_ff-addon-snippet-WinAPI_SendMessage - How to use SendMessage. [jsctypes] [winapi]

_ff-addon-snippet-WinAPI_SendMessage.js

Cu.import('resource://gre/modules/Services.jsm');
Cu.import('resource://gre/modules/ctypes.jsm');

if (ctypes.voidptr_t.size == 4 /* 32-bit */ ) {
	var is64bit = false;
} else if (ctypes.voidptr_t.size == 8 /* 64-bit */ ) {
	var is64bit = true;
} else {
	throw new Error('huh??? not 32 or 64 bit?!?!');
}


var user32 = ctypes.open('user32.dll');

var SetCursorPos = user32.declare('SetCursorPos', ctypes.winapi_abi,
	ctypes.bool, // return
	ctypes.int, // x
	ctypes.int // y
);

var POINT = ctypes.StructType('_tagPoint', [
	{x: ctypes.long},
	{y: ctypes.long}
]);
var LPPOINT = POINT.ptr;

var GetCursorPos = user32.declare('GetCursorPos', ctypes.winapi_abi,
	ctypes.bool, // return
	LPPOINT // lpPoint
);

var LONG_PTR = is64bit ? ctypes.int64_t : ctypes.long;
var LRESULT = LONG_PTR;

var UINT_PTR = is64bit ? ctypes.uint64_t : ctypes.unsigned_int;
var WPARAM = UINT_PTR;
var LPARAM = LONG_PTR;

var SendMessage = user32.declare('SendMessageW', ctypes.winapi_abi,
	LRESULT,	// return
	ctypes.voidptr_t,	// hWnd
	ctypes.unsigned_int,	// Msg
	WPARAM, // wParam
	LPARAM	// lParam
);

var WM_GETTEXT = 0x000D;
var WM_GETTEXTLENGTH = 0x000E;

var DWORD = ctypes.uint32_t;
var LPDWORD = DWORD.ptr;

var WCHAR = ctypes.jschar

function doIt() {

    var browserWindow = Services.wm.getMostRecentWindow('navigator:browser');
    if (!browserWindow) {
        throw new Error('No browser window found');
    }

    var baseWindow = browserWindow.QueryInterface(Ci.nsIInterfaceRequestor)
        .getInterface(Ci.nsIWebNavigation)
        .QueryInterface(Ci.nsIDocShellTreeItem)
        .treeOwner
        .QueryInterface(Ci.nsIInterfaceRequestor)
        .getInterface(Ci.nsIBaseWindow);

    var hToString = baseWindow.nativeHandle;
    var hTo = ctypes.voidptr_t(ctypes.UInt64(hToString));

	
	var rez_SM = SendMessage(hTo, 0x000E, 0, 0);
	console.log('rez_SM:', rez_SM, rez_SM.toString());
	
	var titleLength = parseInt(rez_SM.toString());
	console.info('the title of the window WITHOUT null term is this long:', titleLength);
	
	
	var buffer = WCHAR.array(titleLength+1)(); // because docs say we should allocate a buffer that is title length plus null term
	var addressOfBuffer_asLPARAM = ctypes.cast(buffer.address(), LPARAM);
	console.log('addressOfBuffer_asLPARAM:', addressOfBuffer_asLPARAM.toString());
	var rez_SM = SendMessage(hTo, WM_GETTEXT, buffer.length, addressOfBuffer_asLPARAM);
	
	console.log('rez_SM:', rez_SM, rez_SM.toString()); // return of SendMessage with WM_GETTEXT is the length of the stirng without the null term
	console.log('buffer.readString()', buffer.readString());
}

doIt();

README

Rev1

• Taken from this topic here: http://forums.mozillazine.org/viewtopic.php?f=19&t=650630&p=12527153&hilit=ctypes#p12527153

• The C version of this code looks like this (from topic linked above):

  COPYDATASTRUCT cs;
  unsigned char myData[] = {10,11,12,13,14,15}; /* 15 is useless here! */
  cs.dwData = 12345;
  cs.cbData = 5;
  cs.lpData = &(myData[0]);
  SendMessage(destWindow,WM_COPYDATA,sourceWindow,(LPARAM)&cs);

Rev2

• Added WINAPI_ to file and gist name

Rev3

• This example gets the length of the title of a window, and then reads it, it uses readString so if the title has any non-UTF8 characters it will fail, but thats a non-ctypes fix, just fix up readString to do manually or use readStringRepalceMalformed if you dont care about actually reading the bad chars.

Rev4

• Updated gist description

Rev5

• Updated gist file name