Windows CE Programming

If you are running a kiosk mode app but need to provide the camercapture dialog on Windows Mobile 5 or later, you may need to disable the one or other click in the CameraCapture dialog.

This article uses a technique known as subclassing as already used and decribed in my StartButtonHookWM65 article. For the CameraCapture dialog the code has been revised and you can now subclass any known window class and disable clicks within the Windows Mobile menu bar.

        private string _winClassName = "HHTaskbar";
        public string winClassName
        {
            get { return _winClassName; }
            set {
                if (this.oldWndProc == IntPtr.Zero) //only allow change before subclassing
                    _winClassName = value;
            }
        }
...
        /// <summary>
        /// SubClassing: Install the wndproc hook
        /// </summary>
        /// <returns></returns>
        private bool hookWindow()
        {
            //find the window to hook
            IntPtr hWndHooked = FindWindow(_winClassName, IntPtr.Zero);
            if (hWndHooked == IntPtr.Zero)
                return false;
            //enable the taskbar, not realy necessary
            EnableWindow(hWndHooked, true);
            //already installed?
            if (oldWndProc == IntPtr.Zero)
            {
                //find the menu_worker window
                IntPtr hwndMenu_Worker = FindWindow("menu_worker", IntPtr.Zero);
                if (hwndMenu_Worker != IntPtr.Zero)
                {
                    //get the child window which has the buttons on it
                    IntPtr hwndToolbar = GetWindow(hwndMenu_Worker, GetWindow_Cmd.GW_CHILD);
                    if (hwndToolbar != IntPtr.Zero)
                    {
                        _mHwnd = hwndToolbar;       //store to remember
                        SubclassHWnd(hwndToolbar);  //subclass the wndproc
                    }
                }
            }
            return true;
        }

As the call to CameraCaptureDialog will block and you can not subclass it before it is launched, I use a timer that will subclass the dialog assuming it will show after the call to .ShowDialog().

        private System.Windows.Forms.Timer timer;
        hwndutils subClassUtils;
        private void ShowCamera()
        {
            CameraCaptureDialog cdlg = new CameraCaptureDialog();
            cdlg.DefaultFileName="picture.jpg";
            cdlg.InitialDirectory = "\\My Documents";
            cdlg.Mode = CameraCaptureMode.Still;
            cdlg.Owner = this.pictureBox1;
            cdlg.StillQuality = CameraCaptureStillQuality.High;
            cdlg.Title = "Take a picture and Select";
            cdlg.Resolution = new Size(240, 320);
            cdlg.VideoTypes = CameraCaptureVideoTypes.All;

            //subclass main window with delay
            subClassUtils = new hwndutils();
            timer = new Timer();
            timer.Interval = 1000;
            timer.Tick += new EventHandler(timer_Tick);
            timer.Enabled = true;

            DialogResult dRes = cdlg.ShowDialog();
...
        void timer_Tick(object sender, EventArgs e)
        {
            subClassUtils.winClassName = "Camera View";
            subClassUtils.CloseButtonDisabled = true;
            System.Threading.Thread.Sleep(500);
            if(subClassUtils.CloseButtonDisabled)
                timer.Enabled = false;

        }

In the line “subClassUtils.CloseButtonDisabled = true;” the subclassing (or the hook) will be activated and clicks on (OK) will not be accepted.

Code subclassing.cs download: [Download not found]

Although I dont recommend this, it may be usefull if your kiosk mode app watches and manages the battery level: you can disable the low battery warning. Sometimes such hacks are hard to find, now there is one more location in internet.

In the registry find the key

[HKEY_CURRENT_USER\ControlPanel\Notifications\{A877D663-239C-47a7-9304-0D347F580408}]

This is the entry responsible for low battery warnings

Add a new REG_SZ key: “Default” with for example the text “Low Battery Warning”

"Default"="Low Battery Warning"

This entry is used to display the notification in the list of notifications in Start-Settings-Sounds&Notifications. To disable the notification itself it is not really necessary, but easier to control.

The Options entry in the registry defines which options your selected in Start-Settings-Sounds&Notifications, for example play a sound or display a user notification. Set Options to REG_DWORD=0x00 and there will be no notification when the battery goes down to 10% (depends on the device) and lower.

Here is the change in full:

REGEDIT4
[HKEY_CURRENT_USER\ControlPanel\Notifications\{A877D663-239C-47a7-9304-0D347F580408}]
"Options"=dword:00000000
"Default"="LowBattWarning"

You need to reboot the device after the change!

Only a small tipp

Are you looking for a tool that periodically pings a list of hosts? Here is a toolset that will reschedule a ping utilitiy. This ping utility pings a list of hosts and will create notifications if one or most hosts failed to answer.

I have done this toolset with three separate applications. The scheduler and the notification tool are written in C/C++ win32 API cause this API provided the best access to all the possibilities of the used functions. The user notification API is only supported with basic functionality by CF2. The CEUserNotification API is not supported by CF2 at all.

Although OpenNetCF provides an C# interface to the used APIs, I did not like to include all the unneeded stuff. On the other hand the scheduler is fast and small written in C/C++. With C# I had problems with the notification, especially for removing existing notifications and why should the main tool reside in memory just for showing the notification.

The ping tool is written in C# targeting Compact Framework 2. C# was the easiest to implement the GUI.

All source is available thru one Visual Studio 2008 solution. Yes, you can mix C/C++ and CF2 within one solution.

Continue reading ‘Mobile Development-PingAlert: watch your servers’ »

Help needed! [Edit: Partially solved, see bottom]

this site is hosted on a cheap hosting site like many others. Recently I tried a backup of the WP database and files without success. The backups stuck (do never finsih and hang at a file or table) or just reported “success” (EZPZ backup). I also tried the hosters PHPAdmin to backup the WP database without success, I got out of memory errors.

Finally the cause of all these strange results is a limitation of the hosting, it has a limit of 20MB per file. As most backup tools for wordpress and even PHPAdmin use temporary files on my host, the backup fails as soon as the limit is reached.

I was finally able to backup the WP database by excluding the larger tables from the backup. To get the table sizes I used the following php script:

Code:
<?php
$link = mysql_connect('xxxxxxx.strato.de', 'username', 'password');
$db_name = "databasename";
$tables = array();
$txtOut="";
mysql_select_db($db_name, $link);
$result = mysql_query("SHOW TABLE STATUS");

while($row = mysql_fetch_array($result)) {
    /* We return the size in Kilobytes */
    $total_size = ($row[ "Data_length" ] +
                   $row[ "Index_length" ]) / 1024;
    $tables[$row['Name']] = sprintf("%.2f", $total_size);
	$txtOut=$txtOut."<tr><td>".$row['Name']."</td><td align=\"right\">".$tables[$row['Name']]."</td></tr>";
}

echo "<h1>Database table sizes</h1>";
echo "<table border=\"1\">";
echo $txtOut;
echo "</table>";
//print_r($tables);
//var_dump($tables);
?>

The “success” failing backups may be related to a problem in php fwrite as described here. Excerpt:

====================================================
This means the example fwrite_stream() code  from the docs, as well as all the "helper" functions posted by others in  the comments are all broken. You *must* check for a return value of 0  and either abort immediately or track a maximum number of retries.

Below is the example from the docs. This code is BAD, as a broken pipe will result in fwrite() infinitely looping with a return value of 0. Since the loop only breaks if fwrite() returns false or successfully writes all bytes, an infinite loop will occur on failure.

<?php
// BROKEN function – infinite loop when fwrite() returns 0s
function fwrite_stream($fp, $string) {
for ($written = 0; $written < strlen($string); $written += $fwrite) {
$fwrite = fwrite($fp, substr($string, $written));
if ($fwrite === false) {
return $written;
}
}
return $written;
}
?>

====================================================

So, if your WP backups fail, check with your hoster about file size limitations. I found this out myself as the backup folder on the site showed backup files with exact same file size of 21MB.

Please leave a mail or comment if you know a WP backup solution that  use splitted files and handles maximum file size limitations.

And as last guess never trust a backup, always try a restore or at least check the backup files.

[Edit 1. march 2011]

Fortunately strato.de support gave a hint and led me to try MySqlDumper. This sql dumper is able to split files and works also with limitted file size on the host. I even got a perl script now that I can simply invoke and that backups the whole database. The uncompressed dump is about 52MB and MySqlDumper did backup it into a 6MB gzipped dump file.

The only wish left is to have it run periodically but that would need cronjob access on the hoster site and is not included with the package I own at the hoster.

So if you need to backup a large WordPress MySql database you may give MySqlDumper a try.