From f46115c8fbef8b68bdb426cf7d25ba84b864cdbe Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sat, 30 Apr 2022 14:29:13 -0700
Subject: New a, d commands to advance or delay triggers.

---
 pw.1 | 10 ++++++++++
 pw.c | 28 ++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/pw.1 b/pw.1
index 1cc8bc7..0738873 100644
--- a/pw.1
+++ b/pw.1
@@ -289,6 +289,16 @@ is shown followed by the list of triggers in parentheses.
 Patterns which have a position other than 1 are preceded by
 the position shown in square brackets.
 
+.IP "[\fIcount\fP]\fBa\fP, [\fIcount\fP]\fBd\fP"
+Advance or delay the currently active triggers by
+.I count
+lines, defaulting to 1. Advancing means that all of the triggers are assigned
+to more recently received lines closer to the head of the FIFO.
+on earlier data. Delaying is the opposite: the triggers are assigned to
+less recently received items, closer to the tail of the FIFO.
+The advance/delay commands will not move any trigger to a position which
+corresponds to a line that is not displayed.
+
 .IP "[\fIcount\fP]\fB+\fP"
 Increases the display size by
 .I count
diff --git a/pw.c b/pw.c
index 4c25464..81494de 100644
--- a/pw.c
+++ b/pw.c
@@ -909,6 +909,34 @@ int main(int argc, char **argv)
             cmdbuf[1] = 0;
             curcmd = cmdbuf;
             break;
+          case 'a': case 'd':
+            if ((stat & (stat_htmode | stat_ttmode))) {
+              int step = ((((stat & stat_htmode) && ch == 'a') ||
+                           ((stat & stat_ttmode) && ch == 'd'))
+                          ? -1 : 1);
+
+              if (cmdcount == UINT_MAX)
+                cmdcount = 1;
+
+              if (step < 0) {
+                for (; cmdcount && !triglist[0]; cmdcount --) {
+                  memmove(triglist, triglist + 1,
+                          (maxtrig - 1) * sizeof *triglist);
+                  triglist[maxtrig - 1] = 0;
+                }
+              } else if (nlines <= maxtrig) {
+                for (; (cmdcount &&
+                        !triglist[nlines - 1] &&
+                        !triglist[maxtrig - 1]);
+                     cmdcount --)
+                {
+                  memmove(triglist + 1, triglist,
+                          (maxtrig - 1) * sizeof *triglist);
+                  triglist[0] = 0;
+                }
+              }
+            }
+            break;
           case '+':
             if (ws.ws_row && maxlines >= ws.ws_row - 1) {
               break;
-- 
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