libvncserver: fbu hooks

Author: Volodymyr Samokhatko

include/rfb/rfb.h

@@ -207,6 +207,8 @@ enum rfbProtocolExtensionHookType {
     RFB_PROTOCOL_EXTENSION_HOOK_CLOSE,
     RFB_PROTOCOL_EXTENSION_HOOK_USAGE,
     RFB_PROTOCOL_EXTENSION_HOOK_PROCESS_ARGUMENT,
+    RFB_PROTOCOL_EXTENSION_HOOK_PRE_FBU,
+    RFB_PROTOCOL_EXTENSION_HOOK_POST_FBU,
 };
 
 typedef void* rfbProtocolExtensionHookGeneric;
@@ -248,6 +250,13 @@ _Static_assert(sizeof(rfbProtocolExtensionHookGeneric) == sizeof(rfbProtocolExte
 typedef int (*rfbProtocolExtensionHookProcessArgument)(int argc, char *argv[]);
 _Static_assert(sizeof(rfbProtocolExtensionHookGeneric) == sizeof(rfbProtocolExtensionHookProcessArgument), "extension hook size doesn't match");
 
+/** returns TRUE if proceed with the framebuffer update (PostFbu is called in any case). */
+typedef rfbBool (*rfbProtocolExtensionHookPreFbu)(struct _rfbClientRec* client, void* data);
+_Static_assert(sizeof(rfbProtocolExtensionHookGeneric) == sizeof(rfbProtocolExtensionHookPreFbu), "extension hook size doesn't match");
+
+typedef void (*rfbProtocolExtensionHookPostFbu)(struct _rfbClientRec* client, void* data);
+_Static_assert(sizeof(rfbProtocolExtensionHookGeneric) == sizeof(rfbProtocolExtensionHookPostFbu), "extension hook size doesn't match");
+
 typedef struct _rfbProtocolExtensionElement {
     union {
         /** for the type 1 extensions */
@@ -261,6 +270,9 @@ typedef struct _rfbProtocolExtensionElement {
         rfbProtocolExtensionHookClose close;
         rfbProtocolExtensionHookUsage usage;
         rfbProtocolExtensionHookProcessArgument processArgument;
+
+        rfbProtocolExtensionHookPreFbu preFbu;
+        rfbProtocolExtensionHookPostFbu postFbu;
     } hook;
     /** which hook it is */
     int type;

src/libvncserver/rfbserver.c

@@ -3411,6 +3411,22 @@ rfbSendFramebufferUpdate(rfbClientPtr cl,
      * Now send the update.
      */
 
+    rfbBool extensionsAllowProceed = TRUE;
+    rfbExtension2Data *e = cl->extensions2;
+    for (; e; e = e->next) {
+        rfbProtocolExtensionElement* el = e->extension2->elements;
+        for (; el && el < e->extension2->elements + e->extension2->elementsCount; ++el) {
+            if (el->type == RFB_PROTOCOL_EXTENSION_HOOK_PRE_FBU) {
+                extensionsAllowProceed = extensionsAllowProceed && el->hook.preFbu(cl, e->data);
+                break;
+            }
+        }
+    }
+
+    if (!extensionsAllowProceed) {
+        goto updateFailed;
+    }
+
     rfbStatRecordMessageSent(cl, rfbFramebufferUpdate, 0, 0);
     if (cl->preferredEncoding == rfbEncodingCoRRE) {
         nUpdateRegionRects = 0;
@@ -3647,6 +3663,17 @@ rfbSendFramebufferUpdate(rfbClientPtr cl,
 	result = FALSE;
     }
 
+    e = cl->extensions2;
+    for (; e; e = e->next) {
+        rfbProtocolExtensionElement* el = e->extension2->elements;
+        for (; el && el < e->extension2->elements + e->extension2->elementsCount; ++el) {
+            if (el->type == RFB_PROTOCOL_EXTENSION_HOOK_POST_FBU) {
+                el->hook.postFbu(cl, e->data);
+                break;
+            }
+        }
+    }
+
     if (!cl->enableCursorShapeUpdates) {
       rfbHideCursor(cl);
     }