Rebuild CFDE_TextEditEngine.

This CL rebuilds the text edit engine in a simpler fashion. Instead of
depending on multiple pages, paragraphs and buffer fields there is a
single text edit engine which contains a gap buffer.

This makes the code easier to understand and follow.

Change-Id: I10fe85603fa9ed15a647eaac2d931f113cd0c7b0
Reviewed-on: https://pdfium-review.googlesource.com/11990
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: Ryan Harrison <rharrison@chromium.org>

6 files changed, 311 insertions, 396 deletions

diff --git a/xfa/fwl/cfwl_combobox.cpp b/xfa/fwl/cfwl_combobox.cpp
index a3dbe8c946..cbfbd9a447 100644
--- a/xfa/fwl/cfwl_combobox.cpp
+++ b/xfa/fwl/cfwl_combobox.cpp
@@ -11,8 +11,8 @@
 #include <utility>
 
 #include "third_party/base/ptr_util.h"
+#include "xfa/fde/cfde_texteditengine.h"
 #include "xfa/fde/cfde_textout.h"
-#include "xfa/fde/cfde_txtedtengine.h"
 #include "xfa/fwl/cfwl_app.h"
 #include "xfa/fwl/cfwl_event.h"
 #include "xfa/fwl/cfwl_eventselectchanged.h"
diff --git a/xfa/fwl/cfwl_combobox.h b/xfa/fwl/cfwl_combobox.h
index 0e1f815872..7242b1f450 100644
--- a/xfa/fwl/cfwl_combobox.h
+++ b/xfa/fwl/cfwl_combobox.h
@@ -76,7 +76,7 @@ class CFWL_ComboBox : public CFWL_Widget {
   bool EditCanRedo() const { return m_pEdit->CanRedo(); }
   bool EditUndo() { return m_pEdit->Undo(); }
   bool EditRedo() { return m_pEdit->Redo(); }
-  bool EditCanCopy() const { return m_pEdit->CountSelRanges() > 0; }
+  bool EditCanCopy() const { return m_pEdit->HasSelection(); }
   bool EditCanCut() const {
     if (m_pEdit->GetStylesEx() & FWL_STYLEEXT_EDT_ReadOnly)
       return false;
@@ -88,9 +88,9 @@ class CFWL_ComboBox : public CFWL_Widget {
   bool EditPaste(const CFX_WideString& wsPaste) {
     return m_pEdit->Paste(wsPaste);
   }
-  void EditSelectAll() { m_pEdit->AddSelRange(0); }
+  void EditSelectAll() { m_pEdit->SelectAll(); }
   void EditDelete() { m_pEdit->ClearText(); }
-  void EditDeSelect() { m_pEdit->ClearSelections(); }
+  void EditDeSelect() { m_pEdit->ClearSelection(); }
 
   CFX_RectF GetBBox() const;
   void EditModifyStylesEx(uint32_t dwStylesExAdded, uint32_t dwStylesExRemoved);
diff --git a/xfa/fwl/cfwl_comboedit.cpp b/xfa/fwl/cfwl_comboedit.cpp
index 68cde76707..2e53dbdf80 100644
--- a/xfa/fwl/cfwl_comboedit.cpp
+++ b/xfa/fwl/cfwl_comboedit.cpp
@@ -9,7 +9,7 @@
 #include <memory>
 #include <utility>
 
-#include "xfa/fde/cfde_txtedtengine.h"
+#include "xfa/fde/cfde_texteditengine.h"
 #include "xfa/fwl/cfwl_combobox.h"
 #include "xfa/fwl/cfwl_messagemouse.h"
 
@@ -22,14 +22,16 @@ CFWL_ComboEdit::CFWL_ComboEdit(
 }
 
 void CFWL_ComboEdit::ClearSelected() {
-  ClearSelections();
+  ClearSelection();
   RepaintRect(GetRTClient());
 }
 
 void CFWL_ComboEdit::SetSelected() {
   FlagFocus(true);
-  GetTxtEdtEngine()->MoveCaretPos(FDE_CaretMove::End, false);
-  AddSelRange(0);
+
+  // TODO(dsinclair): Fix CFWL_CombEdit::SetSelected
+  // GetTxtEdtEngine()->MoveCaretPos(FDE_CaretMove::End, false);
+  SelectAll();
 }
 
 void CFWL_ComboEdit::FlagFocus(bool bSet) {
diff --git a/xfa/fwl/cfwl_datetimepicker.h b/xfa/fwl/cfwl_datetimepicker.h
index fa7653ecf0..ece489e276 100644
--- a/xfa/fwl/cfwl_datetimepicker.h
+++ b/xfa/fwl/cfwl_datetimepicker.h
@@ -8,6 +8,7 @@
 #define XFA_FWL_CFWL_DATETIMEPICKER_H_
 
 #include <memory>
+#include <utility>
 
 #include "xfa/fwl/cfwl_datetimeedit.h"
 #include "xfa/fwl/cfwl_event.h"
@@ -51,9 +52,10 @@ class CFWL_DateTimePicker : public CFWL_Widget {
   void SetEditText(const CFX_WideString& wsText);
   CFX_WideString GetEditText() const;
 
-  int32_t CountSelRanges() const { return m_pEdit->CountSelRanges(); }
-  int32_t GetSelRange(int32_t nIndex, int32_t* nStart) const {
-    return m_pEdit->GetSelRange(nIndex, nStart);
+  bool HasSelection() const { return m_pEdit->HasSelection(); }
+  // Returns <start, end> indices of the selection.
+  std::pair<size_t, size_t> GetSelection() const {
+    return m_pEdit->GetSelection();
   }
 
   CFX_RectF GetBBox() const;
diff --git a/xfa/fwl/cfwl_edit.cpp b/xfa/fwl/cfwl_edit.cpp
index 5ec9378f09..72adb5392b 100644
--- a/xfa/fwl/cfwl_edit.cpp
+++ b/xfa/fwl/cfwl_edit.cpp
@@ -13,10 +13,8 @@
 
 #include "third_party/base/ptr_util.h"
 #include "third_party/base/stl_util.h"
+#include "xfa/fde/cfde_texteditengine.h"
 #include "xfa/fde/cfde_textout.h"
-#include "xfa/fde/cfde_txtedtengine.h"
-#include "xfa/fde/cfde_txtedtpage.h"
-#include "xfa/fde/cfde_txtedttextset.h"
 #include "xfa/fgas/font/cfgas_gefont.h"
 #include "xfa/fwl/cfwl_app.h"
 #include "xfa/fwl/cfwl_caret.h"
@@ -38,6 +36,12 @@ namespace {
 
 const int kEditMargin = 3;
 
+#if (_FX_OS_ == _FX_MACOSX_)
+constexpr int kEditingModifier = FWL_KEYFLAG_Command;
+#else
+constexpr int kEditingModifier = FWL_KEYFLAG_Ctrl;
+#endif
+
 bool FxEditIsLatinWord(wchar_t c) {
   return c == 0x2D || (c <= 0x005A && c >= 0x0041) ||
          (c <= 0x007A && c >= 0x0061) || (c <= 0x02AF && c >= 0x00C0) ||
@@ -65,24 +69,22 @@ CFWL_Edit::CFWL_Edit(const CFWL_App* app,
       m_fScrollOffsetX(0.0f),
       m_fScrollOffsetY(0.0f),
       m_bLButtonDown(false),
-      m_nSelStart(0),
+      m_CursorPosition(0),
       m_nLimit(-1),
       m_fFontSize(0),
       m_bSetRange(false),
-      m_iMax(0xFFFFFFF),
-      m_iCurRecord(-1),
-      m_iMaxRecord(128) {
+      m_iMax(0xFFFFFFF) {
   m_rtClient.Reset();
   m_rtEngine.Reset();
   m_rtStatic.Reset();
 
   InitCaret();
+  m_EdtEngine.SetDelegate(this);
 }
 
 CFWL_Edit::~CFWL_Edit() {
   if (m_pProperties->m_dwStates & FWL_WGTSTATE_Focused)
     HideCaret(nullptr);
-  ClearRecord();
 }
 
 FWL_Type CFWL_Edit::GetClassID() const {
@@ -108,12 +110,14 @@ CFX_RectF CFWL_Edit::GetWidgetRect() {
 
 CFX_RectF CFWL_Edit::GetAutosizedWidgetRect() {
   CFX_RectF rect;
-  if (m_EdtEngine.GetTextLength() > 0) {
-    CFX_SizeF sz = CalcTextSize(
-        m_EdtEngine.GetText(0, -1), m_pProperties->m_pThemeProvider,
+
+  if (m_EdtEngine.GetLength() > 0) {
+    CFX_SizeF size = CalcTextSize(
+        m_EdtEngine.GetText(), m_pProperties->m_pThemeProvider,
         !!(m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_MultiLine));
-    rect = CFX_RectF(0, 0, sz);
+    rect = CFX_RectF(0, 0, size);
   }
+
   InflateWidgetRect(rect);
   return rect;
 }
@@ -163,23 +167,16 @@ void CFWL_Edit::AddSpellCheckObj(CXFA_Path& PathData,
                                  int32_t nCount,
                                  float fOffSetX,
                                  float fOffSetY) {
-  float fStartX = 0.0f;
-  float fEndX = 0.0f;
-  float fY = 0.0f;
-  float fStep = 0.0f;
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  const FDE_TXTEDTPARAMS* txtEdtParams = m_EdtEngine.GetEditParams();
-  float fAsent = static_cast<float>(txtEdtParams->pFont->GetAscent()) *
-                 txtEdtParams->fFontSize / 1000;
-
-  std::vector<CFX_RectF> rectArray;
-  pPage->CalcRangeRectArray(nStart, nCount, &rectArray);
-
-  for (const auto& rectText : rectArray) {
-    fY = rectText.top + fAsent + fOffSetY;
-    fStep = txtEdtParams->fFontSize / 16.0f;
-    fStartX = rectText.left + fOffSetX;
-    fEndX = fStartX + rectText.Width();
+  float fStep = m_EdtEngine.GetFontSize() / 16.0f;
+  float font_ascent = m_EdtEngine.GetFontAscent();
+
+  std::vector<CFX_RectF> rects =
+      m_EdtEngine.GetCharacterRectsInRange(nStart, nCount);
+  for (const auto& rect : rects) {
+    float fY = rect.top + font_ascent + fOffSetY;
+    float fStartX = rect.left + fOffSetX;
+    float fEndX = fStartX + rect.Width();
+
     AddSquigglyPath(&PathData, fStartX, fEndX, fY, fStep);
   }
 }
@@ -273,35 +270,36 @@ void CFWL_Edit::SetThemeProvider(IFWL_ThemeProvider* pThemeProvider) {
 }
 
 void CFWL_Edit::SetText(const CFX_WideString& wsText) {
-  m_EdtEngine.SetText(wsText);
+  m_EdtEngine.Clear();
+  m_EdtEngine.Insert(0, wsText);
 }
 
 int32_t CFWL_Edit::GetTextLength() const {
-  return m_EdtEngine.GetTextLength();
+  return m_EdtEngine.GetLength();
 }
 
 CFX_WideString CFWL_Edit::GetText() const {
-  return m_EdtEngine.GetText(0, -1);
+  return m_EdtEngine.GetText();
 }
 
 void CFWL_Edit::ClearText() {
-  m_EdtEngine.ClearText();
+  m_EdtEngine.Clear();
 }
 
-void CFWL_Edit::AddSelRange(int32_t nStart) {
-  m_EdtEngine.AddSelRange(nStart, -1);
+void CFWL_Edit::SelectAll() {
+  m_EdtEngine.SelectAll();
 }
 
-int32_t CFWL_Edit::CountSelRanges() const {
-  return m_EdtEngine.CountSelRanges();
+bool CFWL_Edit::HasSelection() const {
+  return m_EdtEngine.HasSelection();
 }
 
-int32_t CFWL_Edit::GetSelRange(int32_t nIndex, int32_t* nStart) const {
-  return m_EdtEngine.GetSelRange(nIndex, nStart);
+std::pair<size_t, size_t> CFWL_Edit::GetSelection() const {
+  return m_EdtEngine.GetSelection();
 }
 
-void CFWL_Edit::ClearSelections() {
-  m_EdtEngine.ClearSelection();
+void CFWL_Edit::ClearSelection() {
+  return m_EdtEngine.ClearSelection();
 }
 
 int32_t CFWL_Edit::GetLimit() const {
@@ -310,7 +308,13 @@ int32_t CFWL_Edit::GetLimit() const {
 
 void CFWL_Edit::SetLimit(int32_t nLimit) {
   m_nLimit = nLimit;
-  m_EdtEngine.SetLimit(nLimit);
+
+  if (m_nLimit > 0) {
+    m_EdtEngine.SetHasCharacterLimit(true);
+    m_EdtEngine.SetCharacterLimit(nLimit);
+  } else {
+    m_EdtEngine.SetHasCharacterLimit(false);
+  }
 }
 
 void CFWL_Edit::SetAliasChar(wchar_t wAlias) {
@@ -318,73 +322,55 @@ void CFWL_Edit::SetAliasChar(wchar_t wAlias) {
 }
 
 bool CFWL_Edit::Copy(CFX_WideString& wsCopy) {
-  int32_t nCount = m_EdtEngine.CountSelRanges();
-  if (nCount == 0)
+  if (!m_EdtEngine.HasSelection())
     return false;
 
-  wsCopy.clear();
-  int32_t nStart;
-  int32_t nLength;
-  for (int32_t i = 0; i < nCount; i++) {
-    nLength = m_EdtEngine.GetSelRange(i, &nStart);
-    wsCopy += m_EdtEngine.GetText(nStart, nLength);
-  }
+  wsCopy = m_EdtEngine.GetSelectedText();
   return true;
 }
 
 bool CFWL_Edit::Cut(CFX_WideString& wsCut) {
-  int32_t nCount = m_EdtEngine.CountSelRanges();
-  if (nCount == 0)
+  if (!m_EdtEngine.HasSelection())
     return false;
 
-  wsCut.clear();
-  CFX_WideString wsTemp;
-  int32_t nStart, nLength;
-  for (int32_t i = 0; i < nCount; i++) {
-    nLength = m_EdtEngine.GetSelRange(i, &nStart);
-    wsTemp = m_EdtEngine.GetText(nStart, nLength);
-    wsCut += wsTemp;
-    wsTemp.clear();
-  }
-  m_EdtEngine.Delete(false);
+  wsCut = m_EdtEngine.DeleteSelectedText();
   return true;
 }
 
 bool CFWL_Edit::Paste(const CFX_WideString& wsPaste) {
-  FDE_EditResult iError = m_EdtEngine.Insert(wsPaste);
-  if (iError != FDE_EditResult::kSuccess) {
-    ProcessInsertError(iError);
-    return false;
-  }
+  if (m_EdtEngine.HasSelection())
+    m_EdtEngine.ReplaceSelectedText(wsPaste);
+  else
+    m_EdtEngine.Insert(m_CursorPosition, wsPaste);
+
   return true;
 }
 
 bool CFWL_Edit::Undo() {
-  if (!CanUndo())
-    return false;
-  m_EdtEngine.Undo(m_DoRecords[m_iCurRecord--].get());
-  return true;
+  return CanUndo() ? m_EdtEngine.Undo() : false;
 }
 
 bool CFWL_Edit::Redo() {
-  if (!CanRedo())
-    return false;
-  m_EdtEngine.Redo(m_DoRecords[++m_iCurRecord].get());
-  return true;
+  return CanRedo() ? m_EdtEngine.Redo() : false;
 }
 
 bool CFWL_Edit::CanUndo() {
-  return m_iCurRecord >= 0;
+  return m_EdtEngine.CanUndo();
 }
 
 bool CFWL_Edit::CanRedo() {
-  return m_iCurRecord < pdfium::CollectionSize<int32_t>(m_DoRecords) - 1;
+  return m_EdtEngine.CanRedo();
 }
 
 void CFWL_Edit::SetOuter(CFWL_Widget* pOuter) {
   m_pOuter = pOuter;
 }
 
+void CFWL_Edit::NotifyTextFull() {
+  CFWL_Event evt(CFWL_Event::Type::TextFull, this);
+  DispatchEvent(&evt);
+}
+
 void CFWL_Edit::OnCaretChanged() {
   if (m_rtEngine.IsEmpty())
     return;
@@ -425,10 +411,6 @@ void CFWL_Edit::OnSelChanged() {
   RepaintRect(GetClientRect());
 }
 
-void CFWL_Edit::OnAddDoRecord(std::unique_ptr<IFDE_TxtEdtDoRecord> pRecord) {
-  AddDoRecord(std::move(pRecord));
-}
-
 bool CFWL_Edit::OnValidate(const CFX_WideString& wsText) {
   CFWL_Widget* pDst = GetOuter();
   if (!pDst)
@@ -480,17 +462,15 @@ void CFWL_Edit::DrawTextBk(CXFA_Graphics* pGraphics,
 void CFWL_Edit::DrawContent(CXFA_Graphics* pGraphics,
                             IFWL_ThemeProvider* pTheme,
                             const CFX_Matrix* pMatrix) {
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  if (!pPage)
-    return;
-
   pGraphics->SaveGraphState();
+
   if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_CombText)
     pGraphics->SaveGraphState();
 
   CFX_RectF rtClip = m_rtEngine;
   float fOffSetX = m_rtEngine.left - m_fScrollOffsetX;
   float fOffSetY = m_rtEngine.top - m_fScrollOffsetY + m_fVAlignOffset;
+
   CFX_Matrix mt(1, 0, 0, 1, fOffSetX, fOffSetY);
   if (pMatrix) {
     rtClip = pMatrix->TransformRect(rtClip);
@@ -498,28 +478,15 @@ void CFWL_Edit::DrawContent(CXFA_Graphics* pGraphics,
   }
 
   bool bShowSel = !!(m_pProperties->m_dwStates & FWL_WGTSTATE_Focused);
-  int32_t nSelCount = m_EdtEngine.CountSelRanges();
-  if (bShowSel && nSelCount > 0) {
-    int32_t nPageCharStart = pPage->GetCharStart();
-    int32_t nPageCharCount = pPage->GetCharCount();
-    int32_t nPageCharEnd = nPageCharStart + nPageCharCount - 1;
-    int32_t nCharCount;
-    int32_t nCharStart;
-    std::vector<CFX_RectF> rectArr;
-    for (int32_t i = 0; i < nSelCount; i++) {
-      nCharCount = m_EdtEngine.GetSelRange(i, &nCharStart);
-      int32_t nCharEnd = nCharStart + nCharCount - 1;
-      if (nCharEnd < nPageCharStart || nCharStart > nPageCharEnd)
-        continue;
-
-      int32_t nBgn = std::max(nCharStart, nPageCharStart);
-      int32_t nEnd = std::min(nCharEnd, nPageCharEnd);
-      pPage->CalcRangeRectArray(nBgn - nPageCharStart, nEnd - nBgn + 1,
-                                &rectArr);
-    }
+  if (bShowSel && m_EdtEngine.HasSelection()) {
+    size_t sel_start;
+    size_t sel_end;
+    std::tie(sel_start, sel_end) = m_EdtEngine.GetSelection();
+    std::vector<CFX_RectF> rects = m_EdtEngine.GetCharacterRectsInRange(
+        sel_start, sel_end - sel_start + 1);
 
     CXFA_Path path;
-    for (auto& rect : rectArr) {
+    for (auto& rect : rects) {
       rect.left += fOffSetX;
       rect.top += fOffSetY;
       path.AddRectangle(rect.left, rect.top, rect.width, rect.height);
@@ -539,10 +506,11 @@ void CFWL_Edit::DrawContent(CXFA_Graphics* pGraphics,
   if (!pRenderDev)
     return;
 
-  RenderText(pRenderDev, rtClip, *pPage, mt);
+  RenderText(pRenderDev, rtClip, mt);
 
   if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_CombText) {
     pGraphics->RestoreGraphState();
+
     CXFA_Path path;
     int32_t iLimit = m_nLimit > 0 ? m_nLimit : 1;
     float fStep = m_rtEngine.width / iLimit;
@@ -566,83 +534,66 @@ void CFWL_Edit::DrawContent(CXFA_Graphics* pGraphics,
 
 void CFWL_Edit::RenderText(CFX_RenderDevice* pRenderDev,
                            const CFX_RectF& clipRect,
-                           const CFDE_TxtEdtPage& pPage,
                            const CFX_Matrix& mt) {
   ASSERT(pRenderDev);
 
-  CFDE_TxtEdtTextSet* pTextSet = pPage.GetTextSet();
-  if (!pTextSet)
-    return;
-
-  CFDE_TxtEdtEngine* engine = pPage.GetEngine();
-  ASSERT(engine);
-  const FDE_TXTEDTPARAMS* params = engine->GetEditParams();
-  ASSERT(params);
-
-  CFX_RetainPtr<CFGAS_GEFont> pFont = params->pFont;
-  if (!pFont)
+  CFX_RetainPtr<CFGAS_GEFont> font = m_EdtEngine.GetFont();
+  if (!font)
     return;
 
   pRenderDev->SetClip_Rect(clipRect);
 
   CFX_RectF rtDocClip = clipRect;
   if (rtDocClip.IsEmpty()) {
-    rtDocClip.left = rtDocClip.top = 0;
+    rtDocClip.left = 0;
+    rtDocClip.top = 0;
     rtDocClip.width = static_cast<float>(pRenderDev->GetWidth());
     rtDocClip.height = static_cast<float>(pRenderDev->GetHeight());
   }
   rtDocClip = mt.GetInverse().TransformRect(rtDocClip);
 
-  std::vector<FXTEXT_CHARPOS> char_pos;
-
-  for (size_t i = 0; i < pPage.GetTextPieceCount(); ++i) {
-    const FDE_TEXTEDITPIECE& pText = pPage.GetTextPiece(i);
-    if (!rtDocClip.IntersectWith(pTextSet->GetRect(pText)))
+  for (const FDE_TEXTEDITPIECE& info : m_EdtEngine.GetTextPieces()) {
+    // If this character is outside the clip, skip it.
+    if (!rtDocClip.IntersectWith(info.rtPiece))
       continue;
 
-    int32_t iCount = pTextSet->GetDisplayPos(pText, nullptr);
-    if (iCount < 1)
+    std::vector<FXTEXT_CHARPOS> char_pos = m_EdtEngine.GetDisplayPos(info);
+    if (char_pos.empty())
       continue;
-    if (char_pos.size() < static_cast<size_t>(iCount))
-      char_pos.resize(iCount, FXTEXT_CHARPOS());
 
-    iCount = pTextSet->GetDisplayPos(pText, char_pos.data());
-    CFDE_TextOut::DrawString(pRenderDev, params->dwFontColor, pFont,
-                             char_pos.data(), iCount, params->fFontSize, &mt);
+    CFDE_TextOut::DrawString(pRenderDev, m_EdtEngine.GetFontColor(), font,
+                             char_pos.data(), char_pos.size(),
+                             m_EdtEngine.GetFontSize(), &mt);
   }
 }
 
 void CFWL_Edit::UpdateEditEngine() {
   UpdateEditParams();
   UpdateEditLayout();
-  if (m_nLimit > -1)
-    m_EdtEngine.SetLimit(m_nLimit);
 }
 
 void CFWL_Edit::UpdateEditParams() {
-  FDE_TXTEDTPARAMS params;
-  params.fPlateWidth = m_rtEngine.width;
-  params.fPlateHeight = m_rtEngine.height;
-  if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_CombText)
-    params.dwLayoutStyles |= FDE_TEXTEDITLAYOUT_CombText;
-  if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_LastLineHeight)
-    params.dwLayoutStyles |= FDE_TEXTEDITLAYOUT_LastLineHeight;
-  if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_Validate)
-    params.dwMode |= FDE_TEXTEDITMODE_Validate;
-  if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_Password)
-    params.dwMode |= FDE_TEXTEDITMODE_Password;
+  m_EdtEngine.SetAvailableWidth(m_rtEngine.width);
+  m_EdtEngine.SetCombText(
+      !!(m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_CombText));
+
+  m_EdtEngine.EnableValidation(
+      !!(m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_Validate));
+  m_EdtEngine.EnablePasswordMode(
+      !!(m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_Password));
 
+  uint32_t alignment = 0;
   switch (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_HAlignMask) {
     case FWL_STYLEEXT_EDT_HNear: {
-      params.dwAlignment |= FDE_TEXTEDITALIGN_Left;
+      alignment |= CFX_TxtLineAlignment_Left;
       break;
     }
     case FWL_STYLEEXT_EDT_HCenter: {
-      params.dwAlignment |= FDE_TEXTEDITALIGN_Center;
+      alignment |= CFX_TxtLineAlignment_Center;
       break;
     }
     case FWL_STYLEEXT_EDT_HFar: {
-      params.dwAlignment |= FDE_TEXTEDITALIGN_Right;
+      alignment |= CFX_TxtLineAlignment_Right;
       break;
     }
     default:
@@ -650,88 +601,74 @@ void CFWL_Edit::UpdateEditParams() {
   }
   switch (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_HAlignModeMask) {
     case FWL_STYLEEXT_EDT_Justified: {
-      params.dwAlignment |= FDE_TEXTEDITALIGN_Justified;
+      alignment |= CFX_TxtLineAlignment_Justified;
       break;
     }
     default:
       break;
   }
+  m_EdtEngine.SetAlignment(alignment);
+
+  bool auto_hscroll =
+      !!(m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_AutoHScroll);
   if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_MultiLine) {
-    params.dwMode |= FDE_TEXTEDITMODE_MultiLines;
-    if ((m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_AutoHScroll) == 0) {
-      params.dwMode |=
-          FDE_TEXTEDITMODE_AutoLineWrap | FDE_TEXTEDITMODE_LimitArea_Horz;
-    }
-    if ((m_pProperties->m_dwStyles & FWL_WGTSTYLE_VScroll) == 0 &&
-        (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_AutoVScroll) == 0) {
-      params.dwMode |= FDE_TEXTEDITMODE_LimitArea_Vert;
-    } else {
-      params.fPlateHeight = 0x00FFFFFF;
-    }
-  } else if ((m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_AutoHScroll) ==
-             0) {
-    params.dwMode |= FDE_TEXTEDITMODE_LimitArea_Horz;
+    m_EdtEngine.EnableMultiLine(true);
+    m_EdtEngine.EnableLineWrap(!auto_hscroll);
+    m_EdtEngine.LimitVerticalScroll(
+        (m_pProperties->m_dwStyles & FWL_WGTSTYLE_VScroll) == 0 &&
+        (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_AutoVScroll) == 0);
+  } else {
+    m_EdtEngine.EnableMultiLine(false);
+    m_EdtEngine.EnableLineWrap(false);
+    m_EdtEngine.LimitVerticalScroll(false);
   }
+  m_EdtEngine.LimitHorizontalScroll(!auto_hscroll);
 
   IFWL_ThemeProvider* theme = GetAvailableTheme();
   CFWL_ThemePart part;
   part.m_pWidget = this;
-  m_fFontSize = theme ? theme->GetFontSize(&part) : FWLTHEME_CAPACITY_FontSize;
 
-  if (!theme)
+  if (!theme) {
+    m_fFontSize = FWLTHEME_CAPACITY_FontSize;
     return;
-
-  params.dwFontColor = theme->GetTextColor(&part);
-  params.fLineSpace = theme->GetLineHeight(&part);
+  }
+  m_fFontSize = theme->GetFontSize(&part);
 
   CFX_RetainPtr<CFGAS_GEFont> pFont = theme->GetFont(&part);
   if (!pFont)
     return;
 
-  params.pFont = pFont;
-  params.fFontSize = m_fFontSize;
-  params.nLineCount = (int32_t)(params.fPlateHeight / params.fLineSpace);
-  if (params.nLineCount <= 0)
-    params.nLineCount = 1;
-  params.fTabWidth = params.fFontSize * 1;
-  params.pEventSink = this;
-  m_EdtEngine.SetEditParams(params);
+  m_EdtEngine.SetFont(pFont);
+  m_EdtEngine.SetFontColor(theme->GetTextColor(&part));
+  m_EdtEngine.SetFontSize(m_fFontSize);
+  m_EdtEngine.SetLineSpace(theme->GetLineHeight(&part));
+  m_EdtEngine.SetTabWidth(m_fFontSize);
+  m_EdtEngine.SetVisibleLineCount(m_rtEngine.height /
+                                  theme->GetLineHeight(&part));
 }
 
 void CFWL_Edit::UpdateEditLayout() {
-  if (m_EdtEngine.GetTextLength() <= 0)
-    m_EdtEngine.SetText(L"");
-
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  if (pPage)
-    pPage->UnloadPage();
-
   m_EdtEngine.Layout();
-
-  pPage = m_EdtEngine.GetPage(0);
-  if (pPage)
-    pPage->LoadPage();
 }
 
 bool CFWL_Edit::UpdateOffset() {
-  CFX_RectF rtCaret = m_EdtEngine.GetCaretRect();
+  CFX_RectF rtCaret = m_rtCaret;
+
   float fOffSetX = m_rtEngine.left - m_fScrollOffsetX;
   float fOffSetY = m_rtEngine.top - m_fScrollOffsetY + m_fVAlignOffset;
   rtCaret.Offset(fOffSetX, fOffSetY);
-  const CFX_RectF& rtEidt = m_rtEngine;
-  if (rtEidt.Contains(rtCaret)) {
-    CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-    if (!pPage)
-      return false;
 
-    CFX_RectF rtFDE = pPage->GetContentsBox();
-    rtFDE.Offset(fOffSetX, fOffSetY);
-    if (rtFDE.right() < rtEidt.right() && m_fScrollOffsetX > 0) {
-      m_fScrollOffsetX += rtFDE.right() - rtEidt.right();
+  const CFX_RectF& edit_bounds = m_rtEngine;
+  if (edit_bounds.Contains(rtCaret)) {
+    CFX_RectF contents_bounds = m_EdtEngine.GetContentsBoundingBox();
+    contents_bounds.Offset(fOffSetX, fOffSetY);
+    if (contents_bounds.right() < edit_bounds.right() && m_fScrollOffsetX > 0) {
+      m_fScrollOffsetX += contents_bounds.right() - edit_bounds.right();
       m_fScrollOffsetX = std::max(m_fScrollOffsetX, 0.0f);
     }
-    if (rtFDE.bottom() < rtEidt.bottom() && m_fScrollOffsetY > 0) {
-      m_fScrollOffsetY += rtFDE.bottom() - rtEidt.bottom();
+    if (contents_bounds.bottom() < edit_bounds.bottom() &&
+        m_fScrollOffsetY > 0) {
+      m_fScrollOffsetY += contents_bounds.bottom() - edit_bounds.bottom();
       m_fScrollOffsetY = std::max(m_fScrollOffsetY, 0.0f);
     }
     return false;
@@ -739,18 +676,20 @@ bool CFWL_Edit::UpdateOffset() {
 
   float offsetX = 0.0;
   float offsetY = 0.0;
-  if (rtCaret.left < rtEidt.left)
-    offsetX = rtCaret.left - rtEidt.left;
-  if (rtCaret.right() > rtEidt.right())
-    offsetX = rtCaret.right() - rtEidt.right();
-  if (rtCaret.top < rtEidt.top)
-    offsetY = rtCaret.top - rtEidt.top;
-  if (rtCaret.bottom() > rtEidt.bottom())
-    offsetY = rtCaret.bottom() - rtEidt.bottom();
+  if (rtCaret.left < edit_bounds.left)
+    offsetX = rtCaret.left - edit_bounds.left;
+  if (rtCaret.right() > edit_bounds.right())
+    offsetX = rtCaret.right() - edit_bounds.right();
+  if (rtCaret.top < edit_bounds.top)
+    offsetY = rtCaret.top - edit_bounds.top;
+  if (rtCaret.bottom() > edit_bounds.bottom())
+    offsetY = rtCaret.bottom() - edit_bounds.bottom();
+
   m_fScrollOffsetX += offsetX;
   m_fScrollOffsetY += offsetY;
   if (m_fFontSize > m_rtEngine.height)
     m_fScrollOffsetY = 0;
+
   return true;
 }
 
@@ -763,12 +702,6 @@ bool CFWL_Edit::UpdateOffset(CFWL_ScrollBar* pScrollBar, float fPosChanged) {
 }
 
 void CFWL_Edit::UpdateVAlignment() {
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  if (!pPage)
-    return;
-
-  const CFX_RectF& rtFDE = pPage->GetContentsBox();
-  float fOffsetY = 0.0f;
   float fSpaceAbove = 0.0f;
   float fSpaceBelow = 0.0f;
   IFWL_ThemeProvider* theme = GetAvailableTheme();
@@ -777,23 +710,21 @@ void CFWL_Edit::UpdateVAlignment() {
     part.m_pWidget = this;
 
     CFX_SizeF pSpace = theme->GetSpaceAboveBelow(&part);
-    fSpaceAbove = pSpace.width;
-    fSpaceBelow = pSpace.height;
+    fSpaceAbove = pSpace.width >= 0.1f ? pSpace.width : 0.0f;
+    fSpaceBelow = pSpace.height >= 0.1f ? pSpace.height : 0.0f;
   }
-  if (fSpaceAbove < 0.1f)
-    fSpaceAbove = 0;
-  if (fSpaceBelow < 0.1f)
-    fSpaceBelow = 0;
 
+  float fOffsetY = 0.0f;
+  CFX_RectF contents_bounds = m_EdtEngine.GetContentsBoundingBox();
   if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_VCenter) {
-    fOffsetY = (m_rtEngine.height - rtFDE.height) / 2;
-    if (fOffsetY < (fSpaceAbove + fSpaceBelow) / 2 &&
+    fOffsetY = (m_rtEngine.height - contents_bounds.height) / 2.0f;
+    if (fOffsetY < (fSpaceAbove + fSpaceBelow) / 2.0f &&
         fSpaceAbove < fSpaceBelow) {
       return;
     }
-    fOffsetY += (fSpaceAbove - fSpaceBelow) / 2;
+    fOffsetY += (fSpaceAbove - fSpaceBelow) / 2.0f;
   } else if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_VFar) {
-    fOffsetY = (m_rtEngine.height - rtFDE.height);
+    fOffsetY = (m_rtEngine.height - contents_bounds.height);
     fOffsetY -= fSpaceBelow;
   } else {
     fOffsetY += fSpaceAbove;
@@ -802,11 +733,9 @@ void CFWL_Edit::UpdateVAlignment() {
 }
 
 void CFWL_Edit::UpdateCaret() {
-  CFX_RectF rtFDE = m_EdtEngine.GetCaretRect();
-
-  rtFDE.Offset(m_rtEngine.left - m_fScrollOffsetX,
-               m_rtEngine.top - m_fScrollOffsetY + m_fVAlignOffset);
-  CFX_RectF rtCaret(rtFDE.left, rtFDE.top, rtFDE.width, rtFDE.height);
+  CFX_RectF rtCaret = m_rtCaret;
+  rtCaret.Offset(m_rtEngine.left - m_fScrollOffsetX,
+                 m_rtEngine.top - m_fScrollOffsetY + m_fVAlignOffset);
 
   CFX_RectF rtClient = GetClientRect();
   rtCaret.Intersect(rtClient);
@@ -832,17 +761,13 @@ CFWL_ScrollBar* CFWL_Edit::UpdateScroll() {
   if (!bShowHorz && !bShowVert)
     return nullptr;
 
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  if (!pPage)
-    return nullptr;
-
-  const CFX_RectF& rtFDE = pPage->GetContentsBox();
+  CFX_RectF contents_bounds = m_EdtEngine.GetContentsBoundingBox();
   CFWL_ScrollBar* pRepaint = nullptr;
   if (bShowHorz) {
     CFX_RectF rtScroll = m_pHorzScrollBar->GetWidgetRect();
-    if (rtScroll.width < rtFDE.width) {
+    if (rtScroll.width < contents_bounds.width) {
       m_pHorzScrollBar->LockUpdate();
-      float fRange = rtFDE.width - rtScroll.width;
+      float fRange = contents_bounds.width - rtScroll.width;
       m_pHorzScrollBar->SetRange(0.0f, fRange);
 
       float fPos = pdfium::clamp(m_fScrollOffsetX, 0.0f, fRange);
@@ -866,10 +791,11 @@ CFWL_ScrollBar* CFWL_Edit::UpdateScroll() {
 
   if (bShowVert) {
     CFX_RectF rtScroll = m_pVertScrollBar->GetWidgetRect();
-    if (rtScroll.height < rtFDE.height) {
+    if (rtScroll.height < contents_bounds.height) {
       m_pVertScrollBar->LockUpdate();
-      float fStep = m_EdtEngine.GetEditParams()->fLineSpace;
-      float fRange = std::max(rtFDE.height - m_rtEngine.height, fStep);
+      float fStep = m_EdtEngine.GetLineSpace();
+      float fRange =
+          std::max(contents_bounds.height - m_rtEngine.height, fStep);
 
       m_pVertScrollBar->SetRange(0.0f, fRange);
       float fPos = pdfium::clamp(m_fScrollOffsetY, 0.0f, fRange);
@@ -907,27 +833,7 @@ bool CFWL_Edit::IsShowScrollBar(bool bVert) {
 }
 
 bool CFWL_Edit::IsContentHeightOverflow() {
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  if (!pPage)
-    return false;
-  return pPage->GetContentsBox().height > m_rtEngine.height + 1.0f;
-}
-
-int32_t CFWL_Edit::AddDoRecord(std::unique_ptr<IFDE_TxtEdtDoRecord> pRecord) {
-  int32_t nCount = pdfium::CollectionSize<int32_t>(m_DoRecords);
-  if (m_iCurRecord == nCount - 1) {
-    if (nCount == m_iMaxRecord) {
-      m_DoRecords.pop_front();
-      m_iCurRecord--;
-    }
-  } else {
-    m_DoRecords.erase(m_DoRecords.begin() + m_iCurRecord + 1,
-                      m_DoRecords.end());
-  }
-
-  m_DoRecords.push_back(std::move(pRecord));
-  m_iCurRecord = pdfium::CollectionSize<int32_t>(m_DoRecords) - 1;
-  return m_iCurRecord;
+  return m_EdtEngine.GetContentsBoundingBox().height > m_rtEngine.height + 1.0f;
 }
 
 void CFWL_Edit::Layout() {
@@ -1143,42 +1049,47 @@ bool CFWL_Edit::ValidateNumberChar(wchar_t cNum) {
   if (!m_bSetRange)
     return true;
 
-  CFX_WideString wsText = m_EdtEngine.GetText(0, -1);
+  CFX_WideString wsText = m_EdtEngine.GetText();
   if (wsText.IsEmpty())
     return cNum != L'0';
 
-  if (CountSelRanges() != 0)
+  if (HasSelection())
     return wsText.GetInteger() <= m_iMax;
-
-  int32_t caretPos = m_EdtEngine.GetCaretPos();
-  if (cNum == L'0' && caretPos == 0)
+  if (cNum == L'0' && m_CursorPosition == 0)
     return false;
 
   int32_t nLen = wsText.GetLength();
-  CFX_WideString l = wsText.Left(caretPos);
-  CFX_WideString r = wsText.Right(nLen - caretPos);
+  CFX_WideString l = wsText.Left(m_CursorPosition);
+  CFX_WideString r = wsText.Right(nLen - m_CursorPosition);
   CFX_WideString wsNew = l + cNum + r;
   return wsNew.GetInteger() <= m_iMax;
 }
 
 void CFWL_Edit::InitCaret() {
   m_pCaret.reset();
+  m_rtCaret = CFX_RectF();
 }
 
-void CFWL_Edit::ClearRecord() {
-  m_iCurRecord = -1;
-  m_DoRecords.clear();
-}
+void CFWL_Edit::UpdateCursorRect() {
+  int32_t bidi_level = 0;
+  m_rtCaret = CFX_RectF();
+  std::tie(bidi_level, m_rtCaret) =
+      m_EdtEngine.GetCharacterInfo(m_CursorPosition);
+  // TODO(dsinclair): This should handle bidi level  ...
 
-void CFWL_Edit::ProcessInsertError(FDE_EditResult iError) {
-  // TODO(dsinclair): This should probably also send events for Validation
-  // failure ....
+  if (m_rtCaret.width == 0 && m_rtCaret.left > 1.0f)
+    m_rtCaret.left -= 1.0f;
 
-  if (iError != FDE_EditResult::kFull)
+  m_rtCaret.width = 1.0f;
+}
+
+void CFWL_Edit::SetCursorPosition(size_t position) {
+  if (m_CursorPosition == position)
     return;
 
-  CFWL_Event textFullEvent(CFWL_Event::Type::TextFull, this);
-  DispatchEvent(&textFullEvent);
+  m_CursorPosition = position;
+  UpdateCursorRect();
+  OnCaretChanged();
 }
 
 void CFWL_Edit::OnProcessMessage(CFWL_Message* pMessage) {
@@ -1202,7 +1113,7 @@ void CFWL_Edit::OnProcessMessage(CFWL_Message* pMessage) {
           OnLButtonUp(pMsg);
           break;
         case FWL_MouseCommand::LeftButtonDblClk:
-          OnButtonDblClk(pMsg);
+          OnButtonDoubleClick(pMsg);
           break;
         case FWL_MouseCommand::Move:
           OnMouseMove(pMsg);
@@ -1251,14 +1162,13 @@ void CFWL_Edit::DoButtonDown(CFWL_MessageMouse* pMsg) {
   if ((m_pProperties->m_dwStates & FWL_WGTSTATE_Focused) == 0)
     SetFocus(true);
 
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  if (!pPage)
-    return;
+  // TODO(dsinclair): Handle DoButtonDown
+  //  bool bBefore = true;
+  //  int32_t nIndex =
+  //      std::max(0, pPage->GetCharIndex(DeviceToEngine(pMsg->m_pos),
+  //      bBefore));
 
-  bool bBefore = true;
-  int32_t nIndex =
-      std::max(0, pPage->GetCharIndex(DeviceToEngine(pMsg->m_pos), bBefore));
-  m_EdtEngine.SetCaretPos(nIndex, bBefore);
+  // SetCursorPosition(nIndex);
 }
 
 void CFWL_Edit::OnFocusChanged(CFWL_Message* pMsg, bool bSet) {
@@ -1273,15 +1183,11 @@ void CFWL_Edit::OnFocusChanged(CFWL_Message* pMsg, bool bSet) {
     m_pProperties->m_dwStates &= ~FWL_WGTSTATE_Focused;
     HideCaret(nullptr);
 
-    int32_t nSel = CountSelRanges();
-    if (nSel > 0) {
-      ClearSelections();
+    if (HasSelection()) {
+      ClearSelection();
       bRepaint = true;
     }
-    m_EdtEngine.SetCaretPos(0, true);
     UpdateOffset();
-
-    ClearRecord();
   }
 
   LayoutScrollBar();
@@ -1300,21 +1206,24 @@ void CFWL_Edit::OnLButtonDown(CFWL_MessageMouse* pMsg) {
   m_bLButtonDown = true;
   SetGrab(true);
   DoButtonDown(pMsg);
-  int32_t nIndex = m_EdtEngine.GetCaretPos();
+
   bool bRepaint = false;
-  if (m_EdtEngine.CountSelRanges() > 0) {
+  if (m_EdtEngine.HasSelection()) {
     m_EdtEngine.ClearSelection();
     bRepaint = true;
   }
 
-  if ((pMsg->m_dwFlags & FWL_KEYFLAG_Shift) && m_nSelStart != nIndex) {
-    int32_t iStart = std::min(m_nSelStart, nIndex);
-    int32_t iEnd = std::max(m_nSelStart, nIndex);
-    m_EdtEngine.AddSelRange(iStart, iEnd - iStart);
+  size_t index_at_click =
+      m_EdtEngine.GetIndexForPoint(DeviceToEngine(pMsg->m_pos));
+  if (index_at_click != m_CursorPosition &&
+      !!(pMsg->m_dwFlags & FWL_KEYFLAG_Shift)) {
+    size_t start = std::min(m_CursorPosition, index_at_click);
+    size_t end = std::max(m_CursorPosition, index_at_click);
+
+    m_EdtEngine.SetSelection(start, end);
     bRepaint = true;
-  } else {
-    m_nSelStart = nIndex;
   }
+
   if (bRepaint)
     RepaintRect(m_rtEngine);
 }
@@ -1324,80 +1233,83 @@ void CFWL_Edit::OnLButtonUp(CFWL_MessageMouse* pMsg) {
   SetGrab(false);
 }
 
-void CFWL_Edit::OnButtonDblClk(CFWL_MessageMouse* pMsg) {
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  if (!pPage)
-    return;
-
-  int32_t nCount = 0;
-  int32_t nIndex = pPage->SelectWord(DeviceToEngine(pMsg->m_pos), nCount);
-  if (nIndex < 0)
-    return;
-
-  m_EdtEngine.AddSelRange(nIndex, nCount);
-  m_EdtEngine.SetCaretPos(nIndex + nCount - 1, false);
+void CFWL_Edit::OnButtonDoubleClick(CFWL_MessageMouse* pMsg) {
+  // TODO(dsinclair): Handle OnButtonDoubleClick
+  //  int32_t nCount = 0;
+  //  int32_t nIndex = pPage->SelectWord(DeviceToEngine(pMsg->m_pos), nCount);
+  //  if (nIndex < 0)
+  //    return;
+  //
+  //  m_EdtEngine.AddSelRange(nIndex, nCount);
+  // SetCursorPosition(nIndex + nCount - 1);
   RepaintRect(m_rtEngine);
 }
 
 void CFWL_Edit::OnMouseMove(CFWL_MessageMouse* pMsg) {
-  if (m_nSelStart == -1 || !m_bLButtonDown)
+  bool shift = !!(pMsg->m_dwFlags & FWL_KEYFLAG_Shift);
+  if (!m_bLButtonDown || !shift)
     return;
 
-  CFDE_TxtEdtPage* pPage = m_EdtEngine.GetPage(0);
-  if (!pPage)
+  size_t old_cursor_pos = m_CursorPosition;
+  SetCursorPosition(m_EdtEngine.GetIndexForPoint(DeviceToEngine(pMsg->m_pos)));
+  if (old_cursor_pos == m_CursorPosition)
     return;
 
-  bool bBefore = true;
-  int32_t nIndex = pPage->GetCharIndex(DeviceToEngine(pMsg->m_pos), bBefore);
-  m_EdtEngine.SetCaretPos(nIndex, bBefore);
-  nIndex = m_EdtEngine.GetCaretPos();
-  m_EdtEngine.ClearSelection();
+  size_t length = m_EdtEngine.GetLength();
+  if (m_CursorPosition > length)
+    SetCursorPosition(length);
 
-  if (nIndex == m_nSelStart)
-    return;
-
-  int32_t nLen = m_EdtEngine.GetTextLength();
-  if (m_nSelStart >= nLen)
-    m_nSelStart = nLen;
-
-  m_EdtEngine.AddSelRange(std::min(m_nSelStart, nIndex),
-                          abs(nIndex - m_nSelStart));
+  size_t sel_start;
+  size_t sel_end;
+  std::tie(sel_start, sel_end) = m_EdtEngine.GetSelection();
+  m_EdtEngine.SetSelection(std::min(sel_start, m_CursorPosition),
+                           std::max(sel_end, m_CursorPosition));
 }
 
 void CFWL_Edit::OnKeyDown(CFWL_MessageKey* pMsg) {
   bool bShift = !!(pMsg->m_dwFlags & FWL_KEYFLAG_Shift);
   bool bCtrl = !!(pMsg->m_dwFlags & FWL_KEYFLAG_Ctrl);
+
+  size_t sel_start = m_CursorPosition;
+  if (m_EdtEngine.HasSelection()) {
+    size_t start_idx;
+    size_t end_idx;
+    std::tie(start_idx, end_idx) = m_EdtEngine.GetSelection();
+    sel_start = start_idx;
+  }
+
   switch (pMsg->m_dwKeyCode) {
     case FWL_VKEY_Left:
-      m_EdtEngine.MoveCaretPos(FDE_CaretMove::Left, bShift);
+      SetCursorPosition(m_EdtEngine.GetIndexLeft(m_CursorPosition));
       break;
     case FWL_VKEY_Right:
-      m_EdtEngine.MoveCaretPos(FDE_CaretMove::Right, bShift);
+      SetCursorPosition(m_EdtEngine.GetIndexRight(m_CursorPosition));
       break;
     case FWL_VKEY_Up:
-      m_EdtEngine.MoveCaretPos(FDE_CaretMove::Up, bShift);
+      SetCursorPosition(m_EdtEngine.GetIndexUp(m_CursorPosition));
       break;
     case FWL_VKEY_Down:
-      m_EdtEngine.MoveCaretPos(FDE_CaretMove::Down, bShift);
+      SetCursorPosition(m_EdtEngine.GetIndexDown(m_CursorPosition));
       break;
     case FWL_VKEY_Home:
-      m_EdtEngine.MoveCaretPos(
-          bCtrl ? FDE_CaretMove::Home : FDE_CaretMove::LineStart, bShift);
+      SetCursorPosition(
+          bCtrl ? 0 : m_EdtEngine.GetIndexAtStartOfLine(m_CursorPosition));
       break;
     case FWL_VKEY_End:
-      m_EdtEngine.MoveCaretPos(
-          bCtrl ? FDE_CaretMove::End : FDE_CaretMove::LineEnd, bShift);
+      SetCursorPosition(
+          bCtrl ? m_EdtEngine.GetLength()
+                : m_EdtEngine.GetIndexAtEndOfLine(m_CursorPosition));
       break;
     case FWL_VKEY_Delete: {
       if ((m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_ReadOnly) ||
           (m_pProperties->m_dwStates & FWL_WGTSTATE_Disabled)) {
         break;
       }
-#if (_FX_OS_ == _FX_MACOSX_)
-      m_EdtEngine.Delete(true);
-#else
-      m_EdtEngine.Delete(false);
-#endif
+
+      if (m_CursorPosition > 0) {
+        SetCursorPosition(m_EdtEngine.GetIndexBefore(m_CursorPosition));
+        m_EdtEngine.Delete(m_CursorPosition, 1);
+      }
       break;
     }
     case FWL_VKEY_Insert:
@@ -1406,6 +1318,13 @@ void CFWL_Edit::OnKeyDown(CFWL_MessageKey* pMsg) {
     default:
       break;
   }
+
+  // Update the selection.
+  if (bShift && sel_start != m_CursorPosition) {
+    m_EdtEngine.SetSelection(std::min(sel_start, m_CursorPosition),
+                             std::max(sel_start, m_CursorPosition));
+    RepaintRect(m_rtEngine);
+  }
 }
 
 void CFWL_Edit::OnChar(CFWL_MessageKey* pMsg) {
@@ -1414,25 +1333,27 @@ void CFWL_Edit::OnChar(CFWL_MessageKey* pMsg) {
     return;
   }
 
-  FDE_EditResult iError = FDE_EditResult::kSuccess;
   wchar_t c = static_cast<wchar_t>(pMsg->m_dwKeyCode);
   switch (c) {
     case FWL_VKEY_Back:
-      m_EdtEngine.Delete(true);
+      if (m_CursorPosition > 0) {
+        SetCursorPosition(m_EdtEngine.GetIndexBefore(m_CursorPosition));
+        m_EdtEngine.Delete(m_CursorPosition, 1);
+      }
       break;
     case FWL_VKEY_NewLine:
     case FWL_VKEY_Escape:
       break;
-    case FWL_VKEY_Tab: {
-      iError = m_EdtEngine.Insert(L"\t");
+    case FWL_VKEY_Tab:
+      m_EdtEngine.Insert(m_CursorPosition, L"\t");
+      SetCursorPosition(m_CursorPosition + 1);
       break;
-    }
-    case FWL_VKEY_Return: {
+    case FWL_VKEY_Return:
       if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_WantReturn) {
-        iError = m_EdtEngine.Insert(L"\n");
+        m_EdtEngine.Insert(m_CursorPosition, L"\n");
+        SetCursorPosition(m_CursorPosition + 1);
       }
       break;
-    }
     default: {
       if (!m_pWidgetMgr->IsFormDisabled()) {
         if (m_pProperties->m_dwStyleExes & FWL_STYLEEXT_EDT_Number) {
@@ -1445,20 +1366,14 @@ void CFWL_Edit::OnChar(CFWL_MessageKey* pMsg) {
             break;
         }
       }
-#if (_FX_OS_ == _FX_MACOSX_)
-      if (pMsg->m_dwFlags & FWL_KEYFLAG_Command)
-#else
-      if (pMsg->m_dwFlags & FWL_KEYFLAG_Ctrl)
-#endif
-      {
+      if (pMsg->m_dwFlags & kEditingModifier)
         break;
-      }
-      iError = m_EdtEngine.Insert(CFX_WideString(c));
+
+      m_EdtEngine.Insert(m_CursorPosition, CFX_WideString(c));
+      SetCursorPosition(m_CursorPosition + 1);
       break;
     }
   }
-  if (iError != FDE_EditResult::kSuccess)
-    ProcessInsertError(iError);
 }
 
 bool CFWL_Edit::OnScroll(CFWL_ScrollBar* pScrollBar,
diff --git a/xfa/fwl/cfwl_edit.h b/xfa/fwl/cfwl_edit.h
index 4a30904b0a..310cb81578 100644
--- a/xfa/fwl/cfwl_edit.h
+++ b/xfa/fwl/cfwl_edit.h
@@ -7,12 +7,11 @@
 #ifndef XFA_FWL_CFWL_EDIT_H_
 #define XFA_FWL_CFWL_EDIT_H_
 
-#include <deque>
 #include <memory>
+#include <utility>
 #include <vector>
 
-#include "xfa/fde/cfde_txtedtengine.h"
-#include "xfa/fde/ifde_txtedtdorecord.h"
+#include "xfa/fde/cfde_texteditengine.h"
 #include "xfa/fwl/cfwl_event.h"
 #include "xfa/fwl/cfwl_scrollbar.h"
 #include "xfa/fwl/cfwl_widget.h"
@@ -39,15 +38,13 @@
 #define FWL_STYLEEXT_EDT_HAlignModeMask (3L << 22)
 #define FWL_STYLEEXT_EDT_ShowScrollbarFocus (1L << 25)
 #define FWL_STYLEEXT_EDT_OuterScrollbar (1L << 26)
-#define FWL_STYLEEXT_EDT_LastLineHeight (1L << 27)
 
-class IFDE_TxtEdtDoRecord;
 class CFWL_Edit;
 class CFWL_MessageMouse;
 class CFWL_WidgetProperties;
 class CFWL_Caret;
 
-class CFWL_Edit : public CFWL_Widget {
+class CFWL_Edit : public CFWL_Widget, public CFDE_TextEditEngine::Delegate {
  public:
   CFWL_Edit(const CFWL_App* app,
             std::unique_ptr<CFWL_WidgetProperties> properties,
@@ -74,10 +71,12 @@ class CFWL_Edit : public CFWL_Widget {
   CFX_WideString GetText() const;
   void ClearText();
 
-  void AddSelRange(int32_t nStart);
-  int32_t CountSelRanges() const;
-  int32_t GetSelRange(int32_t nIndex, int32_t* nStart) const;
-  void ClearSelections();
+  void SelectAll();
+  void ClearSelection();
+  bool HasSelection() const;
+  // Returns <start, end> indices of the selection.
+  std::pair<size_t, size_t> GetSelection() const;
+
   int32_t GetLimit() const;
   void SetLimit(int32_t nLimit);
   void SetAliasChar(wchar_t wAlias);
@@ -91,23 +90,23 @@ class CFWL_Edit : public CFWL_Widget {
 
   void SetOuter(CFWL_Widget* pOuter);
 
-  void OnCaretChanged();
-  void OnTextChanged(const CFX_WideString& prevText);
-  void OnSelChanged();
-  void OnAddDoRecord(std::unique_ptr<IFDE_TxtEdtDoRecord> pRecord);
-  bool OnValidate(const CFX_WideString& wsText);
-  void SetScrollOffset(float fScrollOffset);
+  // CFDE_TextEditEngine::Delegate
+  void NotifyTextFull() override;
+  void OnCaretChanged() override;
+  void OnTextChanged(const CFX_WideString& prevText) override;
+  void OnSelChanged() override;
+  bool OnValidate(const CFX_WideString& wsText) override;
+  void SetScrollOffset(float fScrollOffset) override;
 
  protected:
   void ShowCaret(CFX_RectF* pRect);
   void HideCaret(CFX_RectF* pRect);
   const CFX_RectF& GetRTClient() const { return m_rtClient; }
-  CFDE_TxtEdtEngine* GetTxtEdtEngine() { return &m_EdtEngine; }
+  CFDE_TextEditEngine* GetTxtEdtEngine() { return &m_EdtEngine; }
 
  private:
   void RenderText(CFX_RenderDevice* pRenderDev,
                   const CFX_RectF& clipRect,
-                  const CFDE_TxtEdtPage& pPage,
                   const CFX_Matrix& mt);
   void DrawTextBk(CXFA_Graphics* pGraphics,
                   IFWL_ThemeProvider* pTheme,
@@ -133,22 +132,21 @@ class CFWL_Edit : public CFWL_Widget {
   void InitEngine();
   void InitCaret();
   bool ValidateNumberChar(wchar_t cNum);
-  void ClearRecord();
   bool IsShowScrollBar(bool bVert);
   bool IsContentHeightOverflow();
-  int32_t AddDoRecord(std::unique_ptr<IFDE_TxtEdtDoRecord> pRecord);
-  void ProcessInsertError(FDE_EditResult iError);
   void AddSpellCheckObj(CXFA_Path& PathData,
                         int32_t nStart,
                         int32_t nCount,
                         float fOffSetX,
                         float fOffSetY);
+  void SetCursorPosition(size_t position);
+  void UpdateCursorRect();
 
   void DoButtonDown(CFWL_MessageMouse* pMsg);
   void OnFocusChanged(CFWL_Message* pMsg, bool bSet);
   void OnLButtonDown(CFWL_MessageMouse* pMsg);
   void OnLButtonUp(CFWL_MessageMouse* pMsg);
-  void OnButtonDblClk(CFWL_MessageMouse* pMsg);
+  void OnButtonDoubleClick(CFWL_MessageMouse* pMsg);
   void OnMouseMove(CFWL_MessageMouse* pMsg);
   void OnKeyDown(CFWL_MessageKey* pMsg);
   void OnChar(CFWL_MessageKey* pMsg);
@@ -159,12 +157,13 @@ class CFWL_Edit : public CFWL_Widget {
   CFX_RectF m_rtClient;
   CFX_RectF m_rtEngine;
   CFX_RectF m_rtStatic;
+  CFX_RectF m_rtCaret;
   float m_fVAlignOffset;
   float m_fScrollOffsetX;
   float m_fScrollOffsetY;
-  CFDE_TxtEdtEngine m_EdtEngine;
+  CFDE_TextEditEngine m_EdtEngine;
   bool m_bLButtonDown;
-  int32_t m_nSelStart;
+  size_t m_CursorPosition;
   int32_t m_nLimit;
   float m_fFontSize;
   bool m_bSetRange;
@@ -174,9 +173,6 @@ class CFWL_Edit : public CFWL_Widget {
   std::unique_ptr<CFWL_Caret> m_pCaret;
   CFX_WideString m_wsCache;
   CFX_WideString m_wsFont;
-  std::deque<std::unique_ptr<IFDE_TxtEdtDoRecord>> m_DoRecords;
-  int32_t m_iCurRecord;
-  int32_t m_iMaxRecord;
 };
 
 #endif  // XFA_FWL_CFWL_EDIT_H_