Itemize and layout text lazily in RenderTextWin.

ui/gfx/render_text_win.cc

Index: ui/gfx/render_text_win.cc
===================================================================
--- ui/gfx/render_text_win.cc	(revision 111162)
+++ ui/gfx/render_text_win.cc	(working copy)
@@ -168,10 +168,12 @@
 }
 
 int RenderTextWin::GetStringWidth() {
+  EnsureLayout();
   return string_width_;
 }
 
 void RenderTextWin::Draw(Canvas* canvas) {
+  EnsureLayout();
   DrawSelection(canvas);
   DrawVisualText(canvas);
   DrawCursor(canvas);
@@ -181,6 +183,7 @@
   if (text().empty())
     return SelectionModel();
 
+  EnsureLayout();
   // Find the run that contains the point and adjust the argument location.
   Point p(ToTextPoint(point));
   size_t run_index = GetRunContainingPoint(p);
@@ -210,6 +213,8 @@
 
 Rect RenderTextWin::GetCursorBounds(const SelectionModel& selection,
                                     bool insert_mode) {
+  EnsureLayout();
+
   // Highlight the logical cursor (selection end) when not in insert mode.
   size_t pos = insert_mode ? selection.caret_pos() : selection.selection_end();
   size_t run_index = GetRunContainingPosition(pos);
@@ -262,6 +267,8 @@
 SelectionModel RenderTextWin::GetLeftSelectionModel(
     const SelectionModel& selection,
     BreakType break_type) {
+  EnsureLayout();
+
   if (break_type == LINE_BREAK || text().empty())
     return LeftEndSelectionModel();
   if (break_type == CHARACTER_BREAK)
@@ -273,6 +280,8 @@
 SelectionModel RenderTextWin::GetRightSelectionModel(
     const SelectionModel& selection,
     BreakType break_type) {
+  EnsureLayout();
+
   if (break_type == LINE_BREAK || text().empty())
     return RightEndSelectionModel();
   if (break_type == CHARACTER_BREAK)
@@ -363,6 +372,7 @@
   if (position == 0 || position == text().length())
     return true;
 
+  EnsureLayout();
   size_t run_index = GetRunContainingPosition(position);
   if (run_index >= runs_.size())
     return false;
@@ -376,13 +386,21 @@
 }
 
 void RenderTextWin::UpdateLayout() {
+  needs_layout_ = true;

[msw, 2011/11/28 21:15:46]

Add a simple comment like "Layout is performed lazily as needed for
drawing/metrics."

[Alexei Svitkine (slow), 2011/11/28 21:58:13]

Done.

+}
+
+void RenderTextWin::EnsureLayout() {

[msw, 2011/11/28 21:15:46]

This should be below IndexOfAdjacentGrapheme to match decl order.

[Alexei Svitkine (slow), 2011/11/28 21:58:13]

Done.

+  if (!needs_layout_)
+    return;
   // TODO(msw): Skip complex processing if ScriptIsComplex returns false.
   ItemizeLogicalText();
   if (!runs_.empty())
     LayoutVisualText();

[msw, 2011/11/28 21:15:46]

I think we actually need to reset |string_width_| here, or you could set
|string_width_ = 0| and then check |if (!runs_.empty())| for early-termination
at the top of LayoutVisualText.

[Alexei Svitkine (slow), 2011/11/28 21:58:13]

Good catch! Done.

+  needs_layout_ = false;
 }
 
 size_t RenderTextWin::IndexOfAdjacentGrapheme(size_t index, bool next) {
+  EnsureLayout();
   size_t run_index = GetRunContainingPosition(index);
   internal::TextRun* run = run_index < runs_.size() ? runs_[run_index] : NULL;
   int start = run ? run->range.start() : 0;
@@ -556,6 +574,7 @@
 }
 
 size_t RenderTextWin::GetRunContainingPosition(size_t position) const {
+  DCHECK(!needs_layout_);
   // Find the text run containing the argument position.
   size_t run = 0;
   for (; run < runs_.size(); ++run)
@@ -566,6 +585,7 @@
 }
 
 size_t RenderTextWin::GetRunContainingPoint(const Point& point) const {
+  DCHECK(!needs_layout_);
   // Find the text run containing the argument point (assumed already offset).
   size_t run = 0;
   for (; run < runs_.size(); ++run)