[omnibox] Implement a rudimentary views::Label for header text

This CL uses a rudimentary views::Label to display header text for
AutocompleteResults that contain matches with headers.

Screenshot: https://i.imgur.com/f61GxWR.png

Bug: 1052522
Change-Id: I042c21a60a8416e243498793cee5c3dabeaac4f4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2137673
Commit-Queue: Tommy Li <tommycli@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756863}

chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.cc

@@ -299,10 +299,11 @@ void OmniboxPopupContentsView::UpdatePopupAppearance() {
                        location_bar_view_->profile()));
     }
   } else {
+    base::Optional<int> previous_row_group_id = base::nullopt;
     for (size_t i = 0; i < result_size; ++i) {
       // Create child views lazily.  Since especially the first result view may
       // be expensive to create due to loading font data, this saves time and
-      // memory during browser startup.
+      // memory during browser startup. https://crbug.com/1021323
       if (children().size() == i) {
         AddChildView(std::make_unique<OmniboxRowView>(
             std::make_unique<OmniboxResultView>(this, i)));
@@ -312,8 +313,19 @@ void OmniboxPopupContentsView::UpdatePopupAppearance() {
           static_cast<OmniboxRowView*>(children()[i]);
       row_view->SetVisible(true);
 
-      OmniboxResultView* const result_view = row_view->result_view();
+      // Show the header if it's distinct from the previous match's header.
       const AutocompleteMatch& match = GetMatchAtIndex(i);
+      if (match.suggestion_group_id.has_value() &&
+          match.suggestion_group_id != previous_row_group_id) {
+        row_view->ShowHeader(match.suggestion_group_id,
+                             model_->result().GetHeaderForGroupId(
+                                 match.suggestion_group_id.value()));
+      } else {
+        row_view->HideHeader();
+      }
+      previous_row_group_id = match.suggestion_group_id;
+
+      OmniboxResultView* const result_view = row_view->result_view();
       result_view->SetMatch(match);
 
       const SkBitmap* bitmap = model_->RichSuggestionBitmapAt(i);

chrome/browser/ui/views/omnibox/omnibox_row_view.cc

@@ -5,8 +5,27 @@
 #include "chrome/browser/ui/views/omnibox/omnibox_row_view.h"
 
 #include "chrome/browser/ui/views/omnibox/omnibox_result_view.h"
+#include "ui/views/controls/label.h"
 #include "ui/views/layout/box_layout.h"
 
+class OmniboxRowView::HeaderView : public views::Label {
+ public:
+  HeaderView() {
+    SetLayoutManager(std::make_unique<views::BoxLayout>(
+        views::BoxLayout::Orientation::kHorizontal));
+
+    header_text_ = AddChildView(std::make_unique<views::Label>());
+  }
+
+  void SetHeaderText(const base::string16& header_text) {
+    header_text_->SetText(header_text);
+  }
+
+ private:
+  // The Label containing the header text. This is never nullptr.
+  views::Label* header_text_;
+};
+
 OmniboxRowView::OmniboxRowView(std::unique_ptr<OmniboxResultView> result_view) {
   DCHECK(result_view);
 
@@ -16,7 +35,17 @@ OmniboxRowView::OmniboxRowView(std::unique_ptr<OmniboxResultView> result_view) {
   result_view_ = AddChildView(std::move(result_view));
 }
 
-void OmniboxRowView::SetHeader(base::Optional<int> suggestion_group_id,
+void OmniboxRowView::ShowHeader(base::Optional<int> suggestion_group_id,
                                 const base::string16& header_text) {
-  // TODO(tommycli): Create a child header view here. Not implemented yet.
+  // Create the header (at index 0) if it doesn't exist.
+  if (header_view_ == nullptr)
+    header_view_ = AddChildViewAt(std::make_unique<HeaderView>(), 0);
+
+  header_view_->SetHeaderText(header_text);
+  header_view_->SetVisible(true);
+}
+
+void OmniboxRowView::HideHeader() {
+  if (header_view_)
+    header_view_->SetVisible(false);
 }

chrome/browser/ui/views/omnibox/omnibox_row_view.h

@@ -22,15 +22,24 @@ class OmniboxRowView : public views::View {
  public:
   explicit OmniboxRowView(std::unique_ptr<OmniboxResultView> result_view);
 
-  // Sets the header that appears above this row. |suggestion_group_id| can be
-  // base::nullopt, and that will hide the header.
-  void SetHeader(base::Optional<int> suggestion_group_id,
+  // Sets the header that appears above this row. Also shows the header.
+  void ShowHeader(base::Optional<int> suggestion_group_id,
                   const base::string16& header_text);
 
+  // Hides the header.
+  void HideHeader();
+
   // The result view associated with this row.
   OmniboxResultView* result_view() const { return result_view_; }
 
  private:
+  class HeaderView;
+
+  // Non-owning pointer to the header view for this row. This is initially
+  // nullptr, and lazily created when a header is first set for this row.
+  // Lazily creating these speeds up browser startup: https://crbug.com/1021323
+  HeaderView* header_view_ = nullptr;
+
   // Non-owning pointer to the result view for this row. This is never nullptr.
   OmniboxResultView* result_view_;
 };

components/omnibox/browser/autocomplete_result.cc

@@ -728,7 +728,7 @@ AutocompleteResult::GetMatchDedupComparators() const {
 }
 
 base::string16 AutocompleteResult::GetHeaderForGroupId(
-    int suggestion_group_id) {
+    int suggestion_group_id) const {
   const auto& it = headers_map_.find(suggestion_group_id);
   if (it != headers_map_.end())
     return it->second;

components/omnibox/browser/autocomplete_result.h

@@ -155,7 +155,9 @@ class AutocompleteResult {
   // Get a list of comparators used for deduping for the matches in this result.
   std::vector<MatchDedupComparator> GetMatchDedupComparators() const;
 
-  base::string16 GetHeaderForGroupId(int suggestion_group_id);
+  // Gets the header string associated with |suggestion_group_id|. Returns an
+  // empty string if no header is found.
+  base::string16 GetHeaderForGroupId(int suggestion_group_id) const;
 
   // Logs metrics for when |new_result| replaces |old_result| asynchronously.
   // |old_result| a list of the comparators for the old matches.