[vte] emulation: Support CSI 3J (clear scrollback)

[Egmont Koblinger <egmontkob src gnome org>]

commit 3111d44927ee755c07eb5c51656935770b0ce59b
Author: Egmont Koblinger <egmont gmail com>
Date:   Sun Dec 28 23:53:22 2014 +0100

    emulation: Support CSI 3J (clear scrollback)
    
    https://bugzilla.gnome.org/show_bug.cgi?id=678042

 src/caps.c        |    8 ++++----
 src/ring.c        |   21 ++++++++++++++++++++-
 src/ring.h        |    1 +
 src/vte-private.h |    1 +
 src/vte.c         |   14 ++++++++++++++
 src/vteseq.c      |   10 ++++++++--
 6 files changed, 48 insertions(+), 7 deletions(-)
---
diff --git a/src/caps.c b/src/caps.c
index edeb97d..b51882f 100644
--- a/src/caps.c
+++ b/src/caps.c
@@ -136,13 +136,13 @@ const char _vte_xterm_capability_strings[] =
         ENTRY(CSI "I", "cursor-forward-tabulation")
         ENTRY(CSI "%dI", "cursor-forward-tabulation")
         ENTRY(CSI "J", "erase-in-display")
-        ENTRY(CSI "%dJ", "erase-in-display")
+        ENTRY(CSI "%mJ", "erase-in-display")
         ENTRY(CSI "?J", "selective-erase-in-display")
-        ENTRY(CSI "?%dJ", "selective-erase-in-display")
+        ENTRY(CSI "?%mJ", "selective-erase-in-display")
         ENTRY(CSI "K", "erase-in-line")
-        ENTRY(CSI "%dK", "erase-in-line")
+        ENTRY(CSI "%mK", "erase-in-line")
         ENTRY(CSI "?K", "selective-erase-in-line")
-        ENTRY(CSI "?%dK", "selective-erase-in-line")
+        ENTRY(CSI "?%mK", "selective-erase-in-line")
         ENTRY(CSI "L", "insert-lines")
         ENTRY(CSI "%dL", "insert-lines")
         ENTRY(CSI "M", "delete-lines")
diff --git a/src/ring.c b/src/ring.c
index 5364aeb..f3fccc6 100644
--- a/src/ring.c
+++ b/src/ring.c
@@ -616,12 +616,31 @@ _vte_ring_append (VteRing * ring)
 
 
 /**
+ * _vte_ring_drop_scrollback:
+ * @ring: a #VteRing
+ * @position: drop contents up to this point, which must be in the writable region.
+ *
+ * Drop the scrollback (offscreen contents).
+ *
+ * TODOegmont: We wouldn't need the position argument after addressing 708213#c29.
+ */
+void
+_vte_ring_drop_scrollback (VteRing * ring, gulong position)
+{
+        _vte_ring_ensure_writable (ring, position);
+
+        ring->start = ring->writable = position;
+        _vte_ring_reset_streams (ring, position);
+}
+
+
+/**
  * _vte_ring_set_visible_rows:
  * @ring: a #VteRing
  *
  * Set the number of visible rows.
  * It's required to be set correctly for the alternate screen so that it
- * never hits the streams.
+ * never hits the streams. It's also required for clearing the scrollback.
  */
 void
 _vte_ring_set_visible_rows (VteRing *ring, gulong rows)
diff --git a/src/ring.h b/src/ring.h
index 7e6078a..58b8731 100644
--- a/src/ring.h
+++ b/src/ring.h
@@ -87,6 +87,7 @@ void _vte_ring_shrink (VteRing *ring, gulong max_len);
 VteRowData *_vte_ring_insert (VteRing *ring, gulong position);
 VteRowData *_vte_ring_append (VteRing *ring);
 void _vte_ring_remove (VteRing *ring, gulong position);
+void _vte_ring_drop_scrollback (VteRing *ring, gulong position);
 void _vte_ring_set_visible_rows (VteRing *ring, gulong rows);
 void _vte_ring_rewrap (VteRing *ring, glong columns, VteVisualPosition **markers);
 gboolean _vte_ring_write_contents (VteRing *ring,
diff --git a/src/vte-private.h b/src/vte-private.h
index dded036..3a40131 100644
--- a/src/vte-private.h
+++ b/src/vte-private.h
@@ -474,6 +474,7 @@ void _vte_terminal_queue_contents_changed(VteTerminal *terminal);
 void _vte_terminal_emit_text_deleted(VteTerminal *terminal);
 void _vte_terminal_emit_text_inserted(VteTerminal *terminal);
 void _vte_terminal_cursor_down (VteTerminal *terminal);
+void _vte_terminal_drop_scrollback (VteTerminal *terminal);
 void _vte_terminal_restore_cursor (VteTerminal *terminal, VteScreen *screen);
 void _vte_terminal_save_cursor (VteTerminal *terminal, VteScreen *screen);
 gboolean _vte_terminal_insert_char(VteTerminal *terminal, gunichar c,
diff --git a/src/vte.c b/src/vte.c
index 362aa3b..59eceec 100644
--- a/src/vte.c
+++ b/src/vte.c
@@ -3025,6 +3025,20 @@ _vte_terminal_cursor_down (VteTerminal *terminal)
        }
 }
 
+/* Drop the scrollback. */
+void
+_vte_terminal_drop_scrollback (VteTerminal *terminal)
+{
+        /* Only for normal screen; alternate screen doesn't have a scrollback. */
+        _vte_ring_drop_scrollback (terminal->pvt->normal_screen.row_data,
+                                   terminal->pvt->normal_screen.insert_delta);
+
+        if (terminal->pvt->screen == &terminal->pvt->normal_screen) {
+                vte_terminal_queue_adjustment_value_changed (terminal, 
terminal->pvt->normal_screen.insert_delta);
+                _vte_terminal_adjust_adjustments_full (terminal);
+        }
+}
+
 /* Restore cursor on a screen. */
 void
 _vte_terminal_restore_cursor (VteTerminal *terminal, VteScreen *screen)
diff --git a/src/vteseq.c b/src/vteseq.c
index 4d2b461..b2f4b7d 100644
--- a/src/vteseq.c
+++ b/src/vteseq.c
@@ -2470,13 +2470,14 @@ vte_sequence_handler_erase_in_display (VteTerminal *terminal, GValueArray *param
        guint i;
        /* The default parameter is 0. */
        param = 0;
-       /* Pull out a parameter. */
+        /* Pull out the first parameter. */
        for (i = 0; (params != NULL) && (i < params->n_values); i++) {
                value = g_value_array_get_nth(params, i);
                if (!G_VALUE_HOLDS_LONG(value)) {
                        continue;
                }
                param = g_value_get_long(value);
+                break;
        }
        /* Clear the right area. */
        switch (param) {
@@ -2495,6 +2496,10 @@ vte_sequence_handler_erase_in_display (VteTerminal *terminal, GValueArray *param
                /* Clear the entire screen. */
                _vte_terminal_clear_screen (terminal);
                break;
+        case 3:
+                /* Drop the scrollback. */
+                _vte_terminal_drop_scrollback (terminal);
+                break;
        default:
                break;
        }
@@ -2511,13 +2516,14 @@ vte_sequence_handler_erase_in_line (VteTerminal *terminal, GValueArray *params)
        guint i;
        /* The default parameter is 0. */
        param = 0;
-       /* Pull out a parameter. */
+        /* Pull out the first parameter. */
        for (i = 0; (params != NULL) && (i < params->n_values); i++) {
                value = g_value_array_get_nth(params, i);
                if (!G_VALUE_HOLDS_LONG(value)) {
                        continue;
                }
                param = g_value_get_long(value);
+                break;
        }
        /* Clear the right area. */
        switch (param) {