Fix bug #10075 with cursor drawing in an hscrolled window.

 src/xdisp.c (x_write_glyphs, draw_phys_cursor_glyph)
 (erase_phys_cursor, update_window_cursor, show_mouse_face)
 (cursor_in_mouse_face_p): If the cursor position is out of bounds,
 behave as if the cursor position were at the window margin.
 src/window.c (get_phys_cursor_glyph): If the window is hscrolled,
 and the cursor position is out of bounds, behave as if the cursor
 position were at the window margin.

3 files changed, 107 insertions, 15 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 1fff4517c0b..2973ecc4b57 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2011-11-19  Eli Zaretskii  <eliz@gnu.org>
+
+        * xdisp.c (x_write_glyphs, draw_phys_cursor_glyph)
+        (erase_phys_cursor, update_window_cursor, show_mouse_face)
+        (cursor_in_mouse_face_p): If the cursor position is out of bounds,
+        behave as if the cursor position were at the window margin.
+
+        * window.c (get_phys_cursor_glyph): If the window is hscrolled,
+        and the cursor position is out of bounds, behave as if the cursor
+        position were at the window margin.  (Bug#10075)
+
 2011-11-18  Chong Yidong  <cyd@gnu.org>
 
         * window.c (Fwindow_combination_limit): Make first argument
diff --git a/src/window.c b/src/window.c
index ae0c7431f74..776f097b59e 100644
--- a/src/window.c
+++ b/src/window.c
@@ -5773,13 +5773,30 @@ get_phys_cursor_glyph (struct window *w)
 {
   struct glyph_row *row;
   struct glyph *glyph;
+  int hpos = w->phys_cursor.hpos;
 
-  if (w->phys_cursor.vpos >= 0
-      && w->phys_cursor.vpos < w->current_matrix->nrows
-      && (row = MATRIX_ROW (w->current_matrix, w->phys_cursor.vpos),
-          row->enabled_p)
-      && row->used[TEXT_AREA] > w->phys_cursor.hpos)
-    glyph = row->glyphs[TEXT_AREA] + w->phys_cursor.hpos;
+  if (!(w->phys_cursor.vpos >= 0
+        && w->phys_cursor.vpos < w->current_matrix->nrows))
+    return NULL;
+
+  row = MATRIX_ROW (w->current_matrix, w->phys_cursor.vpos);
+  if (!row->enabled_p)
+    return NULL;
+
+  if (w->hscroll)
+    {
+      /* When the window is hscrolled, cursor hpos can legitimately be
+         out of bounds, but we draw the cursor at the corresponding
+         window margin in that case.  */
+      if (!row->reversed_p && hpos < 0)
+        hpos = 0;
+      if (row->reversed_p && hpos >= row->used[TEXT_AREA])
+        hpos = row->used[TEXT_AREA] - 1;
+    }
+
+  if (row->used[TEXT_AREA] > hpos
+      && 0 <= hpos)
+    glyph = row->glyphs[TEXT_AREA] + hpos;
   else
     glyph = NULL;
 
diff --git a/src/xdisp.c b/src/xdisp.c
index 1c913ca9612..bc7a7a053db 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -24671,9 +24671,17 @@ x_produce_glyphs (struct it *it)
 void
 x_write_glyphs (struct glyph *start, int len)
 {
-  int x, hpos;
+  int x, hpos, chpos = updated_window->phys_cursor.hpos;
 
   xassert (updated_window && updated_row);
+  /* When the window is hscrolled, cursor hpos can legitimately be out
+     of bounds, but we draw the cursor at the corresponding window
+     margin in that case.  */
+  if (!updated_row->reversed_p && chpos < 0)
+    chpos = 0;
+  if (updated_row->reversed_p && chpos >= updated_row->used[TEXT_AREA])
+    chpos = updated_row->used[TEXT_AREA] - 1;
+
   BLOCK_INPUT;
 
   /* Write glyphs.  */
@@ -24688,8 +24696,8 @@ x_write_glyphs (struct glyph *start, int len)
   if (updated_area == TEXT_AREA
       && updated_window->phys_cursor_on_p
       && updated_window->phys_cursor.vpos == output_cursor.vpos
-      && updated_window->phys_cursor.hpos >= hpos
-      && updated_window->phys_cursor.hpos < hpos + len)
+      && chpos >= hpos
+      && chpos < hpos + len)
     updated_window->phys_cursor_on_p = 0;
 
   UNBLOCK_INPUT;
@@ -25199,8 +25207,17 @@ draw_phys_cursor_glyph (struct window *w, struct glyph_row *row,
     {
       int on_p = w->phys_cursor_on_p;
       int x1;
-      x1 = draw_glyphs (w, w->phys_cursor.x, row, TEXT_AREA,
-                        w->phys_cursor.hpos, w->phys_cursor.hpos + 1,
+      int hpos = w->phys_cursor.hpos;
+
+      /* When the window is hscrolled, cursor hpos can legitimately be
+         out of bounds, but we draw the cursor at the corresponding
+         window margin in that case.  */
+      if (!row->reversed_p && hpos < 0)
+        hpos = 0;
+      if (row->reversed_p && hpos >= row->used[TEXT_AREA])
+        hpos = row->used[TEXT_AREA] - 1;
+
+      x1 = draw_glyphs (w, w->phys_cursor.x, row, TEXT_AREA, hpos, hpos + 1,
                         hl, 0);
       w->phys_cursor_on_p = on_p;
 
@@ -25288,6 +25305,14 @@ erase_phys_cursor (struct window *w)
        : (w->phys_cursor.hpos >= cursor_row->used[TEXT_AREA])))
     goto mark_cursor_off;
 
+  /* When the window is hscrolled, cursor hpos can legitimately be out
+     of bounds, but we draw the cursor at the corresponding window
+     margin in that case.  */
+  if (!cursor_row->reversed_p && hpos < 0)
+    hpos = 0;
+  if (cursor_row->reversed_p && hpos >= cursor_row->used[TEXT_AREA])
+    hpos = cursor_row->used[TEXT_AREA] - 1;
+
   /* If the cursor is in the mouse face area, redisplay that when
      we clear the cursor.  */
   if (! NILP (hlinfo->mouse_face_window)
@@ -25431,8 +25456,26 @@ update_window_cursor (struct window *w, int on)
      of being deleted.  */
   if (w->current_matrix)
     {
+      int hpos = w->phys_cursor.hpos;
+      int vpos = w->phys_cursor.vpos;
+      struct glyph_row *row;
+
+      if (vpos >= w->current_matrix->nrows
+          || hpos >= w->current_matrix->matrix_w)
+        return;
+
+      row = MATRIX_ROW (w->current_matrix, vpos);
+
+      /* When the window is hscrolled, cursor hpos can legitimately be
+         out of bounds, but we draw the cursor at the corresponding
+         window margin in that case.  */
+      if (!row->reversed_p && hpos < 0)
+        hpos = 0;
+      if (row->reversed_p && hpos >= row->used[TEXT_AREA])
+        hpos = row->used[TEXT_AREA] - 1;
+
       BLOCK_INPUT;
-      display_and_set_cursor (w, on, w->phys_cursor.hpos, w->phys_cursor.vpos,
+      display_and_set_cursor (w, on, hpos, vpos,
                               w->phys_cursor.x, w->phys_cursor.y);
       UNBLOCK_INPUT;
     }
@@ -25602,9 +25645,18 @@ show_mouse_face (Mouse_HLInfo *hlinfo, enum draw_glyphs_face draw)
       if (FRAME_WINDOW_P (f)
           && phys_cursor_on_p && !w->phys_cursor_on_p)
         {
+          int hpos = w->phys_cursor.hpos;
+
+          /* When the window is hscrolled, cursor hpos can legitimately be
+             out of bounds, but we draw the cursor at the corresponding
+             window margin in that case.  */
+          if (!row->reversed_p && hpos < 0)
+            hpos = 0;
+          if (row->reversed_p && hpos >= row->used[TEXT_AREA])
+            hpos = row->used[TEXT_AREA] - 1;
+
           BLOCK_INPUT;
-          display_and_set_cursor (w, 1,
-                                  w->phys_cursor.hpos, w->phys_cursor.vpos,
+          display_and_set_cursor (w, 1, hpos, w->phys_cursor.vpos,
                                   w->phys_cursor.x, w->phys_cursor.y);
           UNBLOCK_INPUT;
         }
@@ -25703,7 +25755,19 @@ coords_in_mouse_face_p (struct window *w, int hpos, int vpos)
 int
 cursor_in_mouse_face_p (struct window *w)
 {
-  return coords_in_mouse_face_p (w, w->phys_cursor.hpos, w->phys_cursor.vpos);
+  int hpos = w->phys_cursor.hpos;
+  int vpos = w->phys_cursor.vpos;
+  struct glyph_row *row = MATRIX_ROW (w->current_matrix, vpos);
+
+  /* When the window is hscrolled, cursor hpos can legitimately be out
+     of bounds, but we draw the cursor at the corresponding window
+     margin in that case.  */
+  if (!row->reversed_p && hpos < 0)
+    hpos = 0;
+  if (row->reversed_p && hpos >= row->used[TEXT_AREA])
+    hpos = row->used[TEXT_AREA] - 1;
+
+  return coords_in_mouse_face_p (w, hpos, vpos);
 }