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.

diff --git a/src/xdisp.c b/src/xdisp.c
index 2be057fd211b3c4e267d9b1bd561c2894d7dfa2e..5a89f4c988b373a40d3f362e524711e31c9bcaaf 100644 (file)
--- 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;