Lock screen when drawing on the calendar/notification panel

Lock the screen if either the calendar panel or the notification bar is
updated to avoid race conditions.

Addresses BUG#6.

Note that we currently always use a screen-level lock, even if only one
window is affected. This is to be changed in the future.

Signed-off-by: Lukas Fleischer <calcurse@cryptocrack.de>

4 files changed, 61 insertions, 3 deletions

diff --git a/src/calcurse.h b/src/calcurse.h
index e35fe9a..7a7f4f2 100644
--- a/src/calcurse.h
+++ b/src/calcurse.h
@@ -975,6 +975,10 @@ void vars_init(void);
 
 /* wins.c */
 extern struct window win[NBWINS];
+unsigned wins_nbar_lock(void);
+void wins_nbar_unlock(void);
+unsigned wins_calendar_lock(void);
+void wins_calendar_unlock(void);
 int wins_refresh(void);
 int wins_wrefresh(WINDOW *);
 int wins_doupdate(void);
diff --git a/src/calendar.c b/src/calendar.c
index 48ac84d..42ee449 100644
--- a/src/calendar.c
+++ b/src/calendar.c
@@ -297,6 +297,7 @@ draw_monthly_view(struct window *cwin, struct date *current_day,
   c_day_1 = (int)((ymd_to_scalar(yr, mo, 1 + sunday_first) - (long)1) % 7L);
 
   /* Write the current month and year on top of the calendar */
+  wins_calendar_lock();
   custom_apply_attr(cwin->p, ATTR_HIGHEST);
   mvwprintw(cwin->p, ofs_y,
             (SBAR_WIDTH - (strlen(_(monthnames[mo - 1])) + 5)) / 2,
@@ -310,6 +311,7 @@ draw_monthly_view(struct window *cwin, struct date *current_day,
     mvwaddstr(cwin->p, ofs_y, ofs_x + 4 * j, _(daynames[1 + j - sunday_first]));
   }
   custom_remove_attr(cwin->p, ATTR_HIGHEST);
+  wins_calendar_unlock();
 
   day_1_sav = (c_day_1 + 1) * 3 + c_day_1 - 7;
 
@@ -327,11 +329,12 @@ draw_monthly_view(struct window *cwin, struct date *current_day,
       ofs_x = OFFX - day_1_sav - 4 * c_day;
     }
 
-    /* This is today, so print it in yellow. */
+    wins_calendar_lock();
     if (c_day == current_day->dd
         && current_day->mm == slctd_day.mm
         && current_day->yyyy == slctd_day.yyyy
         && current_day->dd != slctd_day.dd) {
+      /* This is today, so print it in yellow. */
       custom_apply_attr(cwin->p, ATTR_LOWEST);
       mvwprintw(cwin->p, ofs_y + 1,
                 ofs_x + day_1_sav + 4 * c_day + 1, "%2d", c_day);
@@ -347,10 +350,12 @@ draw_monthly_view(struct window *cwin, struct date *current_day,
       mvwprintw(cwin->p, ofs_y + 1,
                 ofs_x + day_1_sav + 4 * c_day + 1, "%2d", c_day);
       custom_remove_attr(cwin->p, ATTR_LOW);
-    } else
+    } else {
       /* otherwise, print normal days in black */
       mvwprintw(cwin->p, ofs_y + 1,
                 ofs_x + day_1_sav + 4 * c_day + 1, "%2d", c_day);
+    }
+    wins_calendar_unlock();
   }
 }
 
@@ -454,9 +459,11 @@ draw_weekly_view(struct window *cwin, struct date *current_day,
 
   /* Print the week number. */
   weeknum = ISO8601weeknum(&t);
+  wins_calendar_lock();
   custom_apply_attr(cwin->p, ATTR_HIGHEST);
   mvwprintw(cwin->p, 2, cwin->w - 9, "(# %02d)", weeknum);
   custom_remove_attr(cwin->p, ATTR_HIGHEST);
+  wins_calendar_unlock();
 
   /* Now draw calendar view. */
   for (j = 0; j < WEEKINDAYS; j++) {
@@ -488,22 +495,28 @@ draw_weekly_view(struct window *cwin, struct date *current_day,
     else
       attr = 0;
 
+    wins_calendar_lock();
     if (attr)
       custom_apply_attr(cwin->p, attr);
     mvwprintw(cwin->p, OFFY + 1, OFFX + 1 + 4 * j, "%02d", t.tm_mday);
     if (attr)
       custom_remove_attr(cwin->p, attr);
+    wins_calendar_unlock();
 
     /* Draw slices indicating appointment times. */
     memset(slices, 0, DAYSLICESNO * sizeof *slices);
     if (day_chk_busy_slices(date, DAYSLICESNO, slices)) {
       for (i = 0; i < DAYSLICESNO; i++) {
-        if (j != WEEKINDAYS - 1 && i != DAYSLICESNO - 1)
+        if (j != WEEKINDAYS - 1 && i != DAYSLICESNO - 1) {
+          wins_calendar_lock();
           mvwhline(cwin->p, OFFY + 2 + i, OFFX + 3 + 4 * j, ACS_S9, 2);
+          wins_calendar_unlock();
+        }
         if (slices[i]) {
           int highlight;
 
           highlight = (t.tm_mday == slctd_day.dd) ? 1 : 0;
+          wins_calendar_lock();
           if (highlight)
             custom_apply_attr(cwin->p, attr);
           wattron(cwin->p, A_REVERSE);
@@ -512,6 +525,7 @@ draw_weekly_view(struct window *cwin, struct date *current_day,
           wattroff(cwin->p, A_REVERSE);
           if (highlight)
             custom_remove_attr(cwin->p, attr);
+          wins_calendar_unlock();
         }
       }
     }
@@ -521,11 +535,13 @@ draw_weekly_view(struct window *cwin, struct date *current_day,
   }
 
   /* Draw marks to indicate midday on the sides of the calendar. */
+  wins_calendar_lock();
   custom_apply_attr(cwin->p, ATTR_HIGHEST);
   mvwhline(cwin->p, OFFY + 1 + DAYSLICESNO / 2, OFFX, ACS_S9, 1);
   mvwhline(cwin->p, OFFY + 1 + DAYSLICESNO / 2,
            OFFX + WCALWIDTH - 3, ACS_S9, 1);
   custom_remove_attr(cwin->p, ATTR_HIGHEST);
+  wins_calendar_unlock();
 
 #undef DAYSLICESNO
 }
@@ -537,8 +553,12 @@ void calendar_update_panel(struct window *cwin)
   unsigned sunday_first;
 
   calendar_store_current_date(&current_day);
+
+  wins_calendar_lock();
   erase_window_part(cwin->p, 1, 3, cwin->w - 2, cwin->h - 2);
   mvwhline(cwin->p, 2, 1, ACS_HLINE, cwin->w - 2);
+  wins_calendar_unlock();
+
   sunday_first = calendar_week_begins_on_monday()? 0 : 1;
 
   draw_calendar[calendar_view] (cwin, &current_day, sunday_first);
diff --git a/src/notify.c b/src/notify.c
index 10bc0f7..6ac94b9 100644
--- a/src/notify.c
+++ b/src/notify.c
@@ -240,11 +240,13 @@ void notify_update_bar(void)
   app_pos = file_pos + strlen(notify.apts_file) + 2 + space;
   txt_max_len = col - (app_pos + 12 + space);
 
+  wins_nbar_lock();
   custom_apply_attr(notify.win, ATTR_HIGHEST);
   wattron(notify.win, A_UNDERLINE | A_REVERSE);
   mvwhline(notify.win, 0, 0, ACS_HLINE, col);
   mvwprintw(notify.win, 0, date_pos, "[ %s | %s ]", notify.date, notify.time);
   mvwprintw(notify.win, 0, file_pos, "(%s)", notify.apts_file);
+  wins_nbar_unlock();
 
   pthread_mutex_lock(&notify_app.mutex);
   if (notify_app.got_app) {
@@ -271,6 +273,7 @@ void notify_update_bar(void)
       else
         blinking = 0;
 
+      wins_nbar_lock();
       if (blinking)
         wattron(notify.win, A_BLINK);
       if (too_long)
@@ -281,6 +284,7 @@ void notify_update_bar(void)
                   hours_left, minutes_left, notify_app.txt);
       if (blinking)
         wattroff(notify.win, A_BLINK);
+      wins_nbar_unlock();
 
       if (blinking)
         notify_launch_cmd();
@@ -295,8 +299,10 @@ void notify_update_bar(void)
   }
   pthread_mutex_unlock(&notify_app.mutex);
 
+  wins_nbar_lock();
   wattroff(notify.win, A_UNDERLINE | A_REVERSE);
   custom_remove_attr(notify.win, ATTR_HIGHEST);
+  wins_nbar_unlock();
   wins_wrefresh(notify.win);
 
   pthread_mutex_unlock(&notify.mutex);
diff --git a/src/wins.c b/src/wins.c
index d518377..64dd962 100644
--- a/src/wins.c
+++ b/src/wins.c
@@ -76,6 +76,32 @@ static void screen_release(void)
   pthread_mutex_unlock(&screen_mutex);
 }
 
+/*
+ * FIXME: The following functions currently lock the whole screen. Use both
+ * window-level and screen-level mutexes (or use use_screen() and use_window(),
+ * see curs_threads(3)) to avoid locking too much.
+ */
+
+unsigned wins_nbar_lock(void)
+{
+  return screen_acquire();
+}
+
+void wins_nbar_unlock(void)
+{
+  screen_release();
+}
+
+unsigned wins_calendar_lock(void)
+{
+  return screen_acquire();
+}
+
+void wins_calendar_unlock(void)
+{
+  screen_release();
+}
+
 int wins_refresh(void)
 {
   int rc;
@@ -476,10 +502,12 @@ static void border_nocolor(WINDOW * window)
 void wins_update_border(int flags)
 {
   if (flags & FLAG_CAL) {
+    wins_calendar_lock();
     if (slctd_win == CAL)
       border_color(win[CAL].p);
     else
       border_nocolor(win[CAL].p);
+    wins_calendar_unlock();
   }
   if (flags & FLAG_APP) {
     if (slctd_win == APP)