Add wxFSInputStream providing stream interface to wxFileSystem.

This class allows using virtual wxFSFiles with any wx functions taking
streams. E.g. it makes it possible to load images and animations from
wxFileSystem.

Closes #14185.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71206 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/common/filesys.cpp

@@ -756,5 +756,29 @@ class wxFileSystemModule : public wxModule
 
 IMPLEMENT_DYNAMIC_CLASS(wxFileSystemModule, wxModule)
 
+//// wxFSInputStream
+
+wxFSInputStream::wxFSInputStream(const wxString& filename, int flags)
+{
+    wxFileSystem fs;
+    m_file = fs.OpenFile(filename, flags | wxFS_READ);
+
+    if ( m_file )
+    {
+        wxInputStream* const stream = m_file->GetStream();
+        if ( stream )
+        {
+            // Notice that we pass the stream by reference: it shouldn't be
+            // deleted by us as it's owned by m_file already.
+            InitParentStream(*stream);
+        }
+    }
+}
+
+wxFSInputStream::~wxFSInputStream()
+{
+    delete m_file;
+}
+
 #endif
   // wxUSE_FILESYSTEM