Update control flow images.

asio/src/doc/overview/async_op1.dot

@@ -25,69 +25,54 @@ digraph g
       arrowhead="open"
     ]
 
-  operating_system
-    [
-      label="Operating System",
-      shape=ellipse
-    ];
+  // Program elements.
+  {
+    operating_system [ label="Operating System", shape=ellipse ];
+    io_service [ label="io_service" ];
+    io_object [ label="I/O Object\ne.g. socket" ];
+    your_program [ label="Your Program" ];
+    your_completion_handler [ label="Your Completion Handler" ];
+  }
 
-  io_service
-    [
-      label="io_service"
-    ];
+  // Owning relationships.
+  {
+    edge [ arrowtail="diamond" ];
+    your_program:e -> your_completion_handler:n;
+    your_program:w -> io_object:nw;
+    your_program:se -> io_service:ne;
+  }
 
-  io_object
-    [
-      label="I/O Object\ne.g. socket"
-    ];
+  // Non-owning relationships;
+  {
+    io_object:sw -> io_service:w;
+  }
 
-  your_program
-    [
-      label="Your Program"
-    ];
+  // Visible actions.
+  {
+    edge [ style="dashed", color="#808080" ];
 
-  your_completion_handler
-    [
-      label="Your Completion Handler"
-    ];
+    // Forward actions.
+    {
+      your_program:sw -> io_object:n [ label="1" ];
+      io_object:s -> io_service:nw [ label="2" ];
+      io_service:s -> operating_system:n [ label="3" ];
+    }
+  }
 
-  your_program:e -> your_completion_handler:n
-    [
-      arrowtail="diamond"
-    ];
+  // Invisible actions.
+  {
+    edge [ style="invis" ];
 
-  your_program:sw -> io_object:nw
-    [
-      arrowtail="diamond"
-    ];
+    // Forward actions.
+    {
+      your_program:s -> io_service:n [ label="5" ];
+    }
 
-  your_program:se -> io_service:ne
-    [
-      arrowtail="diamond"
-    ];
-
-  io_object:sw -> io_service:w
-    [
-    ];
-
-  your_program:s -> io_object:ne
-    [
-      style="dashed",
-      label="1"
-      color="#808080"
-    ];
-
-  io_object:se -> io_service:n
-    [
-      style="dashed",
-      label="2"
-      color="#808080"
-    ];
-
-  io_service:s -> operating_system:n
-    [
-      style="dashed",
-      label="3"
-      color="#808080"
-    ];
+    // Reverse actions.
+    {
+      edge [ arrowhead="none", arrowtail="open" ];
+      //io_service:s -> operating_system:n [ label="4" ];
+      your_completion_handler:s -> io_service:e [ label="6" ];
+    }
+  }
 }

asio/src/doc/overview/async_op2.dot

@@ -25,77 +25,54 @@ digraph g
       arrowhead="open"
     ]
 
-  operating_system
-    [
-      label="Operating System",
-      shape=ellipse
-    ];
+  // Program elements.
+  {
+    operating_system [ label="Operating System", shape=ellipse ];
+    io_service [ label="io_service" ];
+    io_object [ label="I/O Object\ne.g. socket" ];
+    your_program [ label="Your Program" ];
+    your_completion_handler [ label="Your Completion Handler" ];
+  }
 
-  io_service
-    [
-      label="io_service"
-    ];
+  // Owning relationships.
+  {
+    edge [ arrowtail="diamond" ];
+    your_program:e -> your_completion_handler:n;
+    your_program:w -> io_object:nw;
+    your_program:se -> io_service:ne;
+  }
 
-  io_object
-    [
-      label="I/O Object\ne.g. socket"
-    ];
+  // Non-owning relationships;
+  {
+    io_object:sw -> io_service:w;
+  }
 
-  your_program
-    [
-      label="Your Program"
-    ];
+  // Visible actions.
+  {
+    edge [ style="dashed", color="#808080" ];
 
-  your_completion_handler
-    [
-      label="Your Completion Handler"
-    ];
+    // Forward actions.
+    {
+      your_program:s -> io_service:n [ label="5" ];
+    }
 
-  your_program:e -> your_completion_handler:n
-    [
-      arrowtail="diamond"
-    ];
+    // Reverse actions.
+    {
+      edge [ arrowhead="none", arrowtail="open" ];
+      io_service:s -> operating_system:n [ label="4" ];
+      your_completion_handler:s -> io_service:e [ label="6" ];
+    }
+  }
 
-  your_program:sw -> io_object:nw
-    [
-      arrowtail="diamond"
-    ];
+  // Invisible actions.
+  {
+    edge [ style="invis" ];
 
-  your_program:se -> io_service:ne
-    [
-      arrowtail="diamond"
-    ];
-
-  io_object:sw -> io_service:w
-    [
-    ];
-
-  your_program:s -> io_object:ne
-    [
-      style="invis",
-      label="1"
-    ];
-
-  io_object:se -> io_service:n
-    [
-      style="invis",
-      label="2"
-    ];
-
-  io_service:s -> operating_system:n
-    [
-      style="dashed",
-      label="4"
-      color="#808080"
-      arrowhead="none"
-      arrowtail="open"
-    ];
-
-  io_service:e -> your_completion_handler:s
-    [
-      style="dashed",
-      label="5"
-      color="#808080"
-      constraint="false"
-    ];
+    // Forward actions.
+    {
+      your_program:sw -> io_object:n [ label="1" ];
+      io_object:s -> io_service:nw [ label="2" ];
+      //io_service:s -> operating_system:n [ label="3" ];
+    }
+  }
 }

asio/src/doc/overview/sync_op.dot

@@ -25,83 +25,43 @@ digraph g
       arrowhead="open"
     ]
 
-  operating_system
-    [
-      label="Operating System",
-      shape=ellipse
-    ];
+  // Program elements.
+  {
+    operating_system [ label="Operating System", shape=ellipse ];
+    io_service [ label="io_service" ];
+    io_object [ label="I/O Object\ne.g. socket" ];
+    your_program [ label="Your Program" ];
+  }
 
-  io_service
-    [
-      label="io_service"
-    ];
+  // Owning relationships.
+  {
+    edge [ arrowtail="diamond" ];
+    your_program:w -> io_object:nw;
+    your_program:se -> io_service:ne;
+  }
 
-  io_object
-    [
-      label="I/O Object\ne.g. socket"
-    ];
+  // Non-owning relationships;
+  {
+    io_object:sw -> io_service:w;
+  }
 
-  your_program
-    [
-      label="Your Program"
-    ];
+  // Actions.
+  {
+    edge [ style="dashed", color="#808080" ];
 
-  your_program:w -> io_object:nw
-    [
-      arrowtail="diamond"
-    ];
+    // Forward actions.
+    {
+      your_program:sw -> io_object:n [ label="1" ];
+      io_object:s -> io_service:nw [ label="2" ];
+      io_service:sw -> operating_system:nw [ label="3" ];
+    }
 
-  your_program:se -> io_service:ne
-    [
-      arrowtail="diamond"
-    ];
-
-  io_object:sw -> io_service:w
-    [
-    ];
-
-  your_program:s -> io_object:ne
-    [
-      style="dashed",
-      label="1"
-      color="#808080"
-    ];
-
-  io_object:se -> io_service:n
-    [
-      style="dashed",
-      label="2"
-      color="#808080"
-    ];
-
-  io_service:sw -> operating_system:nw
-    [
-      style="dashed",
-      label="3"
-      color="#808080"
-    ];
-
-  operating_system:ne -> io_service:se
-    [
-      style="dashed",
-      label="4"
-      color="#808080"
-      constraint="false"
-    ];
-
-  io_service:nw -> io_object:s
-    [
-      style="dashed",
-      label="5",
-      color="#808080"
-      constraint="false"
-    ];
-
-  io_object:n -> your_program:sw
-    [
-      style="dashed",
-      label="6",
-      color="#808080"
-      constraint="false"
-    ];
+    // Reverse actions.
+    {
+      edge [ arrowhead="none", arrowtail="open" ];
+      io_service:se -> operating_system:ne [ label="4" ];
+      io_object:se -> io_service:n [ label="5" ];
+      your_program:s -> io_object:ne [ label="6" ];
+    }
+  }
 }