1: Allow /env/pageppi to set the default PPI for PS and PDF documents.

2: Don't abort if a non-default PPI is specified for graphics files. Just
   ignore the setting; it's documented to only apply to PS and PDF, anyway.

Reference: /n/sources/patch/maybe/page-env-ppi
Date: Thu Oct 29 19:11:48 CET 2009
Signed-off-by: lyndon@orthanc.ca

--- /sys/src/cmd/page/page.c	Thu Oct 29 19:08:38 2009
+++ /sys/src/cmd/page/page.c	Thu Oct 29 19:08:36 2009
@@ -82,6 +82,11 @@
 	enum { Ninput = 16 };
 	uchar buf[Ninput+1];
 	int readstdin;
+	char *envppi;
+
+	envppi = getenv("pageppi");
+	if(envppi != nil)
+		ppi = atoi(envppi);
 
 	ARGBEGIN{
 	/* "temporary" debugging options */
@@ -197,10 +202,6 @@
 	else if(strncmp((char*)buf, "x T ", 4) == 0)
 		doc = inittroff(b, argc, argv, buf, Ninput);
 	else {
-		if(ppi != 100) {
-			fprint(2, "page: you can't specify -p with graphic files\n");
-			wexits("-p and graphics");
-		}
 		doc = initgfx(b, argc, argv, buf, Ninput);
 	}
 
--- /sys/man/1/page	Thu Oct 29 19:08:42 2009
+++ /sys/man/1/page	Thu Oct 29 19:08:40 2009
@@ -75,7 +75,8 @@
 .B -p 
 option sets the resolution for PostScript and PDF
 files, in pixels per inch.
-The default is 100 ppi.
+The default is 100 ppi, or the value of
+.BR $pageppi .
 The
 .B -r
 option reverses the order in which pages are displayed.