Add soversion, version macros, and reserved term_options words

The shared library now carries its major version in the SONAME
(libterm.so.0), so an ABI break gets a new file name. The header
gains TERM_VERSION, TERM_VERSION_MAJOR/MINOR/PATCH and
TERM_VERSION_CODE, and term_version() returns the code the library was
built with. A test checks the macros against meson.build's project
version and against the runtime value.

term_options ends with uint32_t reserved[8]. term_new() returns NULL if
a word is nonzero, so later versions can give those words a meaning
without misreading a caller's leftover data. All-zero options stay
valid.

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/term/term.h b/include/term/term.h
index dc41114..aa3178e 100644
--- a/include/term/term.h
+++ b/include/term/term.h
@@ -41,6 +41,16 @@ struct term_snapshot;
 #define TERM_SCROLLBACK_DEFAULT 10000
 
 /*
+ * The version of this header. A host compares TERM_VERSION_CODE with
+ * term_version() to check that the library matches the header.
+ */
+#define TERM_VERSION(major, minor, patch) (((major) << 16) | ((minor) << 8) | (patch))
+#define TERM_VERSION_MAJOR 0
+#define TERM_VERSION_MINOR 1
+#define TERM_VERSION_PATCH 0
+#define TERM_VERSION_CODE TERM_VERSION(TERM_VERSION_MAJOR, TERM_VERSION_MINOR, TERM_VERSION_PATCH)
+
+/*
  * Colors. A term_color is either a direct color (alpha 0xFF, then RGB) or a
  * palette slot: an index 0-255, the default foreground, or the default
  * background. A slot resolves when a snapshot is painted, so a theme change
@@ -147,12 +157,17 @@ struct term_options {
     enum term_cursor_style cursor_style;
     bool cursor_steady;         /* false: the cursor blinks */
     struct term_callbacks callbacks;
+    /* Must be zero. term_new() returns NULL if any word is nonzero, so a
+     * later version can give a word a meaning. */
+    uint32_t reserved[8];
 };
 
 /* NULL when memory runs out. */
 /* The Unicode version of the width tables, such as "18.0.0". A host can
  * pass it to programs as UNICODE_VERSION. */
 TERM_API const char *term_unicode_version(void);
+/* The TERM_VERSION_CODE the library was built with. */
+TERM_API unsigned term_version(void);
 
 /* The length of the prefix of buf made of bytes in [0x20, hi). With hi
  * 0x7f, it finds a run of printable ASCII in UTF-8 text, so a host can