Scrollback viewing position, and selection endpoints, now keep pace

with the scrollback movement. (The former is of course only
detectable when reset-scrollback-on-activity is disabled.)

git-svn-id: svn://svn.tartarus.org/sgt/putty@1266 cda61777-01e9-0310-a592-d414129be87e

diff --git a/terminal.c b/terminal.c
index 9fc1787..7300e96 100644 (file)
--- a/terminal.c
+++ b/terminal.c
@@ -587,7 +587,7 @@ static void check_selection(pos from, pos to)
 static void scroll(int topline, int botline, int lines, int sb)
 {
     unsigned long *line, *line2;
-    int i;
+    int i, seltop;
 
     if (topline != 0 || alt_which != 0)
        sb = FALSE;
@@ -637,6 +637,23 @@ static void scroll(int topline, int botline, int lines, int sb)
                }
                addpos234(scrollback, line, sblen);
                line = line2;
+
+               /*
+                * If the user is currently looking at part of the
+                * scrollback, and they haven't enabled any options
+                * that are going to reset the scrollback as a
+                * result of this movement, then the chances are
+                * they'd like to keep looking at the same line. So
+                * we move their viewpoint at the same rate as the
+                * scroll, at least until their viewpoint hits the
+                * top end of the scrollback buffer, at which point
+                * we don't have the choice any more.
+                * 
+                * Thanks to Jan Holmen Holsten for the idea and
+                * initial implementation.
+                */
+               if (disptop > -savelines && disptop < 0)
+                   disptop--;
            }
             line = resizeline(line, cols);
            for (i = 0; i < cols; i++)
@@ -644,17 +661,26 @@ static void scroll(int topline, int botline, int lines, int sb)
            line[cols + 1] = 0;
            addpos234(screen, line, botline);
 
-           if (selstart.y >= topline && selstart.y <= botline) {
+           /*
+            * If the selection endpoints move into the scrollback,
+            * we keep them moving until they hit the top. However,
+            * of course, if the line _hasn't_ moved into the
+            * scrollback then we don't do this, and cut them off
+            * at the top of the scroll region.
+            */
+           seltop = sb ? -savelines : 0;
+
+           if (selstart.y >= seltop && selstart.y <= botline) {
                selstart.y--;
-               if (selstart.y < topline) {
-                   selstart.y = topline;
+               if (selstart.y < seltop) {
+                   selstart.y = seltop;
                    selstart.x = 0;
                }
            }
-           if (selend.y >= topline && selend.y <= botline) {
+           if (selend.y >= seltop && selend.y <= botline) {
                selend.y--;
-               if (selend.y < topline) {
-                   selend.y = topline;
+               if (selend.y < seltop) {
+                   selend.y = seltop;
                    selend.x = 0;
                }
            }