New feature: highlight differences between snapshots.

1 files changed, 57 insertions, 13 deletions

diff --git a/pw.c b/pw.c
index d1a652f..4c52ab8 100644
--- a/pw.c
+++ b/pw.c
@@ -410,17 +410,28 @@ static void hloff(int *phlite)
        hloff(&hlite);                                                         \
   } while (0)
 
-static void drawline(pwstate *pw, const char *line, int lineno, char *diffline)
+#define with_hlonoff(onoff, hlite, expr)                                      \
+  do {                                                                        \
+    (onoff ? hlon : hloff)(&hlite);                                           \
+    expr;                                                                     \
+  } while(0)
+
+static int diff(const char *line, const char *dline, int dlen, int i)
+{
+  return i >= dlen || line[i] != dline[i];
+}
+
+static void drawline(pwstate *pw, const char *line, int lineno, char *dline)
 {
-  const char *oline = line;
   int olen = (int) dslen(line), len = olen, pos = 0;
+  int dlen = dslen(dline);
   int columns = pw->columns;
   int vsplit1 = pw->vsplit1;
   int vsplit2 = pw->vsplit2;
   int vs2pos = pw->vs2pos;
   int endmark = 0;
   int hlpanel = (pw->stat & stat_hlite) != 0;
-  int hldiff = (pw->stat & stat_diff) != 0 && diffline != 0;
+  int hldiff = (pw->stat & stat_diff) != 0 && dline != 0;
   int hlite = 0;
 
   if (lineno >= 0)
@@ -429,11 +440,21 @@ static void drawline(pwstate *pw, const char *line, int lineno, char *diffline)
   if (vsplit1 > 0) {
     if (len <= vsplit1) {
       if (!vsplit2) {
-        fputs(line, stdout);
+        if (!hldiff)
+          fputs(line, stdout);
+        else
+          for (int i = 0; i < len; i++)
+            with_hlonoff (diff(line, dline, dlen, i), hlite, putchar(line[i]));
         columns -= len;
       } else {
         int spaces = vsplit1 - len;
-        fputs(line, stdout);
+        if (!hldiff)
+          fputs(line, stdout);
+        else
+          for (int i = 0; i < len; i++)
+            with_hlonoff (diff(line, dline, dlen, i), hlite, putchar(line[i]));
+        if (spaces)
+          hloff(&hlite);
         for (int i = 0; i < spaces; i++)
           putchar(' ');
         columns -= vsplit1;
@@ -441,8 +462,12 @@ static void drawline(pwstate *pw, const char *line, int lineno, char *diffline)
       pos += len;
       len = 0;
     } else {
-      for (int i = 0; i < vsplit1; i++)
-        putchar(line[i]);
+      if (!hldiff)
+        for (int i = 0; i < vsplit1; i++)
+          putchar(line[i]);
+      else
+        for (int i = 0; i < vsplit1; i++)
+          with_hlonoff (diff(line, dline, dlen, i), hlite, putchar(line[i]));
       len -= vsplit1;
       pos += vsplit1;
       columns -= vsplit1;
@@ -461,13 +486,19 @@ static void drawline(pwstate *pw, const char *line, int lineno, char *diffline)
 
     if (vs2pos < olen) {
       int nchar = min(olen - vs2pos, width);
-      const char *ptr = oline + vs2pos + i;
-      for (; i < nchar; i++)
-        putchar(*ptr++);
+      if (!hldiff)
+        for (; i < nchar; i++)
+          putchar(line[vs2pos + i]);
+      else
+        for (; i < nchar; i++)
+          with_hlonoff (diff(line, dline, dlen, vs2pos + i), hlite,
+                        putchar(line[vs2pos + i]));
       endmark = 1;
     }
 
     if (len > vsplit2 + pw->hpos) {
+      if (i < width)
+        hloff(&hlite);
       for (; i < width; i++)
         putchar(' ');
 
@@ -489,12 +520,23 @@ static void drawline(pwstate *pw, const char *line, int lineno, char *diffline)
       with_hl (hlpanel, hldiff, hlite, putchar('>'));
       columns--;
     }
+
     if (len < columns) {
-      fputs(line + pos, stdout);
+      if (!hldiff)
+        fputs(line + pos, stdout);
+      else
+        for (; pos < olen; pos++)
+          with_hlonoff (diff(line, dline, dlen, pos), hlite,
+                        putchar(line[pos]));
       clreol(1);
     } else {
-      for (int i = 0; i < columns - 1; i++)
-        putchar(line[pos + i]);
+      if (!hldiff)
+        for (int i = 0; i < columns - 1; i++)
+          putchar(line[pos + i]);
+      else
+        for (int i = 0; i < columns - 1; i++)
+          with_hlonoff (diff(line, dline, dlen, pos + i), hlite,
+                        putchar(line[pos + i]));
       with_hl (hlpanel, hldiff, hlite, putchar('<'));
       putchar('\n');
     }
@@ -598,6 +640,8 @@ static void redraw(pwstate *pw)
       pw->stat |= stat_susp;
     pw->stat &= ~(stat_dirty | stat_trgrd | stat_oneshot);
     updln = 1;
+    if (pw->prevhist == 0 && pw->hist == 0)
+      pw->prevhist = 1;
   } else if ((pw->stat & stat_force)) {
     pw->stat &= ~stat_force;
     updln = 1;