三维未激活采样显示灰点，二维增加深度叠箭头。

分析对话框默认使用传感器对话框保存的标定，关闭按钮改为保存。框选曲线时数值卡片仍显示光标读数。相关单测通过。

shared/tests/test_image_backend.py

@@ -36,12 +36,22 @@ def test_a_live_frame_offers_the_derived_modes_and_needs_no_note():
     plan = backend.plan_image(
         backend.ImageFrame(_image(), flow=_flow(), depth=np.ones((12, 16)))
     )
-    assert plan.available_modes == ("arrows_pure", "arrows_stitched", "depth")
+    assert plan.available_modes == ("arrows_pure", "arrows_stitched", "depth", "depth_arrows")
     assert plan.default_mode == "arrows_pure"
     assert plan.missing == ()
     assert plan.note_key == ""
 
 
+def test_depth_arrows_draws_the_flow_on_the_depth_picture():
+    depth = np.linspace(0.0, 1.0, 12 * 16, dtype=np.float32).reshape(12, 16)
+    frame = backend.ImageFrame(_image(), flow=_flow(), depth=depth)
+    plain = backend.render_image(frame, mode="depth", draw_style="finger")
+    over = backend.render_image(frame, mode="depth_arrows", draw_style="finger")
+    assert plain is not None and over is not None
+    assert over.shape == plain.shape
+    assert not np.array_equal(over, plain)
+
+
 def test_a_recorded_frame_is_raw_and_says_so():
     """No flow and no depth: the frame *is* the picture, and the note explains it."""
     plan = backend.plan_image(backend.ImageFrame(_image(), source=backend.SOURCE_REPLAY))
@@ -723,9 +733,12 @@ def test_hiding_the_idle_dots_leaves_the_3d_figure_where_it_was():
         f"{int(active.sum())} active of {samples.rows.size} candidates"
     )
     assert overlay_on is not None and overlay_off is not None
-    assert overlay_on.origins.shape[0] == int(active.sum()), (
+    assert int(np.count_nonzero(overlay_on.lengths > 0.0)) == int(active.sum()), (
         "the 3D overlay is not drawing the active samples the 2D canvas draws"
     )
+    assert int(np.count_nonzero(overlay_on.lengths < 0.0)) > 0, (
+        "inactive samples are not drawn as grey points"
+    )
     assert np.array_equal(overlay_on.origins, overlay_off.origins)
     assert np.array_equal(overlay_on.directions, overlay_off.directions)
     assert not np.array_equal(dots_on, dots_off), "the switch changed nothing to hide"