First draft to correct issue #6035 and to write relevant unit tests. Does break old unit tests of fancyarrow (test_arrow_patches.py)!

afvincent · jenshnielsen · commit d1fddc76b852 · 2016-05-30T13:35:46.000+01:00
diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -4056,18 +4056,22 @@ def __init__(self, posA=None, posB=None,
 
         self._mutation_scale = mutation_scale
         self._mutation_aspect = mutation_aspect
+        # Provide a ref. to scale '_mutation_scale' when setting '_dpi_cor'.
+        self._genuine_mutation_scale = mutation_scale
 
         self.set_dpi_cor(dpi_cor)
         #self._draw_in_display_coordinate = True
 
     def set_dpi_cor(self, dpi_cor):
         """
         dpi_cor is currently used for linewidth-related things and
-        shrink factor. Mutation scale is not affected by this.
+        shrink factor. Mutation scale *is* affected by this.
         """
 
         self._dpi_cor = dpi_cor
         self.stale = True
+        # Scale `_mutation_scale` properly with the new DPI (see issue #6035).
+        self._mutation_scale = self._genuine_mutation_scale * dpi_cor
 
     def get_dpi_cor(self):
         """
diff --git a/lib/matplotlib/tests/test_arrow_patches.py b/lib/matplotlib/tests/test_arrow_patches.py
@@ -52,6 +52,54 @@ def test_boxarrow():
                   bbox=dict(boxstyle=stylename, fc="w", ec="k"))
 
 
+def prepare_fancyarrow_for_head_size_test():
+    """
+    Convenience function that prepares and return a FancyArrowPatch. It aims
+    at being used to test that the size of the arrow head does not depend on
+    the DPI value of the exported picture. 
+
+    NB: this function *is not* a test in itself!
+    """
+    fig = plt.figure(figsize=(6, 4), dpi=50)
+    ax = fig.add_subplot(111)
+    ax.set_xlim([0, 1])
+    ax.set_ylim([0, 1])
+    ax.add_patch(mpatches.FancyArrowPatch(posA=(0.3, 0.4), posB=(0.8, 0.6),
+                                          lw=3, arrowstyle=u'->', 
+                                          mutation_scale=150))    
+    return fig
+
+
+@image_comparison(baseline_images=['fancyarrow_head_size_100dpi'], 
+                  remove_text=True, extensions=['svg', 'pdf', 'png'], 
+                  savefig_kwarg=dict(dpi=100))    
+def test_fancy_arrow_patch_head_size_100dpi():
+    """
+    Check the export of a FancyArrowPatch @ 100 DPI. The FancyArrowPatch 
+    is instanciated through a dedicated function because another similar test
+    checks the same export but with a different DPI value.
+
+    Remark: may be more explicit to create a dedicated test for SVG and PDF,
+    as a DPI value is not very relevant here...
+    """
+    
+    prepare_fancyarrow_for_head_size_test()
+
+
+@image_comparison(baseline_images=['fancyarrow_head_size_300dpi'], 
+                  remove_text=True, 
+                  extensions=['png'], # pdf and svg already tested @ 100 DPI
+                  savefig_kwarg=dict(dpi=300))    
+def test_fancy_arrow_patch_head_size_300dpi():
+    """
+    Check the export of a FancyArrowPatch @ 300 DPI. The FancyArrowPatch 
+    is instanciated through a dedicated function because another similar test
+    checks the same export but with a different DPI value.
+    """
+    
+    prepare_fancyarrow_for_head_size_test()
+
+
 if __name__ == '__main__':
     import nose
     nose.runmodule(argv=['-s', '--with-doctest'], exit=False)
