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/*
* Copyright (C) 2024 Mark Hills <mark@xwax.org>
*
* This file is part of "xwax".
*
* "xwax" is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License, version 3 as
* published by the Free Software Foundation.
*
* "xwax" is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <https://www.gnu.org/licenses/>.
*
*/
#include <assert.h>
#include "listbox.h"
void listbox_init(struct listbox *s)
{
s->lines = 0;
s->entries = 0;
s->offset = 0;
s->selected = -1;
}
/*
* Set the number of lines displayed on screen
*
* Zero is valid, to mean that the display is hidden. In all other
* cases, the current selection is moved to within range.
*/
void listbox_set_lines(struct listbox *s, unsigned int lines)
{
s->lines = lines;
if (s->selected >= s->offset + s->lines)
s->selected = s->offset + s->lines - 1;
if (s->offset + s->lines > s->entries) {
s->offset = s->entries - s->lines;
if (s->offset < 0)
s->offset = 0;
}
}
/*
* Set the number of entries in the list which backs the scrolling
* display. Bring the current selection within the bounds given.
*/
void listbox_set_entries(struct listbox *s, unsigned int entries)
{
s->entries = entries;
if (s->selected >= s->entries)
s->selected = s->entries - 1;
if (s->offset + s->lines > s->entries) {
s->offset = s->entries - s->lines;
if (s->offset < 0)
s->offset = 0;
}
/* If we went previously had zero entries, reset the selection */
if (s->selected < 0)
s->selected = 0;
}
/*
* Scroll the selection up by n lines. Move the window offset if
* needed
*/
void listbox_up(struct listbox *s, unsigned int n)
{
s->selected -= n;
if (s->selected < 0)
s->selected = 0;
/* Move the viewing offset up, if necessary */
if (s->selected < s->offset) {
s->offset = s->selected + s->lines / 2 - s->lines + 1;
if (s->offset < 0)
s->offset = 0;
}
}
void listbox_down(struct listbox *s, unsigned int n)
{
s->selected += n;
if (s->selected >= s->entries)
s->selected = s->entries - 1;
/* Move the viewing offset down, if necessary */
if (s->selected >= s->offset + s->lines) {
s->offset = s->selected - s->lines / 2;
if (s->offset + s->lines > s->entries)
s->offset = s->entries - s->lines;
}
}
/*
* Scroll to the first entry on the list
*/
void listbox_first(struct listbox *s)
{
s->selected = 0;
s->offset = 0;
}
/*
* Scroll to the final entry on the list
*/
void listbox_last(struct listbox *s)
{
s->selected = s->entries - 1;
s->offset = s->selected - s->lines + 1;
if (s->offset < 0)
s->offset = 0;
}
/*
* Scroll to an entry by index
*/
void listbox_to(struct listbox *s, unsigned int n)
{
int p;
assert(s->selected != -1);
assert(n < s->entries);
/* Retain the on-screen position of the current selection */
p = s->selected - s->offset;
s->selected = n;
s->offset = s->selected - p;
if (s->offset < 0)
s->offset = 0;
}
/*
* Return the index of the current selected list entry, or -1 if
* no current selection
*/
int listbox_current(const struct listbox *s)
{
if (s->entries == 0)
return -1;
else
return s->selected;
}
/*
* Translate the given row on-screen (starting with row zero)
* into a position in the list
*
* Return: -1 if the row is out of range, otherwise entry number
*/
int listbox_map(const struct listbox *s, int row)
{
int e;
assert(row >= 0);
if (row >= s->lines)
return -1;
e = s->offset + row;
if (e >= s->entries)
return -1;
return e;
}
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