WASM --enable-wasm-strip now skips lots of LO code

... resulting in a stripped-down, Writer-only build to decrease
the resulting WASM bytecode size.

It removes the following code from the build:
* All other major modules: Base, Calc, Chart, Draw, Impress and
  Math and related writerperfect filters
* The premultiply tables
* The (auto-)recovery functionality
* All accessibility (but not the accessibility document checker)
* The LanguageGuess component
* EPUB support
* The start center / BackingWindow
* The TipOfTheDay functionality
* The splash screen communication

Currently crashs with anything different then soffice --writer.
Closing the document also still crashes.

FYI: many of these features are now behind ENABLE_WASM_STRIP_*
defines, but they normally don't work on their own, globally!
That's because we started with stripping the main components.

Change-Id: Ib9c0f9452815910c0a2aceaf142ba1ad4a9cb0d7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/126182
Tested-by: Jenkins
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>

3 files changed, 115 insertions, 0 deletions

diff --git a/vcl/source/bitmap/BitmapTools.cxx b/vcl/source/bitmap/BitmapTools.cxx
index b22661c628d7..da9a88bf67c9 100644
--- a/vcl/source/bitmap/BitmapTools.cxx
+++ b/vcl/source/bitmap/BitmapTools.cxx
@@ -300,7 +300,9 @@ BitmapEx* CreateFromCairoSurface(Size aSize, cairo_surface_t * pSurface)
     cairo_surface_flush(pPixels);
     unsigned char *pSrc = cairo_image_surface_get_data( pPixels );
     unsigned int nStride = cairo_image_surface_get_stride( pPixels );
+#if !ENABLE_WASM_STRIP_PREMULTIPLY
     vcl::bitmap::lookup_table const & unpremultiply_table = vcl::bitmap::get_unpremultiply_table();
+#endif
     for( tools::Long y = 0; y < aSize.Height(); y++ )
     {
         sal_uInt32 *pPix = reinterpret_cast<sal_uInt32 *>(pSrc + nStride * y);
@@ -320,9 +322,15 @@ BitmapEx* CreateFromCairoSurface(Size aSize, cairo_surface_t * pSurface)
             if( nAlpha != 0 && nAlpha != 255 )
             {
                 // Cairo uses pre-multiplied alpha - we do not => re-multiply
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                nR = vcl::bitmap::unpremultiply(nAlpha, nR);
+                nG = vcl::bitmap::unpremultiply(nAlpha, nG);
+                nB = vcl::bitmap::unpremultiply(nAlpha, nB);
+#else
                 nR = unpremultiply_table[nAlpha][nR];
                 nG = unpremultiply_table[nAlpha][nG];
                 nB = unpremultiply_table[nAlpha][nB];
+#endif
             }
             pRGBWrite->SetPixel( y, x, BitmapColor( nR, nG, nB ) );
             pMaskWrite->SetPixelIndex( y, x, 255 - nAlpha );
@@ -693,7 +701,9 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
     ::Color aColor;
     unsigned int nAlpha = 255;
 
+#if !ENABLE_WASM_STRIP_PREMULTIPLY
     vcl::bitmap::lookup_table const & premultiply_table = vcl::bitmap::get_premultiply_table();
+#endif
     for( nY = 0; nY < nHeight; nY++ )
     {
         ::Scanline pReadScan;
@@ -722,13 +732,25 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
                 aColor = pBitmapReadAcc->GetPaletteColor(*pReadScan++);
 
 #ifdef OSL_BIGENDIAN
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetRed());
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetGreen());
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetBlue());
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetRed()];
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetGreen()];
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetBlue()];
+#endif
+#else
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetBlue());
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetGreen());
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetRed());
 #else
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetBlue()];
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetGreen()];
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetRed()];
+#endif
                 nOff++;
 #endif
             }
@@ -746,18 +768,30 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
                     nAlpha = data[ nOff ];
                 else
                     nAlpha = data[ nOff ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff + 3 ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff + 2 ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff + 1 ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+#else
                 data[ nOff + 3 ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff + 2 ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff + 1 ] = premultiply_table[nAlpha][*pReadScan++];
+#endif
                 nOff += 4;
 #else
                 if( pAlphaReadAcc )
                     nAlpha = data[ nOff + 3 ];
                 else
                     nAlpha = data[ nOff + 3 ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
+#endif
                 nOff++;
 #endif
             }
@@ -775,17 +809,29 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
                     nAlpha = data[ nOff++ ];
                 else
                     nAlpha = data[ nOff++ ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
+#endif
 #else
                 if( pAlphaReadAcc )
                     nAlpha = data[ nOff + 3 ];
                 else
                     nAlpha = data[ nOff + 3 ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 2 ]);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 1 ]);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 0 ]);
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 2 ]];
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 1 ]];
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 0 ]];
+#endif
                 pReadScan += 3;
                 nOff++;
 #endif
@@ -804,18 +850,30 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
                     nAlpha = data[ nOff++ ];
                 else
                     nAlpha = data[ nOff++ ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 2 ]);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 1 ]);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 0 ]);
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 2 ]];
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 1 ]];
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 0 ]];
+#endif
                 pReadScan += 4;
 #else
                 if( pAlphaReadAcc )
                     nAlpha = data[ nOff + 3 ];
                 else
                     nAlpha = data[ nOff + 3 ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
+#endif
                 pReadScan++;
                 nOff++;
 #endif
@@ -834,18 +892,30 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
                     nAlpha = data[ nOff ++ ];
                 else
                     nAlpha = data[ nOff ++ ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, *pReadScan++);
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
                 data[ nOff++ ] = premultiply_table[nAlpha][*pReadScan++];
+#endif
                 pReadScan++;
 #else
                 if( pAlphaReadAcc )
                     nAlpha = data[ nOff + 3 ];
                 else
                     nAlpha = data[ nOff + 3 ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 2 ]);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 1 ]);
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, pReadScan[ 0 ]);
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 2 ]];
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 1 ]];
                 data[ nOff++ ] = premultiply_table[nAlpha][pReadScan[ 0 ]];
+#endif
                 pReadScan += 4;
                 nOff++;
 #endif
@@ -869,17 +939,29 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
                     nAlpha = data[ nOff++ ];
                 else
                     nAlpha = data[ nOff++ ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetRed());
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetGreen());
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetBlue());
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetRed()];
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetGreen()];
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetBlue()];
+#endif
 #else
                 if( pAlphaReadAcc )
                     nAlpha = data[ nOff + 3 ];
                 else
                     nAlpha = data[ nOff + 3 ] = 255;
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetBlue());
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetGreen());
+                data[ nOff++ ] = vcl::bitmap::premultiply(nAlpha, aColor.GetRed());
+#else
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetBlue()];
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetGreen()];
                 data[ nOff++ ] = premultiply_table[nAlpha][aColor.GetRed()];
+#endif
                 nOff ++;
 #endif
             }
@@ -1043,6 +1125,17 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
         return bRet;
     }
 
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+    sal_uInt8 unpremultiply(sal_uInt8 c, sal_uInt8 a)
+    {
+        return (a == 0) ? 0 : (c * 255 + a / 2) / a;
+    }
+
+    sal_uInt8 premultiply(sal_uInt8 c, sal_uInt8 a)
+    {
+        return (c * a + 127) / 255;
+    }
+#else
     sal_uInt8 unpremultiply(sal_uInt8 c, sal_uInt8 a)
     {
         return get_unpremultiply_table()[a][c];
@@ -1100,6 +1193,7 @@ void CanvasCairoExtractBitmapData( BitmapEx const & aBmpEx, Bitmap & aBitmap, un
             std::make_integer_sequence<int, 256>{});
         return premultiply_table;
     }
+#endif
 
 bool convertBitmap32To24Plus8(BitmapEx const & rInput, BitmapEx & rResult)
 {
diff --git a/vcl/source/filter/png/PngImageReader.cxx b/vcl/source/filter/png/PngImageReader.cxx
index 13c19feaf1ad..70ae63240227 100644
--- a/vcl/source/filter/png/PngImageReader.cxx
+++ b/vcl/source/filter/png/PngImageReader.cxx
@@ -291,7 +291,9 @@ bool reader(SvStream& rStream, BitmapEx& rBitmapEx,
                     png_read_row(pPng, pScanline, nullptr);
                 }
             }
+#if !ENABLE_WASM_STRIP_PREMULTIPLY
             const vcl::bitmap::lookup_table& premultiply = vcl::bitmap::get_premultiply_table();
+#endif
             if (eFormat == ScanlineFormat::N32BitTcAbgr || eFormat == ScanlineFormat::N32BitTcArgb)
             { // alpha first and premultiply
                 for (png_uint_32 y = 0; y < height; y++)
@@ -300,9 +302,15 @@ bool reader(SvStream& rStream, BitmapEx& rBitmapEx,
                     for (size_t i = 0; i < aRowSizeBytes; i += 4)
                     {
                         const sal_uInt8 alpha = pScanline[i + 3];
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                        pScanline[i + 3] = vcl::bitmap::premultiply(alpha, pScanline[i + 2]);
+                        pScanline[i + 2] = vcl::bitmap::premultiply(alpha, pScanline[i + 1]);
+                        pScanline[i + 1] = vcl::bitmap::premultiply(alpha, pScanline[i]);
+#else
                         pScanline[i + 3] = premultiply[alpha][pScanline[i + 2]];
                         pScanline[i + 2] = premultiply[alpha][pScanline[i + 1]];
                         pScanline[i + 1] = premultiply[alpha][pScanline[i]];
+#endif
                         pScanline[i] = alpha;
                     }
                 }
@@ -315,9 +323,15 @@ bool reader(SvStream& rStream, BitmapEx& rBitmapEx,
                     for (size_t i = 0; i < aRowSizeBytes; i += 4)
                     {
                         const sal_uInt8 alpha = pScanline[i + 3];
+#if ENABLE_WASM_STRIP_PREMULTIPLY
+                        pScanline[i] = vcl::bitmap::premultiply(alpha, pScanline[i]);
+                        pScanline[i + 1] = vcl::bitmap::premultiply(alpha, pScanline[i + 1]);
+                        pScanline[i + 2] = vcl::bitmap::premultiply(alpha, pScanline[i + 2]);
+#else
                         pScanline[i] = premultiply[alpha][pScanline[i]];
                         pScanline[i + 1] = premultiply[alpha][pScanline[i + 1]];
                         pScanline[i + 2] = premultiply[alpha][pScanline[i + 2]];
+#endif
                     }
                 }
             }
diff --git a/vcl/source/helper/svtaccessiblefactory.cxx b/vcl/source/helper/svtaccessiblefactory.cxx
index 9e9404da7417..82845ec041d9 100644
--- a/vcl/source/helper/svtaccessiblefactory.cxx
+++ b/vcl/source/helper/svtaccessiblefactory.cxx
@@ -18,6 +18,7 @@
  */
 
 #include <config_feature_desktop.h>
+#include <config_wasm_strip.h>
 
 #include <vcl/svtaccessiblefactory.hxx>
 #include <vcl/accessiblefactory.hxx>
@@ -41,8 +42,10 @@ namespace vcl
         oslModule                                s_hAccessibleImplementationModule = nullptr;
 #endif
 #if HAVE_FEATURE_DESKTOP
+#if !ENABLE_WASM_STRIP_ACCESSIBILITY
         GetSvtAccessibilityComponentFactory      s_pAccessibleFactoryFunc = nullptr;
 #endif
+#endif
         ::rtl::Reference< IAccessibleFactory >   s_pFactory;
 
 
@@ -206,6 +209,7 @@ namespace vcl
     {
     }
 
+#if !ENABLE_WASM_STRIP_ACCESSIBILITY
 #if HAVE_FEATURE_DESKTOP
 #ifndef DISABLE_DYNLOADING
     extern "C" { static void thisModule() {} }
@@ -213,6 +217,7 @@ namespace vcl
     extern "C" void* getSvtAccessibilityComponentFactory();
 #endif
 #endif // HAVE_FEATURE_DESKTOP
+#endif // ENABLE_WASM_STRIP_ACCESSIBILITY
 
     void AccessibleFactoryAccess::ensureInitialized()
     {
@@ -221,6 +226,7 @@ namespace vcl
 
         ::osl::MutexGuard aGuard( ::osl::Mutex::getGlobalMutex() );
 
+#if !ENABLE_WASM_STRIP_ACCESSIBILITY
 #if HAVE_FEATURE_DESKTOP
         // load the library implementing the factory
         if (!s_pFactory)
@@ -252,6 +258,7 @@ namespace vcl
             }
         }
 #endif // HAVE_FEATURE_DESKTOP
+#endif // ENABLE_WASM_STRIP_ACCESSIBILITY
 
         if (!s_pFactory)
             // the attempt to load the lib, or to create the factory, failed