pdf_io: add partial parsing of 'config' special

In upstream dvipdfmx the `dvidpfmx:config` DVI special can be used to
pass arguments to dvipdfmx. This has seen some use in XeTeX packages.

For example, the ubiqitous package "hyperref" uses:

    \special{dvipdfmx:config C 0x0010}

This is normally parsed by dvipdfmx as command line arguments, i.e. as
if xdvipdfmx was ran as:

    xdvipdfmx -C 0x0010

The `C` option is a bitset of compatibility flags. In this case hyperref
needs the option `OPT_PDFDOC_NO_DEST_REMOVE`, which makes dvipdfmx
handle PDF destinations differently (I didn't check thoroughly how).

The `opt_flags` global variable used to hold these bitflags and the
`dvipdfmx:config` special could be used to set them. tectonic-typesetting#92 removed that
option.

While passing arbitrary command line arguments to dvidpfmx is probably
not what we want, I definitely know, that we at least need the
compatibility flags to work, and there is probably no other way packages
can set them.

The code that does the option parsing is mostly port from the 'C' option
parsing from dvipdfmx's `read_config_special` and `do_args_second_pass`.
IMHO the way `opt_flags` gets modified is undefined behaviour and does
other weird things with negative values, but the purpose of this commit
is to increase compatibility with upstream, not to fix things (which
should preferably be done upstream IMO).

Like with other options, instead of having a global variable, the
pointer to the value in `dvipdfmx_main` is passed around instead.

While at it, I also added `z` and `g` options which also seem to be used
by LaTeX, so this should be enough for a while.

Hopefully fixes tectonic-typesetting#904.

Author: vlasakm

crates/engine_xdvipdfmx/xdvipdfmx/dvipdfmx.c

@@ -66,19 +66,14 @@ typedef struct page_range
   int last;
 } PageRange;
 
+/* Compatibility options */
 #define OPT_TPIC_TRANSPARENT_FILL (1 << 1)
 #define OPT_CIDFONT_FIXEDPITCH    (1 << 2)
 #define OPT_FONTMAP_FIRST_MATCH   (1 << 3)
 #define OPT_PDFDOC_NO_DEST_REMOVE (1 << 4)
 #define OPT_PDFOBJ_NO_PREDICTOR   (1 << 5)
 #define OPT_PDFOBJ_NO_OBJSTM      (1 << 6)
 
-static int    pdf_version_major = 1;
-static int    pdf_version_minor = 5;
-static int    compression_level = 9;
-
-static double annot_grow_x = 0.0;
-static double annot_grow_y = 0.0;
 static char     ignore_colors = 0;
 static int      bookmark_open = 0;
 static double   mag           = 1.0;
@@ -248,10 +243,18 @@ do_dvi_pages (void)
         xo = x_offset; yo = y_offset;
         dvi_scan_specials(page_no,
                           &w, &h, &xo, &yo, &lm,
+                          /* No PDF version */
+                          NULL, NULL,
+                          /* No compression */
+                          NULL,
+                          /* No annotation grow */
+                          NULL, NULL,
                           /* No need for encryption options */
-                          NULL, NULL, NULL, NULL, NULL, NULL, NULL,
+                          NULL, NULL, NULL, NULL, NULL,
                           /* No trailer IDs */
-                          NULL, NULL, NULL);
+                          NULL, NULL, NULL,
+                          /* No opt_flags */
+                          NULL);
         if (lm != landscape_mode) { /* already swapped for the first page */
           SWAP(w, h);
           landscape_mode = lm;
@@ -369,8 +372,12 @@ dvipdfmx_main (
    * code bits. */
 
   select_paper(paperspec);
-  annot_grow_x = 0;
-  annot_grow_y = 0;
+
+  int pdf_version_major = 1;
+  int pdf_version_minor = 5;
+  int compression_level = 9;
+  double annot_grow_x = 0;
+  double annot_grow_y = 0;
   bookmark_open = 0;
   key_bits = 40;
   permission = 0x003C;
@@ -397,8 +404,10 @@ dvipdfmx_main (
                       &paper_width, &paper_height,
                       &x_offset, &y_offset, &landscape_mode,
                       &pdf_version_major, &pdf_version_minor,
+                      &compression_level,
+                      &annot_grow_x, &annot_grow_y,
                       &do_encryption, &key_bits, &permission, oplain, uplain,
-                      &has_id, id1, id2);
+                      &has_id, id1, id2, &opt_flags);
   }
 
   /*kpse_init_prog("", font_dpi, NULL, NULL);
@@ -518,4 +527,4 @@ tt_engine_xdvipdfmx_main(
 
   ttbc_global_engine_exit();
   return rv;
-}
+}

crates/pdf_io/pdf_io/dpx-dvi.c

@@ -2490,12 +2490,75 @@ scan_special_trailerid (unsigned char *id1, unsigned char *id2,
   return error;
 }
 
+static void
+scan_special_config (const char **start, const char *end, int *opt_flags,
+                     int *compression_level,
+                     double *annot_grow_x, double *annot_grow_y)
+{
+  skip_white(start, end);
+  if (*start >= end)
+    return;
+
+  char *option = parse_ident(start, end);
+  if (!option)
+    return;
+
+  char *arg = NULL;
+  skip_white(start, end);
+  if (*start < end) {
+    if (**start == '"')
+      arg = parse_c_string(start, end);
+    else
+      arg = parse_ident(start, end);
+  }
+
+  if (streq_ptr(option, "C") && arg && opt_flags) {
+    char *num_end;
+    int flags = (unsigned) strtol(arg, &num_end, 0);
+    if (num_end == arg)
+      dpx_warning("Invalid dvipdfmx compatibility flag: '%s'", arg);
+    else if (flags < 0)
+      *opt_flags  = -flags;
+    else
+      *opt_flags |=  flags;
+  } else if (streq_ptr(option, "z") && arg && compression_level) {
+    *compression_level = atoi(arg);
+  } else if (streq_ptr(option, "g") && arg && annot_grow_x && annot_grow_y) {
+    const char *comma = strchr(arg, ',');
+    const char *arg_ptr = arg; /* dpx_until_read_length changes the pointer */
+    const char *arg_end = arg + strlen(arg);
+    int error;
+    if (comma) {
+      error = dpx_util_read_length(annot_grow_x, 1.0, &arg_ptr, comma);
+      arg_ptr = comma + 1;
+      if (!error)
+        error = dpx_util_read_length(annot_grow_y, 1.0, &arg_ptr, arg_end);
+    } else {
+      error = dpx_util_read_length(annot_grow_x, 1.0, &arg_ptr, arg_end);
+      if (!error)
+        *annot_grow_y = *annot_grow_x;
+    }
+    if (error) {
+      dpx_warning("Error reading argument for \"-g\" option: %s", arg);
+    }
+  } else {
+    dpx_warning("Tectonic doesn't support '%s' config special"
+                " or the argument is missing", option);
+  }
+
+  free(arg);
+  free(option);
+}
+
 static int
 scan_special (double *wd, double *ht, double *xo, double *yo, int *lm,
               int *majorversion, int *minorversion,
+              int *compression_level,
+              double *annot_grow_x, double *annot_grow_y,
               int *enable_encryption, int *key_bits, int32_t *permission,
               char *opassword, char *upassword,
               int *has_id, unsigned char *id1, unsigned char *id2,
+              int *opt_flags,
               const char *buf, uint32_t size)
 {
     char  *q;
@@ -2626,7 +2689,7 @@ scan_special (double *wd, double *ht, double *xo, double *yo, int *lm,
             *enable_encryption = 1;
             error = scan_special_encrypt(key_bits, permission, opassword, upassword, &p, endptr);
         } else if (ns_dvipdfmx && streq_ptr(q, "config")) {
-            dpx_warning("Tectonic does not support `config' special. Ignored.");
+            scan_special_config(&p, endptr, opt_flags, compression_level, annot_grow_x, annot_grow_y);
         } else if (has_id && id1 && id2 && ns_pdf && !strcmp(q, "trailerid")) {
             error = scan_special_trailerid(id1, id2, &p, endptr);
             if (error) {
@@ -2648,9 +2711,12 @@ dvi_scan_specials (int page_no,
                    double *page_width, double *page_height,
                    double *x_offset, double *y_offset, int *landscape,
                    int *majorversion, int *minorversion,
+                   int *compression_level,
+                   double *annot_grow_x, double *annot_grow_y,
                    int *do_enc, int *key_bits, int32_t *permission,
                    char *owner_pw, char *user_pw,
-                   int *has_id, unsigned char *id1, unsigned char *id2)
+                   int *has_id, unsigned char *id1, unsigned char *id2,
+                   int *opt_flags)
 {
     uint32_t       offset;
     unsigned char  opcode;
@@ -2694,8 +2760,11 @@ dvi_scan_specials (int page_no,
                 _tt_abort("Reading DVI file failed!");
             if (scan_special(page_width, page_height, x_offset, y_offset, landscape,
                              majorversion, minorversion,
+                             compression_level,
+                             annot_grow_x, annot_grow_y,
                              do_enc, key_bits, permission, owner_pw, user_pw,
                              has_id, id1, id2,
+                             opt_flags,
                              buf, size))
                 dpx_warning("Reading special command failed: \"%.*s\"", size, buf);
 #undef buf

crates/pdf_io/pdf_io/dpx-dvi.h

@@ -75,8 +75,11 @@ void  dvi_scan_specials (int page_no,
                                 double *width, double *height,
                                 double *x_offset, double *y_offset, int *landscape,
                                 int *majorversion, int *minorversion,
+                                int *compression_level,
+                                double *annot_grow_x, double *annot_grow_y,
                                 int *do_enc, int *keybits, int32_t *perm,
-                                char *opasswd, char *upasswd, int *has_id, unsigned char *id1, unsigned char *id2);
+                                char *opasswd, char *upasswd, int *has_id, unsigned char *id1, unsigned char *id2,
+                                int *opt_flags);
 unsigned int dvi_locate_font (const char *name, spt_t ptsize);
 
 /* link or nolink: