PageRenderTime 52ms CodeModel.GetById 13ms RepoModel.GetById 0ms app.codeStats 0ms

/AutoHotkey.docset/Contents/Resources/Documents/commands/OnMessage.htm

https://gitlab.com/ahkscript/Autohotkey.docset
HTML | 241 lines | 208 code | 33 blank | 0 comment | 0 complexity | ba8d5dc7ae1806d13c1a2d76771f1efa MD5 | raw file
    

  1. <!DOCTYPE HTML>
    2. 

  2. <html>
    3. 

  3. <head>
    4. 

  4. <title>OnMessage</title>
    5. 

  5. <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
    6. 

  6. <meta http-equiv="X-UA-Compatible" content="IE=edge">
    7. 

  7. <link href="../static/theme.css" rel="stylesheet" type="text/css" />
    8. 

  8. <script src="../static/content.js" type="text/javascript"></script>
    9. 

  9. </head>
    10. 

  10. <body>
    11. 

  11. 

  12. <h1>OnMessage()</h1>
    13. 

  13. 

  14. <p>Specifies a <a href="../Functions.htm">function</a> or <a href="../objects/Functor.htm">function object</a> to call automatically when the script receives the specified message.</p>
    15. 

  15. 

  16. <pre class="Syntax">OnMessage(MsgNumber [, Function, MaxThreads])</pre>
    17. 

  17. <h3>Parameters</h3>
    18. 

  18. <dl>
    19. 

  19. 

  20.   <dt>MsgNumber</dt>
    21. 

  21.   <dd><p>The number of the message to monitor or query, which should be between 0 and 4294967295 (0xFFFFFFFF). If you do not wish to monitor a <a href="../misc/SendMessageList.htm">system message</a> (that is, one below 0x400), it is best to choose a number greater than 4096 (0x1000) to the extent you have a choice. This reduces the chance of interfering with messages used internally by current and future versions of AutoHotkey.</p></dd>
    22. 

  22. 

  23.   <dt>Function</dt>
    24. 

  24.   <dd><p>A <a href="../Functions.htm">function</a>'s name or, in <span class="ver">[v1.1.20+]</span>, a <a href="../objects/Functor.htm">function object</a>. To pass a literal function name, it must be enclosed in quotes.</p>
    25. 

  25.   <p>How the function is registered and the return value of OnMessage depend on whether this parameter is a string or a function object.  See <a href="#Name_v_Object">Function Name vs Object</a> for details.</p>
    26. 

  26.   </dd>
    27. 

  27. 

  28.   <dt id="MaxThreads">MaxThreads <span class="ver">[v1.0.47+]</span></dt>
    29. 

  29.   <dd><p>This integer is normally omitted, in which case the monitor function is limited to one <a href="../misc/Threads.htm">thread</a> at a time. This is usually best because otherwise, the script would process messages out of chronological order whenever the monitor function interrupts itself. Therefore, as an alternative to <em>MaxThreads</em>, consider using <em>Critical</em> as described <a href="#Critical">below</a>.</p>
    30. 

  30.   <p><span class="ver">[v1.1.20+]:</span> By default, when multiple functions are registered for a single <em>MsgNumber</em>, they are called in the order that they were registered. To register a function to be called before any previously registered functions, specify a negative value for <em>MaxThreads</em>. For example, <code>OnMessage(Msg, Fn, -2)</code> registers <code>Fn</code> to be called before any other functions previously registered for <em>Msg</em>, and allows <em>Fn</em> a maximum of 2 threads. However, if the function is already registered, the order will not change unless it is unregistered and then re-registered.</p></dd>
    31. 

  31. 

  32. </dl>
    33. 

  33. 

  34. <h3 id="Name_v_Object">Function Name vs Object</h3>
    35. 

  35. <p>OnMessage's return value and behavior depends on whether the <em>Function</em> parameter is a function name or an object.</p>
    36. 

    37. 

  37. <h4>Function Name</h4>
    38. 

  38. <p>For backward compatibility, at most one function can be registered by name to monitor each unique <em>MsgNumber</em> -- this is referred to as the "legacy" monitor.</p>
    39. 

  39. <p>When the legacy monitor is first registered, whether it is called before or after previously registered monitors depends on the <em>MaxThreads</em> parameter. Updating the monitor to call a different function does not affect the order unless the monitor is unregistered first.</p>
    40. 

  40. <p>This registers or updates the current legacy monitor for <em>MsgNumber</em> (omit the quote marks if passing a variable):</p>
    41. 

  41. <pre class="Syntax">Name := OnMessage(MsgNumber, "FunctionName")</pre>
    42. 

  42. <p>The return value is one of the following:</p>
    43. 

  43. <ul>
    44. 

  44.   <li>An empty string on <a href="#Failure">failure</a>.</li>
    45. 

  45.   <li>The name of the previous function, if there was one.</li>
    46. 

  46.   <li>Otherwise, the name of the new function.</li>
    47. 

  47. </ul>
    48. 

  48. <p>This unregisters the current legacy monitor for <em>MsgNumber</em> (if any) and returns its name (blank if none):</p>
    49. 

  49. <pre class="Syntax">Name := OnMessage(MsgNumber, "")</pre>
    50. 

  50. <p>This returns the name of the current legacy monitor for <em>MsgNumber</em> (blank if none):</p>
    51. 

  51. <pre class="Syntax">Name := OnMessage(MsgNumber)</pre>
    52. 

  52. 

  53. <h4>Function Object</h4>
    54. 

  54. <p>Any number of <a href="../objects/Functor.htm">function objects</a> (including <a href="../objects/Func.htm">normal functions</a>) can monitor a given <em>MsgNumber</em>.</p>
    55. 

  55. <p>Either of these two lines registers a function object to be called <strong>after</strong> any previously registered functions:</p>
    56. 

  56. <pre class="Syntax">
    57. 

  57. OnMessage(MsgNumber, FuncObj)     <em>; Option 1</em>
    58. 

  58. OnMessage(MsgNumber, FuncObj, 1)  <em>; Option 2 (MaxThreads = 1)</em>
    59. 

  59. </pre>
    60. 

  60. <p>This registers a function object to be called <strong>before</strong> any previously registered functions:</p>
    61. 

  61. <pre class="Syntax">OnMessage(MsgNumber, FuncObj, -1)</pre>
    62. 

  62. <p>To unregister a function object, specify 0 for <em>MaxThreads</em>:</p>
    63. 

  63. <pre class="Syntax">OnMessage(MsgNumber, FuncObj, 0)</pre>
    64. 

  64. 

  65. <h3 id="Failure">Failure</h3>
    66. 

  66. <p>Failure occurs when <em>Function</em>:</p>
    67. 

  67. <ol>
    68. 

  68.   <li>is not an object, the name of a user-defined function, or an empty string;</li>
    69. 

  69.   <li>is known to require more than four parameters; or</li>
    70. 

  70.   <li>in v1.0.48.05 or older, has any <a href="../Functions.htm#ByRef">ByRef</a> or <a href="../Functions.htm#optional">optional</a> parameters.</li>
    71. 

  71. </ol>
    72. 

  72. <p>In v1.1.19.03 or older, failure also occurs if the script attempts to monitor a new message when there are already 500 messages being monitored.</p>
    73. 

  73. <p>If <em>Function</em> is an object, an exception is thrown on failure. Otherwise, an empty string is returned.</p>
    74. 

  74. 

  75. <h3>The Function's Parameters</h3>
    76. 

  76. <p>A <a href="../Functions.htm">function</a> assigned to monitor one or more messages can accept up to four parameters:</p>
    77. 

  77. <pre>MyMessageMonitor(wParam, lParam, msg, hwnd)
    78. 

  78. {
    79. 

  79.     ... body of function...
    80. 

  80. }</pre>
    81. 

  81. <p>Although the names you give the parameters do not matter, the following information is sequentially assigned to them:</p>
    82. 

  82. <p>Parameter #1: The message's WPARAM value.<br>
    83. 

  83. Parameter #2: The message's LPARAM value.<br>
    84. 

  84. Parameter #3: The message number, which is useful in cases where a function monitors more than one message.<br>
    85. 

  85. Parameter #4: The HWND (unique ID) of the window or control to which the message was sent. The HWND can be used with <a href="../misc/WinTitle.htm#ahk_id">ahk_id</a>.</p>
    86. 

  86. <p>WPARAM and LPARAM are unsigned 32-bit integers (from 0 to 2<sup>32</sup>-1) or signed 64-bit integers (from -2<sup>63</sup> to 2<sup>63</sup>-1) depending on whether the exe running the script is 32-bit or 64-bit. For 32-bit scripts, if an incoming parameter is intended to be a signed integer, any negative numbers can be revealed by following this example:</p>
    87. 

  87. <pre>if (A_PtrSize = 4 &amp;&amp; wParam &gt; 0x7FFFFFFF)  <em>; Checking <a href="../Variables.htm#PtrSize">A_PtrSize</a> ensures the script is 32-bit.</em>
    88. 

  88.     wParam := -(~wParam) - 1</pre>
    89. 

  89. <p>You can omit one or more parameters from the end of the list if the corresponding information is not needed. For example, a function defined as <code>MyMsgMonitor(wParam, lParam)</code> would receive only the first two parameters, and one defined as <code>MyMsgMonitor()</code> would receive none of them.</p>
    90. 

  90. 

  91. <h3>Additional Information Available to the Function</h3>
    92. 

  92. <p>In addition to the parameters received above, the function may also consult the values in the following built-in variables:</p>
    93. 

  93. <ul>
    94. 

  94.   <li><a href="../Variables.htm#Gui">A_Gui</a>: Blank unless the message was sent to a GUI window or control, in which case A_Gui is the <a href="Gui.htm#MultiWin">Gui Window number</a> (this window is also set as the function's <a href="Gui.htm#DefaultWin">default GUI window</a>).</li>
    95. 

  95.   <li><a href="../Variables.htm#GuiControl">A_GuiControl</a>: Blank unless the message was sent to a GUI control, in which case it contains the control's variable name or other value as described at <a href="../Variables.htm#GuiControl">A_GuiControl</a>. Some controls never receive certain types of messages. For example, when the user clicks a <a href="GuiControls.htm#Text">text control</a>, the operating system sends WM_LBUTTONDOWN to the parent window rather than the control; consequently, A_GuiControl is blank.</li>
    96. 

  96.   <li><a href="../Variables.htm#GuiX">A_GuiX</a> and <a href="../Variables.htm#GuiY">A_GuiY</a>: Both contain -2147483648 if the incoming message was sent via <a href="PostMessage.htm">SendMessage</a>. If it was sent via <a href="PostMessage.htm">PostMessage</a>, they contain the mouse cursor's coordinates (relative to the screen) at the time the message was posted.</li>
    97. 

  97.   <li><a href="../Variables.htm#EventInfo">A_EventInfo</a>: Contains 0 if the message was sent via SendMessage. If sent via PostMessage, it contains the <a href="../Variables.htm#TickCount">tick-count time</a> the message was posted.</li>
    98. 

  98. </ul>
    99. 

  99. <p>A monitor function's <a href="../misc/WinTitle.htm#LastFoundWindow">last found window</a> starts off as the parent window to which the message was sent (even if it was sent to a control). If the window is hidden but not a GUI window (such as the script's main window), turn on <a href="DetectHiddenWindows.htm">DetectHiddenWindows</a> before using it. For example:</p>
    100. 

  100. <pre>DetectHiddenWindows On
    101. 

  101. MsgParentWindow := WinExist()  <em>; This stores the unique ID of the window to which the message was sent.</em></pre>
    102. 

  102. 

  103. <h3>What the Function Should <em>Return</em></h3>
    104. 

  104. <p>If a monitor function uses <a href="Return.htm">Return</a> without any parameters, or it specifies a blank value such as &quot;&quot; (or it never uses Return at all), the incoming message goes on to be processed normally when the function finishes. The same thing happens if the function <a href="Exit.htm">Exits</a> or causes a runtime error such as <a href="Run.htm">running</a> a nonexistent file. By contrast, returning an integer causes it to be sent immediately as a reply; that is, the program does not process the message any further. For example, a function monitoring WM_LBUTTONDOWN (0x201) may return an integer to prevent the target window from being notified that a mouse click has occurred. In many cases (such as a message arriving via <a href="PostMessage.htm">PostMessage</a>), it does not matter which integer is returned; but if in doubt, 0 is usually safest.</p>
    105. 

  105. <p>The range of valid return values depends on whether the exe running the script is 32-bit or 64-bit. Non-empty return values must be between -2<sup>31</sup> and 2<sup>32</sup>-1 for 32-bit scripts (<code><a href="../Variables.htm#PtrSize">A_PtrSize</a> = 4</code>) and between -2<sup>63</sup> and 2<sup>63</sup>-1 for 64-bit scripts (<code><a href="../Variables.htm#PtrSize">A_PtrSize</a> = 8</code>).</p>
    106. 

  106. <p><span class="ver">[v1.1.20+]:</span> If there are multiple functions monitoring a given message number, they are called one by one until one returns a non-empty value.</p>
    107. 

  107. 

  108. <h3 id="Remarks">General Remarks</h3>
    109. 

  109. <p>Unlike a normal function-call, the arrival of a monitored message calls the function as a new <a href="../misc/Threads.htm">thread</a>. Because of this, the function starts off fresh with the default values for settings such as <a href="SendMode.htm">SendMode</a> and <a href="DetectHiddenWindows.htm">DetectHiddenWindows</a>. These defaults can be changed in the <a href="../Scripts.htm#auto">auto-execute section</a>.</p>
    110. 

  110. <p>Messages sent to a control (rather than being posted) are not monitored because the system routes them directly to the control behind the scenes. This is seldom an issue for system-generated messages because most of them are posted.</p>
    111. 

  111. <p>Any script that calls OnMessage anywhere is automatically <a href="_Persistent.htm">persistent</a>. It is also single-instance unless <a href="_SingleInstance.htm">#SingleInstance</a> has been used to override that.</p>
    112. 

  112. <p id="Critical">If a message arrives while its function is still running due to a previous arrival of the same message, the function will not be called again (except if <a href="#MaxThreads">MaxThreads</a> is greater than 1); instead, the message will be treated as unmonitored. If this is undesirable, a message greater than or equal to 0x312 can be buffered until its function completes by specifying <a href="Critical.htm">Critical</a> as the first line of the function. Alternatively, <a href="Thread.htm">Thread Interrupt</a> can achieve the same thing as long as it lasts long enough for the function to finish. By contrast, a message less than 0x312 cannot be buffered by Critical or Thread Interrupt (however, in v1.0.46+, Critical may help because it checks messages <a href="Critical.htm#Interval">less often</a>, which gives the function more time to finish). The only way to guarantee that no such messages are missed is to ensure the function finishes in under 6 milliseconds (though this limit can be raised via <a href="Critical.htm#Interval"><em>Critical 30</em></a>). One way to do this is to have it queue up a future thread by <a href="PostMessage.htm">posting</a> to its own script a monitored message number higher than 0x312. That message's function should use <a href="Critical.htm">Critical</a> as its first line to ensure that its messages are buffered.</p>
    113. 

  113. <p>If a monitored message that is numerically less than 0x312 arrives while the script is absolutely uninterruptible -- such as while a <a href="Menu.htm">menu</a> is displayed, a <a href="SetKeyDelay.htm">KeyDelay</a>/<a href="SetMouseDelay.htm">MouseDelay</a> is in progress, or the clipboard is being <a href="_ClipboardTimeout.htm">opened</a> -- the message's function will not be called and the message will be treated as unmonitored.  By contrast, a monitored message of 0x312 or higher will be buffered during  these uninterruptible periods; that is, its function will be called when the script becomes interruptible.</p>
    114. 

  114. <p>If a monitored message numerically less than 0x312 arrives while the script is uninterruptible merely due to the settings of <a href="Thread.htm">Thread Interrupt</a> or <a href="Critical.htm">Critical</a>, the current thread will be interrupted so that the function can be called. By contrast, a monitored message of 0x312 or higher will be buffered until the thread finishes or becomes interruptible.</p>
    115. 

  115. <p>The <a href="../misc/Threads.htm">priority</a> of OnMessage threads is always 0. Consequently, no messages are monitored or buffered when the current thread's priority is higher than 0.</p>
    116. 

  116. <p>Caution should be used when monitoring system messages (those below 0x400). For example, if a monitor function does not finish quickly, the response to the message might take longer than the system expects, which might cause side-effects. Unwanted behavior may also occur if a monitor function returns an integer to suppress further processing of a message, but the system expected different processing or a different response.</p>
    117. 

  117. <p>When the script is displaying a system dialog such as <a href="MsgBox.htm">MsgBox</a>, any message posted to a control is not monitored. For example, if the script is displaying a MsgBox and the user clicks a button in a GUI window, the WM_LBUTTONDOWN message is sent directly to the button without calling the monitor function.</p>
    118. 

  118. <p>Although an external program may post messages directly to a script's thread via PostThreadMessage() or other API call, this is not recommended because the messages would be lost if the script is displaying a system window such as a <a href="MsgBox.htm">MsgBox</a>. Instead, it is usually best to post or send the messages to the script's main window or one of its GUI windows.</p>
    119. 

  119. <h3>Related</h3>
    120. 

  120. <p><a href="RegisterCallback.htm">RegisterCallback()</a>, <a href="OnExit.htm">OnExit</a>, <a href="OnClipboardChange.htm">OnClipboardChange</a>, <a href="PostMessage.htm">Post/SendMessage</a>, <a href="../Functions.htm">Functions</a>, <a href="../misc/SendMessageList.htm">List of Windows Messages</a>, <a href="../misc/Threads.htm">Threads</a>, <a href="Critical.htm">Critical</a>, <a href="DllCall.htm">DllCall()</a></p>
    121. 

  121. <h3>Examples</h3>
    122. 

  122. <pre class="NoIndent"><em>; Example: The following is a working script that monitors mouse clicks in a GUI window.
    123. 

  123. ; Related topic: <a href="Gui.htm#GuiContextMenu">GuiContextMenu</a></em>
    124. 

  124. 

  125. Gui, Add, Text,, Click anywhere in this window.
    126. 

  126. Gui, Add, Edit, w200 vMyEdit
    127. 

  127. Gui, Show
    128. 

  128. OnMessage(0x201, &quot;WM_LBUTTONDOWN&quot;)
    129. 

  129. return
    130. 

  130. 

  131. WM_LBUTTONDOWN(wParam, lParam)
    132. 

  132. {
    133. 

  133.     X := lParam &amp; 0xFFFF
    134. 

  134.     Y := lParam &gt;&gt; 16
    135. 

  135.     if A_GuiControl
    136. 

  136.         Control := &quot;`n(in control &quot; . A_GuiControl . &quot;)&quot;
    137. 

  137.     ToolTip You left-clicked in Gui window #%A_Gui% at client coordinates %X%x%Y%.%Control%
    138. 

  138. }
    139. 

    140. 

  140. GuiClose:
    141. 

  141. ExitApp</pre>
    142. 

    143. 

  143. <pre class="NoIndent" id="shutdown"><em>; Example: The following script detects system shutdown/logoff and allows you to abort it (this is
    144. 

  144. ; reported NOT to work on Windows Vista and later).
    145. 

  145. ; Related topic: <a href="OnExit.htm">OnExit</a></em>
    146. 

    147. 

  147. <em>; The following DllCall is optional: it tells the OS to shut down this script <i>first</i> (prior to all other applications).</em>
    148. 

  148. DllCall(&quot;kernel32.dll\SetProcessShutdownParameters&quot;, UInt, 0x4FF, UInt, 0)
    149. 

  149. OnMessage(0x11, &quot;WM_QUERYENDSESSION&quot;)
    150. 

  150. return
    151. 

    152. 

  152. WM_QUERYENDSESSION(wParam, lParam)
    153. 

  153. {
    154. 

  154.     ENDSESSION_LOGOFF = 0x80000000
    155. 

  155.     if (lParam &amp; ENDSESSION_LOGOFF)  <em>; User is logging off.</em>
    156. 

  156.         EventType = Logoff
    157. 

  157.     else  <em>; System is either shutting down or restarting.</em>
    158. 

  158.         EventType = Shutdown
    159. 

  159.     MsgBox, 4,, %EventType% in progress.  Allow it?
    160. 

  160.     IfMsgBox Yes
    161. 

  161.         return true  <em>; Tell the OS to allow the shutdown/logoff to continue.</em>
    162. 

  162.     else
    163. 

  163.         return false  <em>; Tell the OS to abort the shutdown/logoff.</em>
    164. 

  164. }</pre>
    165. 

    166. 

  166. <pre class="NoIndent"><em>; Example: Have a script receive a custom message and up to two numbers from some other script or program
    167. 

  167. ; (to send strings rather than numbers, see the example after this one).</em>
    168. 

    169. 

  169. OnMessage(0x5555, &quot;MsgMonitor&quot;)
    170. 

  170. OnMessage(0x5556, &quot;MsgMonitor&quot;)
    171. 

    172. 

  172. MsgMonitor(wParam, lParam, msg)
    173. 

  173. {
    174. 

  174.     <em>; Since returning quickly is often important, it is better to use a ToolTip than</em>
    175. 

  175.     <em>; something like MsgBox that would prevent the function from finishing:</em>
    176. 

  176.     ToolTip Message %msg% arrived:`nWPARAM: %wParam%`nLPARAM: %lParam%
    177. 

  177. }
    178. 

    179. 

  179. <em>; The following could be used inside some other script to run the function inside the above script:</em>
    180. 

  180. SetTitleMatchMode 2
    181. 

  181. DetectHiddenWindows On
    182. 

  182. if WinExist(&quot;Name of Receiving Script.ahk ahk_class AutoHotkey&quot;)
    183. 

  183.     PostMessage, 0x5555, 11, 22  <em>; The message is sent  to the &quot;<a href="../misc/WinTitle.htm#LastFoundWindow">last found window</a>&quot; due to WinExist() above.</em>
    184. 

  184. DetectHiddenWindows Off  <em>; Must not be turned off until after PostMessage.</em></pre>
    185. 

    186. 

  186. <pre class="NoIndent" id="SendString"><em>; Example: Send a string of any length from one script to another.  This is a working example.
    187. 

  187. ; To use it, save and run both of the following scripts then press Win+Space to show an
    188. 

  188. ; InputBox that will prompt you to type in a string.</em>
    189. 

    190. 

  190. <em>; Save the following script as &quot;<strong>Receiver.ahk</strong>&quot; then launch it:</em>
    191. 

  191. #SingleInstance
    192. 

  192. OnMessage(0x4a, &quot;Receive_WM_COPYDATA&quot;)  <em>; 0x4a is WM_COPYDATA</em>
    193. 

  193. return
    194. 

    195. 

  195. Receive_WM_COPYDATA(wParam, lParam)
    196. 

  196. {
    197. 

  197.     StringAddress := NumGet(lParam + 2*A_PtrSize)  <em>; Retrieves the CopyDataStruct's lpData member.</em>
    198. 

  198.     CopyOfData := StrGet(StringAddress)  <em>; Copy the string out of the structure.</em>
    199. 

  199.     <em>; Show it with ToolTip vs. MsgBox so we can return in a timely fashion:</em>
    200. 

  200.     ToolTip %A_ScriptName%`nReceived the following string:`n%CopyOfData%
    201. 

  201.     return true  <em>; Returning 1 (true) is the traditional way to acknowledge this message.</em>
    202. 

  202. }
    203. 

    204. 

  204. <em>; Save the following script as &quot;<strong>Sender.ahk</strong>&quot; then launch it.  After that, press the Win+Space hotkey.</em>
    205. 

  205. TargetScriptTitle = Receiver.ahk ahk_class AutoHotkey
    206. 

    207. 

  207. #space::  <em>; Win+Space hotkey. Press it to show an InputBox for entry of a message string.</em>
    208. 

  208. InputBox, StringToSend, Send text via WM_COPYDATA, Enter some text to Send:
    209. 

  209. if ErrorLevel  <em>; User pressed the Cancel button.</em>
    210. 

  210.     return
    211. 

  211. result := Send_WM_COPYDATA(StringToSend, TargetScriptTitle)
    212. 

  212. if result = FAIL
    213. 

  213.     MsgBox SendMessage failed. Does the following WinTitle exist?:`n%TargetScriptTitle%
    214. 

  214. else if result = 0
    215. 

  215.     MsgBox Message sent but the target window responded with 0, which may mean it ignored it.
    216. 

  216. return
    217. 

  217. 

  218. Send_WM_COPYDATA(ByRef StringToSend, ByRef TargetScriptTitle)  <em>; ByRef saves a little memory in this case.
    219. 

  219. ; This function sends the specified string to the specified window and returns the reply.
    220. 

  220. ; The reply is 1 if the target window processed the message, or 0 if it ignored it.</em>
    221. 

  221. {
    222. 

  222.     VarSetCapacity(CopyDataStruct, 3*A_PtrSize, 0)  <em>; Set up the structure's memory area.</em>
    223. 

  223.     <em>; First set the structure's cbData member to the size of the string, including its zero terminator:</em>
    224. 

  224.     SizeInBytes := (StrLen(StringToSend) + 1) * (A_IsUnicode ? 2 : 1)
    225. 

  225.     NumPut(SizeInBytes, CopyDataStruct, A_PtrSize)  <em>; OS requires that this be done.</em>
    226. 

  226.     NumPut(&amp;StringToSend, CopyDataStruct, 2*A_PtrSize)  <em>; Set lpData to point to the string itself.</em>
    227. 

  227.     Prev_DetectHiddenWindows := A_DetectHiddenWindows
    228. 

  228.     Prev_TitleMatchMode := A_TitleMatchMode
    229. 

  229.     DetectHiddenWindows On
    230. 

  230.     SetTitleMatchMode 2
    231. 

  231.     SendMessage, 0x4a, 0, &amp;CopyDataStruct,, %TargetScriptTitle%  <em>; 0x4a is WM_COPYDATA. Must use Send not Post.</em>
    232. 

  232.     DetectHiddenWindows %Prev_DetectHiddenWindows%  <em>; Restore original setting for the caller.</em>
    233. 

  233.     SetTitleMatchMode %Prev_TitleMatchMode%         <em>; Same.</em>
    234. 

  234.     return ErrorLevel  <em>; Return SendMessage's reply back to our caller.</em>
    235. 

  235. }</pre>
    236. 

  236. 

  237. <pre class="NoIndent"><em>; Example: See the <a href="../scripts/WinLIRC.htm">WinLIRC client script</a> for a demonstration of how to use OnMessage() to receive
    238. 

  238. ; notification when data has arrived on a network connection.</em></pre>
    239. 

  239. 

  240. </body>
    241. 

  241. </html>
    242. 

  242.