Support drag&drop for startup pages

chrome/browser/custom_home_pages_table_model.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/custom_home_pages_table_model.h"
 
 #include "base/i18n/rtl.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 48 matching lines @@
     entries_[i].url = urls[i];
     entries_[i].title.erase();
     entries_[i].icon.reset();
     LoadTitleAndFavicon(&(entries_[i]));
   }
   // Complete change, so tell the view to just rebuild itself.
   if (observer_)
     observer_->OnModelChanged();
 }
 
+/**
+ * Move a number of existing entries to a new position, reordering the table.
+ *
+ * We determine the range of elements affected by the move, save the moved
+ * elements, compact the remaining ones, and re-insert moved elements.
+ */
+void CustomHomePagesTableModel::MoveURLs(int insert_before,
+                                         const std::vector<int>& index_list)

[csilv, 2011/06/13 22:57:02]

Should we be concerned about this not working properly if index_list is not in
sorted order?  This won't happen in the current implementation, just thinking
defensively against future changes.

[groby-ooo-7-16, 2011/06/13 23:45:27]

Since the underlying SelectionModel uses Object.keys it's guaranteed to return
an ordered list. And it seems all other JS referring to selected items also
relies on the selection being ordered.

I've added a comment to that effect so people will at least be aware of this.

[csilv, 2011/06/14 00:06:12]

A comment is prefect, thanks.

On 2011/06/13 23:45:27, groby wrote:

+{
+  DCHECK(insert_before >= 0 && insert_before <= RowCount());
+
+  // The range of elements that needs to be reshuffled is [ |first|, |last| ).

[csilv, 2011/06/13 22:57:02]

nit picky: the end of the comment opens with a bracket and closes with a
parenthesis.

[groby-ooo-7-16, 2011/06/13 23:45:27]

Actually intentional - that's the standard range notation STL uses. In this
case, indicating a half-open range including first, excluding last.

[csilv, 2011/06/14 00:06:12]

Ah, that thought crossed my mind.  (I'm not familiar w/ STL notation as you can
see.)

On 2011/06/13 23:45:27, groby wrote:

+  int first = std::min(insert_before,index_list.front());

[csilv, 2011/06/13 22:57:02]

style nit: space after comma

[groby-ooo-7-16, 2011/06/13 23:45:27]

Done.

+  int last = std::max(insert_before, index_list.back() + 1);
+
+  // Save the dragged elements. Also, adjust insertion point if it is before a
+  // dragged element.
+  std::vector<Entry> moved_entries;
+  for (size_t i = 0; i < index_list.size(); ++i) {
+    moved_entries.push_back(entries_[index_list[i]]);
+    if (index_list[i] == insert_before)
+      insert_before++;
+  }
+
+  // Compact the range between beginning and insertion point, moving downwards.
+  size_t skip_count = 0;
+  for (int i = first; i < insert_before; ++i) {
+    if (skip_count < index_list.size() && index_list[skip_count] == i)
+      skip_count++;
+    else
+      entries_[i - skip_count]=entries_[i];
+  }
+
+  // Moving items down created a gap. We start compacting up after it.
+  first = insert_before;
+  insert_before -= skip_count;
+
+  // Now compact up for elements after the insertion point.
+  skip_count = 0;
+  for (int i = last - 1; i >= first; --i) {
+    if (skip_count < index_list.size() &&
+        index_list[index_list.size() - skip_count - 1] == i) {
+      skip_count++;
+    } else {
+      entries_[i + skip_count] = entries_[i];
+    }
+  }
+
+  // Insert moved elements.
+  std::copy(moved_entries.begin(), moved_entries.end(),
+      entries_.begin() + insert_before);
+
+  // Possibly large change, so tell the view to just rebuild itself.
+  if (observer_)
+    observer_->OnModelChanged();
+}
+
 void CustomHomePagesTableModel::Add(int index, const GURL& url) {
   DCHECK(index >= 0 && index <= RowCount());
   entries_.insert(entries_.begin() + static_cast<size_t>(index), Entry());
   entries_[index].url = url;
   LoadTitleAndFavicon(&(entries_[index]));
   if (observer_)
     observer_->OnItemsAdded(index, 1);
 }
 
 void CustomHomePagesTableModel::Remove(int index) {
@@ skipping 151 matching lines @@
   return NULL;
 }
 
 string16 CustomHomePagesTableModel::FormattedURL(int row) const {
   std::string languages =
       profile_->GetPrefs()->GetString(prefs::kAcceptLanguages);
   string16 url = net::FormatUrl(entries_[row].url, languages);
   url = base::i18n::GetDisplayStringInLTRDirectionality(url);
   return url;
 }