imgmath: Fix embed mode

We need to use the location of the temporary image
instead of the final image for base64 rendering.

sphinx/ext/imgmath.py

@@ -242,7 +242,7 @@ def render_math(
             depth = read_png_depth(outfn)
         elif image_format == 'svg':
             depth = read_svg_depth(outfn)
-        return relfn, depth, None, outfn
+        return relfn, depth, outfn, outfn
 
     # if latex or dvipng (dvisvgm) has failed once, don't bother to try again
     if hasattr(self.builder, '_imgmath_warned_latex') or \
@@ -308,7 +308,7 @@ def html_visit_math(self: HTMLTranslator, node: nodes.math) -> None:
         raise nodes.SkipNode from exc
     if self.builder.config.imgmath_embed:
         image_format = self.builder.config.imgmath_image_format.lower()
-        img_src = render_maths_to_base64(image_format, outfn)
+        img_src = render_maths_to_base64(image_format, imgpath)
     else:
         # Move generated image on tempdir to build dir
         if imgpath is not None:
@@ -350,7 +350,7 @@ def html_visit_displaymath(self: HTMLTranslator, node: nodes.math_block) -> None
         self.body.append('</span>')
     if self.builder.config.imgmath_embed:
         image_format = self.builder.config.imgmath_image_format.lower()
-        img_src = render_maths_to_base64(image_format, outfn)
+        img_src = render_maths_to_base64(image_format, imgpath)
     else:
         # Move generated image on tempdir to build dir
         if imgpath is not None:

tests/test_ext_math.py

@@ -74,6 +74,24 @@ def test_imgmath_svg_embed(app, status, warning):
     assert re.search(html, content, re.DOTALL)
 
 
+@pytest.mark.skipif(not has_binary('dvisvgm'),
+                    reason='Requires dvisvgm" binary')
+@pytest.mark.sphinx('html', testroot='ext-math',
+                    confoverrides={'extensions': ['sphinx.ext.imgmath'],
+                                   'imgmath_image_format': 'svg',
+                                   'imgmath_embed': True})
+def test_imgmath_svg_embed2(app, status, warning):
+    app.builder.build_all()
+    if "LaTeX command 'latex' cannot be run" in warning.getvalue():
+        pytest.skip('LaTeX command "latex" is not available')
+    if "dvisvgm command 'dvisvgm' cannot be run" in warning.getvalue():
+        pytest.skip('dvisvgm command "dvisvgm" is not available')
+
+    content = (app.outdir / 'index.html').read_text(encoding='utf8')
+    html = r'<img src="data:image/svg\+xml;base64,[\w\+/=]+"'
+    assert re.search(html, content, re.DOTALL)
+
+
 @pytest.mark.sphinx('html', testroot='ext-math',
                     confoverrides={'extensions': ['sphinx.ext.mathjax'],
                                    'mathjax_options': {'integrity': 'sha384-0123456789'}})