Converted low-hanging cpwl classes in CFX_ByteTextBuf to ostringstream.

Bug: pdfium:731
Change-Id: I3faf5a4ec4b2af6145348e526f39ccbc2055e62e
Reviewed-on: https://pdfium-review.googlesource.com/7050
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

14 files changed, 306 insertions, 323 deletions

diff --git a/fpdfsdk/pdfwindow/cpwl_caret.cpp b/fpdfsdk/pdfwindow/cpwl_caret.cpp
index 3275dd1b33..a6a165f9a0 100644
--- a/fpdfsdk/pdfwindow/cpwl_caret.cpp
+++ b/fpdfsdk/pdfwindow/cpwl_caret.cpp
@@ -6,6 +6,8 @@
 
 #include "fpdfsdk/pdfwindow/cpwl_caret.h"
 
+#include <sstream>
+
 #include "core/fxge/cfx_graphstatedata.h"
 #include "core/fxge/cfx_pathdata.h"
 #include "core/fxge/cfx_renderdevice.h"
@@ -24,70 +26,68 @@ CFX_ByteString CPWL_Caret::GetClassName() const {
   return "CPWL_Caret";
 }
 
-void CPWL_Caret::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
-  GetCaretApp(sAppStream, CFX_PointF());
+void CPWL_Caret::GetThisAppearanceStream(std::ostringstream* psAppStream) {
+  GetCaretApp(CFX_PointF(), psAppStream);
 }
 
 void CPWL_Caret::DrawThisAppearance(CFX_RenderDevice* pDevice,
                                     CFX_Matrix* pUser2Device) {
-  if (IsVisible() && m_bFlash) {
-    CFX_FloatRect rcRect = GetCaretRect();
-    CFX_FloatRect rcClip = GetClipRect();
-    CFX_PathData path;
-
-    float fCaretX = rcRect.left + m_fWidth * 0.5f;
-    float fCaretTop = rcRect.top;
-    float fCaretBottom = rcRect.bottom;
-    if (!rcClip.IsEmpty()) {
-      rcRect.Intersect(rcClip);
-      if (rcRect.IsEmpty())
-        return;
-
-      fCaretTop = rcRect.top;
-      fCaretBottom = rcRect.bottom;
-    }
+  if (!IsVisible() || !m_bFlash)
+    return;
+
+  CFX_FloatRect rcRect = GetCaretRect();
+  CFX_FloatRect rcClip = GetClipRect();
+  CFX_PathData path;
+
+  float fCaretX = rcRect.left + m_fWidth * 0.5f;
+  float fCaretTop = rcRect.top;
+  float fCaretBottom = rcRect.bottom;
+  if (!rcClip.IsEmpty()) {
+    rcRect.Intersect(rcClip);
+    if (rcRect.IsEmpty())
+      return;
+
+    fCaretTop = rcRect.top;
+    fCaretBottom = rcRect.bottom;
+  }
 
-    path.AppendPoint(CFX_PointF(fCaretX, fCaretBottom), FXPT_TYPE::MoveTo,
-                     false);
-    path.AppendPoint(CFX_PointF(fCaretX, fCaretTop), FXPT_TYPE::LineTo, false);
+  path.AppendPoint(CFX_PointF(fCaretX, fCaretBottom), FXPT_TYPE::MoveTo, false);
+  path.AppendPoint(CFX_PointF(fCaretX, fCaretTop), FXPT_TYPE::LineTo, false);
 
-    CFX_GraphStateData gsd;
-    gsd.m_LineWidth = m_fWidth;
-    pDevice->DrawPath(&path, pUser2Device, &gsd, 0, ArgbEncode(255, 0, 0, 0),
-                      FXFILL_ALTERNATE);
-  }
+  CFX_GraphStateData gsd;
+  gsd.m_LineWidth = m_fWidth;
+  pDevice->DrawPath(&path, pUser2Device, &gsd, 0, ArgbEncode(255, 0, 0, 0),
+                    FXFILL_ALTERNATE);
 }
 
-void CPWL_Caret::GetCaretApp(CFX_ByteTextBuf& sAppStream,
-                             const CFX_PointF& ptOffset) {
-  if (IsVisible() && m_bFlash) {
-    CFX_ByteTextBuf sCaret;
-
-    CFX_FloatRect rcRect = GetCaretRect();
-    CFX_FloatRect rcClip = GetClipRect();
+void CPWL_Caret::GetCaretApp(const CFX_PointF& ptOffset,
+                             std::ostringstream* psAppStream) {
+  if (!IsVisible() || !m_bFlash)
+    return;
 
-    rcRect = CPWL_Utils::OffsetRect(rcRect, ptOffset.x, ptOffset.y);
-    rcClip = CPWL_Utils::OffsetRect(rcClip, ptOffset.x, ptOffset.y);
+  CFX_FloatRect rcRect = GetCaretRect();
+  CFX_FloatRect rcClip = GetClipRect();
 
-    sCaret << "q\n";
-    if (!rcClip.IsEmpty()) {
-      sCaret << rcClip.left << " " << rcClip.bottom + 2.5f << " "
-             << rcClip.right - rcClip.left << " "
-             << rcClip.top - rcClip.bottom - 4.5f << " re W n\n";
-    }
-    sCaret << m_fWidth << " w\n0 G\n";
-    sCaret << rcRect.left + m_fWidth / 2 << " " << rcRect.bottom << " m\n";
-    sCaret << rcRect.left + m_fWidth / 2 << " " << rcRect.top << " l S\nQ\n";
+  rcRect = CPWL_Utils::OffsetRect(rcRect, ptOffset.x, ptOffset.y);
+  rcClip = CPWL_Utils::OffsetRect(rcClip, ptOffset.x, ptOffset.y);
 
-    sAppStream << sCaret;
+  *psAppStream << "q\n";
+  if (!rcClip.IsEmpty()) {
+    *psAppStream << rcClip.left << " " << rcClip.bottom + 2.5f << " "
+                 << rcClip.right - rcClip.left << " "
+                 << rcClip.top - rcClip.bottom - 4.5f << " re W n\n";
   }
+  *psAppStream << m_fWidth << " w\n0 G\n"
+               << rcRect.left + m_fWidth / 2 << " " << rcRect.bottom << " m\n"
+               << rcRect.left + m_fWidth / 2 << " " << rcRect.top
+               << " l S\nQ\n";
 }
 
 CFX_ByteString CPWL_Caret::GetCaretAppearanceStream(
     const CFX_PointF& ptOffset) {
-  CFX_ByteTextBuf sCaret;
-  GetCaretApp(sCaret, ptOffset);
-  return sCaret.MakeString();
+  std::ostringstream sCaret;
+  GetCaretApp(ptOffset, &sCaret);
+  return CFX_ByteString(sCaret);
 }
 
 void CPWL_Caret::TimerProc() {
diff --git a/fpdfsdk/pdfwindow/cpwl_caret.h b/fpdfsdk/pdfwindow/cpwl_caret.h
index 325f13b7eb..7c723b96b3 100644
--- a/fpdfsdk/pdfwindow/cpwl_caret.h
+++ b/fpdfsdk/pdfwindow/cpwl_caret.h
@@ -25,7 +25,7 @@ class CPWL_Caret : public CPWL_Wnd {
 
   // CPWL_Wnd
   CFX_ByteString GetClassName() const override;
-  void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) override;
+  void GetThisAppearanceStream(std::ostringstream* psAppStream) override;
   void DrawThisAppearance(CFX_RenderDevice* pDevice,
                           CFX_Matrix* pUser2Device) override;
   void InvalidateRect(CFX_FloatRect* pRect = nullptr) override;
@@ -39,7 +39,7 @@ class CPWL_Caret : public CPWL_Wnd {
   void SetInvalidRect(CFX_FloatRect rc) { m_rcInvalid = rc; }
 
  private:
-  void GetCaretApp(CFX_ByteTextBuf& sAppStream, const CFX_PointF& ptOffset);
+  void GetCaretApp(const CFX_PointF& ptOffset, std::ostringstream* psAppStream);
   CFX_FloatRect GetCaretRect() const;
 
   bool m_bFlash;
diff --git a/fpdfsdk/pdfwindow/cpwl_combo_box.cpp b/fpdfsdk/pdfwindow/cpwl_combo_box.cpp
index 2929aac90f..3a6f08c6cd 100644
--- a/fpdfsdk/pdfwindow/cpwl_combo_box.cpp
+++ b/fpdfsdk/pdfwindow/cpwl_combo_box.cpp
@@ -7,6 +7,7 @@
 #include "fpdfsdk/pdfwindow/cpwl_combo_box.h"
 
 #include <algorithm>
+#include <sstream>
 
 #include "core/fxge/cfx_pathdata.h"
 #include "core/fxge/cfx_renderdevice.h"
@@ -96,35 +97,33 @@ bool CPWL_CBListBox::OnCharWithExit(uint16_t nChar,
   return true;
 }
 
-void CPWL_CBButton::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
-  CPWL_Wnd::GetThisAppearanceStream(sAppStream);
+void CPWL_CBButton::GetThisAppearanceStream(std::ostringstream* psAppStream) {
+  CPWL_Wnd::GetThisAppearanceStream(psAppStream);
 
   CFX_FloatRect rectWnd = CPWL_Wnd::GetWindowRect();
 
-  if (IsVisible() && !rectWnd.IsEmpty()) {
-    CFX_ByteTextBuf sButton;
-
-    CFX_PointF ptCenter = GetCenterPoint();
-
-    CFX_PointF pt1(ptCenter.x - PWL_CBBUTTON_TRIANGLE_HALFLEN,
-                   ptCenter.y + PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
-    CFX_PointF pt2(ptCenter.x + PWL_CBBUTTON_TRIANGLE_HALFLEN,
-                   ptCenter.y + PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
-    CFX_PointF pt3(ptCenter.x,
-                   ptCenter.y - PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
-
-    if (IsFloatBigger(rectWnd.right - rectWnd.left,
-                      PWL_CBBUTTON_TRIANGLE_HALFLEN * 2) &&
-        IsFloatBigger(rectWnd.top - rectWnd.bottom,
-                      PWL_CBBUTTON_TRIANGLE_HALFLEN)) {
-      sButton << "0 g\n";
-      sButton << pt1.x << " " << pt1.y << " m\n";
-      sButton << pt2.x << " " << pt2.y << " l\n";
-      sButton << pt3.x << " " << pt3.y << " l\n";
-      sButton << pt1.x << " " << pt1.y << " l f\n";
-
-      sAppStream << "q\n" << sButton << "Q\n";
-    }
+  if (!IsVisible() || rectWnd.IsEmpty())
+    return;
+
+  CFX_PointF ptCenter = GetCenterPoint();
+
+  CFX_PointF pt1(ptCenter.x - PWL_CBBUTTON_TRIANGLE_HALFLEN,
+                 ptCenter.y + PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
+  CFX_PointF pt2(ptCenter.x + PWL_CBBUTTON_TRIANGLE_HALFLEN,
+                 ptCenter.y + PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
+  CFX_PointF pt3(ptCenter.x, ptCenter.y - PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
+
+  if (IsFloatBigger(rectWnd.right - rectWnd.left,
+                    PWL_CBBUTTON_TRIANGLE_HALFLEN * 2) &&
+      IsFloatBigger(rectWnd.top - rectWnd.bottom,
+                    PWL_CBBUTTON_TRIANGLE_HALFLEN)) {
+    *psAppStream << "q\n"
+                 << "0 g\n"
+                 << pt1.x << " " << pt1.y << " m\n"
+                 << pt2.x << " " << pt2.y << " l\n"
+                 << pt3.x << " " << pt3.y << " l\n"
+                 << pt1.x << " " << pt1.y << " l f\n"
+                 << "Q\n";
   }
 }
 
@@ -134,30 +133,30 @@ void CPWL_CBButton::DrawThisAppearance(CFX_RenderDevice* pDevice,
 
   CFX_FloatRect rectWnd = CPWL_Wnd::GetWindowRect();
 
-  if (IsVisible() && !rectWnd.IsEmpty()) {
-    CFX_PointF ptCenter = GetCenterPoint();
-
-    CFX_PointF pt1(ptCenter.x - PWL_CBBUTTON_TRIANGLE_HALFLEN,
-                   ptCenter.y + PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
-    CFX_PointF pt2(ptCenter.x + PWL_CBBUTTON_TRIANGLE_HALFLEN,
-                   ptCenter.y + PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
-    CFX_PointF pt3(ptCenter.x,
-                   ptCenter.y - PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
-
-    if (IsFloatBigger(rectWnd.right - rectWnd.left,
-                      PWL_CBBUTTON_TRIANGLE_HALFLEN * 2) &&
-        IsFloatBigger(rectWnd.top - rectWnd.bottom,
-                      PWL_CBBUTTON_TRIANGLE_HALFLEN)) {
-      CFX_PathData path;
-      path.AppendPoint(pt1, FXPT_TYPE::MoveTo, false);
-      path.AppendPoint(pt2, FXPT_TYPE::LineTo, false);
-      path.AppendPoint(pt3, FXPT_TYPE::LineTo, false);
-      path.AppendPoint(pt1, FXPT_TYPE::LineTo, false);
-
-      pDevice->DrawPath(&path, pUser2Device, nullptr,
-                        PWL_DEFAULT_BLACKCOLOR.ToFXColor(GetTransparency()), 0,
-                        FXFILL_ALTERNATE);
-    }
+  if (!IsVisible() || rectWnd.IsEmpty())
+    return;
+
+  CFX_PointF ptCenter = GetCenterPoint();
+
+  CFX_PointF pt1(ptCenter.x - PWL_CBBUTTON_TRIANGLE_HALFLEN,
+                 ptCenter.y + PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
+  CFX_PointF pt2(ptCenter.x + PWL_CBBUTTON_TRIANGLE_HALFLEN,
+                 ptCenter.y + PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
+  CFX_PointF pt3(ptCenter.x, ptCenter.y - PWL_CBBUTTON_TRIANGLE_HALFLEN * 0.5f);
+
+  if (IsFloatBigger(rectWnd.right - rectWnd.left,
+                    PWL_CBBUTTON_TRIANGLE_HALFLEN * 2) &&
+      IsFloatBigger(rectWnd.top - rectWnd.bottom,
+                    PWL_CBBUTTON_TRIANGLE_HALFLEN)) {
+    CFX_PathData path;
+    path.AppendPoint(pt1, FXPT_TYPE::MoveTo, false);
+    path.AppendPoint(pt2, FXPT_TYPE::LineTo, false);
+    path.AppendPoint(pt3, FXPT_TYPE::LineTo, false);
+    path.AppendPoint(pt1, FXPT_TYPE::LineTo, false);
+
+    pDevice->DrawPath(&path, pUser2Device, nullptr,
+                      PWL_DEFAULT_BLACKCOLOR.ToFXColor(GetTransparency()), 0,
+                      FXFILL_ALTERNATE);
   }
 }
 
diff --git a/fpdfsdk/pdfwindow/cpwl_combo_box.h b/fpdfsdk/pdfwindow/cpwl_combo_box.h
index 549374f3e8..f8da84ad2e 100644
--- a/fpdfsdk/pdfwindow/cpwl_combo_box.h
+++ b/fpdfsdk/pdfwindow/cpwl_combo_box.h
@@ -40,7 +40,7 @@ class CPWL_CBButton : public CPWL_Wnd {
   ~CPWL_CBButton() override {}
 
   // CPWL_Wnd
-  void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) override;
+  void GetThisAppearanceStream(std::ostringstream* psAppStream) override;
   void DrawThisAppearance(CFX_RenderDevice* pDevice,
                           CFX_Matrix* pUser2Device) override;
   bool OnLButtonDown(const CFX_PointF& point, uint32_t nFlag) override;
diff --git a/fpdfsdk/pdfwindow/cpwl_edit.cpp b/fpdfsdk/pdfwindow/cpwl_edit.cpp
index d807f32c34..aa257b9308 100644
--- a/fpdfsdk/pdfwindow/cpwl_edit.cpp
+++ b/fpdfsdk/pdfwindow/cpwl_edit.cpp
@@ -8,6 +8,7 @@
 
 #include <algorithm>
 #include <memory>
+#include <sstream>
 #include <vector>
 
 #include "core/fpdfapi/font/cpdf_font.h"
@@ -188,54 +189,56 @@ void CPWL_Edit::SetParamByFlag() {
   }
 }
 
-void CPWL_Edit::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
-  CPWL_Wnd::GetThisAppearanceStream(sAppStream);
+void CPWL_Edit::GetThisAppearanceStream(std::ostringstream* psAppStream) {
+  CPWL_Wnd::GetThisAppearanceStream(psAppStream);
 
   CFX_FloatRect rcClient = GetClientRect();
-  CFX_ByteTextBuf sLine;
 
   int32_t nCharArray = m_pEdit->GetCharArray();
 
   if (nCharArray > 0) {
     switch (GetBorderStyle()) {
       case BorderStyle::SOLID: {
-        sLine << "q\n"
-              << GetBorderWidth() << " w\n"
-              << CPWL_Utils::GetColorAppStream(GetBorderColor(), false)
-                     .AsStringC()
-              << " 2 J 0 j\n";
+        *psAppStream << "q\n"
+                     << GetBorderWidth() << " w\n"
+                     << CPWL_Utils::GetColorAppStream(GetBorderColor(), false)
+                     << " 2 J 0 j\n";
 
         for (int32_t i = 1; i < nCharArray; i++) {
-          sLine << rcClient.left +
-                       ((rcClient.right - rcClient.left) / nCharArray) * i
-                << " " << rcClient.bottom << " m\n"
-                << rcClient.left +
-                       ((rcClient.right - rcClient.left) / nCharArray) * i
-                << " " << rcClient.top << " l S\n";
+          *psAppStream << rcClient.left +
+                              ((rcClient.right - rcClient.left) / nCharArray) *
+                                  i
+                       << " " << rcClient.bottom << " m\n"
+                       << rcClient.left +
+                              ((rcClient.right - rcClient.left) / nCharArray) *
+                                  i
+                       << " " << rcClient.top << " l S\n";
         }
 
-        sLine << "Q\n";
+        *psAppStream << "Q\n";
         break;
       }
       case BorderStyle::DASH: {
-        sLine << "q\n"
-              << GetBorderWidth() << " w\n"
-              << CPWL_Utils::GetColorAppStream(GetBorderColor(), false)
-                     .AsStringC()
-              << " 2 J 0 j\n"
-              << "[" << GetBorderDash().nDash << " " << GetBorderDash().nGap
-              << "] " << GetBorderDash().nPhase << " d\n";
+        *psAppStream << "q\n"
+                     << GetBorderWidth() << " w\n"
+                     << CPWL_Utils::GetColorAppStream(GetBorderColor(), false)
+                     << " 2 J 0 j\n"
+                     << "[" << GetBorderDash().nDash << " "
+                     << GetBorderDash().nGap << "] " << GetBorderDash().nPhase
+                     << " d\n";
 
         for (int32_t i = 1; i < nCharArray; i++) {
-          sLine << rcClient.left +
-                       ((rcClient.right - rcClient.left) / nCharArray) * i
-                << " " << rcClient.bottom << " m\n"
-                << rcClient.left +
-                       ((rcClient.right - rcClient.left) / nCharArray) * i
-                << " " << rcClient.top << " l S\n";
+          *psAppStream << rcClient.left +
+                              ((rcClient.right - rcClient.left) / nCharArray) *
+                                  i
+                       << " " << rcClient.bottom << " m\n"
+                       << rcClient.left +
+                              ((rcClient.right - rcClient.left) / nCharArray) *
+                                  i
+                       << " " << rcClient.top << " l S\n";
         }
 
-        sLine << "Q\n";
+        *psAppStream << "Q\n";
         break;
       }
       default:
@@ -243,9 +246,7 @@ void CPWL_Edit::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
     }
   }
 
-  sAppStream << sLine;
-
-  CFX_ByteTextBuf sText;
+  std::ostringstream sText;
   CFX_PointF ptOffset;
   CPVT_WordRange wrWhole = m_pEdit->GetWholeWordRange();
   CPVT_WordRange wrSelect = GetSelectWordRange();
@@ -260,8 +261,8 @@ void CPWL_Edit::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
       CPWL_Utils::GetEditSelAppStream(m_pEdit.get(), ptOffset, &wrTemp);
 
   if (sEditSel.GetLength() > 0)
-    sText << CPWL_Utils::GetColorAppStream(PWL_DEFAULT_SELBACKCOLOR).AsStringC()
-          << sEditSel.AsStringC();
+    sText << CPWL_Utils::GetColorAppStream(PWL_DEFAULT_SELBACKCOLOR)
+          << sEditSel;
 
   wrTemp = CPWL_Utils::OverlapWordRange(wrVisible, wrSelBefore);
   CFX_ByteString sEditBefore = CPWL_Utils::GetEditAppStream(
@@ -270,8 +271,8 @@ void CPWL_Edit::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
 
   if (sEditBefore.GetLength() > 0)
     sText << "BT\n"
-          << CPWL_Utils::GetColorAppStream(GetTextColor()).AsStringC()
-          << sEditBefore.AsStringC() << "ET\n";
+          << CPWL_Utils::GetColorAppStream(GetTextColor()) << sEditBefore
+          << "ET\n";
 
   wrTemp = CPWL_Utils::OverlapWordRange(wrVisible, wrSelect);
   CFX_ByteString sEditMid = CPWL_Utils::GetEditAppStream(
@@ -281,8 +282,7 @@ void CPWL_Edit::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
   if (sEditMid.GetLength() > 0)
     sText << "BT\n"
           << CPWL_Utils::GetColorAppStream(CPWL_Color(COLORTYPE_GRAY, 1))
-                 .AsStringC()
-          << sEditMid.AsStringC() << "ET\n";
+          << sEditMid << "ET\n";
 
   wrTemp = CPWL_Utils::OverlapWordRange(wrVisible, wrSelAfter);
   CFX_ByteString sEditAfter = CPWL_Utils::GetEditAppStream(
@@ -291,21 +291,21 @@ void CPWL_Edit::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
 
   if (sEditAfter.GetLength() > 0)
     sText << "BT\n"
-          << CPWL_Utils::GetColorAppStream(GetTextColor()).AsStringC()
-          << sEditAfter.AsStringC() << "ET\n";
+          << CPWL_Utils::GetColorAppStream(GetTextColor()) << sEditAfter
+          << "ET\n";
 
-  if (sText.GetLength() > 0) {
+  if (sText.tellp() > 0) {
     CFX_FloatRect rect = GetClientRect();
-    sAppStream << "q\n/Tx BMC\n";
+    *psAppStream << "q\n/Tx BMC\n";
 
     if (!HasFlag(PES_TEXTOVERFLOW))
-      sAppStream << rect.left << " " << rect.bottom << " "
-                 << rect.right - rect.left << " " << rect.top - rect.bottom
-                 << " re W n\n";
+      *psAppStream << rect.left << " " << rect.bottom << " "
+                   << rect.right - rect.left << " " << rect.top - rect.bottom
+                   << " re W n\n";
 
-    sAppStream << sText;
+    *psAppStream << sText.str();
 
-    sAppStream << "EMC\nQ\n";
+    *psAppStream << "EMC\nQ\n";
   }
 }
 
@@ -314,7 +314,6 @@ void CPWL_Edit::DrawThisAppearance(CFX_RenderDevice* pDevice,
   CPWL_Wnd::DrawThisAppearance(pDevice, pUser2Device);
 
   CFX_FloatRect rcClient = GetClientRect();
-  CFX_ByteTextBuf sLine;
 
   int32_t nCharArray = m_pEdit->GetCharArray();
   FX_SAFE_INT32 nCharArraySafe = nCharArray;
@@ -487,14 +486,13 @@ CPVT_WordRange CPWL_Edit::GetSelectWordRange() const {
 
 CFX_ByteString CPWL_Edit::GetTextAppearanceStream(
     const CFX_PointF& ptOffset) const {
-  CFX_ByteTextBuf sRet;
+  std::ostringstream sRet;
   CFX_ByteString sEdit = CPWL_Utils::GetEditAppStream(m_pEdit.get(), ptOffset);
   if (sEdit.GetLength() > 0) {
     sRet << "BT\n"
-         << CPWL_Utils::GetColorAppStream(GetTextColor()).AsStringC()
-         << sEdit.AsStringC() << "ET\n";
+         << CPWL_Utils::GetColorAppStream(GetTextColor()) << sEdit << "ET\n";
   }
-  return sRet.MakeString();
+  return CFX_ByteString(sRet);
 }
 
 CFX_ByteString CPWL_Edit::GetCaretAppearanceStream(
diff --git a/fpdfsdk/pdfwindow/cpwl_edit.h b/fpdfsdk/pdfwindow/cpwl_edit.h
index 5e82a5746b..31296f664a 100644
--- a/fpdfsdk/pdfwindow/cpwl_edit.h
+++ b/fpdfsdk/pdfwindow/cpwl_edit.h
@@ -51,7 +51,7 @@ class CPWL_Edit : public CPWL_EditCtrl {
   void OnCreated() override;
   void RePosChildWnd() override;
   CFX_FloatRect GetClientRect() const override;
-  void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) override;
+  void GetThisAppearanceStream(std::ostringstream* psAppStream) override;
   void DrawThisAppearance(CFX_RenderDevice* pDevice,
                           CFX_Matrix* pUser2Device) override;
   bool OnLButtonDown(const CFX_PointF& point, uint32_t nFlag) override;
diff --git a/fpdfsdk/pdfwindow/cpwl_icon.cpp b/fpdfsdk/pdfwindow/cpwl_icon.cpp
index 1464a09348..6650311915 100644
--- a/fpdfsdk/pdfwindow/cpwl_icon.cpp
+++ b/fpdfsdk/pdfwindow/cpwl_icon.cpp
@@ -7,6 +7,7 @@
 #include "fpdfsdk/pdfwindow/cpwl_icon.h"
 
 #include <algorithm>
+#include <sstream>
 
 #include "core/fpdfapi/parser/cpdf_array.h"
 #include "core/fpdfapi/parser/cpdf_stream.h"
@@ -18,7 +19,7 @@ CPWL_Image::CPWL_Image() : m_pPDFStream(nullptr) {}
 CPWL_Image::~CPWL_Image() {}
 
 CFX_ByteString CPWL_Image::GetImageAppStream() {
-  CFX_ByteTextBuf sAppStream;
+  std::ostringstream sAppStream;
 
   CFX_ByteString sAlias = GetImageAlias();
   CFX_FloatRect rcPlate = GetClientRect();
@@ -44,11 +45,11 @@ CFX_ByteString CPWL_Image::GetImageAppStream() {
     sAppStream << mt.a << " " << mt.b << " " << mt.c << " " << mt.d << " "
                << mt.e << " " << mt.f << " cm\n";
 
-    sAppStream << "0 g 0 G 1 w /" << sAlias.AsStringC() << " Do\n"
+    sAppStream << "0 g 0 G 1 w /" << sAlias << " Do\n"
                << "Q\n";
   }
 
-  return sAppStream.MakeString();
+  return CFX_ByteString(sAppStream);
 }
 
 void CPWL_Image::SetPDFStream(CPDF_Stream* pStream) {
diff --git a/fpdfsdk/pdfwindow/cpwl_list_box.cpp b/fpdfsdk/pdfwindow/cpwl_list_box.cpp
index 5c161bfdda..f612c2945b 100644
--- a/fpdfsdk/pdfwindow/cpwl_list_box.cpp
+++ b/fpdfsdk/pdfwindow/cpwl_list_box.cpp
@@ -6,6 +6,8 @@
 
 #include "fpdfsdk/pdfwindow/cpwl_list_box.h"
 
+#include <sstream>
+
 #include "fpdfsdk/fxedit/fxet_edit.h"
 #include "fpdfsdk/fxedit/fxet_list.h"
 #include "fpdfsdk/pdfwindow/cpwl_edit.h"
@@ -95,10 +97,10 @@ void CPWL_ListBox::OnDestroy() {
   m_pListNotify.reset();
 }
 
-void CPWL_ListBox::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
-  CPWL_Wnd::GetThisAppearanceStream(sAppStream);
+void CPWL_ListBox::GetThisAppearanceStream(std::ostringstream* psAppStream) {
+  CPWL_Wnd::GetThisAppearanceStream(psAppStream);
 
-  CFX_ByteTextBuf sListItems;
+  std::ostringstream sListItems;
 
   CFX_FloatRect rcPlate = m_pList->GetPlateRect();
   for (int32_t i = 0, sz = m_pList->GetCount(); i < sz; i++) {
@@ -110,40 +112,36 @@ void CPWL_ListBox::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
     CFX_PointF ptOffset(rcItem.left, (rcItem.top + rcItem.bottom) * 0.5f);
     if (m_pList->IsItemSelected(i)) {
       sListItems << CPWL_Utils::GetRectFillAppStream(rcItem,
-                                                     PWL_DEFAULT_SELBACKCOLOR)
-                        .AsStringC();
+                                                     PWL_DEFAULT_SELBACKCOLOR);
       CFX_ByteString sItem =
           CPWL_Utils::GetEditAppStream(m_pList->GetItemEdit(i), ptOffset);
       if (sItem.GetLength() > 0) {
         sListItems << "BT\n"
                    << CPWL_Utils::GetColorAppStream(PWL_DEFAULT_SELTEXTCOLOR)
-                          .AsStringC()
-                   << sItem.AsStringC() << "ET\n";
+                   << sItem << "ET\n";
       }
     } else {
       CFX_ByteString sItem =
           CPWL_Utils::GetEditAppStream(m_pList->GetItemEdit(i), ptOffset);
       if (sItem.GetLength() > 0) {
         sListItems << "BT\n"
-                   << CPWL_Utils::GetColorAppStream(GetTextColor()).AsStringC()
-                   << sItem.AsStringC() << "ET\n";
+                   << CPWL_Utils::GetColorAppStream(GetTextColor()) << sItem
+                   << "ET\n";
       }
     }
   }
 
-  if (sListItems.GetLength() > 0) {
-    CFX_ByteTextBuf sClip;
-    CFX_FloatRect rcClient = GetClientRect();
-
-    sClip << "q\n";
-    sClip << rcClient.left << " " << rcClient.bottom << " "
-          << rcClient.right - rcClient.left << " "
-          << rcClient.top - rcClient.bottom << " re W n\n";
-
-    sClip << sListItems << "Q\n";
+  if (sListItems.tellp() <= 0)
+    return;
 
-    sAppStream << "/Tx BMC\n" << sClip << "EMC\n";
-  }
+  CFX_FloatRect rcClient = GetClientRect();
+  *psAppStream << "/Tx BMC\n"
+               << "q\n"
+               << rcClient.left << " " << rcClient.bottom << " "
+               << rcClient.right - rcClient.left << " "
+               << rcClient.top - rcClient.bottom << " re W n\n"
+               << sListItems.str() << "Q\n"
+               << "EMC\n";
 }
 
 void CPWL_ListBox::DrawThisAppearance(CFX_RenderDevice* pDevice,
diff --git a/fpdfsdk/pdfwindow/cpwl_list_box.h b/fpdfsdk/pdfwindow/cpwl_list_box.h
index 6cf37ae40c..3eeed0d641 100644
--- a/fpdfsdk/pdfwindow/cpwl_list_box.h
+++ b/fpdfsdk/pdfwindow/cpwl_list_box.h
@@ -53,7 +53,7 @@ class CPWL_ListBox : public CPWL_Wnd {
   CFX_ByteString GetClassName() const override;
   void OnCreated() override;
   void OnDestroy() override;
-  void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) override;
+  void GetThisAppearanceStream(std::ostringstream* psAppStream) override;
   void DrawThisAppearance(CFX_RenderDevice* pDevice,
                           CFX_Matrix* pUser2Device) override;
   bool OnKeyDown(uint16_t nChar, uint32_t nFlag) override;
diff --git a/fpdfsdk/pdfwindow/cpwl_scroll_bar.cpp b/fpdfsdk/pdfwindow/cpwl_scroll_bar.cpp
index 2f234b2432..33bdedbf2f 100644
--- a/fpdfsdk/pdfwindow/cpwl_scroll_bar.cpp
+++ b/fpdfsdk/pdfwindow/cpwl_scroll_bar.cpp
@@ -6,6 +6,8 @@
 
 #include "fpdfsdk/pdfwindow/cpwl_scroll_bar.h"
 
+#include <sstream>
+
 #include "core/fxge/cfx_pathdata.h"
 #include "core/fxge/cfx_renderdevice.h"
 #include "fpdfsdk/pdfwindow/cpwl_utils.h"
@@ -122,20 +124,17 @@ void CPWL_SBButton::OnCreate(PWL_CREATEPARAM& cp) {
   cp.eCursorType = FXCT_ARROW;
 }
 
-void CPWL_SBButton::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
-  CPWL_Wnd::GetThisAppearanceStream(sAppStream);
+void CPWL_SBButton::GetThisAppearanceStream(std::ostringstream* psAppStream) {
+  CPWL_Wnd::GetThisAppearanceStream(psAppStream);
 
   if (!IsVisible())
     return;
 
-  CFX_ByteTextBuf sButton;
-
   CFX_FloatRect rectWnd = GetWindowRect();
-
   if (rectWnd.IsEmpty())
     return;
 
-  sAppStream << "q\n";
+  *psAppStream << "q\n";
 
   CFX_PointF ptCenter = GetCenterPoint();
 
@@ -151,13 +150,11 @@ void CPWL_SBButton::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
 
           if (rectWnd.right - rectWnd.left > PWL_TRIANGLE_HALFLEN * 2 &&
               rectWnd.top - rectWnd.bottom > PWL_TRIANGLE_HALFLEN) {
-            sButton << "0 g\n";
-            sButton << pt1.x << " " << pt1.y << " m\n";
-            sButton << pt2.x << " " << pt2.y << " l\n";
-            sButton << pt3.x << " " << pt3.y << " l\n";
-            sButton << pt1.x << " " << pt1.y << " l f\n";
-
-            sAppStream << sButton;
+            *psAppStream << "0 g\n"
+                         << pt1.x << " " << pt1.y << " m\n"
+                         << pt2.x << " " << pt2.y << " l\n"
+                         << pt3.x << " " << pt3.y << " l\n"
+                         << pt1.x << " " << pt1.y << " l f\n";
           }
         } break;
         case PSBT_MAX: {
@@ -169,13 +166,11 @@ void CPWL_SBButton::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
 
           if (rectWnd.right - rectWnd.left > PWL_TRIANGLE_HALFLEN * 2 &&
               rectWnd.top - rectWnd.bottom > PWL_TRIANGLE_HALFLEN) {
-            sButton << "0 g\n";
-            sButton << pt1.x << " " << pt1.y << " m\n";
-            sButton << pt2.x << " " << pt2.y << " l\n";
-            sButton << pt3.x << " " << pt3.y << " l\n";
-            sButton << pt1.x << " " << pt1.y << " l f\n";
-
-            sAppStream << sButton;
+            *psAppStream << "0 g\n"
+                         << pt1.x << " " << pt1.y << " m\n"
+                         << pt2.x << " " << pt2.y << " l\n"
+                         << pt3.x << " " << pt3.y << " l\n"
+                         << pt1.x << " " << pt1.y << " l f\n";
           }
         } break;
         default:
@@ -193,13 +188,11 @@ void CPWL_SBButton::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
 
           if (rectWnd.right - rectWnd.left > PWL_TRIANGLE_HALFLEN * 2 &&
               rectWnd.top - rectWnd.bottom > PWL_TRIANGLE_HALFLEN) {
-            sButton << "0 g\n";
-            sButton << pt1.x << " " << pt1.y << " m\n";
-            sButton << pt2.x << " " << pt2.y << " l\n";
-            sButton << pt3.x << " " << pt3.y << " l\n";
-            sButton << pt1.x << " " << pt1.y << " l f\n";
-
-            sAppStream << sButton;
+            *psAppStream << "0 g\n"
+                         << pt1.x << " " << pt1.y << " m\n"
+                         << pt2.x << " " << pt2.y << " l\n"
+                         << pt3.x << " " << pt3.y << " l\n"
+                         << pt1.x << " " << pt1.y << " l f\n";
           }
         } break;
         case PSBT_MAX: {
@@ -211,13 +204,11 @@ void CPWL_SBButton::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
 
           if (rectWnd.right - rectWnd.left > PWL_TRIANGLE_HALFLEN * 2 &&
               rectWnd.top - rectWnd.bottom > PWL_TRIANGLE_HALFLEN) {
-            sButton << "0 g\n";
-            sButton << pt1.x << " " << pt1.y << " m\n";
-            sButton << pt2.x << " " << pt2.y << " l\n";
-            sButton << pt3.x << " " << pt3.y << " l\n";
-            sButton << pt1.x << " " << pt1.y << " l f\n";
-
-            sAppStream << sButton;
+            *psAppStream << "0 g\n"
+                         << pt1.x << " " << pt1.y << " m\n"
+                         << pt2.x << " " << pt2.y << " l\n"
+                         << pt3.x << " " << pt3.y << " l\n"
+                         << pt1.x << " " << pt1.y << " l f\n";
           }
         } break;
         default:
@@ -228,7 +219,7 @@ void CPWL_SBButton::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
       break;
   }
 
-  sAppStream << "Q\n";
+  *psAppStream << "Q\n";
 }
 
 void CPWL_SBButton::DrawThisAppearance(CFX_RenderDevice* pDevice,
@@ -652,22 +643,18 @@ void CPWL_ScrollBar::RePosChildWnd() {
   MovePosButton(false);
 }
 
-void CPWL_ScrollBar::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
+void CPWL_ScrollBar::GetThisAppearanceStream(std::ostringstream* psAppStream) {
   CFX_FloatRect rectWnd = GetWindowRect();
 
-  if (IsVisible() && !rectWnd.IsEmpty()) {
-    CFX_ByteTextBuf sButton;
-
-    sButton << "q\n";
-    sButton << "0 w\n"
-            << CPWL_Utils::GetColorAppStream(GetBackgroundColor(), true)
-                   .AsStringC();
-    sButton << rectWnd.left << " " << rectWnd.bottom << " "
-            << rectWnd.right - rectWnd.left << " "
-            << rectWnd.top - rectWnd.bottom << " re b Q\n";
+  if (!IsVisible() || rectWnd.IsEmpty())
+    return;
 
-    sAppStream << sButton;
-  }
+  *psAppStream << "q\n"
+               << "0 w\n"
+               << CPWL_Utils::GetColorAppStream(GetBackgroundColor(), true)
+               << rectWnd.left << " " << rectWnd.bottom << " "
+               << rectWnd.right - rectWnd.left << " "
+               << rectWnd.top - rectWnd.bottom << " re b Q\n";
 }
 
 void CPWL_ScrollBar::DrawThisAppearance(CFX_RenderDevice* pDevice,
diff --git a/fpdfsdk/pdfwindow/cpwl_scroll_bar.h b/fpdfsdk/pdfwindow/cpwl_scroll_bar.h
index 0ab2928f2a..c67109fe39 100644
--- a/fpdfsdk/pdfwindow/cpwl_scroll_bar.h
+++ b/fpdfsdk/pdfwindow/cpwl_scroll_bar.h
@@ -51,7 +51,7 @@ class CPWL_SBButton : public CPWL_Wnd {
   // CPWL_Wnd
   CFX_ByteString GetClassName() const override;
   void OnCreate(PWL_CREATEPARAM& cp) override;
-  void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) override;
+  void GetThisAppearanceStream(std::ostringstream* psAppStream) override;
   void DrawThisAppearance(CFX_RenderDevice* pDevice,
                           CFX_Matrix* pUser2Device) override;
   bool OnLButtonDown(const CFX_PointF& point, uint32_t nFlag) override;
@@ -126,7 +126,7 @@ class CPWL_ScrollBar : public CPWL_Wnd {
   void OnCreate(PWL_CREATEPARAM& cp) override;
   void OnDestroy() override;
   void RePosChildWnd() override;
-  void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) override;
+  void GetThisAppearanceStream(std::ostringstream* psAppStream) override;
   void DrawThisAppearance(CFX_RenderDevice* pDevice,
                           CFX_Matrix* pUser2Device) override;
   bool OnLButtonDown(const CFX_PointF& point, uint32_t nFlag) override;
diff --git a/fpdfsdk/pdfwindow/cpwl_utils.cpp b/fpdfsdk/pdfwindow/cpwl_utils.cpp
index 0a3591923a..ce263eff8b 100644
--- a/fpdfsdk/pdfwindow/cpwl_utils.cpp
+++ b/fpdfsdk/pdfwindow/cpwl_utils.cpp
@@ -8,6 +8,7 @@
 
 #include <algorithm>
 #include <memory>
+#include <sstream>
 
 #include "core/fpdfdoc/cpvt_word.h"
 #include "core/fxge/cfx_graphstatedata.h"
@@ -63,7 +64,7 @@ CFX_ByteString CPWL_Utils::GetAP_Check(const CFX_FloatRect& crBBox) {
     }
   }
 
-  CFX_ByteTextBuf csAP;
+  std::ostringstream csAP;
   csAP << pts[0][0].x << " " << pts[0][0].y << " m\n";
 
   for (size_t i = 0; i < FX_ArraySize(pts); ++i) {
@@ -81,11 +82,11 @@ CFX_ByteString CPWL_Utils::GetAP_Check(const CFX_FloatRect& crBBox) {
          << pts[nNext][0].y << " c\n";
   }
 
-  return csAP.MakeString();
+  return CFX_ByteString(csAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAP_Circle(const CFX_FloatRect& crBBox) {
-  CFX_ByteTextBuf csAP;
+  std::ostringstream csAP;
 
   float fWidth = crBBox.right - crBBox.left;
   float fHeight = crBBox.top - crBBox.bottom;
@@ -123,22 +124,22 @@ CFX_ByteString CPWL_Utils::GetAP_Circle(const CFX_FloatRect& crBBox) {
   csAP << pt4.x - px * FX_BEZIER << " " << pt4.y << " " << pt1.x << " "
        << pt1.y - py * FX_BEZIER << " " << pt1.x << " " << pt1.y << " c\n";
 
-  return csAP.MakeString();
+  return CFX_ByteString(csAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAP_Cross(const CFX_FloatRect& crBBox) {
-  CFX_ByteTextBuf csAP;
+  std::ostringstream csAP;
 
   csAP << crBBox.left << " " << crBBox.top << " m\n";
   csAP << crBBox.right << " " << crBBox.bottom << " l\n";
   csAP << crBBox.left << " " << crBBox.bottom << " m\n";
   csAP << crBBox.right << " " << crBBox.top << " l\n";
 
-  return csAP.MakeString();
+  return CFX_ByteString(csAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAP_Diamond(const CFX_FloatRect& crBBox) {
-  CFX_ByteTextBuf csAP;
+  std::ostringstream csAP;
 
   float fWidth = crBBox.right - crBBox.left;
   float fHeight = crBBox.top - crBBox.bottom;
@@ -154,11 +155,11 @@ CFX_ByteString CPWL_Utils::GetAP_Diamond(const CFX_FloatRect& crBBox) {
   csAP << pt4.x << " " << pt4.y << " l\n";
   csAP << pt1.x << " " << pt1.y << " l\n";
 
-  return csAP.MakeString();
+  return CFX_ByteString(csAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAP_Square(const CFX_FloatRect& crBBox) {
-  CFX_ByteTextBuf csAP;
+  std::ostringstream csAP;
 
   csAP << crBBox.left << " " << crBBox.top << " m\n";
   csAP << crBBox.right << " " << crBBox.top << " l\n";
@@ -166,11 +167,11 @@ CFX_ByteString CPWL_Utils::GetAP_Square(const CFX_FloatRect& crBBox) {
   csAP << crBBox.left << " " << crBBox.bottom << " l\n";
   csAP << crBBox.left << " " << crBBox.top << " l\n";
 
-  return csAP.MakeString();
+  return CFX_ByteString(csAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAP_Star(const CFX_FloatRect& crBBox) {
-  CFX_ByteTextBuf csAP;
+  std::ostringstream csAP;
 
   float fRadius = (crBBox.top - crBBox.bottom) / (1 + (float)cos(FX_PI / 5.0f));
   CFX_PointF ptCenter = CFX_PointF((crBBox.left + crBBox.right) / 2.0f,
@@ -197,12 +198,12 @@ CFX_ByteString CPWL_Utils::GetAP_Star(const CFX_FloatRect& crBBox) {
     csAP << px[nNext] << " " << py[nNext] << " l\n";
   }
 
-  return csAP.MakeString();
+  return CFX_ByteString(csAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAP_HalfCircle(const CFX_FloatRect& crBBox,
                                             float fRotate) {
-  CFX_ByteTextBuf csAP;
+  std::ostringstream csAP;
 
   float fWidth = crBBox.right - crBBox.left;
   float fHeight = crBBox.top - crBBox.bottom;
@@ -232,7 +233,7 @@ CFX_ByteString CPWL_Utils::GetAP_HalfCircle(const CFX_FloatRect& crBBox,
   csAP << pt2.x + px * FX_BEZIER << " " << pt2.y << " " << pt3.x << " "
        << pt3.y + py * FX_BEZIER << " " << pt3.x << " " << pt3.y << " c\n";
 
-  return csAP.MakeString();
+  return CFX_ByteString(csAP);
 }
 
 CFX_FloatRect CPWL_Utils::InflateRect(const CFX_FloatRect& rcRect,
@@ -271,7 +272,7 @@ CFX_FloatRect CPWL_Utils::ScaleRect(const CFX_FloatRect& rcRect, float fScale) {
 
 CFX_ByteString CPWL_Utils::GetRectFillAppStream(const CFX_FloatRect& rect,
                                                 const CPWL_Color& color) {
-  CFX_ByteTextBuf sAppStream;
+  std::ostringstream sAppStream;
   CFX_ByteString sColor = GetColorAppStream(color, true);
   if (sColor.GetLength() > 0) {
     sAppStream << "q\n" << sColor;
@@ -280,17 +281,16 @@ CFX_ByteString CPWL_Utils::GetRectFillAppStream(const CFX_FloatRect& rect,
                << " re f\nQ\n";
   }
 
-  return sAppStream.MakeString();
+  return CFX_ByteString(sAppStream);
 }
 
 CFX_ByteString CPWL_Utils::GetCircleFillAppStream(const CFX_FloatRect& rect,
                                                   const CPWL_Color& color) {
-  CFX_ByteTextBuf sAppStream;
+  std::ostringstream sAppStream;
   CFX_ByteString sColor = GetColorAppStream(color, true);
-  if (sColor.GetLength() > 0) {
+  if (sColor.GetLength() > 0)
     sAppStream << "q\n" << sColor << CPWL_Utils::GetAP_Circle(rect) << "f\nQ\n";
-  }
-  return sAppStream.MakeString();
+  return CFX_ByteString(sAppStream);
 }
 
 CFX_FloatRect CPWL_Utils::GetCenterSquare(const CFX_FloatRect& rect) {
@@ -514,7 +514,7 @@ CFX_ByteString CPWL_Utils::GetPushButtonAppStream(const CFX_FloatRect& rcBBox,
       break;
   }
 
-  CFX_ByteTextBuf sAppStream, sTemp;
+  std::ostringstream sTemp;
 
   if (!rcIcon.IsEmpty()) {
     Icon.Move(rcIcon, false, false);
@@ -533,19 +533,21 @@ CFX_ByteString CPWL_Utils::GetPushButtonAppStream(const CFX_FloatRect& rcBBox,
     }
   }
 
-  if (sTemp.GetSize() > 0) {
-    sAppStream << "q\n"
-               << rcBBox.left << " " << rcBBox.bottom << " "
-               << rcBBox.right - rcBBox.left << " "
-               << rcBBox.top - rcBBox.bottom << " re W n\n";
-    sAppStream << sTemp << "Q\n";
-  }
-  return sAppStream.MakeString();
+  if (sTemp.tellp() <= 0)
+    return CFX_ByteString();
+
+  std::ostringstream sAppStream;
+  sAppStream << "q\n"
+             << rcBBox.left << " " << rcBBox.bottom << " "
+             << rcBBox.right - rcBBox.left << " " << rcBBox.top - rcBBox.bottom
+             << " re W n\n";
+  sAppStream << sTemp.str().c_str() << "Q\n";
+  return CFX_ByteString(sAppStream);
 }
 
 CFX_ByteString CPWL_Utils::GetColorAppStream(const CPWL_Color& color,
                                              const bool& bFillOrStroke) {
-  CFX_ByteTextBuf sColorStream;
+  std::ostringstream sColorStream;
 
   switch (color.nColorType) {
     case COLORTYPE_RGB:
@@ -564,7 +566,7 @@ CFX_ByteString CPWL_Utils::GetColorAppStream(const CPWL_Color& color,
       break;
   }
 
-  return sColorStream.MakeString();
+  return CFX_ByteString(sColorStream);
 }
 
 CFX_ByteString CPWL_Utils::GetBorderAppStream(const CFX_FloatRect& rect,
@@ -574,7 +576,7 @@ CFX_ByteString CPWL_Utils::GetBorderAppStream(const CFX_FloatRect& rect,
                                               const CPWL_Color& crRightBottom,
                                               BorderStyle nStyle,
                                               const CPWL_Dash& dash) {
-  CFX_ByteTextBuf sAppStream;
+  std::ostringstream sAppStream;
   CFX_ByteString sColor;
 
   float fLeft = rect.left;
@@ -680,7 +682,7 @@ CFX_ByteString CPWL_Utils::GetBorderAppStream(const CFX_FloatRect& rect,
     sAppStream << "Q\n";
   }
 
-  return sAppStream.MakeString();
+  return CFX_ByteString(sAppStream);
 }
 
 CFX_ByteString CPWL_Utils::GetCircleBorderAppStream(
@@ -691,7 +693,7 @@ CFX_ByteString CPWL_Utils::GetCircleBorderAppStream(
     const CPWL_Color& crRightBottom,
     BorderStyle nStyle,
     const CPWL_Dash& dash) {
-  CFX_ByteTextBuf sAppStream;
+  std::ostringstream sAppStream;
   CFX_ByteString sColor;
 
   if (fWidth > 0.0f) {
@@ -793,61 +795,61 @@ CFX_ByteString CPWL_Utils::GetCircleBorderAppStream(
     sAppStream << "Q\n";
   }
 
-  return sAppStream.MakeString();
+  return CFX_ByteString(sAppStream);
 }
 
 CFX_ByteString CPWL_Utils::GetAppStream_Check(const CFX_FloatRect& rcBBox,
                                               const CPWL_Color& crText) {
-  CFX_ByteTextBuf sAP;
+  std::ostringstream sAP;
   sAP << "q\n"
       << CPWL_Utils::GetColorAppStream(crText, true)
       << CPWL_Utils::GetAP_Check(rcBBox) << "f\nQ\n";
-  return sAP.MakeString();
+  return CFX_ByteString(sAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAppStream_Circle(const CFX_FloatRect& rcBBox,
                                                const CPWL_Color& crText) {
-  CFX_ByteTextBuf sAP;
+  std::ostringstream sAP;
   sAP << "q\n"
       << CPWL_Utils::GetColorAppStream(crText, true)
       << CPWL_Utils::GetAP_Circle(rcBBox) << "f\nQ\n";
-  return sAP.MakeString();
+  return CFX_ByteString(sAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAppStream_Cross(const CFX_FloatRect& rcBBox,
                                               const CPWL_Color& crText) {
-  CFX_ByteTextBuf sAP;
+  std::ostringstream sAP;
   sAP << "q\n"
       << CPWL_Utils::GetColorAppStream(crText, false)
       << CPWL_Utils::GetAP_Cross(rcBBox) << "S\nQ\n";
-  return sAP.MakeString();
+  return CFX_ByteString(sAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAppStream_Diamond(const CFX_FloatRect& rcBBox,
                                                 const CPWL_Color& crText) {
-  CFX_ByteTextBuf sAP;
+  std::ostringstream sAP;
   sAP << "q\n1 w\n"
       << CPWL_Utils::GetColorAppStream(crText, true)
       << CPWL_Utils::GetAP_Diamond(rcBBox) << "f\nQ\n";
-  return sAP.MakeString();
+  return CFX_ByteString(sAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAppStream_Square(const CFX_FloatRect& rcBBox,
                                                const CPWL_Color& crText) {
-  CFX_ByteTextBuf sAP;
+  std::ostringstream sAP;
   sAP << "q\n"
       << CPWL_Utils::GetColorAppStream(crText, true)
       << CPWL_Utils::GetAP_Square(rcBBox) << "f\nQ\n";
-  return sAP.MakeString();
+  return CFX_ByteString(sAP);
 }
 
 CFX_ByteString CPWL_Utils::GetAppStream_Star(const CFX_FloatRect& rcBBox,
                                              const CPWL_Color& crText) {
-  CFX_ByteTextBuf sAP;
+  std::ostringstream sAP;
   sAP << "q\n"
       << CPWL_Utils::GetColorAppStream(crText, true)
       << CPWL_Utils::GetAP_Star(rcBBox) << "f\nQ\n";
-  return sAP.MakeString();
+  return CFX_ByteString(sAP);
 }
 
 CFX_ByteString CPWL_Utils::GetCheckBoxAppStream(const CFX_FloatRect& rcBBox,
@@ -893,42 +895,42 @@ CFX_ByteString CPWL_Utils::GetRadioButtonAppStream(const CFX_FloatRect& rcBBox,
 }
 
 CFX_ByteString CPWL_Utils::GetDropButtonAppStream(const CFX_FloatRect& rcBBox) {
-  CFX_ByteTextBuf sAppStream;
-
-  if (!rcBBox.IsEmpty()) {
+  if (rcBBox.IsEmpty())
+    return CFX_ByteString();
+
+  std::ostringstream sAppStream;
+  sAppStream << "q\n"
+             << CPWL_Utils::GetColorAppStream(
+                    CPWL_Color(COLORTYPE_RGB, 220.0f / 255.0f, 220.0f / 255.0f,
+                               220.0f / 255.0f),
+                    true)
+             << rcBBox.left << " " << rcBBox.bottom << " "
+             << rcBBox.right - rcBBox.left << " " << rcBBox.top - rcBBox.bottom
+             << " re f\n"
+             << "Q\n";
+
+  sAppStream << "q\n"
+             << CPWL_Utils::GetBorderAppStream(
+                    rcBBox, 2, CPWL_Color(COLORTYPE_GRAY, 0),
+                    CPWL_Color(COLORTYPE_GRAY, 1),
+                    CPWL_Color(COLORTYPE_GRAY, 0.5), BorderStyle::BEVELED,
+                    CPWL_Dash(3, 0, 0))
+             << "Q\n";
+
+  CFX_PointF ptCenter = CFX_PointF((rcBBox.left + rcBBox.right) / 2,
+                                   (rcBBox.top + rcBBox.bottom) / 2);
+  if (IsFloatBigger(rcBBox.right - rcBBox.left, 6) &&
+      IsFloatBigger(rcBBox.top - rcBBox.bottom, 6)) {
     sAppStream << "q\n"
-               << CPWL_Utils::GetColorAppStream(
-                      CPWL_Color(COLORTYPE_RGB, 220.0f / 255.0f,
-                                 220.0f / 255.0f, 220.0f / 255.0f),
-                      true);
-    sAppStream << rcBBox.left << " " << rcBBox.bottom << " "
-               << rcBBox.right - rcBBox.left << " "
-               << rcBBox.top - rcBBox.bottom << " re f\n";
-    sAppStream << "Q\n";
-
-    sAppStream << "q\n"
-               << CPWL_Utils::GetBorderAppStream(
-                      rcBBox, 2, CPWL_Color(COLORTYPE_GRAY, 0),
-                      CPWL_Color(COLORTYPE_GRAY, 1),
-                      CPWL_Color(COLORTYPE_GRAY, 0.5), BorderStyle::BEVELED,
-                      CPWL_Dash(3, 0, 0))
+               << " 0 g\n"
+               << ptCenter.x - 3 << " " << ptCenter.y + 1.5f << " m\n"
+               << ptCenter.x + 3 << " " << ptCenter.y + 1.5f << " l\n"
+               << ptCenter.x << " " << ptCenter.y - 1.5f << " l\n"
+               << ptCenter.x - 3 << " " << ptCenter.y + 1.5f << " l f\n"
                << "Q\n";
-
-    CFX_PointF ptCenter = CFX_PointF((rcBBox.left + rcBBox.right) / 2,
-                                     (rcBBox.top + rcBBox.bottom) / 2);
-    if (IsFloatBigger(rcBBox.right - rcBBox.left, 6) &&
-        IsFloatBigger(rcBBox.top - rcBBox.bottom, 6)) {
-      sAppStream << "q\n"
-                 << " 0 g\n";
-      sAppStream << ptCenter.x - 3 << " " << ptCenter.y + 1.5f << " m\n";
-      sAppStream << ptCenter.x + 3 << " " << ptCenter.y + 1.5f << " l\n";
-      sAppStream << ptCenter.x << " " << ptCenter.y - 1.5f << " l\n";
-      sAppStream << ptCenter.x - 3 << " " << ptCenter.y + 1.5f << " l f\n";
-      sAppStream << "Q\n";
-    }
   }
 
-  return sAppStream.MakeString();
+  return CFX_ByteString(sAppStream);
 }
 
 void CPWL_Utils::DrawFillRect(CFX_RenderDevice* pDevice,
diff --git a/fpdfsdk/pdfwindow/cpwl_wnd.cpp b/fpdfsdk/pdfwindow/cpwl_wnd.cpp
index d44b219110..a8b5c31254 100644
--- a/fpdfsdk/pdfwindow/cpwl_wnd.cpp
+++ b/fpdfsdk/pdfwindow/cpwl_wnd.cpp
@@ -7,6 +7,7 @@
 #include "fpdfsdk/pdfwindow/cpwl_wnd.h"
 
 #include <map>
+#include <sstream>
 #include <vector>
 
 #include "fpdfsdk/pdfwindow/cpwl_scroll_bar.h"
@@ -232,39 +233,36 @@ void CPWL_Wnd::InvalidateRectMove(const CFX_FloatRect& rcOld,
   InvalidateRect(&rcUnion);
 }
 
-void CPWL_Wnd::GetAppearanceStream(CFX_ByteTextBuf& sAppStream) {
+void CPWL_Wnd::GetAppearanceStream(std::ostringstream* psAppStream) {
   if (IsValid() && IsVisible()) {
-    GetThisAppearanceStream(sAppStream);
-    GetChildAppearanceStream(sAppStream);
+    GetThisAppearanceStream(psAppStream);
+    GetChildAppearanceStream(psAppStream);
   }
 }
 
 // if don't set,Get default apperance stream
-void CPWL_Wnd::GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) {
+void CPWL_Wnd::GetThisAppearanceStream(std::ostringstream* psAppStream) {
   CFX_FloatRect rectWnd = GetWindowRect();
   if (rectWnd.IsEmpty())
     return;
 
-  CFX_ByteTextBuf sThis;
-
   if (HasFlag(PWS_BACKGROUND))
-    sThis << CPWL_Utils::GetRectFillAppStream(rectWnd, GetBackgroundColor());
+    *psAppStream << CPWL_Utils::GetRectFillAppStream(rectWnd,
+                                                     GetBackgroundColor());
 
   if (HasFlag(PWS_BORDER)) {
-    sThis << CPWL_Utils::GetBorderAppStream(
+    *psAppStream << CPWL_Utils::GetBorderAppStream(
         rectWnd, (float)GetBorderWidth(), GetBorderColor(),
         GetBorderLeftTopColor(GetBorderStyle()),
         GetBorderRightBottomColor(GetBorderStyle()), GetBorderStyle(),
         GetBorderDash());
   }
-
-  sAppStream << sThis;
 }
 
-void CPWL_Wnd::GetChildAppearanceStream(CFX_ByteTextBuf& sAppStream) {
+void CPWL_Wnd::GetChildAppearanceStream(std::ostringstream* psAppStream) {
   for (CPWL_Wnd* pChild : m_Children) {
     if (pChild)
-      pChild->GetAppearanceStream(sAppStream);
+      pChild->GetAppearanceStream(psAppStream);
   }
 }
 
diff --git a/fpdfsdk/pdfwindow/cpwl_wnd.h b/fpdfsdk/pdfwindow/cpwl_wnd.h
index 704984932b..8d7cc32ec8 100644
--- a/fpdfsdk/pdfwindow/cpwl_wnd.h
+++ b/fpdfsdk/pdfwindow/cpwl_wnd.h
@@ -303,7 +303,7 @@ class CPWL_Wnd : public CPWL_TimerHandler {
 
   virtual void CreateChildWnd(const PWL_CREATEPARAM& cp);
   virtual void RePosChildWnd();
-  virtual void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream);
+  virtual void GetThisAppearanceStream(std::ostringstream* psAppStream);
 
   virtual void DrawThisAppearance(CFX_RenderDevice* pDevice,
                                   CFX_Matrix* pUser2Device);
@@ -315,7 +315,7 @@ class CPWL_Wnd : public CPWL_TimerHandler {
   virtual void OnSetFocus();
   virtual void OnKillFocus();
 
-  void GetAppearanceStream(CFX_ByteTextBuf& sAppStream);
+  void GetAppearanceStream(std::ostringstream* psAppStream);
   void SetNotifyFlag(bool bNotifying = true) { m_bNotifying = bNotifying; }
 
   bool IsValid() const;
@@ -337,7 +337,7 @@ class CPWL_Wnd : public CPWL_TimerHandler {
   CFX_PointF ParentToChild(const CFX_PointF& point) const;
   CFX_FloatRect ParentToChild(const CFX_FloatRect& rect) const;
 
-  void GetChildAppearanceStream(CFX_ByteTextBuf& sAppStream);
+  void GetChildAppearanceStream(std::ostringstream* psAppStream);
   void DrawChildAppearance(CFX_RenderDevice* pDevice, CFX_Matrix* pUser2Device);
 
   FX_RECT PWLtoWnd(const CFX_FloatRect& rect) const;