Fix opening files with spaces on Linux

`wxLaunchDefaultApplication()` fails on files with spaces on Unix
systems due to a programmer error. This is fixed in newer wxWidgets
versions, so let's backport it as a workaround.

common/gestfich.cpp

@@ -37,6 +37,7 @@
 #include <core/arraydim.h>
 #include <gestfich.h>
 #include <string_utils.h>
+#include <launch_ext.h>
 
 void QuoteString( wxString& string )
 {
@@ -164,22 +165,7 @@ bool OpenPDF( const wxString& file )
 
     if( Pgm().UseSystemPdfBrowser() )
     {
-        // wxLaunchDefaultApplication on Unix systems is run as an external process passing
-        // the filename to the appropriate application as a command argument.
-        // depending on wxWidgets version, spaces in the path and/or file name will cause
-        // argument parsing issues so always quote the filename and path.
-        // This is applicable to all Unix platforms with wxWidgets version < 3.1.0.
-        // See https://github.com/wxWidgets/wxWidgets/blob/master/src/unix/utilsx11.cpp#L2654
-#ifdef __WXGTK__
-    #if !wxCHECK_VERSION( 3, 1, 0 )
-        // Quote in case there are spaces in the path.
-        // Not needed on 3.1.4, but needed in 3.0 versions
-        // Moreover, on Linux, 3.1.4 wx version, adding quotes breaks wxLaunchDefaultApplication
-        QuoteString( filename );
-    #endif
-#endif
-
-        if( !wxLaunchDefaultApplication( filename ) )
+        if( !LaunchExternal( filename ) )
         {
             msg.Printf( _( "Unable to find a PDF viewer for '%s'." ), filename );
             DisplayError( nullptr, msg );

common/launch_ext.cpp

@@ -18,18 +18,42 @@
  * with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include <gestfich.h>
 #include <launch_ext.h>
+#include <wx/utils.h>
 
 
-void LaunchExternal( const wxString& aPath )
+bool LaunchExternal( const wxString& aPath )
 {
 #ifdef __WXMAC__
-    const wchar_t* args[] = { L"open", aPath.wc_str(), nullptr };
-    wxExecute( const_cast<wchar_t**>( args ) );
-#else
-    wxString path( aPath );
 
-    wxLaunchDefaultApplication( path );
+    const wchar_t* args[] = { L"open", aPath.wc_str(), nullptr };
+    return wxExecute( const_cast<wchar_t**>( args ) ) != -1;
+
+#elif defined( __WXGTK__ ) && !wxCHECK_VERSION( 3, 1, 1 )
+    // On Unix systems `wxLaunchDefaultApplication()` before wxWidgets 3.1.1 mistakenly uses
+    // `wxExecute(xdg_open + " " + document)`, thereby failing for filenames with spaces. Below is
+    // a backport of the fixed `wxLaunchDefaultApplication()`, to be used until we switch to a
+    // newer version of wxWidgets.
+
+    wxString PATH, xdg_open;
+
+    if( wxGetEnv( "PATH", &PATH ) && wxFindFileInPath( &xdg_open, PATH, "xdg-open" ) )
+    {
+        const char* argv[3];
+        argv[0] = xdg_open.fn_str();
+        argv[1] = aPath.fn_str();
+        argv[2] = nullptr;
+
+        if( wxExecute( const_cast<char**>( argv ) ) )
+            return true;
+    }
+
+    return false;
+
+#else
+
+    wxString path( aPath );
+    return wxLaunchDefaultApplication( path );
+
 #endif
 }

include/launch_ext.h

@@ -27,6 +27,6 @@ class wxString;
  * Launches the given file or folder in the host OS
  * @param aPath is a path to a file or folder
  */
-void LaunchExternal( const wxString& aPath );
+bool LaunchExternal( const wxString& aPath );
 
 #endif