Fix redisplay of large images on expose events

* src/xdisp.c (expose_window, expose_area): Avoid comparisons
between signed negative values and unsigned values.  This
prevented redisplay on expose events when the window showed a very
large image.

1 files changed, 14 insertions, 6 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 2be057fd211..5a89f4c988b 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -30061,8 +30061,11 @@ expose_area (struct window *w, struct glyph_row *row, XRectangle *r,
       /* Find the last one.  */
       last = first;
       first_x = x;
-      while (last < end
-             && x < r->x + r->width)
+      /* Use a signed int intermediate value to avoid catastrophic
+         failures due to comparison between signed and unsigned, when
+         x is negative (can happen for wide images that are hscrolled).  */
+      int r_end = r->x + r->width;
+      while (last < end && x < r_end)
         {
           x += last->pixel_width;
           ++last;
@@ -30336,6 +30339,11 @@ expose_window (struct window *w, XRectangle *fr)
          check later if it is changed.  */
       bool phys_cursor_on_p = w->phys_cursor_on_p;
 
+      /* Use a signed int intermediate value to avoid catastrophic
+         failures due to comparison between signed and unsigned, when
+         y0 or y1 is negative (can happen for tall images).  */
+      int r_bottom = r.y + r.height;
+
       /* Update lines intersecting rectangle R.  */
       first_overlapping_row = last_overlapping_row = NULL;
       for (row = w->current_matrix->rows;
@@ -30345,10 +30353,10 @@ expose_window (struct window *w, XRectangle *fr)
           int y0 = row->y;
           int y1 = MATRIX_ROW_BOTTOM_Y (row);
 
-          if ((y0 >= r.y && y0 < r.y + r.height)
-              || (y1 > r.y && y1 < r.y + r.height)
+          if ((y0 >= r.y && y0 < r_bottom)
+              || (y1 > r.y && y1 < r_bottom)
               || (r.y >= y0 && r.y < y1)
-              || (r.y + r.height > y0 && r.y + r.height < y1))
+              || (r_bottom > y0 && r_bottom < y1))
             {
               /* A header line may be overlapping, but there is no need
                  to fix overlapping areas for them.  KFS 2005-02-12 */
@@ -30385,7 +30393,7 @@ expose_window (struct window *w, XRectangle *fr)
       if (WINDOW_WANTS_MODELINE_P (w)
           && (row = MATRIX_MODE_LINE_ROW (w->current_matrix),
               row->enabled_p)
-          && row->y < r.y + r.height)
+          && row->y < r_bottom)
         {
           if (expose_line (w, row, &r))
             mouse_face_overwritten_p = true;