static int find_top_to_recenter (SLscroll_Window_Type *win)
{
unsigned int nrows;
unsigned int hidden_mask;
SLscroll_Type *prev, *last_prev, *cline;
nrows = win->nrows;
cline = win->current_line;
hidden_mask = win->hidden_mask;
nrows = nrows / 2;
last_prev = prev = cline;
while (nrows && (prev != NULL))
{
nrows--;
last_prev = prev;
do
{
prev = prev->prev;
}
while (hidden_mask
&& (prev != NULL)
&& (prev->flags & hidden_mask));
}
if (prev == NULL) prev = last_prev;
win->top_window_line = prev;
find_window_bottom (win);
return 0;
}
int SLscroll_pageup (SLscroll_Window_Type *win)
{
SLscroll_Type *l, *top;
unsigned int nrows, hidden_mask;
unsigned int n;
if (win == NULL)
return -1;
(void) SLscroll_find_top (win);
nrows = win->nrows;
if ((NULL != (top = win->top_window_line))
&& (nrows > 2))
{
n = 0;
hidden_mask = win->hidden_mask;
l = win->current_line;
while ((l != NULL) && (l != top))
{
l = l->prev;
if ((hidden_mask == 0)
|| ((l != NULL) && (0 == (l->flags & hidden_mask))))
n++;
}
if (l != NULL)
{
unsigned int save_line_num;
int ret = 0;
win->current_line = l;
win->line_num -= n;
/* Compute a new top/bottom header */
save_line_num = win->line_num;
if ((0 == SLscroll_prev_n (win, nrows - 1))
&& (n == 0))
ret = -1;
win->top_window_line = win->current_line;
win->current_line = l;
win->line_num = save_line_num;
find_window_bottom (win);
return ret;
}
}
if (nrows < 2) nrows++;
if (0 == SLscroll_prev_n (win, nrows - 1))
return -1;
return 0;
}
int SLscroll_pagedown (SLscroll_Window_Type *win)
{
SLscroll_Type *l, *bot;
unsigned int nrows, hidden_mask;
unsigned int n;
if (win == NULL)
return -1;
(void) SLscroll_find_top (win);
nrows = win->nrows;
if ((NULL != (bot = win->bot_window_line))
&& (nrows > 2))
{
n = 0;
hidden_mask = win->hidden_mask;
l = win->current_line;
while ((l != NULL) && (l != bot))
{
l = l->next;
if ((hidden_mask == 0)
|| ((l != NULL) && (0 == (l->flags & hidden_mask))))
n++;
}
if (l != NULL)
{
win->current_line = l;
win->top_window_line = l;
win->line_num += n;
find_window_bottom (win);
if (n || (bot != win->bot_window_line))
return 0;
return -1;
}
}
if (nrows < 2) nrows++;
if (0 == SLscroll_next_n (win, nrows - 1))
return -1;
return 0;
}
int SLscroll_find_top (SLscroll_Window_Type *win)
{
unsigned int i;
SLscroll_Type *cline, *prev, *next;
SLscroll_Type *top_window_line;
unsigned int nrows;
unsigned int hidden_mask;
int scroll_mode;
unsigned int border;
cline = win->current_line;
nrows = win->nrows;
scroll_mode = win->cannot_scroll;
border = win->border;
if (scroll_mode == 2)
border = 0;
if ((cline == NULL) || (nrows <= 1))
{
win->top_window_line = cline;
find_window_bottom (win);
return 0;
}
hidden_mask = win->hidden_mask;
/* Note: top_window_line might be a bogus pointer. This means that I cannot
* access it unless it really corresponds to a pointer in the buffer.
*/
top_window_line = win->top_window_line;
if (top_window_line == NULL)
return find_top_to_recenter (win);
/* Chances are that the current line is visible in the window. This means
* that the top window line should be above it.
*/
prev = cline;
i = 0;
while ((i < nrows) && (prev != NULL))
{
if (prev == top_window_line)
{
SLscroll_Type *twl = top_window_line;
int dir = 0;
if (i < border) dir = -1; else if (i + border >= nrows) dir = 1;
if (dir) while (border)
{
if (dir < 0) twl = twl->prev;
else twl = twl->next;
if (twl == NULL)
{
twl = top_window_line;
break;
}
if ((hidden_mask == 0)
|| (0 == (twl->flags & hidden_mask)))
border--;
}
win->top_window_line = twl;
find_window_bottom (win);
return 0;
}
do
{
prev = prev->prev;
}
while (hidden_mask
&& (prev != NULL)
&& (prev->flags & hidden_mask));
i++;
}
/* Now check the borders of the window. Perhaps the current line lies
* outsider the border by a line. Only do this if terminal can scroll.
*/
if (scroll_mode == 1)
return find_top_to_recenter (win);
else if (scroll_mode == -1)
scroll_mode = 0;
next = cline->next;
while (hidden_mask
&& (next != NULL)
&& (next->flags & hidden_mask))
next = next->next;
if ((next != NULL)
&& (next == top_window_line))
{
/* The current line is one line above the window. This means user
* has moved up past the top of the window. If scroll_mode is set
* to scroll by pages, we need to do a page up.
*/
win->top_window_line = cline;
find_window_bottom (win);
if (scroll_mode) return SLscroll_pageup (win);
return 0;
}
prev = cline->prev;
while (hidden_mask
&& (prev != NULL)
&& (prev->flags & hidden_mask))
prev = prev->prev;
if ((prev == NULL)
|| (prev != win->bot_window_line))
return find_top_to_recenter (win);
/* It looks like cline is below window by one line. See what line should
* be at top to scroll it into view. Only do this unless we are scrolling
* by pages.
*/
if (scroll_mode)
{
win->top_window_line = cline;
find_window_bottom (win);
return 0;
}
i = 2;
while ((i < nrows) && (prev != NULL))
{
do
{
prev = prev->prev;
}
while (hidden_mask
&& (prev != NULL)
&& (prev->flags & hidden_mask));
i++;
}
if (prev != NULL)
{
win->top_window_line = prev;
find_window_bottom (win);
return 0;
}
return find_top_to_recenter (win);
}
