Ticket #5956: trac_5956-reviewer.patch

sage/plot/graphics.py

@@ -1278 +1278 @@
         - ``figsize`` - (default: [8.0,6.0]) [width, height] inches. The
           maximum value of each of the width and the height can be 327
           inches, at the default ``dpi`` of 100 dpi, which is just shy of
-          the maximum allowed value of 32768 dots per inch.
+          the maximum allowed value of 32768 dots (pixels).
 
         - ``fig_tight`` - (default: True) whether to clip the drawing
           tightly around drawn objects.  If True, then the resulting
@@ -1759 +1759 @@
 
         TESTS:
 
-        The figsize width and height parameters must be less than 328
-        inches each, corresponding to the maximum allowed dpi of 32768.::
+        The figsize width and height parameters (at default dpi) must be
+        less than 328 inches each, corresponding to the maximum allowed
+        pixels in each direction of 32768.  See :trac:`5956` for more about
+        the next several tests::
 
             sage: p = ellipse((0,0),4,1)
             sage: p.show(figsize=[328,10],dpi=100)
@@ -1786 +1788 @@
             sig_off(). You might want to run Sage under gdb with 'sage
             -gdb' to debug this.  Sage will now terminate.
 
+        The following tests ensure we give a good error message for
+        negative figsizes::
+
+            sage: P = plot(x^2,(x,0,1))
+            sage: P.show(figsize=[-1,1])
+            Traceback (most recent call last):
+            ...
+            AssertionError: figsize should be positive numbers, not -1 and 1
+            sage: P.show(figsize=-1)
+            Traceback (most recent call last):
+            ...
+            AssertionError: figsize should be positive, not -1
+
         """
 
         # This option should not be passed on to save().
@@ -2165 +2180 @@
         self.axes_labels(l=axes_labels)
 
         if figsize is not None and not isinstance(figsize, (list, tuple)):
+            # in this case, figsize is a number and should be positive
+            assert figsize > 0, "figsize should be positive, not {0}".format(figsize)
             default_width, default_height=rcParams['figure.figsize']
             figsize=(figsize, default_height*figsize/default_width)
 
+        if figsize is not None:
+            # then the figsize should be two positive numbers
+            assert figsize[0] > 0 and figsize[1] > 0, "figsize should be positive numbers, not {0} and {1}".format(figsize[0],figsize[1])
+
         if figure is None:
             figure=Figure(figsize=figsize)
         

sage/plot/plot.py

@@ -95 +95 @@
 
     sage: circle((1,1), 1) + plot(x^2, (x,0,5))
 
-Notice that the aspect ratio of the above plot makes the plot very tall because
-the plot adopts the default aspect ratio of the circle (to make the circle appear 
-like a circle).  We can change the aspect ratio to be what we normally expect for a plot
-by explicitly asking for an 'automatic' aspect ratio::
+Notice that the aspect ratio of the above plot makes the plot very tall
+because the plot adopts the default aspect ratio of the circle (to make
+the circle appear like a circle).  We can change the aspect ratio to be
+what we normally expect for a plot by explicitly asking for an
+'automatic' aspect ratio::
 
     sage: show(circle((1,1), 1) + plot(x^2, (x,0,5)), aspect_ratio='automatic')
 
-The aspect ratio describes the apparently height/width ratio of a unit square.  If you want the vertical units to be twice as big as the horizontal units, specify an aspect ratio of 2::
+The aspect ratio describes the apparently height/width ratio of a unit
+square.  If you want the vertical units to be twice as big as the
+horizontal units, specify an aspect ratio of 2::
 
     sage: show(circle((1,1), 1) + plot(x^2, (x,0,5)), aspect_ratio=2)
 
-The ``figsize`` option adjusts the figure size.  The default figsize is 4.  To make a figure that is roughly twice as big, use ``figsize=8``::
+The ``figsize`` option adjusts the figure size.  The default figsize is
+4.  To make a figure that is roughly twice as big, use ``figsize=8``::
 
     sage: show(circle((1,1), 1) + plot(x^2, (x,0,5)), figsize=8)
 
-You can also give separate horizontal and vertical dimensions::
+You can also give separate horizontal and vertical dimensions.  Both
+will be measured in inches::
 
     sage: show(circle((1,1), 1) + plot(x^2, (x,0,5)), figsize=[4,8])
 
+However, do not make the figsize too big (e.g. one dimension greater
+than 327 or both in the mid-200s) as this will lead to errors or crashes.
+See :meth:`~sage.plot.graphics.Graphics.show` for full details.
+
 Note that the axes will not cross if the data is not on both sides of
 both axes, even if it is quite close::