Fix classical control diagram symbols and svg

cirq-core/cirq/contrib/svg/svg.py

@@ -183,13 +183,31 @@ def tdd_to_svg(
     t = (
         f'<svg xmlns="http://www.w3.org/2000/svg" '
         f'width="{col_starts[-1]}" height="{row_starts[-1]}">'
+        '''
+  <defs>
+    <marker id="arrow"
+            viewBox="0 0 10 10"
+            refX="9"
+            refY="5"
+            markerUnits="strokeWidth"
+            markerWidth="5"
+            markerHeight="5"
+            orient="auto">
+      <path d="M 0 0 L 10 5 L 0 10 z" />
+    </marker>
+    <filter id="double" filterUnits="userSpaceOnUse">
+      <feMorphology in="SourceGraphic" result="a" operator="dilate" radius="1" />
+      <feComposite in="SourceGraphic" in2="a" operator="xor" />
+    </filter>
+  </defs>
+  '''
     )
 
     # Developers: uncomment below to draw green lines to debug
     #             col_starts and row_starts
     # t += _debug_spacing(col_starts, row_starts)
 
-    for yi, xi1, xi2, _, _ in tdd.horizontal_lines:
+    for yi, xi1, xi2, _, doubled in tdd.horizontal_lines:
         xi1 = cast(int, xi1)
         xi2 = cast(int, xi2)
         x1 = col_starts[xi1] + col_widths[xi1] / 2
@@ -203,17 +221,26 @@ def tdd_to_svg(
             stroke = QBLUE
         else:
             stroke = 'black'  # pragma: no cover
-        t += f'<line x1="{x1}" x2="{x2}" y1="{y}" y2="{y}" stroke="{stroke}" stroke-width="1" />'
+        t += f'<line x1="{x1}" x2="{x2}" y1="{y}" y2="{y}" stroke="{stroke}" stroke-width="1"'
+        if doubled:
+            t += ' filter="url(#double)"'
+        t += ' />'
 
-    for xi, yi1, yi2, _, _ in tdd.vertical_lines:
+    for xi, yi1, yi2, _, doubled in tdd.vertical_lines:
+        arrow = doubled and tdd.entries[int(xi), int(yi2)].text == 'V'
         yi1 = yi_map[yi1]
         yi2 = yi_map[yi2]
         y1 = row_starts[yi1] + row_heights[yi1] / 2
         y2 = row_starts[yi2] + row_heights[yi2] / 2
 
         xi = cast(int, xi)
         x = col_starts[xi] + col_widths[xi] / 2
-        t += f'<line x1="{x}" x2="{x}" y1="{y1}" y2="{y2}" stroke="black" stroke-width="3" />'
+        t += f'<line x1="{x}" x2="{x}" y1="{y1}" y2="{y2}" stroke="black" stroke-width="3"'
+        if doubled:
+            t += ' filter="url(#double)"'
+        if arrow:
+            t += ' marker-end="url(#arrow)"'
+        t += ' />'
 
     for (xi, yi), v in tdd.entries.items():
         yi = yi_map[yi]
@@ -238,7 +265,7 @@ def tdd_to_svg(
         if v.text == '×':
             t += _text(x, y + 3, '×', fontsize=40)
             continue
-        if v.text == '':
+        if v.text == '' or v.text == 'V':
             continue
 
         v_text = fixup_text(v.text)

cirq-core/cirq/contrib/svg/svg_test.py

@@ -21,12 +21,14 @@ def test_svg() -> None:
             cirq.PhasedXPowGate(exponent=0.123, phase_exponent=0.456).on(c),
             cirq.Z(a),
             cirq.measure(a, b, c, key='z'),
-            cirq.MatrixGate(np.eye(2)).on(a),
+            cirq.MatrixGate(np.eye(2)).on(a).with_classical_controls('z'),
         )
     )
     assert '?' in svg_text
     assert '<svg' in svg_text
     assert '</svg>' in svg_text
+    assert 'double' in svg_text
+    assert 'arrow' in svg_text
 
 
 def test_svg_noise() -> None:

cirq-core/cirq/ops/classically_controlled_operation.py

@@ -49,7 +49,7 @@ class ClassicallyControlledOperation(raw_types.Operation):
                     ║
     1: ─────────────╫───X───
                     ║   ║
-    control_key: ═══@═══^═══
+    control_key: ═══V═══@═══
     >>> circuit2 = cirq.Circuit([
     ...     cirq.measure(a, key='control_key1'),
     ...     cirq.measure(b, key='control_key2'),
@@ -62,9 +62,9 @@ class ClassicallyControlledOperation(raw_types.Operation):
                       ║║
     2: ───────────────╫╫────X───
                       ║║    ║
-    control_key1: ════@╬════^═══
+    control_key1: ════V╬════@═══
                        ║    ║
-    control_key2: ═════@════^═══
+    control_key2: ═════V════@═══
                      └──┘
     """
 
@@ -180,7 +180,7 @@ def _circuit_diagram_info_(
         control_label_count = 0
         if args.label_map is not None:
             control_label_count = len({k for c in self._conditions for k in c.keys})
-        wire_symbols = sub_info.wire_symbols + ('^',) * control_label_count
+        wire_symbols = sub_info.wire_symbols + ('@',) * control_label_count
         if control_label_count == 0 or any(
             not isinstance(c, value.KeyCondition) for c in self._conditions
         ):