Remove infinite looping when stroking with a line width at or close to 0.0. Thanks to Rob Buis <buis@kde.org> and Noah Levitt <nlevitt@columbia.edu> for providing in-the-wild examples of SVG files with stroke-width:0 that demonstrated the problem, (cowboy.svg and albania.svg).

Do nothing if the pen is a degenerate, single point. This happens when the line width is a very small, non-zero value.
Do nothing when asked to stroke a path with a line_width of 0.0. Previously, this would lead to an infinite loop.
Force negative line width to 0.0.
Updated TODO list.

ChangeLog

@@ -1,3 +1,24 @@
+2003-11-17  Carl Worth  <cworth@isi.edu>
+
+	* Remove infinite looping when stroking with a line width at or
+	close to 0.0. Thanks to Rob Buis <buis@kde.org> and Noah Levitt
+	<nlevitt@columbia.edu> for providing in-the-wild examples of SVG
+	files with stroke-width:0 that demonstrated the problem,
+	(cowboy.svg and albania.svg).
+
+	* src/cairo_pen.c (_cairo_pen_stroke_spline): Do nothing if the
+	pen is a degenerate, single point. This happens when the line
+	width is a very small, non-zero value.
+
+	* src/cairo_gstate.c (_cairo_gstate_stroke): Do nothing when asked
+	to stroke a path with a line_width of 0.0. Previously, this would
+	lead to an infinite loop.
+
+	* src/cairo.c (cairo_set_line_width): Force negative line width
+	to 0.0.
+
+	* TODO: Updated TODO list.
+
 2003-11-10  Carl Worth  <cworth@east.isi.edu>
 
 	* configure.in: Fix typo (thanks to John Ellson

TODO

@@ -1,22 +1,30 @@
-* Fix the intersection problem, (see reference to Hobby's paper
-mentioned in cairo_traps.c)
+* Change stroke code to go through one giant polygon. This will fix
+problems with stroking self-intersecting paths.
 
-* Implement support for programmatic patterns
+* Implement cairo_stroke_path, (very easy to do after the above change
+is done).
+
+* Fix the intersection problem, (see reference to Hobby's paper
+mentioned in cairo_traps.c).
+
+* Implement support for programmatic patterns.
 
 * Implement cairo_text_extents, cairo_glyph_extents, cairo_text_path,
 cairo_glyph_path, and cairo_stroke_path, cairo_arc_to.
 
-* Add a few new, needed functions?
+* Investigate what needs to be done so that old X servers aren't
+swamped with image transport. This may involve adding one or more of
+the following functions:
 
    cairo_flush
    cairo_erase
    cairo_mark_dirty
 
-* Verification, profiling, optimization.
-
 * Re-implement the trapezoid rasterization algorithm according to the
 new "specification".
 
+* Verification, profiling, optimization.
+
 A comparison with PostScript
 ============================
 

src/cairo-gstate.c

@@ -1157,6 +1157,9 @@ _cairo_gstate_stroke (cairo_gstate_t *gstate)
     cairo_traps_t traps;
     cairo_matrix_t user_to_source, device_to_source;
 
+    if (gstate->line_width <= 0.0)
+	return CAIRO_STATUS_SUCCESS;
+
     status = _cairo_gstate_ensure_source (gstate);
     if (status)
 	return status;

src/cairo-pen.c

@@ -322,6 +322,11 @@ _cairo_pen_stroke_spline (cairo_pen_t		*pen,
     cairo_status_t status;
     cairo_polygon_t polygon;
 
+    /* If the line width is so small that the pen is reduced to a
+       single point, then we have nothing to do. */
+    if (pen->num_vertices <= 1)
+	return CAIRO_STATUS_SUCCESS;
+
     _cairo_polygon_init (&polygon);
 
     status = _cairo_spline_decompose (spline, tolerance);

src/cairo.c

@@ -265,6 +265,8 @@ cairo_set_line_width (cairo_t *cr, double width)
     if (cr->status)
 	return;
 
+    _cairo_restrict_value (&width, 0.0, width);
+
     cr->status = _cairo_gstate_set_line_width (cr->gstate, width);
 }
 

src/cairo_gstate.c

@@ -1157,6 +1157,9 @@ _cairo_gstate_stroke (cairo_gstate_t *gstate)
     cairo_traps_t traps;
     cairo_matrix_t user_to_source, device_to_source;
 
+    if (gstate->line_width <= 0.0)
+	return CAIRO_STATUS_SUCCESS;
+
     status = _cairo_gstate_ensure_source (gstate);
     if (status)
 	return status;

src/cairo_pen.c

@@ -322,6 +322,11 @@ _cairo_pen_stroke_spline (cairo_pen_t		*pen,
     cairo_status_t status;
     cairo_polygon_t polygon;
 
+    /* If the line width is so small that the pen is reduced to a
+       single point, then we have nothing to do. */
+    if (pen->num_vertices <= 1)
+	return CAIRO_STATUS_SUCCESS;
+
     _cairo_polygon_init (&polygon);
 
     status = _cairo_spline_decompose (spline, tolerance);