build: add mingw64 cross-compiling

CMakeLists.txt

@@ -34,6 +34,10 @@ SET(SOURCES
 	src/libui_sdl/libui/common/matrix.c
 	src/libui_sdl/libui/common/shouldquit.c
 	src/libui_sdl/libui/common/userbugs.c
+)
+
+if (UNIX)
+    LIST(APPEND SOURCES
         src/libui_sdl/libui/unix/alloc.c
         src/libui_sdl/libui/unix/area.c
         src/libui_sdl/libui/unix/box.c
@@ -72,9 +76,9 @@ SET(SOURCES
         src/libui_sdl/libui/unix/tab.c
         src/libui_sdl/libui/unix/text.c
         src/libui_sdl/libui/unix/util.c
-	src/libui_sdl/libui/unix/window.c)
+        src/libui_sdl/libui/unix/window.c
+    )
 
-if (UNIX)
     FIND_PACKAGE(PkgConfig REQUIRED)
     PKG_CHECK_MODULES(GTK3 REQUIRED gtk+-3.0)
 
@@ -86,6 +90,68 @@ if (UNIX)
     if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
         LINK_LIBRARIES("dl")
     endif ()
+elseif (WIN32)
+    LIST(APPEND SOURCES
+        src/libui_sdl/libui/windows/alloc.cpp
+        src/libui_sdl/libui/windows/area.cpp
+        src/libui_sdl/libui/windows/areadraw.cpp
+        src/libui_sdl/libui/windows/areaevents.cpp
+        src/libui_sdl/libui/windows/areascroll.cpp
+        src/libui_sdl/libui/windows/areautil.cpp
+        src/libui_sdl/libui/windows/box.cpp
+        src/libui_sdl/libui/windows/button.cpp
+        src/libui_sdl/libui/windows/checkbox.cpp
+        src/libui_sdl/libui/windows/colorbutton.cpp
+        src/libui_sdl/libui/windows/colordialog.cpp
+        src/libui_sdl/libui/windows/combobox.cpp
+        src/libui_sdl/libui/windows/container.cpp
+        src/libui_sdl/libui/windows/control.cpp
+        src/libui_sdl/libui/windows/d2dscratch.cpp
+        src/libui_sdl/libui/windows/datetimepicker.cpp
+        src/libui_sdl/libui/windows/debug.cpp
+        src/libui_sdl/libui/windows/draw.cpp
+        src/libui_sdl/libui/windows/drawmatrix.cpp
+        src/libui_sdl/libui/windows/drawpath.cpp
+        src/libui_sdl/libui/windows/drawtext.cpp
+        src/libui_sdl/libui/windows/dwrite.cpp
+        src/libui_sdl/libui/windows/editablecombo.cpp
+        #src/libui_sdl/libui/windows/entry.cpp
+        src/libui_sdl/libui/windows/events.cpp
+        src/libui_sdl/libui/windows/fontbutton.cpp
+        src/libui_sdl/libui/windows/fontdialog.cpp
+        src/libui_sdl/libui/windows/form.cpp
+        src/libui_sdl/libui/windows/graphemes.cpp
+        src/libui_sdl/libui/windows/grid.cpp
+        src/libui_sdl/libui/windows/group.cpp
+        src/libui_sdl/libui/windows/init.cpp
+        src/libui_sdl/libui/windows/label.cpp
+        src/libui_sdl/libui/windows/main.cpp
+        src/libui_sdl/libui/windows/menu.cpp
+        src/libui_sdl/libui/windows/multilineentry.cpp
+        src/libui_sdl/libui/windows/parent.cpp
+        src/libui_sdl/libui/windows/progressbar.cpp
+        src/libui_sdl/libui/windows/radiobuttons.cpp
+        src/libui_sdl/libui/windows/separator.cpp
+        src/libui_sdl/libui/windows/sizing.cpp
+        src/libui_sdl/libui/windows/slider.cpp
+        src/libui_sdl/libui/windows/spinbox.cpp
+        src/libui_sdl/libui/windows/stddialogs.cpp
+        #src/libui_sdl/libui/windows/tab.cpp
+        #src/libui_sdl/libui/windows/tabpage.cpp
+        src/libui_sdl/libui/windows/text.cpp
+        src/libui_sdl/libui/windows/utf16.cpp
+        src/libui_sdl/libui/windows/utilwin.cpp
+        src/libui_sdl/libui/windows/window.cpp
+        src/libui_sdl/libui/windows/winpublic.cpp
+        src/libui_sdl/libui/windows/winutil.cpp
+        src/libui_sdl/libui/windows/resources.rc
+    )
+
+    LINK_LIBRARIES("comctl32")
+    LINK_LIBRARIES("d2d1")
+    LINK_LIBRARIES("dwrite")
+    LINK_LIBRARIES("usp10")
+    LINK_LIBRARIES("ws2_32")
 endif (UNIX)
 
 find_package(SDL2 REQUIRED)

cmake/Toolchain-cross-MinGW-w64-x86_64.cmake

@@ -0,0 +1,24 @@
+# https://cmake.org/Wiki/CMake_Cross_Compiling
+
+# the name of the target operating system
+SET(CMAKE_SYSTEM_NAME Windows)
+
+SET(COMPILER_PREFIX "x86_64-w64-mingw32")
+
+# which compilers to use for C and C++
+find_program(CMAKE_C_COMPILER NAMES ${COMPILER_PREFIX}-gcc)
+find_program(CMAKE_CXX_COMPILER NAMES ${COMPILER_PREFIX}-g++)
+find_program(CMAKE_RC_COMPILER NAMES ${COMPILER_PREFIX}-windres)
+
+# pkg-config
+find_program(PKG_CONFIG_EXECUTABLE NAMES ${COMPILER_PREFIX}-pkg-config)
+
+# here is the target environment located
+SET(CMAKE_FIND_ROOT_PATH /usr/${COMPILER_PREFIX}/sys-root/mingw)
+
+# adjust the default behaviour of the FIND_XXX() commands:
+# search headers and libraries in the target environment, search 
+# programs in the host environment
+set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM BOTH)
+set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)