Opacity adjustments for image diffs

* ImageDiffHandler adds the slider; styled in gitblit.css
* imgdiff.js is a little bottom-loaded Javascript that adjusts the
  opacity on sliders' scroll events.
* The three diff pages add this bottom script to the page if needed
* GitBlitDiffFormatter: center image diffs.

5 files changed, 49 insertions, 2 deletions

diff --git a/src/main/java/com/gitblit/wicket/pages/BlobDiffPage.java b/src/main/java/com/gitblit/wicket/pages/BlobDiffPage.java
index 517e80b8..71516ec8 100644
--- a/src/main/java/com/gitblit/wicket/pages/BlobDiffPage.java
+++ b/src/main/java/com/gitblit/wicket/pages/BlobDiffPage.java
@@ -55,6 +55,9 @@ public class BlobDiffPage extends RepositoryPage {
 			ImageDiffHandler handler = new ImageDiffHandler(getContextUrl(), repositoryName,

 					parent.getName(), commit.getName(), imageExtensions);

 			diff = DiffUtils.getDiff(r, commit, blobPath, DiffOutputType.HTML, handler).content;

+			if (handler.getImgDiffCount() > 0) {

+				addBottomScript("scripts/imgdiff.js"); // Tiny support script for image diffs

+			}

 			add(new BookmarkablePageLink<Void>("patchLink", PatchPage.class,

 					WicketUtils.newPathParameter(repositoryName, objectId, blobPath)));

 		} else {

@@ -63,6 +66,9 @@ public class BlobDiffPage extends RepositoryPage {
 			ImageDiffHandler handler = new ImageDiffHandler(getContextUrl(), repositoryName,

 					baseCommit.getName(), commit.getName(), imageExtensions);

 			diff = DiffUtils.getDiff(r, baseCommit, commit, blobPath, DiffOutputType.HTML, handler).content;

+			if (handler.getImgDiffCount() > 0) {

+				addBottomScript("scripts/imgdiff.js"); // Tiny support script for image diffs

+			}

 			add(new BookmarkablePageLink<Void>("patchLink", PatchPage.class,

 					WicketUtils.newBlobDiffParameter(repositoryName, baseObjectId, objectId,

 							blobPath)));

diff --git a/src/main/java/com/gitblit/wicket/pages/CommitDiffPage.java b/src/main/java/com/gitblit/wicket/pages/CommitDiffPage.java
index 77d5ccf3..e40af515 100644
--- a/src/main/java/com/gitblit/wicket/pages/CommitDiffPage.java
+++ b/src/main/java/com/gitblit/wicket/pages/CommitDiffPage.java
@@ -85,6 +85,9 @@ public class CommitDiffPage extends RepositoryPage {
 		final ImageDiffHandler handler = new ImageDiffHandler(getContextUrl(), repositoryName,
 				parents.isEmpty() ? null : parents.get(0), commit.getName(), imageExtensions);
 		final DiffOutput diff = DiffUtils.getCommitDiff(r, commit, DiffOutputType.HTML, handler);
+		if (handler.getImgDiffCount() > 0) {
+			addBottomScript("scripts/imgdiff.js"); // Tiny support script for image diffs
+		}
 
 		// add commit diffstat
 		int insertions = 0;
diff --git a/src/main/java/com/gitblit/wicket/pages/ComparePage.java b/src/main/java/com/gitblit/wicket/pages/ComparePage.java
index dae8d8ea..c0141eba 100644
--- a/src/main/java/com/gitblit/wicket/pages/ComparePage.java
+++ b/src/main/java/com/gitblit/wicket/pages/ComparePage.java
@@ -117,6 +117,9 @@ public class ComparePage extends RepositoryPage {
 					fromCommit.getName(), toCommit.getName(), imageExtensions);
 
 			final DiffOutput diff = DiffUtils.getDiff(r, fromCommit, toCommit, DiffOutputType.HTML, handler);
+			if (handler.getImgDiffCount() > 0) {
+				addBottomScript("scripts/imgdiff.js"); // Tiny support script for image diffs
+			}
 
 			// add compare diffstat
 			int insertions = 0;
diff --git a/src/main/java/com/gitblit/wicket/pages/ImageDiffHandler.java b/src/main/java/com/gitblit/wicket/pages/ImageDiffHandler.java
index 69d84f4e..4278f238 100644
--- a/src/main/java/com/gitblit/wicket/pages/ImageDiffHandler.java
+++ b/src/main/java/com/gitblit/wicket/pages/ImageDiffHandler.java
@@ -40,6 +40,8 @@ public class ImageDiffHandler implements DiffUtils.BinaryDiffHandler {
 	private final String baseUrl;
 	private final List<String> imageExtensions;
 
+	private int imgDiffCount = 0;
+
 	public ImageDiffHandler(final String baseUrl, final String repositoryName, final String oldCommitId,
 			final String newCommitId, final List<String> imageExtensions) {
 		this.baseUrl = baseUrl;
@@ -62,8 +64,10 @@ public class ImageDiffHandler implements DiffUtils.BinaryDiffHandler {
 			String oldUrl = getImageUrl(diffEntry, Side.OLD);
 			String newUrl = getImageUrl(diffEntry, Side.NEW);
 			if (oldUrl != null && newUrl != null) {
+				imgDiffCount++;
+				String id = "imgdiff" + imgDiffCount;
 				HtmlBuilder builder = new HtmlBuilder("div");
-				Element container = builder.root().appendElement("div").attr("class", "imgdiff");
+				Element container = builder.root().attr("align", "center").appendElement("div").attr("class", "imgdiff");
 				Element resizeable = container.appendElement("div").attr("class", "imgdiff-left");
 				// style='max-width:640px;' is necessary for ensuring that the browser limits large images
 				// to some reasonable width, and to override the "img { max-width: 100%; }" from bootstrap.css,
@@ -73,8 +77,11 @@ public class ImageDiffHandler implements DiffUtils.BinaryDiffHandler {
 				// is too wide.
 				// XXX: Maybe add a max-height, too, to limit portrait-oriented images to some reasonable height?
 				// (Like a 300x10000px image...)
-				resizeable.appendElement("img").attr("class", "imgdiff imgdiff-left").attr("style", "max-width:640px;").attr("src", oldUrl);
+				resizeable.appendElement("img").attr("class", "imgdiff-left").attr("id", id).attr("style", "max-width:640px;").attr("src", oldUrl);
 				container.appendElement("img").attr("class", "imgdiff").attr("style", "max-width:640px;").attr("src", newUrl);
+				builder.root().appendElement("br");
+				Element slider = builder.root().appendElement("div").attr("class", "imgdiff-slider").attr("id", "slider-" + id);
+				slider.appendElement("div").attr("class", "imgdiff-slider-inner");
 				return builder.toString();
 			}
 			break;
@@ -90,6 +97,11 @@ public class ImageDiffHandler implements DiffUtils.BinaryDiffHandler {
 		return null;
 	}
 
+	/** Returns the number of image diffs generated so far by this {@link ImageDiffHandler}. */
+	public int getImgDiffCount() {
+		return imgDiffCount;
+	}
+
 	/**
 	 * Constructs a URL that will fetch the designated resource in the git repository. The returned string will
 	 * contain the URL fully URL-escaped, but note that it may still contain unescaped ampersands, so the result
diff --git a/src/main/java/com/gitblit/wicket/pages/scripts/imgdiff.js b/src/main/java/com/gitblit/wicket/pages/scripts/imgdiff.js
new file mode 100644
index 00000000..faa2f334
--- /dev/null
+++ b/src/main/java/com/gitblit/wicket/pages/scripts/imgdiff.js
@@ -0,0 +1,23 @@
+/*
+ * Copyright 2014 Tom <tw201207@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+jQuery(function () {
+	// Runs on jQuery's document.ready and sets up the scroll event handlers for all image diffs.
+	jQuery(".imgdiff-slider").scroll(function() {
+		var w = 1.0 - (this.scrollLeft / (this.scrollWidth - (this.clientWidth || this.offsetWidth)));
+		// We encode the target img id in the slider's id: slider-imgdiffNNN.
+		jQuery('#' + this.id.substr(this.id.indexOf('-') + 1)).css("opacity", w);
+	})
+});