gdb: Fix scrolling in TUI

Hannes Domani pointed out that my previous patch to fix the "list"
command in the TUI instead broke vertical scrolling.  While looking at
this, I found that do_scroll_vertical calls print_source_lines, which
seems like a very roundabout way to change the source window.  This
patch removes this oddity and fixes the bug at the same time.

I've added a new test case.  This is somewhat tricky, because the
obvious approach of sending a dummy command after the scroll did not
work -- due to how the TUI works, sennding a command causes the scroll
to take effect.

gdb/ChangeLog
2019-12-22  Tom Tromey  <tom@tromey.com>

	PR tui/18932:
	* tui/tui-source.c (tui_source_window::do_scroll_vertical): Call
	update_source_window, not print_source_lines.

gdb/testsuite/ChangeLog
2019-12-22  Tom Tromey  <tom@tromey.com>

	PR tui/18932:
	* lib/tuiterm.exp (Term::wait_for): Rename from _accept.  Return a
	meangingful value.
	(Term::command, Term::resize): Update.
	* gdb.tui/basic.exp: Add scrolling test.

Change-Id: I9636a7c8a8cade37431c6165ee996a9d556ef1c8

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2020-01-09  Tom Tromey  <tom@tromey.com>
+
+	PR tui/18932:
+	* tui/tui-source.c (tui_source_window::do_scroll_vertical): Call
+	update_source_window, not print_source_lines.
+
 2020-01-09  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* tui/tui.c (tui_enable): Register tui hooks after calling

gdb/testsuite/ChangeLog

@@ -1,3 +1,11 @@
+2020-01-09  Tom Tromey  <tom@tromey.com>
+
+	PR tui/18932:
+	* lib/tuiterm.exp (Term::wait_for): Rename from _accept.  Return a
+	meangingful value.
+	(Term::command, Term::resize): Update.
+	* gdb.tui/basic.exp: Add scrolling test.
+
 2020-01-09  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.tui/tui-layout-asm.exp: New file.

gdb/testsuite/gdb.tui/basic.exp

@@ -35,6 +35,19 @@ gdb_assert {![string match "No Source Available" $text]} \
 Term::command "list main"
 Term::check_contents "list main" "21 *return 0"
 
+# Get the first source line.
+set line [Term::get_line 1]
+# Send an up arrow.
+send_gdb "\033\[A"
+# Wait for a redraw and check that the first line changed.
+if {[Term::wait_for [string_to_regexp $line]] \
+	&& [Term::get_line 1] != $line\
+	&& [Term::get_line 2] == $line} {
+    pass "scroll up"
+} else {
+    fail "scroll up"
+}
+
 Term::check_box "source box" 0 0 80 15
 
 Term::command "layout asm"

gdb/testsuite/lib/tuiterm.exp

@@ -388,8 +388,10 @@ namespace eval Term {
 	_clear_lines 0 $_rows
     }
 
-    # Accept some output from gdb and update the screen.
-    proc _accept {wait_for} {
+    # Accept some output from gdb and update the screen.  WAIT_FOR is
+    # a regexp matching the line to wait for.  Return 0 on timeout, 1
+    # on success.
+    proc wait_for {wait_for} {
 	global expect_out
 	global gdb_prompt
 	variable _cur_x
@@ -424,7 +426,7 @@ namespace eval Term {
 		timeout {
 		    # Assume a timeout means we somehow missed the
 		    # expected result, and carry on.
-		    return
+		    return 0
 		}
 	    }
 
@@ -443,6 +445,8 @@ namespace eval Term {
 		set wait_for $prompt_wait_for
 	    }
 	}
+
+	return 1
     }
 
     # Like ::clean_restart, but ensures that gdb starts in an
@@ -490,7 +494,7 @@ namespace eval Term {
     # be supplied by this function.
     proc command {cmd} {
 	send_gdb "$cmd\n"
-	_accept [string_to_regexp $cmd]
+	wait_for [string_to_regexp $cmd]
     }
 
     # Return the text of screen line N, without attributes.  Lines are
@@ -682,14 +686,14 @@ namespace eval Term {
 	# Due to the strange column resizing behavior, and because we
 	# don't care about this intermediate resize, we don't check
 	# the size here.
-	_accept "@@ resize done $_resize_count"
+	wait_for "@@ resize done $_resize_count"
 	incr _resize_count
 	# Somehow the number of columns transmitted to gdb is one less
 	# than what we request from expect.  We hide this weird
 	# details from the caller.
 	_do_resize $_rows $cols
 	stty columns [expr {$_cols + 1}] < $gdb_spawn_name
-	_accept "@@ resize done $_resize_count, size = ${_cols}x${rows}"
+	wait_for "@@ resize done $_resize_count, size = ${_cols}x${rows}"
 	incr _resize_count
     }
 }

gdb/tui/tui-source.c

@@ -136,26 +136,29 @@ tui_source_window::do_scroll_vertical (int num_to_scroll)
 {
   if (!content.empty ())
     {
-      struct tui_line_or_address l;
       struct symtab *s;
       struct symtab_and_line cursal = get_current_source_symtab_and_line ();
+      struct gdbarch *arch = gdbarch;
 
       if (cursal.symtab == NULL)
-	s = find_pc_line_symtab (get_frame_pc (get_selected_frame (NULL)));
+	{
+	  struct frame_info *fi = get_selected_frame (NULL);
+	  s = find_pc_line_symtab (get_frame_pc (fi));
+	  arch = get_frame_arch (fi);
+	}
       else
 	s = cursal.symtab;
 
-      l.loa = LOA_LINE;
-      l.u.line_no = start_line_or_addr.u.line_no
-	+ num_to_scroll;
+      int line_no = start_line_or_addr.u.line_no + num_to_scroll;
       const std::vector<off_t> *offsets;
       if (g_source_cache.get_line_charpos (s, &offsets)
-	  && l.u.line_no > offsets->size ())
-	l.u.line_no = start_line_or_addr.u.line_no;
-      if (l.u.line_no <= 0)
-	l.u.line_no = 1;
+	  && line_no > offsets->size ())
+	line_no = start_line_or_addr.u.line_no;
+      if (line_no <= 0)
+	line_no = 1;
 
-      print_source_lines (s, l.u.line_no, l.u.line_no + 1, 0);
+      cursal.line = line_no;
+      update_source_window (arch, cursal);
     }
 }