Fix picking with primitive restart for line loops

Previous fix was not closing the loop on every primitive,
just the last one.

Task-number: QTBUG-71919
Change-Id: I22d52258477b0c4777118ee36a0b3868da982885
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

2 files changed, 52 insertions, 32 deletions

diff --git a/src/render/backend/segmentsvisitor.cpp b/src/render/backend/segmentsvisitor.cpp
index 68deafb15..d9f2d79ec 100644
--- a/src/render/backend/segmentsvisitor.cpp
+++ b/src/render/backend/segmentsvisitor.cpp
@@ -135,39 +135,44 @@ void traverseSegmentStripIndexed(Index *indices,
                                  bool loop)
 {
     uint i = 0;
+    uint stripStartIndex = 0;
+
     const uint verticesStride = vertexInfo.byteStride / sizeof(Vertex);
     const uint maxVerticesDataSize = qMin(vertexInfo.dataSize, 3U);
 
     uint ndx[2];
     Vector3D abc[2];
-
-    startLinePrimitive:ndx[0] = indices[i];
-    uint idx = ndx[0] * verticesStride;
-    for (uint j = 0; j < maxVerticesDataSize; ++j)
-        abc[0][j] = vertices[idx + j];
-    while (i < indexInfo.count - 1) {
-        ndx[1] = indices[i + 1];
-        if (ndx[0] != ndx[1]) {
-            if (indexInfo.restartEnabled && indexInfo.restartIndexValue == static_cast<int>(ndx[1])) {
-                i += 2;
-                goto startLinePrimitive;
-            }
-            idx = ndx[1] * verticesStride;
-            for (uint j = 0; j < maxVerticesDataSize; ++j)
-                abc[1][j] = vertices[idx + j];
-            visitor->visit(ndx[0], abc[0], ndx[1], abc[1]);
+    while (i < indexInfo.count) {
+        if (indexInfo.restartEnabled && indexInfo.restartIndexValue == static_cast<int>(indices[i])) {
+            ++i;
+            continue;
         }
+        stripStartIndex = i;
+        ndx[0] = indices[stripStartIndex];
+        uint idx = ndx[0] * verticesStride;
+        for (uint j = 0; j < maxVerticesDataSize; ++j)
+            abc[0][j] = vertices[idx + j];
         ++i;
-        ndx[0] = ndx[1];
-        abc[0] = abc[1];
-    }
-    if (loop) {
-        ndx[1] = indices[0];
-        if (ndx[0] != ndx[1]) {
-            idx = ndx[1] * verticesStride;
-            for (uint j = 0; j < maxVerticesDataSize; ++j)
-                abc[1][j] = vertices[idx + j];
-            visitor->visit(ndx[0], abc[0], ndx[1], abc[1]);
+        while (i < indexInfo.count && (!indexInfo.restartEnabled || indexInfo.restartIndexValue != static_cast<int>(indices[i]))) {
+            ndx[1] = indices[i];
+            if (ndx[0] != ndx[1]) {
+                idx = ndx[1] * verticesStride;
+                for (uint j = 0; j < maxVerticesDataSize; ++j)
+                    abc[1][j] = vertices[idx + j];
+                visitor->visit(ndx[0], abc[0], ndx[1], abc[1]);
+            }
+            ++i;
+            ndx[0] = ndx[1];
+            abc[0] = abc[1];
+        }
+        if (loop) {
+            ndx[1] = indices[stripStartIndex];
+            if (ndx[0] != ndx[1]) {
+                idx = ndx[1] * verticesStride;
+                for (uint j = 0; j < maxVerticesDataSize; ++j)
+                    abc[1][j] = vertices[idx + j];
+                visitor->visit(ndx[0], abc[0], ndx[1], abc[1]);
+            }
         }
     }
 }
diff --git a/tests/auto/render/segmentvisitor/tst_segmentvisitor.cpp b/tests/auto/render/segmentvisitor/tst_segmentvisitor.cpp
index da420e1ac..427f9c75b 100644
--- a/tests/auto/render/segmentvisitor/tst_segmentvisitor.cpp
+++ b/tests/auto/render/segmentvisitor/tst_segmentvisitor.cpp
@@ -426,12 +426,15 @@ private Q_SLOTS:
         simulateInitialization(dataBuffer.data(), backendBuffer);
 
         QByteArray indexData;
-        indexData.resize(sizeof(uint) * 2 * 4);
+        indexData.resize(sizeof(uint) * 7);
         uint *iDataPtr = reinterpret_cast<uint *>(indexData.data());
         iDataPtr[0] = 0;
         iDataPtr[1] = 1;
         iDataPtr[2] = 2;
         iDataPtr[3] = 3;
+        iDataPtr[4] = static_cast<uint>(-1);
+        iDataPtr[5] = 0;
+        iDataPtr[6] = 1;
         indexDataBuffer->setData(indexData);
 
         Buffer *backendIndexBuffer = nodeManagers->bufferManager()->getOrCreateResource(indexDataBuffer->id());
@@ -450,7 +453,7 @@ private Q_SLOTS:
 
         indexAttribute->setBuffer(indexDataBuffer.data());
         indexAttribute->setVertexBaseType(Qt3DRender::QAttribute::UnsignedInt);
-        indexAttribute->setCount(4);
+        indexAttribute->setCount(7);
         indexAttribute->setAttributeType(Qt3DRender::QAttribute::IndexAttribute);
 
         geometry->addAttribute(positionAttribute.data());
@@ -458,6 +461,8 @@ private Q_SLOTS:
 
         geometryRenderer->setGeometry(geometry);
         geometryRenderer->setPrimitiveType(Qt3DRender::QGeometryRenderer::LineStrip);
+        geometryRenderer->setPrimitiveRestartEnabled(true);
+        geometryRenderer->setRestartIndexValue(-1);
 
         Attribute *backendAttribute = nodeManagers->attributeManager()->getOrCreateResource(positionAttribute->id());
         backendAttribute->setRenderer(&renderer);
@@ -480,10 +485,11 @@ private Q_SLOTS:
         visitor.apply(backendRenderer, Qt3DCore::QNodeId());
 
         // THEN
-        QCOMPARE(visitor.segmentCount(), uint(3));
+        QCOMPARE(visitor.segmentCount(), uint(4));
         QVERIFY(visitor.verifySegment(0, 0,1, Vector3D(0,0,0), Vector3D(1,0,0)));
         QVERIFY(visitor.verifySegment(1, 1,2, Vector3D(1,0,0), Vector3D(1,1,0)));
         QVERIFY(visitor.verifySegment(2, 2,3, Vector3D(1,1,0), Vector3D(0,1,0)));
+        QVERIFY(visitor.verifySegment(3, 0,1, Vector3D(0,0,0), Vector3D(1,0,0)));
     }
 
     void testVisitLineLoop()
@@ -588,12 +594,16 @@ private Q_SLOTS:
         simulateInitialization(dataBuffer.data(), backendBuffer);
 
         QByteArray indexData;
-        indexData.resize(sizeof(uint) * 2 * 4);
+        indexData.resize(sizeof(uint) * 8);
         uint *iDataPtr = reinterpret_cast<uint *>(indexData.data());
         iDataPtr[0] = 0;
         iDataPtr[1] = 1;
         iDataPtr[2] = 2;
         iDataPtr[3] = 3;
+        iDataPtr[4] = static_cast<uint>(-1);
+        iDataPtr[5] = 0;
+        iDataPtr[6] = 1;
+        iDataPtr[7] = 2;
         indexDataBuffer->setData(indexData);
 
         Buffer *backendIndexBuffer = nodeManagers->bufferManager()->getOrCreateResource(indexDataBuffer->id());
@@ -612,7 +622,7 @@ private Q_SLOTS:
 
         indexAttribute->setBuffer(indexDataBuffer.data());
         indexAttribute->setVertexBaseType(Qt3DRender::QAttribute::UnsignedInt);
-        indexAttribute->setCount(4);
+        indexAttribute->setCount(8);
         indexAttribute->setAttributeType(Qt3DRender::QAttribute::IndexAttribute);
 
         geometry->addAttribute(positionAttribute.data());
@@ -620,6 +630,8 @@ private Q_SLOTS:
 
         geometryRenderer->setGeometry(geometry);
         geometryRenderer->setPrimitiveType(Qt3DRender::QGeometryRenderer::LineLoop);
+        geometryRenderer->setPrimitiveRestartEnabled(true);
+        geometryRenderer->setRestartIndexValue(-1);
 
         Attribute *backendAttribute = nodeManagers->attributeManager()->getOrCreateResource(positionAttribute->id());
         backendAttribute->setRenderer(&renderer);
@@ -642,11 +654,14 @@ private Q_SLOTS:
         visitor.apply(backendRenderer, Qt3DCore::QNodeId());
 
         // THEN
-        QCOMPARE(visitor.segmentCount(), uint(4));
+        QCOMPARE(visitor.segmentCount(), uint(7));
         QVERIFY(visitor.verifySegment(0, 0,1, Vector3D(0,0,0), Vector3D(1,0,0)));
         QVERIFY(visitor.verifySegment(1, 1,2, Vector3D(1,0,0), Vector3D(1,1,0)));
         QVERIFY(visitor.verifySegment(2, 2,3, Vector3D(1,1,0), Vector3D(0,1,0)));
         QVERIFY(visitor.verifySegment(3, 3,0, Vector3D(0,1,0), Vector3D(0,0,0)));
+        QVERIFY(visitor.verifySegment(4, 0,1, Vector3D(0,0,0), Vector3D(1,0,0)));
+        QVERIFY(visitor.verifySegment(5, 1,2, Vector3D(1,0,0), Vector3D(1,1,0)));
+        QVERIFY(visitor.verifySegment(6, 2,0, Vector3D(1,1,0), Vector3D(0,0,0)));
     }
 
     void testVisitLineAdjacency()