sdgui: cross-compile for Windows

No one bothered to ask whether it /should/ be done.

The hamburger needs to be replaced with a file open dialog there.

cmake/FindLibIntl.cmake

@@ -0,0 +1,8 @@
+# Public Domain
+
+find_library (LibIntl_LIBRARIES intl)
+
+include (FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS (LibIntl DEFAULT_MSG LibIntl_LIBRARIES)
+
+mark_as_advanced (LibIntl_LIBRARIES)

cmake/Win64CrossToolchain.cmake

@@ -0,0 +1,15 @@
+set (CMAKE_SYSTEM_NAME "Windows")
+set (CMAKE_SYSTEM_PROCESSOR "x86_64")
+
+set (CMAKE_C_COMPILER "x86_64-w64-mingw32-gcc")
+set (CMAKE_CXX_COMPILER "x86_64-w64-mingw32-g++")
+set (CMAKE_RC_COMPILER "x86_64-w64-mingw32-windres")
+
+# Not needed to crosscompile an installation package
+#set (CMAKE_CROSSCOMPILING_EMULATOR "wine64")
+
+set (CMAKE_FIND_ROOT_PATH "/usr/x86_64-w64-mingw32")
+
+set (CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
+set (CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
+set (CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

cmake/Win64Depends.sh

@@ -0,0 +1,74 @@
+#!/bin/sh -e
+# Win64Depends.sh: download dependencies from MSYS2 for cross-compilation
+# Dependencies: AWK, sed, sha256sum, cURL, bsdtar, wine64
+repository=https://repo.msys2.org/mingw/mingw64/
+
+status() {
+	echo "$(tput bold)-- $*$(tput sgr0)"
+}
+
+dbsync() {
+	status Fetching repository DB
+	[ -f db.tsv ] || curl -# "$repository/mingw64.db" | bsdtar -xOf- | awk '
+		function flush() { print f["%NAME%"] f["%FILENAME%"] f["%DEPENDS%"] }
+		NR > 1 && $0 == "%FILENAME%" { flush(); for (i in f) delete f[i] }
+		!/^[^%]/ { field = $0; next } { f[field] = f[field] $0 "\t" }
+		field == "%SHA256SUM%" { path = "*packages/" f["%FILENAME%"]
+			sub(/\t$/, "", path); print $0, path > "db.sums" } END { flush() }
+	' > db.tsv
+}
+
+fetch() {
+	status Resolving "$@"
+	mkdir -p packages
+	awk -F'\t' 'function get(name,    i, a) {
+		if (visited[name]++ || !(name in filenames)) return
+		print filenames[name]; split(deps[name], a); for (i in a) get(a[i])
+	} BEGIN { while ((getline < "db.tsv") > 0) {
+		filenames[$1] = $2; deps[$1] = ""; for (i = 3; i <= NF; i++) {
+			gsub(/[<=>].*/, "", $i); deps[$1] = deps[$1] $i FS }
+	} for (i = 0; i < ARGC; i++) get(ARGV[i]) }' "$@" | while IFS= read -r name
+	do
+		status Fetching "$name"
+		[ -f "packages/$name" ] || curl -#o "packages/$name" "$repository/$name"
+	done
+}
+
+verify() {
+	status Verifying checksums
+	sha256sum --ignore-missing --quiet -c db.sums
+}
+
+extract() {
+	status Extracting packages
+	for subdir in *
+	do [ -d "$subdir" -a "$subdir" != packages ] && rm -rf -- "$subdir"
+	done
+	for i in packages/*
+	do bsdtar -xf "$i" --strip-components 1 mingw64
+	done
+}
+
+configure() {
+	status Configuring packages
+	glib-compile-schemas share/glib-2.0/schemas
+	wine64 bin/gdk-pixbuf-query-loaders.exe \
+		> lib/gdk-pixbuf-2.0/2.10.0/loaders.cache
+
+	# pkgconf has a command line option for this, but CMake can't pass it
+	sed -i "s|^prefix=/mingw64|prefix=$(pwd)|" {share,lib}/pkgconfig/*.pc
+}
+
+mkdir -p win32-depends
+cd win32-depends
+dbsync
+fetch mingw-w64-x86_64-gtk3 mingw-w64-x86_64-icu \
+	mingw-w64-x86_64-libwinpthread-git # because we don't do "provides"?
+verify
+extract
+configure
+
+status Success
+
+# XXX: Why is this override needed to run some GLib-based things under wine64?
+export XDG_DATA_DIRS=$(pwd)/share