[vte] emulation: Fix DECSTBM parameters

[Christian Persch <chpe src gnome org>]

commit 02521cba6add9374f716b1e774a4943cccc626ad
Author: Christian Persch <chpe src gnome org>
Date:   Tue Mar 27 19:40:13 2018 +0200

    emulation: Fix DECSTBM parameters
    
    The comment about requiring 2 lines was inaccurate;
    xterm does not actually work like that.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=791451

 src/vteseq.cc |   13 +++++--------
 1 files changed, 5 insertions(+), 8 deletions(-)
---
diff --git a/src/vteseq.cc b/src/vteseq.cc
index 371bbb1..60a30a8 100644
--- a/src/vteseq.cc
+++ b/src/vteseq.cc
@@ -3486,23 +3486,20 @@ VteTerminalPrivate::DECSTBM(vte::parser::Sequence const& seq)
         seq.collect(0, {&start, &end});
 
         /* Defaults */
-        if (start == -1)
+        if (start <= 0)
                 start = 1;
         if (end == -1)
                 end = m_row_count;
 
-        /* Bail out on garbage, require at least 2 rows, as per xterm. */
-        // FIXMEchpe
-        if (start < 1 || start > m_row_count ||
-            end < (start + 1)) {
+        if (start > m_row_count ||
+            end <= start) {
                 m_scrolling_restricted = FALSE;
                 home_cursor();
                 return;
         }
-        // FIXMEchpe why not reset here too?
-        if (end > m_row_count) {
+
+        if (end > m_row_count)
                 end = m_row_count;
-       }
 
        /* Set the right values. */
         m_scrolling_region.start = start - 1;