Support reading and writing pipes

This is useful when using inkscape from the terminal and piping the
output to further programs.

Example usage:
cat vector.svg | inkscape --export-png - --file - | convert - out.jpg

Fixes bug: 171016

(forward-ported from commit fdb3b41a37f5c37bbb8e49d59e7e6195d5363fcb)

1 files changed, 19 insertions, 0 deletions

diff --git a/src/io/sys.cpp b/src/io/sys.cpp
index 00f91137e..21ee94ed3 100644
--- a/src/io/sys.cpp
+++ b/src/io/sys.cpp
@@ -67,6 +67,21 @@ void Inkscape::IO::dump_fopen_call( char const *utf8name, char const *id )
 FILE *Inkscape::IO::fopen_utf8name( char const *utf8name, char const *mode )
 {
     FILE* fp = nullptr;
+
+    if (Glib::ustring( utf8name ) == Glib::ustring("-")) {
+        // user requests to use pipes
+
+        Glib::ustring how( mode );
+        if ( how.find("w") != Glib::ustring::npos ) {
+#ifdef WIN32
+            setmode(fileno(stdout), O_BINARY)
+#endif
+            return stdout;
+        } else {
+            return stdin;
+        }
+    }
+
     gchar *filename = g_filename_from_utf8( utf8name, -1, nullptr, nullptr, nullptr );
     if ( filename )
     {
@@ -110,6 +125,10 @@ bool Inkscape::IO::file_test( char const *utf8name, GFileTest test )
 {
     bool exists = false;
 
+    // in case the file to check is a pipe it doesn't need to exist
+    if (g_strcmp0(utf8name, "-") == 0 && G_FILE_TEST_IS_REGULAR)
+        return true;
+
     if ( utf8name ) {
         gchar *filename = nullptr;
         if (utf8name && !g_utf8_validate(utf8name, -1, nullptr)) {