Eliminate wasteful redraws of snapshot.

When we do need to redraw the snapshot even though the
data isn't dirty, or we are frozen, or waiting for
a trigger, there is a new stat_force flag to request it.

1 files changed, 22 insertions, 24 deletions

diff --git a/pw.c b/pw.c
index be72687..b9868c6 100644
--- a/pw.c
+++ b/pw.c
@@ -37,7 +37,8 @@ enum status_flags {
   stat_htmode = 8,  // head trigger mode
   stat_ttmode = 16, // tail trigger mode
   stat_trgrd = 32,  // triggered flag
-  stat_grep = 64    // grep mode
+  stat_grep = 64,   // grep mode
+  stat_force = 128  // force refresh even if clean
 };
 
 typedef struct grep {
@@ -308,8 +309,8 @@ static void drawstatus(int columns, unsigned stat, char *cmd)
   fflush(stdout);
 }
 
-static void redraw(char **circbuf, int nlines, int hpos,
-                   int columns, unsigned stat, char *cmd)
+static unsigned redraw(char **circbuf, int nlines, int hpos,
+                       int columns, unsigned stat, char *cmd)
 {
   if ((stat & stat_susp) == 0 &&
       (stat & (stat_htmode | stat_trgrd)) != stat_htmode &&
@@ -325,12 +326,17 @@ static void redraw(char **circbuf, int nlines, int hpos,
       drawline(circbuf[i], hpos, columns);
       snapshot[i] = dsref(circbuf[i]);
     }
-  } else {
+    stat &= ~(stat_dirty | stat_trgrd);
+  } else if ((stat & stat_force)) {
     printf("\r\033[%dA", snaplines);
     for (int i = 0; i < snaplines; i++)
       drawline(snapshot[i], hpos, columns);
+    stat &= ~stat_force;
+  } else {
+    clrline();
   }
   drawstatus(columns, stat, cmd);
+  return stat;
 }
 
 static int getzp(const char *str, char **err)
@@ -670,8 +676,7 @@ int main(int argc, char **argv)
         if (feof(stdin) || (errno != EAGAIN && errno != EWOULDBLOCK)) {
           nfds = 1;
           stat |= stat_eof;
-          redraw(circbuf, nlines, hpos, columns, stat, curcmd);
-          stat &= ~stat_dirty;
+          stat = redraw(circbuf, nlines, hpos, columns, stat, curcmd);
           if (!ferror(stdin))
             exit_status = 0;
           if (auto_quit) {
@@ -745,6 +750,7 @@ int main(int argc, char **argv)
 
         columns = ws.ws_col;
       }
+      stat |= stat_force;
       force = 1;
     }
 
@@ -772,21 +778,16 @@ int main(int argc, char **argv)
         if ((stat & stat_dirty) && nlines == maxlines)
           force = 1;
         lasttime = now;
-        stat &= ~stat_dirty;
       }
     }
 
-    if (force) {
-      redraw(circbuf, nlines, hpos, columns, stat, curcmd);
-      stat &= ~(stat_dirty | stat_trgrd);
-    }
+    if (force)
+      stat = redraw(circbuf, nlines, hpos, columns, stat, curcmd);
 
     if (poll(pe, nfds, pollms) <= 0) {
       if (pollms) {
-        if ((stat & stat_dirty) && nlines == maxlines) {
-          redraw(circbuf, nlines, hpos, columns, stat, curcmd);
-          stat &= ~stat_dirty;
-        }
+        if ((stat & stat_dirty) && nlines == maxlines)
+          stat = redraw(circbuf, nlines, hpos, columns, stat, curcmd);
         if (kbd_state == kbd_esc || kbd_state == kbd_result) {
           kbd_state = kbd_cmd;
           curcmd = 0;
@@ -808,8 +809,7 @@ int main(int argc, char **argv)
           ttyset(ttyfd, &tty_new);
           for (int i = 0; i < nlines; i++)
             puts("");
-          redraw(circbuf, nlines, hpos, columns, stat, curcmd);
-          stat &= ~stat_dirty;
+          stat = redraw(circbuf, nlines, hpos, columns, stat | stat_force, curcmd);
           continue;
         }
 
@@ -828,26 +828,25 @@ int main(int argc, char **argv)
           case 'h':
             if (hpos >= 8) {
               hpos -= 8;
-              stat |= stat_dirty;
+              stat |= stat_force;
             }
             break;
           case 'l':
             if (hpos < 10000) {
               hpos += 8;
-              stat |= stat_dirty;
+              stat |= stat_force;
             }
             break;
           case '0':
             hpos = 0;
-            stat |= stat_dirty;
+            stat |= stat_force;
             break;
           case ' ':
             if ((stat & stat_eof) == 0)
-              stat |= (stat_dirty | stat_susp);
+              stat |= stat_susp;
             break;
           case CR:
             stat &= ~stat_susp;
-            stat |= stat_dirty;
             break;
           case ESC:
             kbd_prev = kbd_state;
@@ -1044,8 +1043,7 @@ int main(int argc, char **argv)
         }
 
         if ((stat & stat_dirty)) {
-          redraw(circbuf, nlines, hpos, columns, stat, curcmd);
-          stat &= ~stat_dirty;
+          stat = redraw(circbuf, nlines, hpos, columns, stat, curcmd);
         } else switch (kbd_state) {
         case kbd_colon: case kbd_trig: case kbd_result: case kbd_cmd:
           clrline();