porting GC logic to livedocument

packages/liveui/livedocument.js

@@ -11,6 +11,7 @@ Meteor.ui._doc = Meteor.ui._doc || {};
   var MARKER_PARSE_REGEX = /^LIVEUI_(.*)$/;
 
   Meteor.ui._TAG = "_liveui";
+  Meteor.ui._HELD = "_liveui_refs"; // XXX _liveui_held
 
   Meteor.ui._doc._newAnnotations = {}; // {id -> options} until range created
   Meteor.ui._doc._newRanges = []; // [LiveRange, ...] until flush time
@@ -113,6 +114,8 @@ Meteor.ui._doc = Meteor.ui._doc || {};
           var range = new Meteor.ui._LiveRange(Meteor.ui._TAG, subFrag);
           // assign options to the LiveRange, including `id`
           _.extend(range, options);
+          // enqueue the new range for onscreen callback processing
+          Meteor.ui._doc._newRanges.push(range);
 
           var next = comment.nextSibling;
 
@@ -138,6 +141,11 @@ Meteor.ui._doc = Meteor.ui._doc || {};
       return frag;
     };
 
+    // at flush time, doCallbacks()
+    var cx = new Meteor.deps.Context;
+    cx.on_invalidate(Meteor.ui._doc._doCallbacks);
+    cx.invalidate();
+
     return makeFrag(topHtml);
   };
 
@@ -156,4 +164,41 @@ Meteor.ui._doc = Meteor.ui._doc || {};
             html + "<!--" + LIVEUI_END_PREFIX + options.id + "-->");
   };
 
+  Meteor.ui._doc.poke = function(range) {
+    // XXX like Sarge.checkOffscreen
+  };
+
+  Meteor.ui._doc.cleanNodes = function(start, end) {
+    // XXX like Sarge.shuck
+  };
+
+  Meteor.ui._doc._doCallbacks = function() {
+    _.each(Meteor.ui._doc._newRanges, function(range) {
+      if (range.onscreen) {
+        var node = range.firstNode();
+        if (! (node.parentNode &&
+               (Meteor.ui._isNodeOnscreen(node) ||
+                Meteor.ui._doc._isNodeHeld(node))))
+          return; // range was created but isn't in the document at flush time
+        range.onscreen();
+        // existence of `killed=false` means range went onscreen and we'll
+        // have to call offscreen() later
+        range.killed = false;
+      }
+    });
+
+    Meteor.ui._doc._newAnnotations = {};
+    Meteor.ui._doc._newRanges.length = 0;
+  };
+
+  // "node holding" is a facility used for unit tests where
+  // we don't GC a DocumentFragment at flush time.
+  Meteor.ui._doc._isNodeHeld = function(node) {
+    while (node.parentNode)
+      node = node.parentNode;
+
+    return node.nodeType !== 3 /*TEXT_NODE*/ &&
+      node[Meteor.ui._HELD];
+  };
+
 })();

packages/liveui/livedocument_tests.js

@@ -1,9 +1,12 @@
 Tinytest.add("livedocument - assembly", function(test) {
 
   var doTest = function(calc) {
+    var onscreens = [];
     var frag = Meteor.ui._doc.materialize(
       calc(function(str, expected) {
-        return Meteor.ui._doc.annotate(str);
+        return Meteor.ui._doc.annotate(str, {onscreen:function() {
+          onscreens.push(this.id);
+        }});
       }));
     var groups = [];
     var html = calc(function(str, expected, noRange) {
@@ -13,7 +16,8 @@ Tinytest.add("livedocument - assembly", function(test) {
         groups.push(str);
       return str;
     });
-    test.equal(WrappedFrag(frag).html(), html);
+    var f = WrappedFrag(frag);
+    test.equal(f.html(), html);
 
     var actualGroups = [];
     var tempRange = new Meteor.ui._LiveRange(Meteor.ui._TAG, frag);
@@ -22,6 +26,13 @@ Tinytest.add("livedocument - assembly", function(test) {
         actualGroups.push(Meteor.ui._rangeToHtml(rng));
     });
     test.equal(actualGroups.join(','), groups.join(','));
+
+    f.hold();
+    Meteor.flush();
+    test.equal(onscreens.length, groups.length);
+    var uniqueOnscreens = _.uniq(onscreens);
+    test.equal(uniqueOnscreens.length, onscreens.length);
+    f.release();
   };
 
   doTest(function(A) { return "<p>Hello</p>"; });

packages/liveui/liveui.js

@@ -8,7 +8,7 @@ Meteor.ui = Meteor.ui || {};
     if (typeof html_func !== "function")
       throw new Error("Meteor.ui.render() requires a function as its first argument.");
 
-    if (Meteor.ui._inRenderMode)
+    if (Materializer.current)
       throw new Error("Can't nest Meteor.ui.render.");
 
     return renderChunk(html_func, options, "fragment").containerNode();
@@ -323,7 +323,7 @@ Meteor.ui = Meteor.ui || {};
         renderChunk(html_func, options, "patch", this);
       });
     };
-    range.destroy = function() {
+    range.destroyed = function() {
       range.context && range.context.invalidate();
       callOffscreen();
     };
@@ -463,7 +463,7 @@ Meteor.ui = Meteor.ui || {};
         range.killed = true;
         // only one of these ever scheduled per range:
         Sarge.atFlushTime(function() {
-          range.destroy && range.destroy();
+          range.destroyed && range.destroyed();
         });
       }
     },