Use a data: URL for the broken qutebrowser logo

It blows our HTML up, but we use error.html from various places with
various security policies, so we can't rely on being able to load
file:// URLs.

qutebrowser/html/error.html

@@ -73,13 +73,13 @@ function searchFor(uri) {
 	<table>
 		<tr>
 			<td style="width: 10%; vertical-align: top;">
-				<img style="width: 100%; display: block; max-width: 256px;" src="{{ resource_url('img/broken_qutebrowser_logo.png') }}" />
+				<img style="width: 100%; display: block; max-width: 256px;" src="{{ data_url('img/broken_qutebrowser_logo.png') }}" />
 			</td>
 			<td style="padding-left: 40px;">
 				<h1>Unable to load page</h1>
 				Error while opening {{ url }}: <br>
 				<p id="error-message-text" style="color: #a31a1a;">{{ error }}</p><br><br>
-				
+
 				<form name="bl">
 					<input type="button" value="Try again" onclick="javascript:tryagain()" />
 				</form>

qutebrowser/utils/jinja.py

@@ -22,6 +22,8 @@
 import os
 import os.path
 import traceback
+import mimetypes
+import base64
 
 import jinja2
 import jinja2.exceptions
@@ -74,6 +76,16 @@ def resource_url(path):
     return QUrl.fromLocalFile(image).toString(QUrl.FullyEncoded)
 
 
+def data_url(path):
+    """Get a data: url for the broken qutebrowser logo."""
+    data = utils.read_file(path, binary=True)
+    filename = utils.resource_filename(path)
+    mimetype = mimetypes.guess_type(filename)
+    assert mimetype is not None, path
+    b64 = base64.b64encode(data).decode('ascii')
+    return 'data:{};charset=utf-8;base64,{}'.format(mimetype[0], b64)
+
+
 def render(template, **kwargs):
     """Render the given template and pass the given arguments to it."""
     try:
@@ -89,3 +101,4 @@ def render(template, **kwargs):
 _env = jinja2.Environment(loader=Loader('html'), autoescape=_guess_autoescape)
 _env.globals['resource_url'] = resource_url
 _env.globals['file_url'] = urlutils.file_url
+_env.globals['data_url'] = data_url

tests/unit/utils/test_jinja.py

@@ -34,21 +34,42 @@ from qutebrowser.utils import utils, jinja
 def patch_read_file(monkeypatch):
     """pytest fixture to patch utils.read_file."""
     real_read_file = utils.read_file
+    real_resource_filename = utils.resource_filename
 
-    def _read_file(path):
+    def _read_file(path, binary=False):
         """A read_file which returns a simple template if the path is right."""
         if path == os.path.join('html', 'test.html'):
+            assert not binary
             return """Hello {{var}}"""
         elif path == os.path.join('html', 'test2.html'):
+            assert not binary
             return """{{ resource_url('utils/testfile') }}"""
+        elif path == os.path.join('html', 'test3.html'):
+            assert not binary
+            return """{{ data_url('testfile.txt') }}"""
+        elif path == 'testfile.txt':
+            assert binary
+            return b'foo'
         elif path == os.path.join('html', 'undef.html'):
+            assert not binary
             return """{{ does_not_exist() }}"""
         elif path == os.path.join('html', 'undef_error.html'):
+            assert not binary
             return real_read_file(path)
         else:
             raise IOError("Invalid path {}!".format(path))
 
+    def _resource_filename(path):
+        if path == 'utils/testfile':
+            return real_resource_filename(path)
+        elif path == 'testfile.txt':
+            return path
+        else:
+            raise IOError("Invalid path {}!".format(path))
+
     monkeypatch.setattr('qutebrowser.utils.jinja.utils.read_file', _read_file)
+    monkeypatch.setattr('qutebrowser.utils.jinja.utils.resource_filename',
+                        _resource_filename)
 
 
 def test_simple_template():
@@ -75,6 +96,15 @@ def test_resource_url():
         assert f.read().splitlines()[0] == "Hello World!"
 
 
+def test_data_url():
+    """Test data_url() which can be used from templates."""
+    data = jinja.render('test3.html')
+    print(data)
+    url = QUrl(data)
+    assert url.isValid()
+    assert data == 'data:text/plain;charset=utf-8;base64,Zm9v'  # 'foo'
+
+
 def test_not_found():
     """Test with a template which does not exist."""
     with pytest.raises(jinja2.TemplateNotFound) as excinfo: