[ft-devel] PATCH: Do not do further load font attempts if a previous attempt has failed but returned error FNT_Err_Invalid_File_Format

[Dmitry Timoshkov]

Hello,

this patch speeds up a lot programs that scan a directory of files and load
every font they find using the code like below:

face_index = 0;
while (1)
{
    if ((ft_err = FT_New_Face(ft_library, fnt_name, face_index, &ft_face)))
        break;
    ...
    FT_Done_Face(ft_face);
    face_index++;
}

The patch avoids trying to load a file as a font if a previous attempt has
failed but returned error FNT_Err_Invalid_File_Format, i.e. file format has
been recognized but no fonts found in the file. That's a different error to
FNT_Err_Unknown_File_Format.

Changelog:
        * src/winfonts/winfnt.c (fnt_face_get_dll_font): Return error
        FNT_Err_Invalid_File_Format if file format was recognized but
        file doesn't contain any FNT(NE) or RT_FONT(PE) resources.
        Add verbose debug logs to make it easier to debug failing load
        attempts.
        * src/winfonts/winfnt.c (FNT_Face_Init): A single FNT font can't
        contain more than 1 face, so return an error if requested face
        index is more than 0.
        Do not do further load font attempts if a previous attempt has
        failed but returned error FNT_Err_Invalid_File_Format, i.e. file
        format has been recognized but no fonts found in the file.

diff -up freetype2/src/winfonts/winfnt.c freetype2/src/winfonts/winfnt.c
--- freetype2/src/winfonts/winfnt.c     Sun Jun 17 12:46:50 2007
+++ freetype2/src/winfonts/winfnt.c     Tue Jun 19 03:53:03 2007
@@ -343,7 +343,7 @@
         if ( !font_count || !font_offset )
         {
           FT_TRACE2(( "this file doesn't contain any FNT resources!\n" ));
-          error = FNT_Err_Unknown_File_Format;
+          error = FNT_Err_Invalid_File_Format;
           goto Exit;
         }
 
@@ -413,6 +413,7 @@
              pe32_header.size_of_optional_header != 0xe0 /* FIXME */         ||
              pe32_header.magic32 != 0x10b                                    )
         {
+          FT_TRACE2(( "this file has invalid PE header\n" ));
           error = FNT_Err_Invalid_File_Format;
           goto Exit;
         }
@@ -435,6 +436,7 @@
             goto Found_rsrc_section;
         }
 
+        FT_TRACE2(( "this file doesn't contain any resources\n" ));
         error = FNT_Err_Invalid_File_Format;
         goto Exit;
 
@@ -553,6 +555,13 @@
         }
       }
 
+      if ( !face->root.num_faces )
+      {
+        FT_TRACE2(( "this file doesn't contain any RT_FONT resources\n" ));
+        error = FNT_Err_Invalid_File_Format;
+        goto Exit;
+      }
+
       if ( face_index >= face->root.num_faces )
       {
         error = FNT_Err_Bad_Argument;
@@ -681,12 +690,18 @@
 
     /* try to load font from a DLL */
     error = fnt_face_get_dll_font( face, face_index );
-    if ( error )
+    if ( error == FNT_Err_Unknown_File_Format )
     {
       /* this didn't work; try to load a single FNT font */
       FNT_Font  font;
 
 
+      if ( face_index > 0 )
+      {
+        error = FNT_Err_Bad_Argument;
+        goto Exit;
+      }
+
       if ( FT_NEW( face->font ) )
         goto Exit;
 
@@ -697,9 +712,10 @@
       font->fnt_size = stream->size;
 
       error = fnt_font_load( font, stream );
-      if ( error )
-        goto Fail;
     }
+
+    if ( error )
+      goto Fail;
 
     /* we now need to fill the root FT_Face fields */
     /* with relevant information                   */