gEDA-cvs: pcb.git: branch: master updated (d2ae471045ac81b6e97d5b441860081bc95eb2e7)

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=========
 Summary
=========

 src/file.c |   46 ++++++++++++++++++++++++++++++++++++++++++++--
 src/file.h |    5 +++++
 2 files changed, 49 insertions(+), 2 deletions(-)


=================
 Commit Messages
=================

commit d2ae471045ac81b6e97d5b441860081bc95eb2e7
Author: DJ Delorie <dj@xxxxxxxxxxx>
Commit: DJ Delorie <dj@xxxxxxxxxxx>

    Make file version smarter.
    
    Restructure the FileVersion[] output to only output the actual
    needed version, in cases where a rarely used feature requires a new
    pcb.  This avoids unnecessary backwards incompatibility.

:100644 100644 973db62... b1c8182... M	src/file.c
:100644 100644 4b9ecf2... d36fdfa... M	src/file.h

=========
 Changes
=========

commit d2ae471045ac81b6e97d5b441860081bc95eb2e7
Author: DJ Delorie <dj@xxxxxxxxxxx>
Commit: DJ Delorie <dj@xxxxxxxxxxx>

    Make file version smarter.
    
    Restructure the FileVersion[] output to only output the actual
    needed version, in cases where a rarely used feature requires a new
    pcb.  This avoids unnecessary backwards incompatibility.

diff --git a/src/file.c b/src/file.c
index 973db62..b1c8182 100644
--- a/src/file.c
+++ b/src/file.c
@@ -135,6 +135,47 @@ static char *pcb_basename (char *p);
 
 /* --------------------------------------------------------------------------- */
 
+/* The idea here is to avoid gratuitously breaking backwards
+   compatibility due to a new but rarely used feature.  The first such
+   case, for example, was the polygon Hole - if your design included
+   polygon holes, you needed a newer PCB to read it, but if your
+   design didn't include holes, PCB would produce a file that older
+   PCBs could read, if only it had the correct version number in it.
+
+   If, however, you have to add or change a feature that really does
+   require a new PCB version all the time, it's time to remove all the
+   tests below and just always output the new version.
+
+   Note: Best practices here is to add support for a feature *first*
+   (and bump PCB_FILE_VERSION in file.h), and note the version that
+   added that support below, and *later* update the file format to
+   need that version (which may then be older than PCB_FILE_VERSION).
+   Hopefully, that allows for one release between adding support and
+   needing it, which should minimize breakage.  Of course, that's not
+   *always* possible, practical, or desirable.
+
+*/
+
+/* Hole[] in Polygon.  */
+#define PCB_FILE_VERSION_HOLES 20100606
+/* First version ever saved.  */
+#define PCB_FILE_VERSION_BASELINE 20070407
+
+int
+PCBFileVersionNeeded (void)
+{
+  ALLPOLYGON_LOOP (PCB->Data);
+  {
+    if (polygon->HoleIndexN > 0)
+      return PCB_FILE_VERSION_HOLES;
+  }
+  ENDALL_LOOP;
+
+  return PCB_FILE_VERSION_BASELINE;
+}
+
+/* --------------------------------------------------------------------------- */
+
 static int
 string_cmp (const char *a, const char *b)
 {
@@ -516,14 +557,15 @@ WritePCBDataHeader (FILE * FP)
    * ************************** README *******************
    *
    * If the file format is modified in any way, update
-   * PCB_FILE_VERSION in file.h
+   * PCB_FILE_VERSION in file.h as well as PCBFileVersionNeeded()
+   * at the top of this file.
    *  
    * ************************** README *******************
    * ************************** README *******************
    */
 
   fprintf (FP, "\n# To read pcb files, the pcb version (or the git source date) must be >= the file version\n");
-  fprintf (FP, "FileVersion[%i]\n", PCB_FILE_VERSION);
+  fprintf (FP, "FileVersion[%i]\n", PCBFileVersionNeeded ());
 
   fputs ("\nPCB[", FP);
   PrintQuotedString (FP, (char *)EMPTY (PCB->Name));
diff --git a/src/file.h b/src/file.h
index 4b9ecf2..d36fdfa 100644
--- a/src/file.h
+++ b/src/file.h
@@ -56,6 +56,11 @@ void sort_netlist (void);
  * guidance to the user as to what the minimum version of pcb required
  * is.
  */
+
+/* This is the version needed by the file we're saving.  */
+int PCBFileVersionNeeded (void);
+
+/* This is the version we support.  */
 #define PCB_FILE_VERSION 20100606
 
 




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