[PATCH libXext] Backwards compat for newer XSync + older servers

[James Jones]

Add infrastructure to make future builds of libXext that
support version of XSync 3.1 compatibile with X servers
exporting XSync version 3.0.  As part of this, don't handle
errors introduced by newer versions of the protocol than the
server supports.  Those error codes could be used by some
other extension.

Signed-off-by: James Jones <jajones at nvidia.com>
Reviewed-by: Aaron Plattner <aplattner at nvidia.com>
---
 src/XSync.c |  125 +++++++++++++++++++++++++++++++++++++++++++++-------------
 1 files changed, 97 insertions(+), 28 deletions(-)

diff --git a/src/XSync.c b/src/XSync.c
index 648c718..553bbf1 100644
--- a/src/XSync.c
+++ b/src/XSync.c
@@ -95,19 +95,103 @@ static char    *sync_error_list[] = {
     "BadAlarm",
 };
 
+typedef struct _SyncVersionInfoRec {
+    short major;
+    short minor;
+    int num_errors;
+} SyncVersionInfo;
+
+static /* const */ SyncVersionInfo supported_versions[] = {
+    { 3 /* major */, 0 /* minor */, 2 /* num_errors */ },
+};
+
+#define NUM_VERSIONS (sizeof(supported_versions)/sizeof(supported_versions[0]))
+#define GET_VERSION(info) ((info) ? (const SyncVersionInfo*)(info)->data : NULL)
+#define IS_VERSION_SUPPORTED(info) (!!GET_VERSION(info))
+
+static
+const SyncVersionInfo* GetVersionInfo(Display *dpy)
+{
+    xSyncInitializeReply rep;
+    xSyncInitializeReq *req;
+    XExtCodes codes;
+    int i;
+
+    if (!XQueryExtension(dpy, sync_extension_name,
+                         &codes.major_opcode,
+                         &codes.first_event,
+                         &codes.first_error))
+        return NULL;
+
+    LockDisplay(dpy);
+    GetReq(SyncInitialize, req);
+    req->reqType = codes.major_opcode;
+    req->syncReqType = X_SyncInitialize;
+    req->majorVersion = SYNC_MAJOR_VERSION;
+    req->minorVersion = SYNC_MINOR_VERSION;
+    if (!_XReply(dpy, (xReply *) & rep, 0, xTrue))
+    {
+	UnlockDisplay(dpy);
+	SyncHandle();
+	return NULL;
+    }
+    UnlockDisplay(dpy);
+    SyncHandle();
+
+    for (i = 0; i < NUM_VERSIONS; i++) {
+	if (supported_versions[i].major == rep.majorVersion &&
+	    supported_versions[i].minor == rep.minorVersion) {
+	    return &supported_versions[i];
+	}
+    }
+
+    return NULL;
+}
+
+static
+XExtDisplayInfo *find_display_create_optional(Display *dpy, Bool create)
+{
+    XExtDisplayInfo *dpyinfo;
+
+    if (!sync_info) {
+        if (!(sync_info = XextCreateExtension())) return NULL;
+    }
+
+    if (!(dpyinfo = XextFindDisplay (sync_info, dpy)) && create) {
+        dpyinfo = XextAddDisplay(sync_info, dpy,
+                                 sync_extension_name,
+                                 &sync_extension_hooks,
+                                 XSyncNumberEvents,
+                                 (XPointer)GetVersionInfo(dpy));
+    }
+
+    return dpyinfo;
+}
+
 static
-XEXT_GENERATE_FIND_DISPLAY(find_display, sync_info,
-			   sync_extension_name,
-			   &sync_extension_hooks,
-			   XSyncNumberEvents, (XPointer) NULL)
+XExtDisplayInfo *find_display (Display *dpy)
+{
+    return find_display_create_optional(dpy, True);
+}
 
 static
 XEXT_GENERATE_CLOSE_DISPLAY(close_display, sync_info)
 
 static
-XEXT_GENERATE_ERROR_STRING(error_string, sync_extension_name,
-			   XSyncNumberErrors, sync_error_list)
+char *error_string(Display *dpy, int code, XExtCodes *codes, char *buf, int n)
+{
+    XExtDisplayInfo *info = find_display_create_optional(dpy, False);
+    int nerr = IS_VERSION_SUPPORTED(info) ? GET_VERSION(info)->num_errors : 0;
 
+    code -= codes->first_error;
+    if (code >= 0 && code < nerr) {
+	char tmp[256];
+	sprintf (tmp, "%s.%d", sync_extension_name, code);
+	XGetErrorDatabaseText (dpy, "XProtoError", tmp, sync_error_list[code], buf, n);
+	return buf;
+    }
+    return (char *)0;
+}
 
 static Bool
 wire_to_event(Display *dpy, XEvent *event, xEvent *wire)
@@ -232,32 +316,17 @@ XSyncInitialize(
     int *major_version_return, int *minor_version_return)
 {
     XExtDisplayInfo *info = find_display(dpy);
-    xSyncInitializeReply rep;
-    xSyncInitializeReq *req;
 
     SyncCheckExtension(dpy, info, False);
 
-    LockDisplay(dpy);
-    GetReq(SyncInitialize, req);
-    req->reqType = info->codes->major_opcode;
-    req->syncReqType = X_SyncInitialize;
-    req->majorVersion = SYNC_MAJOR_VERSION;
-    req->minorVersion = SYNC_MINOR_VERSION;
-    if (!_XReply(dpy, (xReply *) & rep, 0, xTrue))
-    {
-	UnlockDisplay(dpy);
-	SyncHandle();
+    if (IS_VERSION_SUPPORTED(info)) {
+	*major_version_return = GET_VERSION(info)->major;
+	*minor_version_return = GET_VERSION(info)->minor;
+
+	return True;
+    } else {
 	return False;
     }
-    UnlockDisplay(dpy);
-    SyncHandle();
-    *major_version_return = rep.majorVersion;
-    *minor_version_return = rep.minorVersion;
-    return ((rep.majorVersion == SYNC_MAJOR_VERSION)
-#if SYNC_MINOR_VERSION > 0	/* avoid compiler warning */
-	    && (rep.minorVersion >= SYNC_MINOR_VERSION)
-#endif
-	    );
 }
 
 XSyncSystemCounter *
-- 
1.7.1