[vte] Set the caret properly when the cursor is at the top left of the terminal.

[Mike Gorse <mgorse src gnome org>]

commit 3e3e3fdec8302a04c400bc7fbfa1118dbf9cbccd
Author: Jason White <jason jasonjgw net>
Date:   Wed Jan 2 12:34:53 2013 +1100

    Set the caret properly when the cursor is at the top left of the terminal.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=166637

 src/vteaccess.c |   50 ++++++++++++++++++++++++++++++++------------------
 1 files changed, 32 insertions(+), 18 deletions(-)
---
diff --git a/src/vteaccess.c b/src/vteaccess.c
index 9cb1ed4..61d98ad 100644
--- a/src/vteaccess.c
+++ b/src/vteaccess.c
@@ -340,29 +340,43 @@ vte_terminal_accessible_update_private_data_if_needed(VteTerminalAccessible *acc
        _vte_debug_print(VTE_DEBUG_ALLY,
                        "Cursor at (%ld, " "%ld).\n", ccol, crow);
 
-       /* Get the offsets to the beginnings of each line. */
        caret = -1;
-       for (i = 0; i < priv->snapshot_characters->len; i++) {
-               /* Get the attributes for the current cell. */
-               offset = g_array_index(priv->snapshot_characters,
-                                      int, i);
-               attrs = g_array_index(priv->snapshot_attributes,
-                                     struct _VteCharAttributes,
-                                     offset);
-               /* If this cell is "before" the cursor, move the
-                * caret to be "here". */
-               if ((attrs.row < crow) ||
-                   ((attrs.row == crow) && (attrs.column < ccol))) {
-                       caret = i + 1;
-               }
+       if (priv->snapshot_characters->len) {
+         /* If the cursor is at the top left of the screen, move the
+          * caret there. */
+         /* Get the attributes of the first character in the buffer. */
+         attrs = g_array_index(priv->snapshot_attributes,
+                               struct _VteCharAttributes,
+                               0);
+         if ((crow == attrs.row) &&
+             (ccol == 0)) {
+           caret = 0;
+         }
        }
 
-       /* If no cells are before the caret, then the caret must be
-        * at the end of the buffer. */
        if (caret == -1) {
-               caret = priv->snapshot_characters->len;
+         /* Get the offsets to the beginnings of each line. */
+         for (i = 0; i < priv->snapshot_characters->len; i++) {
+           /* Get the attributes for the current cell. */
+           offset = g_array_index(priv->snapshot_characters,
+                                  int, i);
+           attrs = g_array_index(priv->snapshot_attributes,
+                                 struct _VteCharAttributes,
+                                 offset);
+           /* If this cell is "before" the cursor, move the
+            * caret to be "here". */
+           if ((attrs.row < crow) ||
+               ((attrs.row == crow) && (attrs.column < ccol))) {
+             caret = i + 1;
+           }
+         }
+
+         /* If no cells are before the caret, then the caret must be
+          * at the end of the buffer. */
+         if (caret == -1) {
+           caret = priv->snapshot_characters->len;
+         }
        }
-
        /* Notify observers if the caret moved. */
        if (caret != priv->snapshot_caret) {
                priv->snapshot_caret = caret;