====== GTK3 compilation on Win32 =====
Tested on Windows XP, Inkscape trunk revision 11562.

1. Download and uncompress the following files:
(from http://download.opensuse.org/repositories/windows:/mingw:/win32/openSUSE_12.1/noarch/ - the files are needed to run the gtk demo, not sure everything is necessary to run Inkscape)

    mingw32-atk-2.4.0-1.14.noarch.rpm
    mingw32-atk-devel-2.4.0-1.14.noarch.rpm
    mingw32-atkmm-2.22.6-1.20.noarch.rpm
    mingw32-atkmm-devel-2.22.6-1.20.noarch.rpm
    mingw32-cairo-devel-1.10.2-8.14.noarch.rpm
    mingw32-cairomm-1.10.0-1.41.noarch.rpm
    mingw32-cairomm-devel-1.10.0-1.41.noarch.rpm
    mingw32-freetype-2.4.10-1.2.noarch.rpm
    mingw32-freetype-devel-2.4.10-1.2.noarch.rpm
    mingw32-gdk-pixbuf-2.26.1-1.17.noarch.rpm
    mingw32-gdk-pixbuf-devel-2.26.1-1.17.noarch.rpm
    mingw32-gdk-pixbuf-loader-rsvg-2.36.1-1.20.noarch.rpm
    mingw32-glib2-2.32.4-1.1.noarch.rpm
    mingw32-glib2-devel-2.32.4-1.1.noarch.rpm
    mingw32-glib2-lang-2.32.4-1.1.noarch.rpm
    mingw32-glib2-tools-2.32.4-1.1.noarch.rpm
    mingw32-glibmm2-2.32.0-1.10.noarch.rpm
    mingw32-glibmm2-devel-2.32.0-1.10.noarch.rpm
    mingw32-gtk3-3.4.2-2.19.noarch.rpm
    mingw32-gtk3-data-3.4.2-2.19.noarch.rpm
    mingw32-gtk3-devel-3.4.2-2.16.noarch.rpm
    mingw32-gtk3-lang-3.4.2-2.19.noarch.rpm
    mingw32-gtk3-tools-3.4.2-2.19.noarch.rpm
    mingw32-gtkmm3-3.4.0-1.15.noarch.rpm
    mingw32-gtkmm3-devel-3.4.0-1.15.noarch.rpm
    mingw32-libcairo-gobject2-1.10.2-8.14.noarch.rpm
    mingw32-libcairo2-1.10.2-8.14.noarch.rpm
    mingw32-libffi-3.0.10-2.25.noarch.rpm
    mingw32-libffi-devel-3.0.10-2.25.noarch.rpm
    mingw32-libjasper-1.900.1-6.30.noarch.rpm
    mingw32-libjasper-devel-1.900.1-6.30.noarch.rpm
    mingw32-liblzma-5.0.4-1.2.noarch.rpm
    mingw32-liblzma-devel-5.0.4-1.2.noarch.rpm
    mingw32-libopenjpeg-devel-1.5.0-4.20.noarch
    mingw32-libopenjpeg-devel-1.5.0-4.20.noarch.rpm
    mingw32-libopenjpeg1-1.5.0-4.20.noarch
    mingw32-libopenjpeg1-1.5.0-4.20.noarch.rpm
    mingw32-libpng-1.5.11-1.2.noarch.rpm
    mingw32-libpng-devel-1.5.11-1.2.noarch.rpm
    mingw32-libpoppler-0.20.2-1.3.noarch.rpm
    mingw32-libpoppler-devel-0.20.2-1.3.noarch.rpm
    mingw32-libpoppler-glib-0.20.2-1.3.noarch.rpm
    mingw32-libpoppler-glib-devel-0.20.2-1.3.noarch.rpm
    mingw32-libstdc++-4.7.0-3.14.noarch.rpm
    mingw32-libtiff-4.0.2-1.3.noarch.rpm
    mingw32-libtiff-devel-4.0.2-1.3.noarch.rpm
    mingw32-pango-1.30.0-2.19.noarch.rpm
    mingw32-pango-devel-1.30.0-2.19.noarch.rpm
    mingw32-pangomm-2.28.4-1.25.noarch.rpm
    mingw32-pangomm-devel-2.28.4-1.25.noarch.rpm
    mingw32-pixman-0.26.0-1.4.noarch.rpm
    mingw32-pixman-devel-0.26.0-1.4.noarch.rpm

2. Copy the current devlibs and rename it devlibs-gtk3.

3. Copy the uncompressed files in the new devlibs (overwrite the libs with the same name).

4. Remove old libs (gtk2, gtkmm2, gdk2, gdkmm2, gail1, and some others).

5. Download a recent Inkscape trunk revision (from Launchpad).

6. Modify the mingenv.bat file:

-----
@echo Setting environment variables for MinGw build of Inkscape
IF "%DEVLIBS_PATH%"=="" set DEVLIBS_PATH=<your_devlibs_path>\devlibs-gtk3
IF "%MINGW_PATH%"=="" set MINGW_PATH=<your_mingw_path>\mingw
set MINGW_BIN=%MINGW_PATH%\bin
set PKG_CONFIG_PATH=%DEVLIBS_PATH%\lib\pkgconfig
set PATH=%DEVLIBS_PATH%\bin;%DEVLIBS_PATH%\python;%MINGW_BIN%;%PATH%
-----
 
7. Modify the build.xml file with the following patch:

--- build.xml Mon Jul 30 07:50:47 2012
+++ build.xml Mon Jul 30 16:35:57 2012
@@ -198,6 +198,9 @@
 
         #define HAVE_ASPELL                   1
 
+        #define WITH_GTKMM_3_0              1
+        #define WITH_GTKMM_2_24             1
+
         #endif /* _CONFIG_H_ */
     </makefile>
   </target>
@@ -352,26 +355,32 @@
             -DHAVE_SSL
             -DRELAYTOOL_SSL="static const int libssl_is_present=1; static int __attribute__((unused)) libssl_symbol_is_present(char *s){ return 1; }" <!-- inkboard -->
             -DPOPPLER_NEW_GFXFONT <!-- poppler changed the api for 0.8.3 -->
+            -DPOPPLER_NEW_GFXPATCH
     <!-- uncomment below for future devlibs, if poppler >= 0.20.0 -->
-    <!-- -DPOPPLER_NEW_ERRORAPI --> <!-- poppler changed the error api for 0.20.0 -->
+        -DPOPPLER_NEW_ERRORAPI <!-- poppler changed the error api for 0.20.0 -->
             <!-- GTK+3 migration -->
             -DGLIBMM_DISABLE_DEPRECATED
             -DG_DISABLE_DEPRECATED
             -DGTK_DISABLE_SINGLE_INCLUDES
             <!-- -DGTKMM_DISABLE_DEPRECATED -->
             <!-- -DGTK_DISABLE_DEPRECATED  -->
-            -DGDKMM_DISABLE_DEPRECATED
+            <!-- -DGDKMM_DISABLE_DEPRECATED -->
             -DGSEAL_ENABLE
         </defines>
         <includes>
             -I${devlibs}/include
             <!-- GTK / GTKMM -->
-            ${pcc.gtkmm-2.4}
+            ${pcc.gtkmm-3.0}
+            ${pcc.gdkmm-3.0}
+            ${pcc.gtk+-3.0}
+            ${pcc.gdk-3.0}
             <!-- OTHER -->
+            ${pcc.glibmm-2.4}
  ${pcc.Magick++}
  ${pcc.libxml-2.0}
             ${pcc.freetype2}
-            ${pcc.cairo}
+            ${pcc.cairomm-1.0}
+            ${pcc.pangomm-1.4}
             ${pcc.poppler}
             -I${devlibs}/include/gc
             ${pcc.libwpg-0.1} ${pcc.libwpg-stream-0.1}
@@ -466,7 +475,11 @@
        <libs>
            -L${devlibs}/lib
            ${pcl.poppler-cairo} ${pcl.poppler-glib} ${pcl.poppler}
-           ${pcl.gtkmm-2.4}  ${pcl.pangoft2} ${pcl.gthread-2.0}
+           ${pcl.pangoft2} ${pcl.gthread-2.0}
+           ${pcl.gtkmm-3.0} ${pcl.gdkmm-3.0}
+           ${pcl.gtk+-3.0} ${pcl.gdk-3.0}
+           ${pcl.glibmm-2.4} ${pcl.glib-2.0}
+           ${pcl.pangomm-1.4}
            ${devlibs}/bin/libxml2.dll
            ${devlibs}/bin/libxslt.dll
            ${pcl.cairo} ${pcl.cairomm-1.0}
@@ -537,7 +550,11 @@
        <libs>
            -L${devlibs}/lib
            ${pcl.poppler-cairo} ${pcl.poppler-glib} ${pcl.poppler}
-           ${pcl.gtkmm-2.4}  ${pcl.pangoft2} ${pcl.gthread-2.0}
+           ${pcl.pangoft2} ${pcl.gthread-2.0}
+           ${pcl.gtkmm-3.0} ${pcl.gdkmm-3.0}
+           ${pcl.gtk+-3.0} ${pcl.gdk-3.0}
+           ${pcl.glibmm-2.4} ${pcl.glib-2.0}
+           ${pcl.pangomm-1.4}
            ${devlibs}/bin/libxml2.dll
            ${devlibs}/bin/libxslt.dll
            ${pcl.cairo} ${pcl.cairomm-1.0}
@@ -586,7 +603,11 @@
        <libs>
            -L${devlibs}/lib
            ${pcl.poppler-cairo} ${pcl.poppler-glib} ${pcl.poppler}
-           ${pcl.gtkmm-2.4}  ${pcl.pangoft2} ${pcl.gthread-2.0}
+           ${pcl.pangoft2} ${pcl.gthread-2.0}
+           ${pcl.gtkmm-3.0} ${pcl.gdkmm-3.0}
+           ${pcl.gtk+-3.0} ${pcl.gdk-3.0}
+           ${pcl.glibmm-2.4} ${pcl.glib-2.0}
+           ${pcl.pangomm-1.4}
            ${devlibs}/bin/libxml2.dll
            ${devlibs}/bin/libxslt.dll
            ${pcl.cairo} ${pcl.cairomm-1.0}
@@ -624,32 +645,35 @@
     <copy todir="${dist}" file="${devlibs}/bin/libatkmm-1.6-1.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libglibmm-2.4-1.dll"/>
  <copy todir="${dist}" file="${devlibs}/bin/libgiomm-2.4-1.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libgtkmm-2.4-1.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libgdkmm-2.4-1.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libgio-2.0-0.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libgtkmm-3.0-1.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libgdkmm-3.0-1.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libpangomm-1.4-1.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libcairomm-1.0-1.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libcairo-2.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libcairo-gobject-2.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libsigc-2.0-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/freetype6.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libatk-1.0-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libgcc_s_sjlj-1.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libgdk-win32-2.0-0.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libgdk-3-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libgdk_pixbuf-2.0-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libglib-2.0-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libgmodule-2.0-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libgobject-2.0-0.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libgtk-win32-2.0-0.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libgtk-3-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libgthread-2.0-0.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libgio-2.0-0.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libcairo-2.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libjasper-1.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/liblzma-5.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libpixman-1-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libgcc_s_sjlj-1.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libpoppler-5.dll"/>
- <copy todir="${dist}" file="${devlibs}/bin/libpoppler-glib-4.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libpoppler-26.dll"/>
+ <copy todir="${dist}" file="${devlibs}/bin/libpoppler-glib-8.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libpangocairo-1.0-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libpango-1.0-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libpangoft2-1.0-0.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libpangowin32-1.0-0.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/freetype6.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libfreetype-6.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libfontconfig-1.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libxml2.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libxslt.dll"/>
@@ -660,9 +684,9 @@
     <copy todir="${dist}" file="${devlibs}/bin/libwpd-stream-0.8.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libjpeg-7.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libpng12-0.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libpng14-14.dll"/>
-    <copy todir="${dist}" file="${devlibs}/bin/libtiff-3.dll"/>
- <copy todir="${dist}" file="${devlibs}/bin/libopenjpeg-2.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libpng15-15.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libtiff-5.dll"/>
+ <copy todir="${dist}" file="${devlibs}/bin/libopenjpeg-1.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/msvcr70.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/msvcr71.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/zlib1.dll"/>
@@ -676,6 +700,8 @@
     <copy todir="${dist}" file="${devlibs}/bin/intl.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/libintl-8.dll"/>
     <copy todir="${dist}" file="${devlibs}/bin/pthreadGC2.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libffi-5.dll"/>
+    <copy todir="${dist}" file="${devlibs}/bin/libstdc++-6.dll"/>
     <!-- MINGW support DLLs needed for openmp support  -->
     <copy todir="${dist}" file="${mingw_bin}/mingwm10.dll"/>
  <copy todir="${dist}" file="${mingw_bin}/libgomp-1.dll"/>
@@ -694,7 +720,7 @@
 
     <!-- GTK -->
     <copy todir="${dist}">     <fileset dir="${devlibs}/etc"/> </copy>
-    <copy todir="${dist}/lib"> <fileset dir="${devlibs}/lib/gtk-2.0"/> </copy>
+    <!--<copy todir="${dist}/lib"> <fileset dir="${devlibs}/lib/gtk-2.0"/> </copy> -->
     <copy todir="${dist}/lib"> <fileset dir="${devlibs}/lib/glib-2.0"/> </copy>
     <copy todir="${dist}">
         <fileset dir="share">
@@ -727,7 +753,7 @@
     <!-- <copy todir="${dist}/python"> <fileset dir="${devlibs}/python/Scripts"/> </copy> -->
 
     <!--<copy file="${devlibs}/share/themes/MS-Windows/gtk-2.0/gtkrc" todir="${dist}/etc/gtk-2.0"/>-->
-    <makefile file="${dist}/etc/gtk-2.0/gtkrc">
+    <makefile file="${dist}/etc/gtk-3.0/gtkrc">
     gtk-icon-sizes = "gtk-menu=16,16:gtk-small-toolbar=16,16:gtk-large-toolbar=24,24:gtk-dnd=32,32:inkscape-decoration=16,16"
     gtk-toolbar-icon-size = small-toolbar
 

8. In the devlibs includes, modify the giomm.h header file by commenting all the dbus related includes (doesn't work on Windows).

9. Modify some Inkscape files with the following patch (deprecations):

--- src/ui/dialog/filedialogimpl-win32.cpp Mon Jul 30 07:50:47 2012
+++ src/ui/dialog/filedialogimpl-win32.cpp Mon Jul 30 13:55:28 2012
@@ -26,6 +26,7 @@
 #include <gdk/gdkwin32.h>
 #include <glib/gstdio.h>
 #include <glibmm/i18n.h>
+#include <glibmm/thread.h>
 #include <gtkmm/window.h>
 
 //Inkscape includes
@@ -133,7 +134,7 @@
 
     Glib::RefPtr<const Gdk::Window> parentWindow = parent.get_window();
     g_assert(parentWindow->gobj() != NULL);
-    _ownerHwnd = (HWND)gdk_win32_drawable_get_handle((GdkDrawable*)parentWindow->gobj());
+    _ownerHwnd = (HWND)gdk_win32_window_get_handle((GdkWindow*)parentWindow->gobj());
 }
 
 FileDialogBaseWin32::~FileDialogBaseWin32()
@@ -1575,16 +1576,17 @@
     // We can only run one worker thread at a time
     if(_mutex != NULL) return false;
 
+    /*
     if(!Glib::thread_supported())
         Glib::thread_init();
-
+    */
     _result = false;
     _finished = false;
     _file_selected = false;
-    _mutex = new Glib::Mutex();
+    _mutex = new Glib::Threads::Mutex();
     _main_loop = g_main_loop_new(g_main_context_default(), FALSE);
 
-    if(Glib::Thread::create(sigc::mem_fun(*this, &FileOpenDialogImplWin32::GetOpenFileName_thread), true))
+    if(Glib::Threads::Thread::create(sigc::mem_fun(*this, &FileOpenDialogImplWin32::GetOpenFileName_thread)))
     {
         while(1)
         {
@@ -1803,15 +1805,16 @@
 bool
 FileSaveDialogImplWin32::show()
 {
+    /*
     if(!Glib::thread_supported())
         Glib::thread_init();
-
+    */
     _result = false;
     _main_loop = g_main_loop_new(g_main_context_default(), FALSE);
 
     if(_main_loop != NULL)
     {
-        if(Glib::Thread::create(sigc::mem_fun(*this, &FileSaveDialogImplWin32::GetSaveFileName_thread), true))
+        if(Glib::Threads::Thread::create(sigc::mem_fun(*this, &FileSaveDialogImplWin32::GetSaveFileName_thread)))
             g_main_loop_run(_main_loop);
 
         if(_result)
--- src/ui/dialog/filedialogimpl-win32.h Mon Jul 30 07:50:47 2012
+++ src/ui/dialog/filedialogimpl-win32.h Mon Jul 30 13:32:47 2012
@@ -226,7 +226,7 @@
     /// This mutex is used to ensure that the worker thread
     /// that calls GetOpenFileName cannot collide with the
     /// main Inkscape thread
-    Glib::Mutex *_mutex;
+    Glib::Threads::Mutex *_mutex;
 
 
     /// The controller function for the thread which calls

10. Download an upstream GDL version (3.4.2 looks good, 3.5.x introduces deprecations).
(from http://ftp.gnome.org/pub/GNOME/sources/gdl/3.4/)

11. Replace the Inkscape src/libgdl directory with the new one.

12. Replace <gdl/*.h> with "libgdl/*.h" in all the gdl header files.

13. Comment "bindtextdomain (GETTEXT_PACKAGE, GNOMELOCALEDIR);" in gdl-i18n.c

14. Build Inkscape with btool. Run.

Unfortunately, it Inkscape crashes with the following backtrace:

Program received signal SIGSEGV, Segmentation fault.
0x6fc8fd21 in ?? () from D:\Inkscape\inkscape-11562+gtk3\inkscape\libstdc++-6.dll
(gdb) bt
#0  0x6fc8fd21 in ?? () from D:\Inkscape\inkscape-11562+gtk3\inkscape\libstdc++-6.dll
#1  0x011a4e0c in std::__ioinit ()
#2  0x011a4e0c in std::__ioinit ()
#3  0x0022ff0f in ?? ()
#4  0x77c04e00 in onexit () from C:\WINDOWS\system32\msvcrt.dll
#5  0x77c04e29 in onexit () from C:\WINDOWS\system32\msvcrt.dll
#6  0x000001f0 in ?? ()
#7  0x00401098 in __mingw_CRTStartup () at ../mingw/crt1.c:236
#8  0x0040129c in WinMainCRTStartup () at ../mingw/crt1.c:278
------------------------------------------------------------------------------