Factor out clip-path attr handling in backend_svg.

Replace _get_clip (which just returns a clip id) by _get_clip_attrs,
which also takes care of formatting it and preparing to pass it as as
xml attribute.

Author: anntzer

lib/matplotlib/backends/backend_svg.py

@@ -581,7 +581,7 @@ def _get_style_dict(self, gc, rgbFace):
     def _get_style(self, gc, rgbFace):
         return generate_css(self._get_style_dict(gc, rgbFace))
 
-    def _get_clip(self, gc):
+    def _get_clip_attrs(self, gc):
         cliprect = gc.get_clip_rectangle()
         clippath, clippath_trans = gc.get_clip_path()
         if clippath is not None:
@@ -592,8 +592,7 @@ def _get_clip(self, gc):
             y = self.height-(y+h)
             dictkey = (x, y, w, h)
         else:
-            return None
-
+            return {}
         clip = self._clipd.get(dictkey)
         if clip is None:
             oid = self._make_id('p', dictkey)
@@ -603,7 +602,7 @@ def _get_clip(self, gc):
                 self._clipd[dictkey] = (dictkey, oid)
         else:
             clip, oid = clip
-        return oid
+        return {'clip-path': f'url(#{oid})'}
 
     def _write_clips(self):
         if not len(self._clipd):
@@ -663,16 +662,10 @@ def draw_path(self, gc, path, transform, rgbFace=None):
             path, trans_and_flip, clip=clip, simplify=simplify,
             sketch=gc.get_sketch_params())
 
-        attrib = {}
-        attrib['style'] = self._get_style(gc, rgbFace)
-
-        clipid = self._get_clip(gc)
-        if clipid is not None:
-            attrib['clip-path'] = 'url(#%s)' % clipid
-
         if gc.get_url() is not None:
             self.writer.start('a', {'xlink:href': gc.get_url()})
-        self.writer.element('path', d=path_data, attrib=attrib)
+        self.writer.element('path', d=path_data, **self._get_clip_attrs(gc),
+                            style=self._get_style(gc, rgbFace))
         if gc.get_url() is not None:
             self.writer.end('a')
 
@@ -701,12 +694,7 @@ def draw_markers(
             writer.end('defs')
             self._markers[dictkey] = oid
 
-        attrib = {}
-        clipid = self._get_clip(gc)
-        if clipid is not None:
-            attrib['clip-path'] = 'url(#%s)' % clipid
-        writer.start('g', attrib=attrib)
-
+        writer.start('g', **self._get_clip_attrs(gc))
         trans_and_flip = self._make_flip_transform(trans)
         attrib = {'xlink:href': '#%s' % oid}
         clip = (0, 0, self.width*72, self.height*72)
@@ -758,20 +746,20 @@ def draw_path_collection(self, gc, master_transform, paths, all_transforms,
                 gc, master_transform, all_transforms, path_codes, offsets,
                 offsetTrans, facecolors, edgecolors, linewidths, linestyles,
                 antialiaseds, urls, offset_position):
-            clipid = self._get_clip(gc0)
             url = gc0.get_url()
             if url is not None:
                 writer.start('a', attrib={'xlink:href': url})
-            if clipid is not None:
-                writer.start('g', attrib={'clip-path': 'url(#%s)' % clipid})
+            clip_attrs = self._get_clip_attrs(gc0)
+            if clip_attrs:
+                writer.start('g', **clip_attrs)
             attrib = {
                 'xlink:href': '#%s' % path_id,
                 'x': short_float_fmt(xo),
                 'y': short_float_fmt(self.height - yo),
                 'style': self._get_style(gc0, rgbFace)
                 }
             writer.element('use', attrib=attrib)
-            if clipid is not None:
+            if clip_attrs:
                 writer.end('g')
             if url is not None:
                 writer.end('a')
@@ -912,17 +900,10 @@ def draw_gouraud_triangle(self, gc, points, colors, trans):
 
     def draw_gouraud_triangles(self, gc, triangles_array, colors_array,
                                transform):
-        attrib = {}
-        clipid = self._get_clip(gc)
-        if clipid is not None:
-            attrib['clip-path'] = 'url(#%s)' % clipid
-
-        self.writer.start('g', attrib=attrib)
-
+        self.writer.start('g', **self._get_clip_attrs(gc))
         transform = transform.frozen()
         for tri, col in zip(triangles_array, colors_array):
             self.draw_gouraud_triangle(gc, tri, col, transform)
-
         self.writer.end('g')
 
     def option_scale_image(self):
@@ -940,18 +921,18 @@ def draw_image(self, gc, x, y, im, transform=None):
         if w == 0 or h == 0:
             return
 
-        attrib = {}
-        clipid = self._get_clip(gc)
-        if clipid is not None:
-            # Can't apply clip-path directly to the image because the
-            # image has a transformation, which would also be applied
-            # to the clip-path
-            self.writer.start('g', attrib={'clip-path': 'url(#%s)' % clipid})
+        clip_attrs = self._get_clip_attrs(gc)
+        if clip_attrs:
+            # Can't apply clip-path directly to the image because the image has
+            # a transformation, which would also be applied to the clip-path.
+            self.writer.start('g', **clip_attrs)
 
-        oid = gc.get_gid()
         url = gc.get_url()
         if url is not None:
             self.writer.start('a', attrib={'xlink:href': url})
+
+        attrib = {}
+        oid = gc.get_gid()
         if mpl.rcParams['svg.image_inline']:
             buf = BytesIO()
             Image.fromarray(im).save(buf, format="png")
@@ -969,7 +950,6 @@ def draw_image(self, gc, x, y, im, transform=None):
             Image.fromarray(im).save(filename)
             oid = oid or 'Im_' + self._make_id('image', filename)
             attrib['xlink:href'] = filename
-
         attrib['id'] = oid
 
         if transform is None:
@@ -1009,7 +989,7 @@ def draw_image(self, gc, x, y, im, transform=None):
 
         if url is not None:
             self.writer.end('a')
-        if clipid is not None:
+        if clip_attrs:
             self.writer.end('g')
 
     def _update_glyph_map_defs(self, glyph_map_new):
@@ -1246,12 +1226,11 @@ def draw_tex(self, gc, x, y, s, prop, angle, ismath='TeX!', mtext=None):
     def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
         # docstring inherited
 
-        clipid = self._get_clip(gc)
-        if clipid is not None:
+        clip_attrs = self._get_clip_attrs(gc)
+        if clip_attrs:
             # Cannot apply clip-path directly to the text, because
-            # is has a transformation
-            self.writer.start(
-                'g', attrib={'clip-path': 'url(#%s)' % clipid})
+            # it has a transformation
+            self.writer.start('g', **clip_attrs)
 
         if gc.get_url() is not None:
             self.writer.start('a', {'xlink:href': gc.get_url()})
@@ -1264,7 +1243,7 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
         if gc.get_url() is not None:
             self.writer.end('a')
 
-        if clipid is not None:
+        if clip_attrs:
             self.writer.end('g')
 
     def flipy(self):