Fix PlotCommitList to set lanes on child-less commits

In PlotCommitList.enter() commits are positioned on lanes for visual
presentation. This implementation was buggy: commits without
children (often the starting points for the RevWalk) are not positioned
on separate lanes.

The problem was that when handling commits with multiple children
(that's where branches fork out) it was not handled that some of the
children may not have been positioned on a lane yet. I fixed that and
added a number of tests which specifically test the layout of commits
on lanes.

Bug: 300282
Bug: 320263
Change-Id: I267b97ecccb5251cec54cec90207e075ab50503e
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

2 files changed, 385 insertions, 15 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/revplot/PlotCommitListTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revplot/PlotCommitListTest.java
new file mode 100644
index 0000000000..b8e1df7888
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revplot/PlotCommitListTest.java
@@ -0,0 +1,306 @@
+/*
+ * Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com>
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.eclipse.jgit.revplot;
+
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalkTestCase;
+
+public class PlotCommitListTest extends RevWalkTestCase {
+
+	class CommitListAssert {
+		private PlotCommitList<PlotLane> pcl;
+		private PlotCommit<PlotLane> current;
+		private int nextIndex = 0;
+
+		CommitListAssert(PlotCommitList<PlotLane> pcl) {
+			this.pcl = pcl;
+		}
+
+		public CommitListAssert commit(RevCommit id) {
+			assertTrue("Unexpected end of list at pos#"+nextIndex, pcl.size()>nextIndex);
+			current = pcl.get(nextIndex++);
+			assertEquals("Expected commit not found at pos#" + (nextIndex - 1),
+					id.getId(), current.getId());
+			return this;
+		}
+
+		public CommitListAssert lanePos(int pos) {
+			PlotLane lane = current.getLane();
+			assertEquals("Position of lane of commit #" + (nextIndex - 1)
+					+ " not as expected.", pos, lane.getPosition());
+			return this;
+		}
+
+		public CommitListAssert parents(RevCommit... parents) {
+			assertEquals("Number of parents of commit #" + (nextIndex - 1)
+					+ " not as expected.", parents.length,
+					current.getParentCount());
+			for (int i = 0; i < parents.length; i++)
+				assertEquals("Unexpected parent of commit #" + (nextIndex - 1),
+						parents[i], current.getParent(i));
+			return this;
+		}
+
+		public CommitListAssert noMoreCommits() {
+			assertEquals("Unexpected size of list", nextIndex, pcl.size());
+			return this;
+		}
+	}
+
+	@SuppressWarnings("boxing")
+	public void testLinear() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b = commit(a);
+		final RevCommit c = commit(b);
+
+		PlotWalk pw = new PlotWalk(db);
+		pw.markStart(pw.lookupCommit(c.getId()));
+
+		PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
+		pcl.source(pw);
+		pcl.fillTo(Integer.MAX_VALUE);
+
+		CommitListAssert test = new CommitListAssert(pcl);
+		test.commit(c).lanePos(0).parents(b);
+		test.commit(b).lanePos(0).parents(a);
+		test.commit(a).lanePos(0).parents();
+		test.noMoreCommits();
+	}
+
+	@SuppressWarnings("boxing")
+	public void testMerged() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b = commit(a);
+		final RevCommit c = commit(a);
+		final RevCommit d = commit(b, c);
+
+		PlotWalk pw = new PlotWalk(db);
+		pw.markStart(pw.lookupCommit(d.getId()));
+
+		PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
+		pcl.source(pw);
+		pcl.fillTo(Integer.MAX_VALUE);
+
+		CommitListAssert test = new CommitListAssert(pcl);
+		test.commit(d).lanePos(0).parents(b, c);
+		test.commit(c).lanePos(0).parents(a);
+		test.commit(b).lanePos(1).parents(a);
+		test.commit(a).lanePos(0).parents();
+		test.noMoreCommits();
+	}
+
+	@SuppressWarnings("boxing")
+	public void testSideBranch() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b = commit(a);
+		final RevCommit c = commit(a);
+
+		PlotWalk pw = new PlotWalk(db);
+		pw.markStart(pw.lookupCommit(b.getId()));
+		pw.markStart(pw.lookupCommit(c.getId()));
+
+		PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
+		pcl.source(pw);
+		pcl.fillTo(Integer.MAX_VALUE);
+
+		CommitListAssert test = new CommitListAssert(pcl);
+		test.commit(c).lanePos(0).parents(a);
+		test.commit(b).lanePos(1).parents(a);
+		test.commit(a).lanePos(0).parents();
+		test.noMoreCommits();
+	}
+
+	@SuppressWarnings("boxing")
+	public void test2SideBranches() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b = commit(a);
+		final RevCommit c = commit(a);
+		final RevCommit d = commit(a);
+
+		PlotWalk pw = new PlotWalk(db);
+		pw.markStart(pw.lookupCommit(b.getId()));
+		pw.markStart(pw.lookupCommit(c.getId()));
+		pw.markStart(pw.lookupCommit(d.getId()));
+
+		PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
+		pcl.source(pw);
+		pcl.fillTo(Integer.MAX_VALUE);
+
+		CommitListAssert test = new CommitListAssert(pcl);
+		test.commit(d).lanePos(0).parents(a);
+		test.commit(c).lanePos(1).parents(a);
+		test.commit(b).lanePos(1).parents(a);
+		test.commit(a).lanePos(0).parents();
+		test.noMoreCommits();
+	}
+
+	@SuppressWarnings("boxing")
+	public void testBug300282_1() throws Exception {
+		final RevCommit a = commit();
+		final RevCommit b = commit(a);
+		final RevCommit c = commit(a);
+		final RevCommit d = commit(a);
+		final RevCommit e = commit(a);
+		final RevCommit f = commit(a);
+		final RevCommit g = commit(f);
+
+		PlotWalk pw = new PlotWalk(db);
+		// TODO: when we add unnecessary commit's as tips (e.g. a commit which
+		// is a parent of another tip) the walk will return those commits twice.
+		// Find out why!
+		// pw.markStart(pw.lookupCommit(a.getId()));
+		pw.markStart(pw.lookupCommit(b.getId()));
+		pw.markStart(pw.lookupCommit(c.getId()));
+		pw.markStart(pw.lookupCommit(d.getId()));
+		pw.markStart(pw.lookupCommit(e.getId()));
+		// pw.markStart(pw.lookupCommit(f.getId()));
+		pw.markStart(pw.lookupCommit(g.getId()));
+
+		PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
+		pcl.source(pw);
+		pcl.fillTo(Integer.MAX_VALUE);
+
+		CommitListAssert test = new CommitListAssert(pcl);
+		test.commit(g).lanePos(0).parents(f);
+		test.commit(f).lanePos(0).parents(a);
+		test.commit(e).lanePos(1).parents(a);
+		test.commit(d).lanePos(1).parents(a);
+		test.commit(c).lanePos(1).parents(a);
+		test.commit(b).lanePos(1).parents(a);
+		test.commit(a).lanePos(0).parents();
+		test.noMoreCommits();
+	}
+
+	// test the history of the egit project between 9fdaf3c1 and e76ad9170f
+	public void testEgitHistory() throws Exception {
+		final RevCommit merge_fix = commit();
+		final RevCommit add_simple = commit(merge_fix);
+		final RevCommit remove_unused = commit(merge_fix);
+		final RevCommit merge_remove = commit(add_simple, remove_unused);
+		final RevCommit resolve_handler = commit(merge_fix);
+		final RevCommit clear_repositorycache = commit(merge_remove);
+		final RevCommit add_Maven = commit(clear_repositorycache);
+		final RevCommit use_remote = commit(clear_repositorycache);
+		final RevCommit findToolBar_layout = commit(clear_repositorycache);
+		final RevCommit merge_add_Maven = commit(findToolBar_layout, add_Maven);
+		final RevCommit update_eclipse_iplog = commit(merge_add_Maven);
+		final RevCommit changeset_implementation = commit(clear_repositorycache);
+		final RevCommit merge_use_remote = commit(update_eclipse_iplog,
+				use_remote);
+		final RevCommit disable_source = commit(merge_use_remote);
+		final RevCommit update_eclipse_iplog2 = commit(merge_use_remote);
+		final RevCommit merge_disable_source = commit(update_eclipse_iplog2,
+				disable_source);
+		final RevCommit merge_changeset_implementation = commit(
+				merge_disable_source, changeset_implementation);
+		final RevCommit clone_operation = commit(merge_disable_source,
+				merge_changeset_implementation);
+		final RevCommit update_eclipse = commit(add_Maven);
+		final RevCommit merge_resolve_handler = commit(clone_operation,
+				resolve_handler);
+		final RevCommit disable_comment = commit(clone_operation);
+		final RevCommit merge_disable_comment = commit(merge_resolve_handler,
+				disable_comment);
+		final RevCommit fix_broken = commit(merge_disable_comment);
+		final RevCommit add_a_clear = commit(fix_broken);
+		final RevCommit merge_update_eclipse = commit(add_a_clear,
+				update_eclipse);
+		final RevCommit sort_roots = commit(merge_update_eclipse);
+		final RevCommit fix_logged_npe = commit(merge_changeset_implementation);
+		final RevCommit merge_fixed_logged_npe = commit(sort_roots,
+				fix_logged_npe);
+
+		PlotWalk pw = new PlotWalk(db);
+		pw.markStart(pw.lookupCommit(merge_fixed_logged_npe.getId()));
+
+		PlotCommitList<PlotLane> pcl = new PlotCommitList<PlotLane>();
+		pcl.source(pw);
+		pcl.fillTo(Integer.MAX_VALUE);
+
+		CommitListAssert test = new CommitListAssert(pcl);
+
+		test.commit(merge_fixed_logged_npe).parents(sort_roots, fix_logged_npe)
+				.lanePos(0);
+		test.commit(fix_logged_npe).parents(merge_changeset_implementation)
+				.lanePos(0);
+		test.commit(sort_roots).parents(merge_update_eclipse).lanePos(1);
+		test.commit(merge_update_eclipse).parents(add_a_clear, update_eclipse)
+				.lanePos(1);
+		test.commit(add_a_clear).parents(fix_broken).lanePos(1);
+		test.commit(fix_broken).parents(merge_disable_comment).lanePos(1);
+		test.commit(merge_disable_comment)
+				.parents(merge_resolve_handler, disable_comment).lanePos(1);
+		test.commit(disable_comment).parents(clone_operation).lanePos(1);
+		test.commit(merge_resolve_handler)
+				.parents(clone_operation, resolve_handler).lanePos(2);
+		test.commit(update_eclipse).parents(add_Maven).lanePos(3);
+		test.commit(clone_operation)
+				.parents(merge_disable_source, merge_changeset_implementation)
+				.lanePos(1);
+		test.commit(merge_changeset_implementation)
+				.parents(merge_disable_source, changeset_implementation)
+				.lanePos(0);
+		test.commit(merge_disable_source)
+				.parents(update_eclipse_iplog2, disable_source).lanePos(1);
+		test.commit(update_eclipse_iplog2).parents(merge_use_remote).lanePos(0);
+		test.commit(disable_source).parents(merge_use_remote).lanePos(1);
+		test.commit(merge_use_remote).parents(update_eclipse_iplog, use_remote)
+				.lanePos(0);
+		test.commit(changeset_implementation).parents(clear_repositorycache)
+				.lanePos(2);
+		test.commit(update_eclipse_iplog).parents(merge_add_Maven).lanePos(0);
+		test.commit(merge_add_Maven).parents(findToolBar_layout, add_Maven)
+				.lanePos(0);
+		test.commit(findToolBar_layout).parents(clear_repositorycache)
+				.lanePos(0);
+		test.commit(use_remote).parents(clear_repositorycache).lanePos(1);
+		test.commit(add_Maven).parents(clear_repositorycache).lanePos(3);
+		test.commit(clear_repositorycache).parents(merge_remove).lanePos(2);
+		test.commit(resolve_handler).parents(merge_fix).lanePos(4);
+		test.commit(merge_remove).parents(add_simple, remove_unused).lanePos(2);
+		test.commit(remove_unused).parents(merge_fix).lanePos(0);
+		test.commit(add_simple).parents(merge_fix).lanePos(1);
+		test.commit(merge_fix).parents().lanePos(3);
+		test.noMoreCommits();
+	}
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommitList.java b/org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommitList.java
index 55d0206c02..6ffa0336aa 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommitList.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revplot/PlotCommitList.java
@@ -1,5 +1,6 @@
 /*
- * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
+ * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>,
+ * Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com>
  * and other copyright owners as documented in the project's IP log.
  *
  * This program and the accompanying materials are made available
@@ -44,6 +45,7 @@
 package org.eclipse.jgit.revplot;
 
 import java.text.MessageFormat;
+import java.util.BitSet;
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.TreeSet;
@@ -68,17 +70,17 @@ public class PlotCommitList<L extends PlotLane> extends
 		RevCommitList<PlotCommit<L>> {
 	static final int MAX_LENGTH = 25;
 
-	private int lanesAllocated;
+	private int positionsAllocated;
 
-	private final TreeSet<Integer> freeLanes = new TreeSet<Integer>();
+	private final TreeSet<Integer> freePositions = new TreeSet<Integer>();
 
 	private final HashSet<PlotLane> activeLanes = new HashSet<PlotLane>(32);
 
 	@Override
 	public void clear() {
 		super.clear();
-		lanesAllocated = 0;
-		freeLanes.clear();
+		positionsAllocated = 0;
+		freePositions.clear();
 		activeLanes.clear();
 	}
 
@@ -131,42 +133,104 @@ public class PlotCommitList<L extends PlotLane> extends
 				c.lane = nextFreeLane();
 				activeLanes.add(c.lane);
 			}
-
 			for (int r = index - 1; r >= 0; r--) {
 				final PlotCommit rObj = get(r);
 				if (rObj == c)
 					break;
 				rObj.addPassingLane(c.lane);
 			}
+
 			currCommit.lane = c.lane;
 		} else {
 			// More than one child, or our child is a merge.
 			// Use a different lane.
 			//
 
+			// Process all our children. Especially important when there is more
+			// than one child (e.g. a commit is processed where other branches
+			// fork out). For each child the following is done
+			// 1. If no lane was assigned to the child a new lane is created and
+			// assigned
+			// 2. The lane of the child is closed. If this frees a position,
+			// this position will be added freePositions list.
+			// If we have multiple children which where previously not on a lane
+			// each such child will get his own new lane but all those new lanes
+			// will be on the same position. We have to take care that not
+			// multiple newly created (in step 1) lanes occupy that position on
+			// which the
+			// parent's lane will be on. Therefore we delay closing the lane
+			// with the parents position until all children are processed.
+
+			// The lane on that position the current commit will be on
+			PlotLane reservedLane = null;
+
 			for (int i = 0; i < nChildren; i++) {
 				final PlotCommit c = currCommit.children[i];
-				if (activeLanes.remove(c.lane)) {
-					recycleLane((L) c.lane);
-					freeLanes.add(Integer.valueOf(c.lane.getPosition()));
-				}
+				// don't forget to position all of your children if they are
+				// not already positioned.
+				if (c.lane == null) {
+					c.lane = nextFreeLane();
+					activeLanes.add(c.lane);
+					if (reservedLane != null)
+						closeLane(c.lane);
+					else
+						reservedLane = c.lane;
+				} else if (reservedLane == null && activeLanes.contains(c.lane))
+					reservedLane = c.lane;
+				else
+					closeLane(c.lane);
 			}
 
+			// finally all children are processed. We can close the lane on that
+			// position our current commit will be on.
+			if (reservedLane != null)
+				closeLane(reservedLane);
+
 			currCommit.lane = nextFreeLane();
 			activeLanes.add(currCommit.lane);
 
+			// take care: when connecting yourself to your child make sure that
+			// you will not be located on a lane on which a passed commit is
+			// located on. Otherwise we would have to draw a line through a
+			// commit.
 			int remaining = nChildren;
+			BitSet blockedPositions = new BitSet();
 			for (int r = index - 1; r >= 0; r--) {
 				final PlotCommit rObj = get(r);
 				if (currCommit.isChild(rObj)) {
 					if (--remaining == 0)
 						break;
 				}
-				rObj.addPassingLane(currCommit.lane);
+				if (rObj != null) {
+					PlotLane lane = rObj.getLane();
+					if (lane != null)
+						blockedPositions.set(lane.getPosition());
+					rObj.addPassingLane(currCommit.lane);
+				}
+			}
+			// Now let's check whether we have to reposition the lane
+			if (blockedPositions.get(currCommit.lane.getPosition())) {
+				int newPos = -1;
+				for (Integer pos : freePositions)
+					if (!blockedPositions.get(pos)) {
+						newPos = pos;
+						break;
+					}
+				if (newPos == -1)
+					newPos = positionsAllocated++;
+				freePositions.add(currCommit.lane.getPosition());
+				currCommit.lane.position = newPos;
 			}
 		}
 	}
 
+	private void closeLane(PlotLane lane) {
+		recycleLane((L) lane);
+		if (activeLanes.remove(lane)) {
+			freePositions.add(Integer.valueOf(lane.getPosition()));
+		}
+	}
+
 	private void setupChildren(final PlotCommit<L> currCommit) {
 		final int nParents = currCommit.getParentCount();
 		for (int i = 0; i < nParents; i++)
@@ -175,12 +239,12 @@ public class PlotCommitList<L extends PlotLane> extends
 
 	private PlotLane nextFreeLane() {
 		final PlotLane p = createLane();
-		if (freeLanes.isEmpty()) {
-			p.position = lanesAllocated++;
+		if (freePositions.isEmpty()) {
+			p.position = positionsAllocated++;
 		} else {
-			final Integer min = freeLanes.first();
+			final Integer min = freePositions.first();
 			p.position = min.intValue();
-			freeLanes.remove(min);
+			freePositions.remove(min);
 		}
 		return p;
 	}