2 files changed, 47 insertions, 1 deletions

diff --git a/src/cardlayout.cpp b/src/cardlayout.cpp
index 0e118ab..f542df0 100644
--- a/src/cardlayout.cpp
+++ b/src/cardlayout.cpp
@@ -103,7 +103,17 @@ CardLayout CardLayout::compute(const Input &input, const QRect &rect,
 
     // Indent, capped. qMin rather than a branch so depth 5 and depth 50 land
     // in exactly the same place.
-    const int depth = qMin(input.depth, kMaxDepth);
+    //
+    // A MESSAGE row is nested at least one level whatever depth it reports.
+    // notmuch numbers every message of a thread with no usable In-Reply-To as
+    // depth 0, so a flat thread's replies arrived here claiming no nesting and
+    // drew flush against their own thread with no spine, while a nested
+    // thread's replies indented normally: two different shapes on screen for
+    // the same relationship. Being a child row IS the nesting; the depth only
+    // says how much further to go.
+    const int effectiveDepth =
+        input.isMessage ? qMax(1, input.depth) : input.depth;
+    const int depth = qMin(effectiveDepth, kMaxDepth);
     const int indent = depth * kIndentStep;
     out.contentLeft = textLeft + kPaddingX + indent;
 
diff --git a/tests/test_cardlayout.cpp b/tests/test_cardlayout.cpp
index 48bba25..fdc18bf 100644
--- a/tests/test_cardlayout.cpp
+++ b/tests/test_cardlayout.cpp
@@ -30,6 +30,7 @@ private slots:
     void everyCardIsTheSameHeight();
     void threeLinesStackWithoutOverlapping();
     void replyIndentsByDepth();
+    void aDepthZeroReplyStillIndents();
     void indentStopsAtTheCap();
     void expanderSitsOnTheSecondLine();
     void expanderIsEmptyWithoutReplies();
@@ -139,6 +140,41 @@ void TestCardLayout::replyIndentsByDepth()
     }
 }
 
+void TestCardLayout::aDepthZeroReplyStillIndents()
+{
+    // A reply in a FLAT thread carries depth 0, because notmuch reports every
+    // message of a thread with no usable In-Reply-To as a top-level message.
+    // It is still a reply: it is a child row under the root card, and it has
+    // to read as one.
+    //
+    // Treating depth 0 as "no nesting" left those replies flush against their
+    // thread with no spine, while a nested thread's replies indented normally,
+    // so the list showed two different shapes for the same relationship.
+    const QFont font;
+    const int h = CardLayout::heightFor(font);
+    const QRect rect(0, 0, 400, h);
+
+    CardLayout::Input flatReply;
+    flatReply.isMessage = true;
+    flatReply.depth = 0;
+
+    const CardLayout root = CardLayout::compute(threadInput(), rect, font);
+    const CardLayout reply = CardLayout::compute(flatReply, rect, font);
+
+    QVERIFY2(reply.contentLeft > root.contentLeft,
+             "a depth-0 reply sits flush with its thread, so a flat thread's "
+             "replies look like more threads");
+    QVERIFY2(!reply.spines.isEmpty(),
+             "a depth-0 reply has no spine, so nothing joins it to the thread "
+             "above it");
+
+    // And it lands at the same place a depth-1 reply does: the two are the
+    // same relationship and notmuch's numbering is the only difference.
+    const CardLayout nested = CardLayout::compute(replyInput(1), rect, font);
+    QCOMPARE(reply.contentLeft, nested.contentLeft);
+    QCOMPARE(reply.spines.size(), nested.spines.size());
+}
+
 void TestCardLayout::indentStopsAtTheCap()
 {
     const QFont font;