diff --git a/core/fpdfapi/font/cpdf_cidfont.cpp b/core/fpdfapi/font/cpdf_cidfont.cpp
index 59eb923..9c526b1 100644
--- a/core/fpdfapi/font/cpdf_cidfont.cpp
+++ b/core/fpdfapi/font/cpdf_cidfont.cpp
@@ -10,6 +10,7 @@
 #include <limits>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/cmaps/cmap_int.h"
 #include "core/fpdfapi/cpdf_modulemgr.h"
 #include "core/fpdfapi/font/cfx_cttgsubtable.h"
@@ -669,7 +670,7 @@
     if (m_Charset == CIDSET_JAPAN1) {
       if (unicode == '\\') {
         unicode = '/';
-#if _FX_PLATFORM_ != _FX_PLATFORM_APPLE_
+#if !defined(OS_MACOSX)
       } else if (unicode == 0xa5) {
         unicode = 0x5c;
 #endif
diff --git a/core/fpdfapi/font/cpdf_font.cpp b/core/fpdfapi/font/cpdf_font.cpp
index 6c114eb..fb1fd89 100644
--- a/core/fpdfapi/font/cpdf_font.cpp
+++ b/core/fpdfapi/font/cpdf_font.cpp
@@ -11,6 +11,7 @@
 #include <utility>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/cpdf_modulemgr.h"
 #include "core/fpdfapi/font/cpdf_fontencoding.h"
 #include "core/fpdfapi/font/cpdf_tounicodemap.h"
@@ -116,7 +117,7 @@
   return pString.GetLength();
 }
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
 int CPDF_Font::GlyphFromCharCodeExt(uint32_t charcode) {
   return GlyphFromCharCode(charcode, nullptr);
 }
diff --git a/core/fpdfapi/font/cpdf_font.h b/core/fpdfapi/font/cpdf_font.h
index 4bd6e30..ff5ec30 100644
--- a/core/fpdfapi/font/cpdf_font.h
+++ b/core/fpdfapi/font/cpdf_font.h
@@ -10,6 +10,7 @@
 #include <memory>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/parser/cpdf_stream_acc.h"
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/fx_system.h"
@@ -54,7 +55,7 @@
   virtual size_t CountChar(ByteStringView pString) const;
   virtual int AppendChar(char* buf, uint32_t charcode) const;
   virtual int GlyphFromCharCode(uint32_t charcode, bool* pVertGlyph) = 0;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   virtual int GlyphFromCharCodeExt(uint32_t charcode);
 #endif
   virtual WideString UnicodeFromCharCode(uint32_t charcode) const;
diff --git a/core/fpdfapi/font/cpdf_type1font.cpp b/core/fpdfapi/font/cpdf_type1font.cpp
index fa88c75..b78922d 100644
--- a/core/fpdfapi/font/cpdf_type1font.cpp
+++ b/core/fpdfapi/font/cpdf_type1font.cpp
@@ -8,19 +8,20 @@
 
 #include <algorithm>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fxge/cfx_fontmapper.h"
 #include "core/fxge/cfx_gemodule.h"
 #include "core/fxge/fx_font.h"
 #include "core/fxge/fx_freetype.h"
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
 #include "core/fxge/apple/apple_int.h"
 #endif
 
 namespace {
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
 struct GlyphNameMap {
   const char* m_pStrAdobe;    // Raw, POD struct.
   const char* m_pStrUnicode;  // Raw, POD struct.
@@ -40,7 +41,7 @@
   return nullptr;
 }
 
-#endif  // _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#endif  // defined(OS_MACOSX)
 
 bool FT_UseType1Charmap(FXFT_Face face) {
   if (FXFT_Get_Face_CharmapCount(face) == 0) {
@@ -65,7 +66,7 @@
 CPDF_Type1Font::CPDF_Type1Font(CPDF_Document* pDocument,
                                CPDF_Dictionary* pFontDict)
     : CPDF_SimpleFont(pDocument, pFontDict) {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   memset(m_ExtGID, 0xff, sizeof(m_ExtGID));
 #endif
 }
@@ -108,7 +109,7 @@
   return LoadCommon();
 }
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
 int CPDF_Type1Font::GlyphFromCharCodeExt(uint32_t charcode) {
   if (charcode > 0xff)
     return -1;
@@ -122,7 +123,7 @@
   if (!m_Font.GetFace())
     return;
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   bool bCoreText = true;
   CQuartz2D& quartz2d =
       static_cast<CApplePlatform*>(CFX_GEModule::Get()->GetPlatformData())
@@ -146,7 +147,7 @@
           uint16_t unicode = prefix[j] * 256 + charcode;
           m_GlyphIndex[charcode] =
               FXFT_Get_Char_Index(m_Font.GetFace(), unicode);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
           CalcExtGID(charcode);
 #endif
           if (m_GlyphIndex[charcode]) {
@@ -156,7 +157,7 @@
         }
       }
       if (bGotOne) {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
         if (!bCoreText)
           memcpy(m_ExtGID, m_GlyphIndex, 256);
 #endif
@@ -176,25 +177,25 @@
       m_Encoding.SetUnicode(charcode, PDF_UnicodeFromAdobeName(name));
       m_GlyphIndex[charcode] = FXFT_Get_Char_Index(
           m_Font.GetFace(), m_Encoding.UnicodeFromCharCode(charcode));
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
       CalcExtGID(charcode);
 #endif
       if (m_GlyphIndex[charcode] == 0 && strcmp(name, ".notdef") == 0) {
         m_Encoding.SetUnicode(charcode, 0x20);
         m_GlyphIndex[charcode] = FXFT_Get_Char_Index(m_Font.GetFace(), 0x20);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
         CalcExtGID(charcode);
 #endif
       }
     }
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     if (!bCoreText)
       memcpy(m_ExtGID, m_GlyphIndex, 256);
 #endif
     return;
   }
   FT_UseType1Charmap(m_Font.GetFace());
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   if (bCoreText) {
     if (FontStyleIsSymbolic(m_Flags)) {
       for (uint32_t charcode = 0; charcode < 256; charcode++) {
@@ -259,7 +260,7 @@
     }
     return;
   }
-#endif  // _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#endif  // defined(OS_MACOSX)
   if (FontStyleIsSymbolic(m_Flags)) {
     for (int charcode = 0; charcode < 256; charcode++) {
       const char* name =
@@ -286,7 +287,7 @@
         }
       }
     }
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     if (!bCoreText)
       memcpy(m_ExtGID, m_GlyphIndex, 256);
 
@@ -315,13 +316,13 @@
       m_GlyphIndex[charcode] = 0xffff;
     }
   }
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   if (!bCoreText)
     memcpy(m_ExtGID, m_GlyphIndex, 256);
 #endif
 }
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
 void CPDF_Type1Font::SetExtGID(const char* name, uint32_t charcode) {
   CFStringRef name_ct = CFStringCreateWithCStringNoCopy(
       kCFAllocatorDefault, name, kCFStringEncodingASCII, kCFAllocatorNull);
@@ -338,4 +339,4 @@
   name_glyph[255] = 0;
   SetExtGID(name_glyph, charcode);
 }
-#endif  // _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#endif  // defined(OS_MACOSX)
diff --git a/core/fpdfapi/font/cpdf_type1font.h b/core/fpdfapi/font/cpdf_type1font.h
index 86a9812..862e41b 100644
--- a/core/fpdfapi/font/cpdf_type1font.h
+++ b/core/fpdfapi/font/cpdf_type1font.h
@@ -7,6 +7,7 @@
 #ifndef CORE_FPDFAPI_FONT_CPDF_TYPE1FONT_H_
 #define CORE_FPDFAPI_FONT_CPDF_TYPE1FONT_H_
 
+#include "build/build_config.h"
 #include "core/fpdfapi/font/cpdf_simplefont.h"
 #include "core/fxcrt/fx_system.h"
 
@@ -19,7 +20,7 @@
   bool IsType1Font() const override;
   const CPDF_Type1Font* AsType1Font() const override;
   CPDF_Type1Font* AsType1Font() override;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   int GlyphFromCharCodeExt(uint32_t charcode) override;
 #endif
 
@@ -32,7 +33,7 @@
   // CPDF_SimpleFont:
   void LoadGlyphMap() override;
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   void SetExtGID(const char* name, uint32_t charcode);
   void CalcExtGID(uint32_t charcode);
 
diff --git a/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp b/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
index 00796dc..2e90c6c 100644
--- a/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
+++ b/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
@@ -5,6 +5,7 @@
 #include <memory>
 #include <string>
 
+#include "build/build_config.h"
 #include "core/fxcrt/fx_system.h"
 #include "public/cpp/fpdf_scopers.h"
 #include "public/fpdf_edit.h"
@@ -66,7 +67,7 @@
 TEST_F(CPDFSecurityHandlerEmbedderTest, PasswordAfterGenerateSave) {
 #if _FX_PLATFORM_ == _FX_PLATFORM_LINUX_
   const char md5[] = "7048dca58e2ed8f93339008b91e4eb4e";
-#elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#elif defined(OS_MACOSX)
   const char md5[] = "6951b6c9891dfe0332a5b1983e484400";
 #else
   const char md5[] = "041c2fb541c8907cc22ce101b686c79e";
diff --git a/core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp b/core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp
index 2131064..f4b1f32 100644
--- a/core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp
@@ -6,6 +6,7 @@
 #include <memory>
 #include <string>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/parser/fpdf_parser_decode.h"
 #include "public/cpp/fpdf_scopers.h"
 #include "testing/embedder_test.h"
@@ -116,7 +117,7 @@
   FPDF_PAGE page = LoadPage(0);
   ASSERT_TRUE(page);
   ScopedFPDFBitmap bitmap = RenderLoadedPage(page);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char kExpectedMd5sum[] = "b90475ca64d1348c3bf5e2b77ad9187a";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char kExpectedMd5sum[] = "795b7ce1626931aa06af0fa23b7d80bb";
diff --git a/core/fpdfapi/render/cpdf_charposlist.cpp b/core/fpdfapi/render/cpdf_charposlist.cpp
index 8603531..4405274 100644
--- a/core/fpdfapi/render/cpdf_charposlist.cpp
+++ b/core/fpdfapi/render/cpdf_charposlist.cpp
@@ -6,6 +6,7 @@
 
 #include "core/fpdfapi/render/cpdf_charposlist.h"
 
+#include "build/build_config.h"
 #include "core/fpdfapi/font/cpdf_cidfont.h"
 #include "core/fpdfapi/font/cpdf_font.h"
 #include "core/fxge/cfx_renderdevice.h"
@@ -32,7 +33,7 @@
     charpos.m_Unicode = !unicode.IsEmpty() ? unicode[0] : CharCode;
     charpos.m_GlyphIndex = pFont->GlyphFromCharCode(CharCode, &bVert);
     uint32_t GlyphID = charpos.m_GlyphIndex;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     charpos.m_ExtGID = pFont->GlyphFromCharCodeExt(CharCode);
     GlyphID = charpos.m_ExtGID != static_cast<uint32_t>(-1)
                   ? charpos.m_ExtGID
@@ -48,7 +49,7 @@
       charpos.m_GlyphIndex = pFont->FallbackGlyphFromCharcode(
           charpos.m_FallbackFontPosition, CharCode);
       pCurrentFont = pFont->GetFontFallback(charpos.m_FallbackFontPosition);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
       charpos.m_ExtGID = charpos.m_GlyphIndex;
 #endif
     }
diff --git a/core/fpdfapi/render/cpdf_devicebuffer.cpp b/core/fpdfapi/render/cpdf_devicebuffer.cpp
index 4029f2e..091a0c1 100644
--- a/core/fpdfapi/render/cpdf_devicebuffer.cpp
+++ b/core/fpdfapi/render/cpdf_devicebuffer.cpp
@@ -6,6 +6,7 @@
 
 #include "core/fpdfapi/render/cpdf_devicebuffer.h"
 
+#include "build/build_config.h"
 #include "core/fpdfapi/page/cpdf_pageobject.h"
 #include "core/fpdfapi/render/cpdf_rendercontext.h"
 #include "core/fpdfapi/render/cpdf_renderoptions.h"
@@ -28,7 +29,7 @@
   m_Rect = rect;
   m_pObject = pObj;
   m_Matrix.Translate(-rect.left, -rect.top);
-#if _FX_PLATFORM_ != _FX_PLATFORM_APPLE_
+#if !defined(OS_MACOSX)
   int horz_size = pDevice->GetDeviceCaps(FXDC_HORZ_SIZE);
   int vert_size = pDevice->GetDeviceCaps(FXDC_VERT_SIZE);
   if (horz_size && vert_size && max_dpi) {
diff --git a/core/fpdfapi/render/cpdf_dibtransferfunc.cpp b/core/fpdfapi/render/cpdf_dibtransferfunc.cpp
index ee27378..58dbcf0 100644
--- a/core/fpdfapi/render/cpdf_dibtransferfunc.cpp
+++ b/core/fpdfapi/render/cpdf_dibtransferfunc.cpp
@@ -8,6 +8,7 @@
 
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfapi/render/cpdf_transferfunc.h"
 #include "third_party/base/compiler_specific.h"
@@ -25,7 +26,7 @@
   if (m_pSrc->IsAlphaMask())
     return FXDIB_8bppMask;
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   return (m_pSrc->HasAlpha()) ? FXDIB_Argb : FXDIB_Rgb32;
 #else
   return (m_pSrc->HasAlpha()) ? FXDIB_Argb : FXDIB_Rgb;
@@ -59,7 +60,7 @@
           (*dest_buf)[index++] = g0;
           (*dest_buf)[index++] = r0;
         }
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
         index++;
 #endif
       }
@@ -93,7 +94,7 @@
           (*dest_buf)[index++] = m_RampR[src_byte];
         }
         src_buf++;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
         index++;
 #endif
       }
@@ -111,7 +112,7 @@
         (*dest_buf)[index++] = m_RampB[*(src_buf++)];
         (*dest_buf)[index++] = m_RampG[*(src_buf++)];
         (*dest_buf)[index++] = m_RampR[*(src_buf++)];
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
         index++;
 #endif
       }
@@ -128,7 +129,7 @@
         (*dest_buf)[index++] = m_RampR[*(src_buf++)];
         if (!bSkip) {
           (*dest_buf)[index++] = *src_buf;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
         } else {
           index++;
 #endif
@@ -156,7 +157,7 @@
       *dest_buf++ = m_RampR[*(src_buf++)];
     }
   } else {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     if (!m_pSrc->HasAlpha()) {
       for (int i = 0; i < pixels; i++) {
         *dest_buf++ = m_RampB[*(src_buf++)];
@@ -173,7 +174,7 @@
         *dest_buf++ = m_RampR[*(src_buf++)];
         *dest_buf++ = *(src_buf++);
       }
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     }
 #endif
   }
diff --git a/core/fpdfapi/render/cpdf_renderstatus.cpp b/core/fpdfapi/render/cpdf_renderstatus.cpp
index 8f7dd84..b604186 100644
--- a/core/fpdfapi/render/cpdf_renderstatus.cpp
+++ b/core/fpdfapi/render/cpdf_renderstatus.cpp
@@ -13,6 +13,7 @@
 #include <utility>
 #include <vector>
 
+#include "build/build_config.h"
 #include "constants/transparency.h"
 #include "core/fpdfapi/font/cpdf_font.h"
 #include "core/fpdfapi/font/cpdf_type3char.h"
@@ -2524,8 +2525,7 @@
   int width = pClipRect->right - pClipRect->left;
   int height = pClipRect->bottom - pClipRect->top;
   FXDIB_Format format;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_ || defined _SKIA_SUPPORT_ || \
-    defined _SKIA_SUPPORT_PATHS_
+#if defined(OS_MACOSX) || defined _SKIA_SUPPORT_ || defined _SKIA_SUPPORT_PATHS_
   format = bLuminosity ? FXDIB_Rgb32 : FXDIB_8bppMask;
 #else
   format = bLuminosity ? FXDIB_Rgb : FXDIB_8bppMask;
diff --git a/core/fpdfdoc/cpdf_filespec.cpp b/core/fpdfdoc/cpdf_filespec.cpp
index 64a482b..2d670bb 100644
--- a/core/fpdfdoc/cpdf_filespec.cpp
+++ b/core/fpdfdoc/cpdf_filespec.cpp
@@ -8,6 +8,7 @@
 
 #include <vector>
 
+#include "build/build_config.h"
 #include "constants/stream_dict_common.h"
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfapi/parser/cpdf_name.h"
@@ -19,13 +20,12 @@
 
 namespace {
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_ || \
-    _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
+#if defined(OS_MACOSX) || _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
 WideString ChangeSlashToPlatform(const wchar_t* str) {
   WideString result;
   while (*str) {
     if (*str == '/') {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
       result += L':';
 #else
       result += L'\\';
@@ -50,7 +50,7 @@
   }
   return result;
 }
-#endif  // _FX_PLATFORM_APPLE_ || _FX_PLATFORM_WINDOWS_
+#endif  // defined(OS_MACOSX) || _FX_PLATFORM_WINDOWS_
 
 }  // namespace
 
@@ -69,7 +69,7 @@
   if (filepath.GetLength() <= 1)
     return WideString();
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   if (filepath.Left(sizeof("/Mac") - 1) == WideStringView(L"/Mac"))
     return ChangeSlashToPlatform(filepath.c_str() + 1);
   return ChangeSlashToPlatform(filepath.c_str());
@@ -186,7 +186,7 @@
   if (filepath[0] == L'\\')
     return L'/' + ChangeSlashToPDF(filepath.c_str());
   return ChangeSlashToPDF(filepath.c_str());
-#elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#elif defined(OS_MACOSX)
   if (filepath.Left(sizeof("Mac") - 1).EqualsASCII("Mac"))
     return L'/' + ChangeSlashToPDF(filepath.c_str());
   return ChangeSlashToPDF(filepath.c_str());
diff --git a/core/fpdfdoc/cpdf_filespec_unittest.cpp b/core/fpdfdoc/cpdf_filespec_unittest.cpp
index 14c3ad6..82315f2 100644
--- a/core/fpdfdoc/cpdf_filespec_unittest.cpp
+++ b/core/fpdfdoc/cpdf_filespec_unittest.cpp
@@ -6,6 +6,7 @@
 #include <utility>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfapi/parser/cpdf_name.h"
 #include "core/fpdfapi/parser/cpdf_number.h"
@@ -33,7 +34,7 @@
     {L"\\\\pdfdocs\\spec.pdf", L"/pdfdocs/spec.pdf"},
 // Network resource name. It is not supported yet.
 // {L"pclib/eng:\\pdfdocs\\spec.pdf", L"/pclib/eng/pdfdocs/spec.pdf"},
-#elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#elif defined(OS_MACOSX)
     // Absolute path with colon separator.
     {L"Mac HD:PDFDocs:spec.pdf", L"/Mac HD/PDFDocs/spec.pdf"},
     // Relative path with colon separator.
@@ -63,7 +64,7 @@
 #if _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
       L"/C/docs/test.pdf",
       L"C:\\docs\\test.pdf"
-#elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#elif defined(OS_MACOSX)
       L"/Mac HD/docs/test.pdf",
       L"Mac HD:docs:test.pdf"
 #else
@@ -84,7 +85,7 @@
       {L"/E/docs/test.pdf", L"E:\\docs\\test.pdf"},
       {L"/F/docs/test.pdf", L"F:\\docs\\test.pdf"},
       {L"/G/docs/test.pdf", L"G:\\docs\\test.pdf"},
-#elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#elif defined(OS_MACOSX)
       {L"/Mac HD/docs1/test.pdf", L"Mac HD:docs1:test.pdf"},
       {L"/Mac HD/docs2/test.pdf", L"Mac HD:docs2:test.pdf"},
       {L"/Mac HD/docs3/test.pdf", L"Mac HD:docs3:test.pdf"},
@@ -128,7 +129,7 @@
 #if _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
     L"C:\\docs\\test.pdf",
     L"/C/docs/test.pdf"
-#elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#elif defined(OS_MACOSX)
     L"Mac HD:docs:test.pdf",
     L"/Mac HD/docs/test.pdf"
 #else
diff --git a/core/fxcodec/codec/ccodec_progressivedecoder.cpp b/core/fxcodec/codec/ccodec_progressivedecoder.cpp
index e27553f..30d7616 100644
--- a/core/fxcodec/codec/ccodec_progressivedecoder.cpp
+++ b/core/fxcodec/codec/ccodec_progressivedecoder.cpp
@@ -11,6 +11,7 @@
 #include <utility>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fxcodec/codec/cfx_codec_memory.h"
 #include "core/fxcodec/fx_codec.h"
 #include "core/fxcrt/fx_stream.h"
@@ -25,11 +26,11 @@
 namespace {
 
 #ifdef PDF_ENABLE_XFA_PNG
-#if _FX_OS_ == _FX_OS_MACOSX_
+#if defined(OS_MACOSX)
 const double kPngGamma = 1.7;
-#else   // _FX_OS_ == _FX_OS_MACOSX_
+#else
 const double kPngGamma = 2.2;
-#endif  // _FX_OS_ == _FX_OS_MACOSX_
+#endif  // defined(OS_MACOSX)
 #endif  // PDF_ENABLE_XFA_PNG
 
 void RGB2BGR(uint8_t* buffer, int width = 1) {
diff --git a/core/fxcrt/cfx_datetime.cpp b/core/fxcrt/cfx_datetime.cpp
index 286e634..79bc2c1 100644
--- a/core/fxcrt/cfx_datetime.cpp
+++ b/core/fxcrt/cfx_datetime.cpp
@@ -9,8 +9,8 @@
 #include "build/build_config.h"
 #include "core/fxcrt/fx_system.h"
 
-#if _FX_OS_ == _FX_OS_LINUX_ || defined(OS_ANDROID) || \
-    _FX_OS_ == _FX_OS_MACOSX_ || _FX_OS_ == _FX_OS_WASM_
+#if _FX_OS_ == _FX_OS_LINUX_ || defined(OS_ANDROID) || defined(OS_MACOSX) || \
+    _FX_OS_ == _FX_OS_WASM_
 #include <sys/time.h>
 #include <time.h>
 #endif
diff --git a/core/fxcrt/widestring_unittest.cpp b/core/fxcrt/widestring_unittest.cpp
index 08edf48..da77735 100644
--- a/core/fxcrt/widestring_unittest.cpp
+++ b/core/fxcrt/widestring_unittest.cpp
@@ -8,6 +8,7 @@
 #include <iterator>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fxcrt/fx_string.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/base/span.h"
@@ -1549,7 +1550,7 @@
   EXPECT_EQ(L"cla", WideString::Format(L"%.3ls", L"clams"));
   EXPECT_EQ(L"\u043e\u043f", WideString(L"\u043e\u043f"));
 
-#if _FX_OS_ != _FX_OS_MACOSX_
+#if !defined(OS_MACOSX)
   // See https://bugs.chromium.org/p/pdfium/issues/detail?id=1132
   EXPECT_EQ(L"\u043e\u043f", WideString::Format(L"\u043e\u043f"));
   EXPECT_EQ(L"\u043e\u043f", WideString::Format(L"%ls", L"\u043e\u043f"));
diff --git a/core/fxge/agg/fx_agg_driver.cpp b/core/fxge/agg/fx_agg_driver.cpp
index a735d67..89f3f20 100644
--- a/core/fxge/agg/fx_agg_driver.cpp
+++ b/core/fxge/agg/fx_agg_driver.cpp
@@ -9,6 +9,7 @@
 #include <algorithm>
 #include <utility>
 
+#include "build/build_config.h"
 #include "core/fxge/cfx_cliprgn.h"
 #include "core/fxge/cfx_defaultrenderdevice.h"
 #include "core/fxge/cfx_graphstatedata.h"
@@ -1120,13 +1121,9 @@
     const RetainPtr<CFX_DIBitmap>& pBackdropBitmap,
     bool bGroupKnockout)
     : m_pBitmap(pBitmap),
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
-      m_pPlatformGraphics(nullptr),
-#endif
-      m_FillFlags(0),
       m_bRgbByteOrder(bRgbByteOrder),
-      m_pBackdropBitmap(pBackdropBitmap),
-      m_bGroupKnockout(bGroupKnockout) {
+      m_bGroupKnockout(bGroupKnockout),
+      m_pBackdropBitmap(pBackdropBitmap) {
   InitPlatform();
 }
 
@@ -1138,7 +1135,7 @@
   return m_pBitmap->GetBuffer();
 }
 
-#if _FX_PLATFORM_ != _FX_PLATFORM_APPLE_
+#if !defined(OS_MACOSX)
 void CFX_AggDeviceDriver::InitPlatform() {}
 
 void CFX_AggDeviceDriver::DestroyPlatform() {}
@@ -1151,7 +1148,7 @@
                                          uint32_t color) {
   return false;
 }
-#endif  // _FX_PLATFORM_ != _FX_PLATFORM_APPLE_
+#endif  // !defined(OS_MACOSX)
 
 int CFX_AggDeviceDriver::GetDeviceCaps(int caps_id) const {
   switch (caps_id) {
diff --git a/core/fxge/agg/fx_agg_driver.h b/core/fxge/agg/fx_agg_driver.h
index 80fbf73..1aecc50 100644
--- a/core/fxge/agg/fx_agg_driver.h
+++ b/core/fxge/agg/fx_agg_driver.h
@@ -10,6 +10,7 @@
 #include <memory>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fxge/renderdevicedriver_iface.h"
 #include "third_party/agg23/agg_clip_liang_barsky.h"
 #include "third_party/agg23/agg_path_storage.h"
@@ -112,13 +113,13 @@
   RetainPtr<CFX_DIBitmap> m_pBitmap;
   std::unique_ptr<CFX_ClipRgn> m_pClipRgn;
   std::vector<std::unique_ptr<CFX_ClipRgn>> m_StateStack;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
-  void* m_pPlatformGraphics;
+#if defined(OS_MACOSX)
+  void* m_pPlatformGraphics = nullptr;
 #endif
-  int m_FillFlags;
+  int m_FillFlags = 0;
   const bool m_bRgbByteOrder;
-  RetainPtr<CFX_DIBitmap> m_pBackdropBitmap;
   const bool m_bGroupKnockout;
+  RetainPtr<CFX_DIBitmap> m_pBackdropBitmap;
 };
 
 #endif  // CORE_FXGE_AGG_FX_AGG_DRIVER_H_
diff --git a/core/fxge/cfx_facecache.cpp b/core/fxge/cfx_facecache.cpp
index d868bf2..869e464 100644
--- a/core/fxge/cfx_facecache.cpp
+++ b/core/fxge/cfx_facecache.cpp
@@ -11,6 +11,7 @@
 #include <memory>
 #include <utility>
 
+#include "build/build_config.h"
 #include "core/fxcrt/fx_codepage.h"
 #include "core/fxge/cfx_font.h"
 #include "core/fxge/cfx_fontmgr.h"
@@ -262,7 +263,7 @@
   }
 #endif
   ByteString FaceGlyphsKey(keygen.key_, keygen.key_len_);
-#if _FX_PLATFORM_ != _FX_PLATFORM_APPLE_ || defined _SKIA_SUPPORT_ || \
+#if !defined(OS_MACOSX) || defined _SKIA_SUPPORT_ || \
     defined _SKIA_SUPPORT_PATHS_
   return LookUpGlyphBitmap(pFont, matrix, FaceGlyphsKey, glyph_index,
                            bFontStyle, dest_width, anti_alias);
@@ -333,7 +334,7 @@
 }
 #endif
 
-#if _FX_PLATFORM_ != _FX_PLATFORM_APPLE_
+#if !defined(OS_MACOSX)
 void CFX_FaceCache::InitPlatform() {}
 #endif
 
diff --git a/core/fxge/cfx_font.cpp b/core/fxge/cfx_font.cpp
index cd137bd..6234b15 100644
--- a/core/fxge/cfx_font.cpp
+++ b/core/fxge/cfx_font.cpp
@@ -12,6 +12,7 @@
 #include <utility>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fxcrt/fx_codepage.h"
 #include "core/fxcrt/fx_stream.h"
 #include "core/fxge/cfx_facecache.h"
@@ -220,7 +221,7 @@
     {FX_CHARSET_ShiftJIS, "MS Gothic"},
     {FX_CHARSET_Hangul, "Batang"},
     {FX_CHARSET_MSWin_Cyrillic, "Arial"},
-#if _FX_PLATFORM_ == _FX_PLATFORM_LINUX_ || _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if _FX_PLATFORM_ == _FX_PLATFORM_LINUX_ || defined(OS_MACOSX)
     {FX_CHARSET_MSWin_EasternEuropean, "Arial"},
 #else
     {FX_CHARSET_MSWin_EasternEuropean, "Tahoma"},
@@ -336,7 +337,7 @@
   if (m_Face)
     DeleteFace();
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   ReleasePlatformResource();
 #endif
 }
diff --git a/core/fxge/cfx_font.h b/core/fxge/cfx_font.h
index 99b2c0e..bc9cc85 100644
--- a/core/fxge/cfx_font.h
+++ b/core/fxge/cfx_font.h
@@ -10,6 +10,7 @@
 #include <memory>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fxcrt/bytestring.h"
 #include "core/fxcrt/fx_coordinates.h"
 #include "core/fxcrt/unowned_ptr.h"
@@ -94,7 +95,7 @@
   void AdjustMMParams(int glyph_index, int dest_width, int weight) const;
   CFX_PathData* LoadGlyphPathImpl(uint32_t glyph_index,
                                   uint32_t dest_width) const;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   void* GetPlatformFont() const { return m_pPlatformFont; }
   void SetPlatformFont(void* font) { m_pPlatformFont = font; }
 #endif
@@ -128,9 +129,9 @@
   CFX_FaceCache* GetFaceCache() const;
   void DeleteFace();
   void ClearFaceCache();
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   void ReleasePlatformResource();
-#endif  // _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#endif
 
   ByteString GetFamilyNameOrUntitled() const;
 
@@ -142,7 +143,7 @@
   pdfium::span<uint8_t> m_FontData;
   bool m_bEmbedded = false;
   bool m_bVertical = false;
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   void* m_pPlatformFont = nullptr;
 #endif
 };
diff --git a/core/fxge/cfx_fontmapper.cpp b/core/fxge/cfx_fontmapper.cpp
index c4a7237..b3a828e 100644
--- a/core/fxge/cfx_fontmapper.cpp
+++ b/core/fxge/cfx_fontmapper.cpp
@@ -598,7 +598,7 @@
       }
     } else {
       if (Charset == FX_CHARSET_Symbol) {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_ || defined(OS_ANDROID)
+#if defined(OS_MACOSX) || defined(OS_ANDROID)
         if (SubstName == "Symbol") {
           pSubstFont->m_Family = "Chrome Symbol";
           pSubstFont->m_Charset = FX_CHARSET_Symbol;
diff --git a/core/fxge/skia/fx_skia_device.cpp b/core/fxge/skia/fx_skia_device.cpp
index d246b6a..01db196 100644
--- a/core/fxge/skia/fx_skia_device.cpp
+++ b/core/fxge/skia/fx_skia_device.cpp
@@ -8,6 +8,7 @@
 #include <utility>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/page/cpdf_expintfunc.h"
 #include "core/fpdfapi/page/cpdf_function.h"
 #include "core/fpdfapi/page/cpdf_meshstream.h"
@@ -865,7 +866,7 @@
       m_positions[index + count] = {cp.m_Origin.x * flip,
                                     cp.m_Origin.y * vFlip};
       m_glyphs[index + count] = static_cast<uint16_t>(cp.m_GlyphIndex);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
       if (cp.m_ExtGID)
         m_glyphs[index + count] = static_cast<uint16_t>(cp.m_ExtGID);
 #endif
@@ -1592,7 +1593,7 @@
       }
     }
     glyphs[index] = static_cast<uint16_t>(cp.m_GlyphIndex);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     if (cp.m_ExtGID)
       glyphs[index] = static_cast<uint16_t>(cp.m_ExtGID);
 #endif
diff --git a/fpdfsdk/fpdf_annot_embeddertest.cpp b/fpdfsdk/fpdf_annot_embeddertest.cpp
index f64cd3b..7acef50 100644
--- a/fpdfsdk/fpdf_annot_embeddertest.cpp
+++ b/fpdfsdk/fpdf_annot_embeddertest.cpp
@@ -8,6 +8,7 @@
 #include <string>
 #include <vector>
 
+#include "build/build_config.h"
 #include "constants/annotation_common.h"
 #include "core/fxcrt/fx_system.h"
 #include "public/cpp/fpdf_scopers.h"
@@ -474,7 +475,7 @@
 }
 
 TEST_F(FPDFAnnotEmbedderTest, ModifyRectQuadpointsWithAP) {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   static const char kMd5Original[] = "63af8432fab95a67cdebb7cd0e514941";
   static const char kMd5ModifiedHighlight[] =
       "aec26075011349dec9bace891856b5f2";
@@ -682,7 +683,7 @@
 }
 
 TEST_F(FPDFAnnotEmbedderTest, AddAndModifyPath) {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   static const char kMd5Original[] = "c35408717759562d1f8bf33d317483d2";
   static const char kMd5ModifiedPath[] = "9059723a045e17478753d2f0eb33bc03";
   static const char kMd5TwoPaths[] = "7eed0cfba780f1d4dd8068f717d3a6bf";
@@ -884,7 +885,7 @@
 }
 
 TEST_F(FPDFAnnotEmbedderTest, AddAndModifyImage) {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   static const char kMd5Original[] = "c35408717759562d1f8bf33d317483d2";
   static const char kMd5NewImage[] = "ff012f5697436dfcaec25b32d1333596";
   static const char kMd5ModifiedImage[] = "86cf8cb2755a7a2046a543e66d9c1e61";
@@ -969,7 +970,7 @@
 }
 
 TEST_F(FPDFAnnotEmbedderTest, AddAndModifyText) {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   static const char kMd5Original[] = "c35408717759562d1f8bf33d317483d2";
   static const char kMd5NewText[] = "60031c1b0330cf1e1575f7d46687d429";
   static const char kMd5ModifiedText[] = "79f5cfb0b07caaf936f65f6a7a57ce77";
@@ -1109,7 +1110,7 @@
   EXPECT_TRUE(FPDF_SaveAsCopy(document(), this, 0));
   UnloadPage(page);
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   static const char kMd5[] = "4d64e61c9c0f8c60ab3cc3234bb73b1c";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   static const char kMd5[] = "9ee141f698c3fcb56c050dffd6c82624";
diff --git a/fpdfsdk/fpdf_edit_embeddertest.cpp b/fpdfsdk/fpdf_edit_embeddertest.cpp
index 525e9cc..4fdde68 100644
--- a/fpdfsdk/fpdf_edit_embeddertest.cpp
+++ b/fpdfsdk/fpdf_edit_embeddertest.cpp
@@ -7,6 +7,7 @@
 #include <utility>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fpdfapi/font/cpdf_font.h"
 #include "core/fpdfapi/page/cpdf_formobject.h"
 #include "core/fpdfapi/page/cpdf_page.h"
@@ -446,7 +447,7 @@
   // Verify the "Hello, world!" text is gone and "Changed for SetText test" is
   // now displayed.
   ASSERT_EQ(2, FPDFPage_CountObjects(page));
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char kChangedMD5[] = "94c1e7a5af7dd9d77dc2223b1091acb7";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char kChangedMD5[] = "3137fdb27962671f5c3963a5e965eff5";
@@ -485,7 +486,7 @@
 
   // Show what the original file looks like.
   {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     const char kOriginalMD5[] = "b90475ca64d1348c3bf5e2b77ad9187a";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
     const char kOriginalMD5[] = "795b7ce1626931aa06af0fa23b7d80bb";
@@ -504,7 +505,7 @@
 
   // Verify the "Hello, world!" text is gone.
   {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     const char kRemovedMD5[] = "af760c4702467cb1492a57fb8215efaa";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
     const char kRemovedMD5[] = "aae6c5334721f90ec30d3d59f4ef7deb";
@@ -641,7 +642,7 @@
 
   // Show what the original file looks like.
   {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     const char kOriginalMD5[] = "5a5eb63cb21cc15084fea1f14284b8df";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
     const char kOriginalMD5[] = "587c507a40f613f9c530b2ce2d58d655";
@@ -686,7 +687,7 @@
 
   EXPECT_EQ(11, FPDFPage_CountObjects(page));
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char kNonPrimesMD5[] = "57e76dc7375d896704f0fd6d6d1b9e65";
   const char kNonPrimesAfterSaveMD5[] = "6304512d0150bbd5578e8e22d3121103";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
@@ -963,7 +964,7 @@
 
   // Verify the "Hello, world!" text is gone.
   ASSERT_EQ(2, FPDFPage_CountObjects(page));
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char kHelloRemovedMD5[] = "e07a62d412728fc4d6e3ff42f2dd0e11";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char kHelloRemovedMD5[] = "a97d4c72c969ba373c2dce675d277e65";
@@ -1010,7 +1011,7 @@
 
   // Verify the "Greetings, world!" text is gone.
   ASSERT_EQ(2, FPDFPage_CountObjects(page));
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char kGreetingsRemovedMD5[] = "b90475ca64d1348c3bf5e2b77ad9187a";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char kGreetingsRemovedMD5[] = "795b7ce1626931aa06af0fa23b7d80bb";
@@ -1126,7 +1127,7 @@
       EXPECT_EQ(1, cpdf_page_object->GetContentStream()) << i;
   }
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char kStream1RemovedMD5[] = "d2e21fbd5a6de563f619feeeb6163331";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char kStream1RemovedMD5[] = "b4140f203523e38793283a5943d8075b";
@@ -1258,7 +1259,7 @@
   cpdf_page_object = CPDFPageObjectFromFPDFPageObject(page_object);
   ASSERT_EQ(0, cpdf_page_object->GetContentStream());
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char kFirstRemovedMD5[] = "af760c4702467cb1492a57fb8215efaa";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char kFirstRemovedMD5[] = "aae6c5334721f90ec30d3d59f4ef7deb";
@@ -1326,7 +1327,7 @@
   cpdf_page_object = CPDFPageObjectFromFPDFPageObject(page_object);
   ASSERT_EQ(0, cpdf_page_object->GetContentStream());
 
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char kLastRemovedMD5[] = "f8fbd14a048b9e2ea8e5f059f22a910e";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char kLastRemovedMD5[] = "93db13099042bafefb3c22a165bad684";
@@ -1640,7 +1641,7 @@
 
   // Render and check the result. Text is slightly different on Mac.
   ScopedFPDFBitmap bitmap = RenderLoadedPage(page);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char md5[] = "f9e6fa74230f234286bfcada9f7606d8";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char md5[] = "74dd9c393b8b2578d2b7feb032b7daad";
@@ -1785,7 +1786,7 @@
   EXPECT_TRUE(FPDFPage_GenerateContent(page));
   {
     ScopedFPDFBitmap page_bitmap = RenderPage(page);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     const char md5[] = "a4dddc1a3930fa694bbff9789dab4161";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
     const char md5[] = "08d1ff3e5a42801bee6077fd366bef00";
@@ -1810,7 +1811,7 @@
   EXPECT_TRUE(FPDFPage_GenerateContent(page));
   {
     ScopedFPDFBitmap page_bitmap = RenderPage(page);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     const char md5[] = "a5c4ace4c6f27644094813fe1441a21c";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
     const char md5[] = "3755dd35abd4c605755369401ee85b2d";
@@ -1834,7 +1835,7 @@
   EXPECT_TRUE(FPDFPage_GenerateContent(page));
   {
     ScopedFPDFBitmap page_bitmap = RenderPage(page);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     const char md5[] = "40b3ef04f915ff4c4208948001763544";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
     const char md5[] = "aba523a8110d01ed9bd7b7781ff74045";
@@ -2003,7 +2004,7 @@
   FPDFPageObj_Transform(text_object, 1, 0, 0, 1, 20, 20);
   FPDFPage_InsertObject(page.get(), text_object);
   ScopedFPDFBitmap page_bitmap = RenderPage(page.get());
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char md5[] = "a4dddc1a3930fa694bbff9789dab4161";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char md5[] = "08d1ff3e5a42801bee6077fd366bef00";
@@ -2349,13 +2350,13 @@
     FPDFPageObj_Transform(text_object, 1, 0, 0, 1, 400, 400);
     FPDFPage_InsertObject(page, text_object);
     ScopedFPDFBitmap page_bitmap = RenderPage(page);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     const char md5[] = "17d2b6cd574cf66170b09c8927529a94";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
     const char md5[] = "d60ba39f9698e32360d99e727dd93165";
 #else
     const char md5[] = "70592859010ffbf532a2237b8118bcc4";
-#endif  // _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#endif
     CompareBitmap(page_bitmap.get(), 612, 792, md5);
 
     // Add some more text, same font
@@ -2367,13 +2368,13 @@
     FPDFPage_InsertObject(page, text_object2);
   }
   ScopedFPDFBitmap page_bitmap2 = RenderPage(page);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char md5_2[] = "8eded4193ff1f0f77b8b600a825e97ea";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char md5_2[] = "2199b579c49ab5f80c246a586a80ee90";
 #else
   const char md5_2[] = "c1d10cce1761c4a998a16b2562030568";
-#endif  // _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#endif
   CompareBitmap(page_bitmap2.get(), 612, 792, md5_2);
 
   EXPECT_TRUE(FPDFPage_GenerateContent(page));
@@ -2663,7 +2664,7 @@
   EXPECT_EQ(0, memcmp(block_value, buffer, kBlobLen));
 
 // Render and check the bitmap is the expected one.
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char md5[] = "17d2b6cd574cf66170b09c8927529a94";
 #elif _FX_PLATFORM_ == _FX_PLATFORM_WINDOWS_
   const char md5[] = "d60ba39f9698e32360d99e727dd93165";
diff --git a/fpdfsdk/fpdf_formfill_embeddertest.cpp b/fpdfsdk/fpdf_formfill_embeddertest.cpp
index d40ee0b..cefdc7c 100644
--- a/fpdfsdk/fpdf_formfill_embeddertest.cpp
+++ b/fpdfsdk/fpdf_formfill_embeddertest.cpp
@@ -6,6 +6,7 @@
 #include <string>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fxcrt/fx_coordinates.h"
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/fx_system.h"
@@ -789,7 +790,7 @@
 #endif  // PDF_ENABLE_V8
 
 TEST_F(FPDFFormFillEmbedderTest, FormText) {
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   const char md5_1[] = "5f11dbe575fe197a37c3fb422559f8ff";
   const char md5_2[] = "35b1a4b679eafc749a0b6fda750c0e8d";
   const char md5_3[] = "65c64a7c355388f719a752aa1e23f6fe";
diff --git a/fxbarcode/oned/BC_OneDimWriter.cpp b/fxbarcode/oned/BC_OneDimWriter.cpp
index b4d85b4..9349a1c 100644
--- a/fxbarcode/oned/BC_OneDimWriter.cpp
+++ b/fxbarcode/oned/BC_OneDimWriter.cpp
@@ -26,6 +26,7 @@
 #include <memory>
 #include <vector>
 
+#include "build/build_config.h"
 #include "core/fxge/cfx_defaultrenderdevice.h"
 #include "core/fxge/cfx_font.h"
 #include "core/fxge/cfx_graphstatedata.h"
@@ -133,7 +134,7 @@
   charPos[0].m_Origin = CFX_PointF(penX + left, penY + top);
   charPos[0].m_GlyphIndex = encoding->GlyphFromCharCode(charcodes[0]);
   charPos[0].m_FontCharWidth = cFont->GetGlyphWidth(charPos[0].m_GlyphIndex);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
   charPos[0].m_ExtGID = charPos[0].m_GlyphIndex;
 #endif
   penX += (float)(charPos[0].m_FontCharWidth) * (float)fontSize / 1000.0f;
@@ -141,7 +142,7 @@
     charPos[i].m_Origin = CFX_PointF(penX + left, penY + top);
     charPos[i].m_GlyphIndex = encoding->GlyphFromCharCode(charcodes[i]);
     charPos[i].m_FontCharWidth = cFont->GetGlyphWidth(charPos[i].m_GlyphIndex);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
     charPos[i].m_ExtGID = charPos[i].m_GlyphIndex;
 #endif
     penX += (float)(charPos[i].m_FontCharWidth) * (float)fontSize / 1000.0f;
diff --git a/xfa/fgas/font/cfx_fontsourceenum_file.cpp b/xfa/fgas/font/cfx_fontsourceenum_file.cpp
index 386dc59..f9eafb3 100644
--- a/xfa/fgas/font/cfx_fontsourceenum_file.cpp
+++ b/xfa/fgas/font/cfx_fontsourceenum_file.cpp
@@ -18,8 +18,10 @@
 #if _FX_PLATFORM_ == _FX_PLATFORM_LINUX_
     "/usr/share/fonts", "/usr/share/X11/fonts/Type1",
     "/usr/share/X11/fonts/TTF", "/usr/local/share/fonts",
-#elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
-    "~/Library/Fonts", "/Library/Fonts", "/System/Library/Fonts",
+#elif defined(OS_MACOSX)
+    "~/Library/Fonts",
+    "/Library/Fonts",
+    "/System/Library/Fonts",
 #elif defined(OS_ANDROID)
     "/system/fonts",
 #endif
diff --git a/xfa/fgas/font/fgas_fontutils.cpp b/xfa/fgas/font/fgas_fontutils.cpp
index f95a5ad..1c8d911 100644
--- a/xfa/fgas/font/fgas_fontutils.cpp
+++ b/xfa/fgas/font/fgas_fontutils.cpp
@@ -1020,7 +1020,7 @@
      "Sharp,WenQuanYi Micro Hei",
      0, 936},
 };
-#elif _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#elif defined(OS_MACOSX)
 const FGAS_FontInfo g_XFAFontsMap[] = {
     {0x01d5d33e, "SimSun", "STHeiti,Heiti TC,STFangsong", 0, 936},
     {0x01e4f102, "YouYuan", "STHeiti,Heiti TC,STFangsong", 1, 936},
diff --git a/xfa/fgas/layout/cfx_rtfbreak.cpp b/xfa/fgas/layout/cfx_rtfbreak.cpp
index 543f6f3..3ea89cc 100644
--- a/xfa/fgas/layout/cfx_rtfbreak.cpp
+++ b/xfa/fgas/layout/cfx_rtfbreak.cpp
@@ -8,6 +8,7 @@
 
 #include <algorithm>
 
+#include "build/build_config.h"
 #include "core/fxge/cfx_renderdevice.h"
 #include "third_party/base/numerics/safe_math.h"
 #include "third_party/base/stl_util.h"
@@ -782,7 +783,7 @@
       current_char_pos.m_GlyphIndex = pFont->GetGlyphIndex(wForm);
       if (current_char_pos.m_GlyphIndex == 0xFFFF)
         current_char_pos.m_GlyphIndex = pFont->GetGlyphIndex(wch);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
       current_char_pos.m_ExtGID = current_char_pos.m_GlyphIndex;
 #endif
       current_char_pos.m_FontCharWidth = iCharWidth;
diff --git a/xfa/fgas/layout/cfx_txtbreak.cpp b/xfa/fgas/layout/cfx_txtbreak.cpp
index 537de71..456d5b9 100644
--- a/xfa/fgas/layout/cfx_txtbreak.cpp
+++ b/xfa/fgas/layout/cfx_txtbreak.cpp
@@ -8,6 +8,7 @@
 
 #include <algorithm>
 
+#include "build/build_config.h"
 #include "core/fxge/cfx_renderdevice.h"
 #include "third_party/base/stl_util.h"
 #include "xfa/fgas/font/cfgas_gefont.h"
@@ -842,7 +843,7 @@
       }
       if (!bEmptyChar || (bEmptyChar && !bSkipSpace)) {
         pCharPos->m_GlyphIndex = pFont->GetGlyphIndex(wForm);
-#if _FX_PLATFORM_ == _FX_PLATFORM_APPLE_
+#if defined(OS_MACOSX)
         pCharPos->m_ExtGID = pCharPos->m_GlyphIndex;
 #endif
         // TODO(npm): change widths in this method to unsigned to avoid implicit
diff --git a/xfa/fwl/cfwl_edit.cpp b/xfa/fwl/cfwl_edit.cpp
index f17457b..3256c89 100644
--- a/xfa/fwl/cfwl_edit.cpp
+++ b/xfa/fwl/cfwl_edit.cpp
@@ -11,6 +11,7 @@
 #include <utility>
 #include <vector>
 
+#include "build/build_config.h"
 #include "third_party/base/ptr_util.h"
 #include "third_party/base/stl_util.h"
 #include "xfa/fde/cfde_texteditengine.h"
@@ -36,7 +37,7 @@
 
 const int kEditMargin = 3;
 
-#if (_FX_OS_ == _FX_OS_MACOSX_)
+#if defined(OS_MACOSX)
 constexpr int kEditingModifier = FWL_KEYFLAG_Command;
 #else
 constexpr int kEditingModifier = FWL_KEYFLAG_Ctrl;
diff --git a/xfa/fwl/cfwl_notedriver.cpp b/xfa/fwl/cfwl_notedriver.cpp
index 3b18098..9a98edf 100644
--- a/xfa/fwl/cfwl_notedriver.cpp
+++ b/xfa/fwl/cfwl_notedriver.cpp
@@ -9,6 +9,7 @@
 #include <algorithm>
 #include <utility>
 
+#include "build/build_config.h"
 #include "core/fxcrt/fx_extension.h"
 #include "third_party/base/ptr_util.h"
 #include "third_party/base/stl_util.h"
@@ -193,7 +194,7 @@
 
 bool CFWL_NoteDriver::DoKey(CFWL_Message* pMessage, CFWL_Widget* pMessageForm) {
   CFWL_MessageKey* pMsg = static_cast<CFWL_MessageKey*>(pMessage);
-#if (_FX_OS_ != _FX_OS_MACOSX_)
+#if !defined(OS_MACOSX)
   if (pMsg->m_dwCmd == FWL_KeyCommand::KeyDown &&
       pMsg->m_dwKeyCode == FWL_VKEY_Tab) {
     CFWL_WidgetMgr* pWidgetMgr = pMessageForm->GetOwnerApp()->GetWidgetMgr();
diff --git a/xfa/fwl/cfwl_widgetmgr.cpp b/xfa/fwl/cfwl_widgetmgr.cpp
index bf3b7cb..3531bf2 100644
--- a/xfa/fwl/cfwl_widgetmgr.cpp
+++ b/xfa/fwl/cfwl_widgetmgr.cpp
@@ -8,6 +8,7 @@
 
 #include <utility>
 
+#include "build/build_config.h"
 #include "third_party/base/ptr_util.h"
 #include "xfa/fwl/cfwl_app.h"
 #include "xfa/fwl/cfwl_notedriver.h"
@@ -325,7 +326,7 @@
   CFWL_NoteDriver* pNoteDriver = pDstWidget->GetOwnerApp()->GetNoteDriver();
   pNoteDriver->ProcessMessage(pMessage->Clone());
 
-#if (_FX_OS_ == _FX_OS_MACOSX_)
+#if defined(OS_MACOSX)
   CFWL_NoteLoop* pTopLoop = pNoteDriver->GetTopLoop();
   if (pTopLoop)
     pNoteDriver->UnqueueMessageAndProcess(pTopLoop);
diff --git a/xfa/fwl/theme/cfwl_listboxtp.cpp b/xfa/fwl/theme/cfwl_listboxtp.cpp
index 73c4839..a59b774 100644
--- a/xfa/fwl/theme/cfwl_listboxtp.cpp
+++ b/xfa/fwl/theme/cfwl_listboxtp.cpp
@@ -6,6 +6,7 @@
 
 #include "xfa/fwl/theme/cfwl_listboxtp.h"
 
+#include "build/build_config.h"
 #include "xfa/fwl/cfwl_listbox.h"
 #include "xfa/fwl/cfwl_themebackground.h"
 #include "xfa/fwl/cfwl_widget.h"
@@ -61,7 +62,7 @@
     pGraphics->SaveGraphState();
     pGraphics->SetFillColor(CXFA_GEColor(FWLTHEME_COLOR_BKSelected));
     CXFA_GEPath path;
-#if (_FX_OS_ == _FX_OS_MACOSX_)
+#if defined(OS_MACOSX)
     path.AddRectangle(rtItem.left, rtItem.top, rtItem.width - 1,
                       rtItem.height - 1);
 #else