Richard's lazy-scrolling patch. This builds up scroll operations in a list,

combining adjacent ones for the same region, and runs them all in do_paint.
I'm not sure it's entirely right, but it works on my Mac in every case I've
tested.

[originally from svn r2763]

mac/macterm.c

@@ -1,4 +1,4 @@
-/* $Id: macterm.c,v 1.60 2003/01/28 00:35:54 ben Exp $ */
+/* $Id: macterm.c,v 1.61 2003/02/01 12:26:33 ben Exp $ */
 /*
  * Copyright (c) 1999 Simon Tatham
  * Copyright (c) 1999, 2002 Ben Harris
@@ -1506,8 +1506,8 @@ void palette_reset(void *frontend) {
  * Scroll the screen. (`lines' is +ve for scrolling forward, -ve
  * for backward.)
  */
-void do_scroll(void *frontend, int topline, int botline, int lines) {
-    Session *s = frontend;
+void do_scroll(Context ctx, int topline, int botline, int lines) {
+    Session *s = ctx;
     Rect r;
     RgnHandle scrollrgn = NewRgn();
     RgnHandle movedupdate = NewRgn();

putty.h

@@ -494,7 +494,7 @@ void do_text(Context, int, int, char *, int, unsigned long, int);
 void do_cursor(Context, int, int, char *, int, unsigned long, int);
 int char_width(Context ctx, int uc);
 #ifdef OPTIMISE_SCROLL
-void do_scroll(void *, int, int, int);
+void do_scroll(Context, int, int, int);
 #endif
 void set_title(void *frontend, char *);
 void set_icon(void *frontend, char *);

terminal.c

@@ -381,6 +381,9 @@ Terminal *term_init(Config *mycfg, struct unicode_data *ucsdata,
     term->rows = term->cols = -1;
     power_on(term);
     term->beephead = term->beeptail = NULL;
+#ifdef OPTIMISE_SCROLL
+    term->scrollhead = term->scrolltail = NULL;
+#endif /* OPTIMISE_SCROLL */
     term->nbeeps = 0;
     term->lastbeep = FALSE;
     term->beep_overloaded = FALSE;
@@ -794,6 +797,35 @@ static void scroll(Terminal *term, int topline, int botline, int lines, int sb)
 }
 
 #ifdef OPTIMISE_SCROLL
+/*
+ * Add a scroll of a region on the screen into the pending scroll list.
+ * `lines' is +ve for scrolling forward, -ve for backward.
+ *
+ * If the scroll is on the same area as the last scroll in the list,
+ * merge them.
+ */
+void save_scroll(Terminal *term, int topline, int botline, int lines)
+{
+    struct scrollregion *newscroll;
+    if (term->scrolltail &&
+	term->scrolltail->topline == topline && 
+	term->scrolltail->botline == botline) {
+	term->scrolltail->lines += lines;
+    } else {
+	newscroll = smalloc(sizeof(struct scrollregion));
+	newscroll->topline = topline;
+	newscroll->botline = botline;
+	newscroll->lines = lines;
+	newscroll->next = NULL;
+
+	if (!term->scrollhead)
+	    term->scrollhead = newscroll;
+	else
+	    term->scrolltail->next = newscroll;
+	term->scrolltail = newscroll;
+    }
+}
+
 /*
  * Scroll the physical display, and our conception of it in disptext.
  */
@@ -820,7 +852,7 @@ static void scroll_display(Terminal *term, int topline, int botline, int lines)
 	for (i = 0; i < distance; i++)
 	    start[i] |= ATTR_INVALID;
     }
-    do_scroll(term->frontend, topline, botline, lines);
+    save_scroll(term, topline, botline, lines);
 }
 #endif /* OPTIMISE_SCROLL */
 
@@ -3087,6 +3119,9 @@ static void do_paint(Terminal *term, Context ctx, int may_optimise)
     char ch[1024];
     long cursor_background = ERASE_CHAR;
     unsigned long ticks;
+#ifdef OPTIMISE_SCROLL
+    struct scrollregion *sr;
+#endif /* OPTIMISE_SCROLL */
 
     /*
      * Check the visual bell state.
@@ -3149,6 +3184,18 @@ static void do_paint(Terminal *term, Context ctx, int may_optimise)
     }
     term->dispcurs = NULL;
 
+#ifdef OPTIMISE_SCROLL
+    /* Do scrolls */
+    sr = term->scrollhead;
+    while (sr) {
+	struct scrollregion *next = sr->next;
+	do_scroll(ctx, sr->topline, sr->botline, sr->lines);
+	sfree(sr);
+	sr = next;
+    }
+    term->scrollhead = term->scrolltail = NULL;
+#endif /* OPTIMISE_SCROLL */
+
     /* The normal screen data */
     for (i = 0; i < term->rows; i++) {
 	unsigned long *ldata;

terminal.h

@@ -20,6 +20,15 @@ typedef struct {
     int y, x;
 } pos;
 
+#ifdef OPTIMISE_SCROLL
+struct scrollregion {
+    struct scrollregion *next;
+    int topline; /* Top line of scroll region. */
+    int botline; /* Bottom line of scroll region. */
+    int lines; /* Number of lines to scroll by - +ve is forwards. */
+};
+#endif /* OPTIMISE_SCROLL */
+
 struct terminal_tag {
 
     int compatibility_level;
@@ -47,6 +56,10 @@ struct terminal_tag {
     term->cpos = lineptr(term->curs.y) + term->curs.x; \
 } while(0)
 
+#ifdef OPTIMISE_SCROLL
+    struct scrollregion *scrollhead, *scrolltail;
+#endif /* OPTIMISE_SCROLL */
+
     unsigned long curr_attr, save_attr;
     unsigned long erase_char;