[graph] automatically trigger Graph updates

* update graph internals / node status when:
 - an input attribute is set
 - edges are added/removed
* add GraphModification context manager to group graph updates

meshroom/core/graph.py

@@ -11,6 +11,7 @@ import shutil
 import time
 import uuid
 from collections import defaultdict
+from contextlib import contextmanager
 from enum import Enum  # available by default in python3. For python2: "pip install enum34"
 import logging
 
@@ -48,6 +49,29 @@ else:
     basestring = basestring
 
 
+@contextmanager
+def GraphModification(graph):
+    """
+    A Context Manager that can be used to trigger only one Graph update
+    for a group of several modifications.
+    GraphModifications can be nested.
+    """
+    if not isinstance(graph, Graph):
+        raise ValueError("GraphModification expects a Graph instance")
+    # Store update policy
+    enabled = graph.updateEnabled
+    # Disable graph update for nested block
+    # (does nothing if already disabled)
+    graph.updateEnabled = False
+    try:
+        yield  # Execute nested block
+    except Exception:
+        raise
+    finally:
+        # Restore update policy
+        graph.updateEnabled = enabled
+
+
 def hash(v):
     hashObject = hashlib.sha1(str(v).encode('utf-8'))
     return hashObject.hexdigest()
@@ -120,6 +144,14 @@ class Attribute(BaseObject):
         if self._value == value:
             return
         self._value = value
+        # Request graph update when input parameter value is set
+        # and parent node belongs to a graph
+        # Output attributes value are set internally during the update process,
+        # which is why we don't trigger any update in this case
+        # TODO: update only the nodes impacted by this change
+        # TODO: only update the graph if this attribute participates to a UID
+        if self.node.graph and self.attributeDesc.isInput:
+            self.node.graph.update()
         self.valueChanged.emit()
 
     @property
@@ -409,6 +441,7 @@ class Node(BaseObject):
                 self.attributesPerUid[uidIndex].add(attr)
 
     def _applyExpr(self):
+        with GraphModification(self.graph):
             for attr in self._attributes:
                 attr._applyExpr()
 
@@ -690,6 +723,8 @@ class Graph(BaseObject):
     def __init__(self, name, parent=None):
         super(Graph, self).__init__(parent)
         self.name = name
+        self._updateEnabled = True
+        self._updateRequested = False
         self._nodes = DictModel(keyAttrName='name', parent=self)
         self._edges = DictModel(keyAttrName='dst', parent=self)  # use dst attribute as unique key since it can only have one input connection
         self._cacheDir = ''
@@ -718,6 +753,18 @@ class Graph(BaseObject):
         # Create graph edges by resolving attributes expressions
         self._applyExpr()
 
+    @property
+    def updateEnabled(self):
+        return self._updateEnabled
+
+    @updateEnabled.setter
+    def updateEnabled(self, enabled):
+        self._updateEnabled = enabled
+        if enabled and self._updateRequested:
+            # Trigger an update if requested while disabled
+            self.update()
+            self._updateRequested = False
+
     def _addNode(self, node, uniqueName):
         """
         Internal method to add the given node to this Graph, with the given name (must be unique).
@@ -734,10 +781,6 @@ class Graph(BaseObject):
         self._nodes.add(node)
         self.stopExecutionRequested.connect(node.stopProcess)
 
-        # Trigger internal update when an attribute is modified
-        for attr in node.attributes:  # type: Attribute
-            attr.valueChanged.connect(self.updateInternals)
-
     def addNode(self, node, uniqueName=None):
         """
         Add the given node to this Graph with an optional unique name,
@@ -763,6 +806,7 @@ class Graph(BaseObject):
 
         inEdges = {}
         outEdges = {}
+        with GraphModification(self):
             for attr in node._attributes:
                 for edge in self.outEdges(attr):
                     self.edges.remove(edge)
@@ -771,7 +815,6 @@ class Graph(BaseObject):
                     edge = self.edges.pop(attr)
                     inEdges[edge.dst.fullName()] = edge.src.fullName()
 
-        self.updateInternals()
         return inEdges, outEdges
 
     @Slot(str, result=Node)
@@ -838,9 +881,11 @@ class Graph(BaseObject):
         self.edges.add(edge)
         dstAttr.valueChanged.emit()
         dstAttr.isLinkChanged.emit()
+        self.update()
         return edge
 
     def addEdges(self, *edges):
+        with GraphModification(self):
             for edge in edges:
                 self.addEdge(*edge)
 
@@ -850,6 +895,7 @@ class Graph(BaseObject):
         edge = self.edges.pop(dstAttr)
         dstAttr.valueChanged.emit()
         dstAttr.isLinkChanged.emit()
+        self.update()
         return edge
 
     def getDepth(self, node):
@@ -1028,6 +1074,7 @@ class Graph(BaseObject):
         return flowEdges
 
     def _applyExpr(self):
+        with GraphModification(self):
             for node in self._nodes:
                 node._applyExpr()
 
@@ -1060,6 +1107,8 @@ class Graph(BaseObject):
             node.updateStatisticsFromCache()
 
     def update(self):
+        if not self._updateEnabled:
+            self._updateRequested = True
         self.updateInternals()
         self.updateStatusFromCache()