[pango/fix-error-underline] renderer: Fix a division-by-zero

[Matthias Clasen <matthiasc src gnome org>]

commit dd867f41cc653411e716212867537e72107429a9
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Jun 8 12:06:40 2020 -0400

    renderer: Fix a division-by-zero
    
    We need to check if height is zero before dividing by it.
    For completeness, check width at the same time.
    
    This was pointed out in
    https://gitlab.gnome.org/GNOME/pango/-/merge_requests/167

 pango/pango-renderer.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)
---
diff --git a/pango/pango-renderer.c b/pango/pango-renderer.c
index 539df34a..07f81a88 100644
--- a/pango/pango-renderer.c
+++ b/pango/pango-renderer.c
@@ -1096,15 +1096,22 @@ pango_renderer_default_draw_error_underline (PangoRenderer *renderer,
                                             int            width,
                                             int            height)
 {
-  int square = height / HEIGHT_SQUARES;
-  int unit_width = (HEIGHT_SQUARES - 1) * square;
-  int width_units = (width + unit_width / 2) / unit_width;
+  int square;
+  int unit_width;
+  int width_units;
   const PangoMatrix identity = PANGO_MATRIX_INIT;
   const PangoMatrix *matrix;
   double dx, dx0, dy0;
   PangoMatrix total;
   int i;
 
+  if (width <= 0 || height <= 0)
+    return;
+
+  square = height / HEIGHT_SQUARES;
+  unit_width = (HEIGHT_SQUARES - 1) * square;
+  width_units = (width + unit_width / 2) / unit_width;
+
   x += (width - width_units * unit_width) / 2;
 
   if (renderer->matrix)