Patch to allow compiling against CUPS 1.1 (Tiger)

CUPS 1.2 introduced the cups_page_header2_t structure, which adds some fields
to the older cups_page_header_t structure. The previous field names are
unchanged, so we can swap in one for the other in the code with macros in
src/compat.h.

Three fields in particular (cupsInteger, cupsNumColors, and cupsPageSizeName)
are not present in the 1.1 structure. So provide some workarounds in src/main.cc
to store data and use fields that are present on 1.1.

One hack worth noting is that because 1.1 lacks custom integer fields, the
"Toner save mode" is stored in the "compression" field with this patch. The
"compression" field isn't used elsewhere in the driver, so this should be safe.

If this patch breaks, it might be easier to provide a libcups port (the cups-ppdc
port already compiles libcups for its own use) and just compile against that.
However, this will require verifying that filters compiled with a newer libcups
will properly function when speaking to an older, system-provided cupsd.

--- brlaser.drv.in.orig
+++ brlaser.drv.in
@@ -75,8 +75,8 @@ MediaType 7 "ENV-THICK/Thick envelopes"
 MediaType 8 "ENV-THIN/Thin envelopes"
 
 Option "brlaserEconomode/Toner save mode" Boolean AnySetup 10
-  *Choice False/Off "<</cupsInteger10 0>>setpagedevice"
-  Choice True/On "<</cupsInteger10 1>>setpagedevice"
+  *Choice False/Off "<</cupsCompression 0>>setpagedevice"
+  Choice True/On "<</cupsCompression 1>>setpagedevice"
 
 
 {
--- /dev/null
+++ src/compat.h
@@ -0,0 +1,29 @@
+// This file is part of the brlaser printer driver.
+//
+// Copyright 2021 Evan Miller
+//
+// brlaser is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 2 of the License, or
+// (at your option) any later version.
+//
+// brlaser is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with brlaser.  If not, see <http://www.gnu.org/licenses/>.
+
+#ifndef COMPAT_H
+#define COMPAT_H
+
+#include <cups/cups.h>
+
+#if CUPS_VERSION_MAJOR == 1 && CUPS_VERSION_MINOR < 2
+#define _BRLASER_CUPS_COMPAT_OLD
+#define cups_page_header2_t cups_page_header_t
+#define cupsRasterReadHeader2(r, h) cupsRasterReadHeader(r, h)
+#endif
+
+#endif
--- src/debug.cc.orig
+++ src/debug.cc
@@ -93,6 +93,7 @@ void dump_page_header(const cups_page_header2_t &h) {
   d(cupsRowCount);
   d(cupsRowFeed);
   d(cupsRowStep);
+#ifndef _BRLASER_CUPS_COMPAT_OLD
   d(cupsNumColors);
   d(cupsBorderlessScalingFactor);
   d(cupsPageSize);
@@ -103,5 +104,6 @@ void dump_page_header(const cups_page_header2_t &h) {
   d(cupsMarkerType);
   d(cupsRenderingIntent);
   d(cupsPageSizeName);
+#endif
 #undef d
 }
--- src/debug.h.orig
+++ src/debug.h
@@ -18,6 +18,7 @@
 #ifndef DEBUG_H
 #define DEBUG_H
 
+#include "compat.h"
 #include <cups/raster.h>
 
 void dump_page_header(const cups_page_header2_t &h);
--- src/main.cc.orig
+++ src/main.cc
@@ -90,25 +90,26 @@ page_params build_page_params(const cups_page_header2_t &header) {
   static const std::array<std::string, 6> sources = {{
     "AUTO", "T1", "T2", "T3", "MP", "MANUAL"
   }};
-  static const std::map<std::string, std::string> sizes = {
-    { "A4", "A4" },
-    { "A5", "A5" },
-    { "A6", "A6" },
-    { "B5", "B5" },
-    { "B6", "B6" },
-    { "EnvC5", "C5" },
-    { "EnvMonarch", "MONARCH" },
-    { "EnvPRC5", "DL" },
-    { "EnvDL", "DL" },
-    { "Executive", "EXECUTIVE" },
-    { "Legal", "LEGAL" },
-    { "Letter", "LETTER" }
+
+  static const std::map<std::tuple<int, int>, std::string> sizes = {
+      { {595, 842}, "A4" },
+      { {420, 595}, "A5" },
+      { {298, 420}, "A6" },
+      { {499, 709}, "B5" },
+      { {354, 499}, "B6" },
+      { {649, 459}, "C5" },
+      { {312, 624}, "DL" },
+      { {279, 540}, "MONARCH" },
+      { {522, 756}, "EXECUTIVE" },
+      { {612, 792}, "LETTER" },
+      { {612, 1008}, "LEGAL" },
   };
 
   page_params p = { };
+  p.papersize = "A4";
   p.num_copies = header.NumCopies;
   p.resolution = header.HWResolution[0];
-  p.economode = header.cupsInteger[10];
+  p.economode = header.cupsCompression;
   p.mediatype = header.MediaType;
   p.duplex = header.Duplex;
 
@@ -117,11 +118,9 @@ page_params build_page_params(const cups_page_header2_t &header) {
   else
     p.sourcetray = sources[0];
 
-  auto size_it = sizes.find(header.cupsPageSizeName);
+  auto size_it = sizes.find(std::make_tuple(header.PageSize[0], header.PageSize[1]));
   if (size_it != sizes.end())
     p.papersize = size_it->second;
-  else
-    p.papersize = "A4";
 
   return p;
 }
@@ -176,7 +175,7 @@ int main(int argc, char *argv[]) {
     while (!interrupted && cupsRasterReadHeader2(ras, &header)) {
       if (header.cupsBitsPerPixel != 1
           || header.cupsBitsPerColor != 1
-          || header.cupsNumColors != 1
+          || header.cupsColorSpace != 3
           || header.cupsBytesPerLine > 10000) {
         fprintf(stderr, "ERROR: " PACKAGE ": Page %d: Bogus raster data.\n", job.pages() + 1);
         dump_page_header(header);