Elides the beginning of tab titles that have common prefixes. ...

chrome/browser/ui/views/tabs/base_tab_strip.cc

Index: chrome/browser/ui/views/tabs/base_tab_strip.cc
===================================================================
--- chrome/browser/ui/views/tabs/base_tab_strip.cc	(revision 76049)
+++ chrome/browser/ui/views/tabs/base_tab_strip.cc	(working copy)
@@ -4,10 +4,16 @@
 
 #include "chrome/browser/ui/views/tabs/base_tab_strip.h"
 
+#include <vector>
+
+#include "base/command_line.h"
+#include "base/hash_tables.h"
 #include "base/logging.h"
+#include "base/string_split.h"
 #include "chrome/browser/ui/view_ids.h"
 #include "chrome/browser/ui/views/tabs/dragged_tab_controller.h"
 #include "chrome/browser/ui/views/tabs/tab_strip_controller.h"
+#include "chrome/common/chrome_switches.h"
 #include "views/widget/root_view.h"
 #include "views/window/window.h"
 
@@ -145,6 +151,7 @@
 
   TabData d = { tab, gfx::Rect() };
   tab_data_.insert(tab_data_.begin() + ModelIndexToTabIndex(model_index), d);
+  UpdateCommonTitlePrefix();
 
   AddChildView(tab);
 
@@ -175,6 +182,7 @@
   BaseTab* tab = GetBaseTabAtModelIndex(model_index);
   bool mini_state_changed = tab->data().mini != data.mini;
   tab->SetData(data);
+  UpdateCommonTitlePrefix();
   tab->SchedulePaint();
 
   if (mini_state_changed) {
@@ -404,8 +412,105 @@
   tab_data_.erase(tab_data_.begin() + tab_data_index);
 
   delete tab;
+  UpdateCommonTitlePrefix();
 }
 
+void BaseTabStrip::UpdateCommonTitlePrefix() {
+  // Hidden behind a command line flag until we want to enable it always.
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kElideTabTitlePrefix)) {
+    return;
+  }
+
+  // First, we need to identify if there are identical titles,
+  // because we don't want to remove prefixes for those at all.
+  // We do it as a separate pass so that we don't need to remove
+  // previously parsed titles when we find a duplicate title later on.
+  // This set will contain the indexes of the tab that have a duplicate.
+  base::hash_set<int> no_prefix_tab;
+  // This map is used to remember the title and the index of a tab. If
+  // multiple tabs have the same title the index is set to -1 and the indices
+  // of all tabs sharing the same title are placed in no_prefix_tab.
+  base::hash_map<string16, int> existing_title;
+  for (int tab_index = 0; tab_index < tab_count(); ++tab_index) {
+    DCHECK(tab_data_[tab_index].tab != NULL);
+    if (tab_data_[tab_index].tab->data().mini ||
+        tab_data_[tab_index].tab->data().title.empty()) {
+      continue;
+    }
+    // We use pairs to test existence and insert in one shot.
+    std::pair<base::hash_map<string16, int>::iterator, bool> insert_result =
+        existing_title.insert(
+            std::make_pair(tab_data_[tab_index].tab->data().title, tab_index));
+    if (!insert_result.second) {
+      // We found a duplicate title, insert_result.second is false when we
+      // insert a duplicate in the set. insert_result.first is a map iterator
+      // and thus insert_result.first->first is the title key of the map.
+      DCHECK(tab_data_[tab_index].tab->data().title ==
+             insert_result.first->first);
+      no_prefix_tab.insert(tab_index);
+      // insert_result.first->second is the value of the tab index.
+      if (insert_result.first->second != -1) {
+        no_prefix_tab.insert(insert_result.first->second);
+        insert_result.first->second = -1;
+      }
+    }
+  }
+
+  // This next loop accumulates all the potential prefixes,
+  // and remember on which tabs we saw them.
+  base::hash_map<string16, std::vector<int> > prefixes;
+  for (int tab_index = 0; tab_index < tab_count(); ++tab_index) {
+    const TabRendererData& tab_data = tab_data_[tab_index].tab->data();
+    // Mini, title-less, and duplicate title tabs
+    // are not to be included in this process.
+    if (tab_data.mini || tab_data.title.empty() ||
+        no_prefix_tab.find(tab_index) != no_prefix_tab.end()) {
+      continue;
+    }
+
+    // We only create prefixes at word boundaries.
+    std::vector<string16> words;
+    base::SplitStringAlongWhitespace(tab_data.title, &words);
+    if (words.size() > 1) {
+      size_t end_of_word = 0;
+      // We stop this for loop at words.size() - 1 because we don't need to
+      // insert the concatenation of all the words in the prefixes map because
+      // we ignore the complete title matches anyway.
+      for (size_t word_index = 0; word_index < words.size() - 1; ++word_index) {
+        if (!words[word_index].empty()) {
+          end_of_word = tab_data.title.find(words[word_index], end_of_word) +
+                        words[word_index].size();
+          prefixes[tab_data.title.substr(0, end_of_word)].push_back(tab_index);
+        }
+      }
+    }
+  }
+
+  // Now we parse the map to find common prefixes and set the largest per tab.
+  std::vector<size_t> prefix_lengths(tab_count(), 0);
+  for (base::hash_map<string16, std::vector<int> >::iterator iter =
+       prefixes.begin(); iter != prefixes.end(); ++iter) {
+    if (iter->second.size() > 1) {  // Need more than one with same prefix.
+      size_t prefix_length = iter->first.size();
+      for (size_t index = 0; index < iter->second.size(); ++index){
+        if (prefix_lengths[iter->second[index]] < prefix_length) {
+          prefix_lengths[iter->second[index]] = prefix_length;
+        }
+      }
+    }
+  }
+
+  // And finally, reset the tab data for the tabs that changed.
+  for (int tab_index = 0; tab_index < tab_count(); ++tab_index) {
+    TabRendererData data = tab_data_[tab_index].tab->data();
+    if (data.common_prefix_length != prefix_lengths[tab_index]) {
+      data.common_prefix_length = prefix_lengths[tab_index];
+      tab_data_[tab_index].tab->SetData(data);
+    }
+  }
+}
+
 int BaseTabStrip::TabIndexOfTab(BaseTab* tab) const {
   for (int i = 0; i < tab_count(); ++i) {
     if (base_tab_at_tab_index(i) == tab)