I'm not completely sure why we need that 0.5 constant in both
int length = (double) visible_items / tab->item_count
* (visible_items - 1) * 8 + 0.5;
int start = (double) tab->item_top / tab->item_count
* (visible_items - 1) * 8 + 0.5;
struct scrollbar bar = app_compute_scrollbar (tab, visible_items, 8);
bar.length += bar.start;
// Then we make sure the bar is at least one character high, hence +8
int end = start + length + 8;
int start_part = start % 8; start /= 8;
int end_part = end % 8; end /= 8;
int start_part = bar.start % 8; bar.start /= 8;
int end_part = bar.length % 8; bar.length /= 8;
// Even with this, the solid part must be at least one character high
static const char *partials[] = { "█", "▇", "▆", "▅", "▄", "▃", "▂", "▁" };
@ -1243,12 +1239,12 @@ app_draw_scrollbar (void)
for (int row = 0; row < visible_items; row++)
{
chtype attrs = APP_ATTR (SCROLLBAR);
if (row > start && row <= end)
if (row > bar.start && row <= bar.length)
attrs ^= A_REVERSE;
const char *c = " ";
if (row == start) c = partials[start_part];
if (row == end) c = partials[end_part];
if (row == bar.start) c = partials[start_part];
if (row == bar.length) c = partials[end_part];
move (g.header_height + row, COLS - 1);