Recent changes to Using_single_message_response_function

Using_single_message_response_function modified by Vidar Hasfjord

Vidar Hasfjord — Fri, 27 Jun 2014 10:09:02 -0000

--- v2
+++ v3
@@ -1,37 +1,42 @@
-Sometimes, a series of command messages may be related in such a way that it makes more sense to handle them all with a single message-response function than to create a message-response function for each. For example, a Line menu may enable a user to select one of several line thicknesses. It's logical to handle all Line menu commands in a single function whose job it is to set the line width. To perform this trick, you need to use EV_COMMAND_AND_ID macros in your window class's response table. 
+Sometimes, a series of command messages may be related in such a way that it makes more sense to handle them all with a single message-response function than to create a function for each. For example, a Line menu may enable a user to select one of several line thicknesses. It's logical to handle all Line menu commands in a single function whose job it is to set the line width. To perform this trick, you need to use EV_COMMAND_AND_ID macros in your window class's response table.

 ## The Solution

 First, create a response table that contains an EV_COMMAND_AND_ID macro for each message you want handled by the single message-response function, using the same function as the macro's second argument: 

-    <pre>
-    DEFINE_RESPONSE_TABLE1(TWndw, TFrameWindow)
-      EV_COMMAND_AND_ID(CM_COHHAND1, CmCommand),
-      EV_COMMAND_AND_ID(CM_COMMAND2, CmCommand),
-      EV_COMMAND_AND_ID(CM_COMHAND3, CmCommand),
+    DEFINE_RESPONSE_TABLE1(TLineWindow, TFrameWindow)
+      EV_COMMAND_AND_ID(CM_LINEWIDTH1, CmLineWidth),
+      EV_COMMAND_AND_ID(CM_LINEWIDTH2, CmLineWidth),
+      EV_COMMAND_AND_ID(CM_LINEWIDTH3, CmLineWidth),
     END RESPONSE TABLE;

-</pre>
-
-The EV_COMMAND_AND_ID macro takes exactly the same arguments as the EV_COMMAND macro: the message ID and the name of the function that will handle that message. 
-
-The difference is that, when the program calls the message-response function, it sends along the ID of the message that triggered the call. In the message-response function, use this parameter to determine which message you need to respond to: 
+The EV_COMMAND_AND_ID macro takes exactly the same arguments as the EV_COMMAND macro: the message ID and the name of the function that will handle that message. The difference is that when the program calls the message-response function it sends along the ID of the message that triggered the call. In the message-response function, use this parameter to implement the handler appropriately: 

-    <pre>
-    void TWndw::CmCommand(WPARAM messageld)
+    void TLineWindow::CmLineWidth(WPARAM id)
+    {
+      typedef std::map<WPARAM, int> LineWidthMap;
+      const LineWidthMap::value_type v[] = 
+        {{CM_LINEWIDTH1, 1}, {CM_LINEWIDTH2, 5}, {CM_LINEWIDTH3, 10}};
+      static const LineWidthMap m(v, v + COUNTOF(v));
+      SetLineWidth(m[idWidth]); // 0 if not in map
+    } 
+    
+
+On the other hand, beware that if your handler ends up looking like the following you should really consider using separate handlers. Don't do manual dispatch. 
+    
+    
+    void TMyWindow::CmCommand(WPARAM messageld)
     {
       switch (messageld) {
-        case CM_COMMAND1 /* Handle message 1 */
+        case CM_COMMAND1: /* Handle message 1 */
           break;
-        case CM_COMMAND2 /* Handle message 2 */
+        case CM_COMMAND2: /* Handle message 2 */
           break;
-        case CM_COMMAND3 /* Handle message 3 */
+        case CM_COMMAND3: /* Handle message 3 */
           break;
       }
     } 

-
-</pre>

Using_single_message_response_function modified by Ognian Tchernokojev

Ognian Tchernokojev — Fri, 27 Jun 2014 10:09:02 -0000

--- v1
+++ v2
@@ -1,4 +1,6 @@
-Sometimes, a series of command messages may be related in such a way that it makes more sense to handle them all with a single message-response function than to create a message-response function for each. For example, a Line menu may enable a user to select one of several line thicknesses. It's logical to handle all Line menu commands in a single function whose job it is to set the line width. To perform this trick, you need to use EV_COMMAND_AND_ID macros in your window class's response table. The Solution 
+Sometimes, a series of command messages may be related in such a way that it makes more sense to handle them all with a single message-response function than to create a message-response function for each. For example, a Line menu may enable a user to select one of several line thicknesses. It's logical to handle all Line menu commands in a single function whose job it is to set the line width. To perform this trick, you need to use EV_COMMAND_AND_ID macros in your window class's response table. 
+
+## The Solution

 First, create a response table that contains an EV_COMMAND_AND_ID macro for each message you want handled by the single message-response function, using the same function as the macro's second argument:

Using_single_message_response_function modified by Ognian Tchernokojev

Ognian Tchernokojev — Fri, 27 Jun 2014 10:09:01 -0000

Sometimes, a series of command messages may be related in such a way that it makes more sense to handle them all with a single message-response function than to create a message-response function for each. For example, a Line menu may enable a user to select one of several line thicknesses. It's logical to handle all Line menu commands in a single function whose job it is to set the line width. To perform this trick, you need to use EV_COMMAND_AND_ID macros in your window class's response table. The Solution

First, create a response table that contains an EV_COMMAND_AND_ID macro for each message you want handled by the single message-response function, using the same function as the macro's second argument:

&lt;pre&gt;
DEFINE_RESPONSE_TABLE1(TWndw, TFrameWindow)
  EV_COMMAND_AND_ID(CM_COHHAND1, CmCommand),
  EV_COMMAND_AND_ID(CM_COMMAND2, CmCommand),
  EV_COMMAND_AND_ID(CM_COMHAND3, CmCommand),
END RESPONSE TABLE;

</pre>

The EV_COMMAND_AND_ID macro takes exactly the same arguments as the EV_COMMAND macro: the message ID and the name of the function that will handle that message.

The difference is that, when the program calls the message-response function, it sends along the ID of the message that triggered the call. In the message-response function, use this parameter to determine which message you need to respond to:

&lt;pre&gt;
void TWndw::CmCommand(WPARAM messageld)
{
  switch (messageld) {
    case CM_COMMAND1 /* Handle message 1 */
      break;
    case CM_COMMAND2 /* Handle message 2 */
      break;
    case CM_COMMAND3 /* Handle message 3 */
      break;
  }
}

</pre>