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  • Alert visualization recipe: Get out your blender, drop in some sp_send_dbmail, Google Charts API, add your favorite colors and sprinkle with html. Blend till it’s smooth and looks pretty enough to taste.

    - by Maria Zakourdaev
      I really like database monitoring. My email inbox have a constant flow of different types of alerts coming from our production servers with all kinds of information, sometimes more useful and sometimes less useful. Usually database alerts look really simple, it’s usually a plain text email saying “Prod1 Database data file on Server X is 80% used. You’d better grow it manually before some query triggers the AutoGrowth process”. Imagine you could have received email like the one below.  In addition to the alert description it could have also included the the database file growth chart over the past 6 months. Wouldn’t it give you much more information whether the data growth is natural or extreme? That’s truly what data visualization is for. Believe it or not, I have sent the graph below from SQL Server stored procedure without buying any additional data monitoring/visualization tool.   Would you like to visualize your database alerts like I do? Then like myself, you’d love the Google Charts. All you need to know is a little HTML and have a mail profile configured on your SQL Server instance regardless of the SQL Server version. First of all, I hope you know that the sp_send_dbmail procedure has a great parameter @body_format = ‘HTML’, which allows us to send rich and colorful messages instead of boring black and white ones. All that we need is to dynamically create HTML code. This is how, for instance, you can create a table and populate it with some data: DECLARE @html varchar(max) SET @html = '<html>' + '<H3><font id="Text" style='color: Green;'>Top Databases: </H3>' + '<table border="1" bordercolor="#3300FF" style='background-color:#DDF8CC' width='70%' cellpadding='3' cellspacing='3'>' + '<tr><font color="Green"><th>Database Name</th><th>Size</th><th>Physical Name</th></tr>' + CAST( (SELECT TOP 10                             td = name,'',                             td = size * 8/1024 ,'',                             td = physical_name              FROM sys.master_files               ORDER BY size DESC             FOR XML PATH ('tr'),TYPE ) AS VARCHAR(MAX)) + '</table>' EXEC msdb.dbo.sp_send_dbmail @recipients = '[email protected]', @subject ='Top databases', @body = @html, @body_format = 'HTML' This is the result:   If you want to add more visualization effects, you can use Google Charts Tools https://google-developers.appspot.com/chart/interactive/docs/index which is a free and rich library of data visualization charts, they’re also easy to populate and embed. There are two versions of the Google Charts Image based charts: https://google-developers.appspot.com/chart/image/docs/gallery/chart_gall This is an old version, it’s officially deprecated although it will be up for a next few years or so. I really enjoy using this one because it can be viewed within the email body. For mobile devices you need to change the “Load remote images” property in your email application configuration.           Charts based on JavaScript classes: https://google-developers.appspot.com/chart/interactive/docs/gallery This API is newer, with rich and highly interactive charts, and it’s much more easier to understand and configure. The only downside of it is that they cannot be viewed within the email body. Outlook, Gmail and many other email clients, as part of their security policy, do not run any JavaScript that’s placed within the email body. However, you can still enjoy this API by sending the report as an email attachment. Here is an example of the old version of Google Charts API, sending the same top databases report as in the previous example but instead of a simple table, this script is using a pie chart right from  the T-SQL code DECLARE @html  varchar(8000) DECLARE @Series  varchar(800),@Labels  varchar(8000),@Legend  varchar(8000);     SET @Series = ''; SET @Labels = ''; SET @Legend = ''; SELECT TOP 5 @Series = @Series + CAST(size * 8/1024 as varchar) + ',',                         @Labels = @Labels +CAST(size * 8/1024 as varchar) + 'MB'+'|',                         @Legend = @Legend + name + '|' FROM sys.master_files ORDER BY size DESC SELECT @Series = SUBSTRING(@Series,1,LEN(@Series)-1),         @Labels = SUBSTRING(@Labels,1,LEN(@Labels)-1),         @Legend = SUBSTRING(@Legend,1,LEN(@Legend)-1) SET @html =   '<H3><font color="Green"> '+@@ServerName+' top 5 databases : </H3>'+    '<br>'+    '<img src="http://chart.apis.google.com/chart?'+    'chf=bg,s,DDF8CC&'+    'cht=p&'+    'chs=400x200&'+    'chco=3072F3|7777CC|FF9900|FF0000|4A8C26&'+    'chd=t:'+@Series+'&'+    'chl='+@Labels+'&'+    'chma=0,0,0,0&'+    'chdl='+@Legend+'&'+    'chdlp=b"'+    'alt="'+@@ServerName+' top 5 databases" />'              EXEC msdb.dbo.sp_send_dbmail @recipients = '[email protected]',                             @subject = 'Top databases',                             @body = @html,                             @body_format = 'HTML' This is what you get. Isn’t it great? Chart parameters reference: chf     Gradient fill  bg - backgroud ; s- solid cht     chart type  ( p - pie) chs        chart size width/height chco    series colors chd        chart data string        1,2,3,2 chl        pir chart labels        a|b|c|d chma    chart margins chdl    chart legend            a|b|c|d chdlp    chart legend text        b - bottom of chart   Line graph implementation is also really easy and powerful DECLARE @html varchar(max) DECLARE @Series varchar(max) DECLARE @HourList varchar(max) SET @Series = ''; SET @HourList = ''; SELECT @HourList = @HourList + SUBSTRING(CONVERT(varchar(13),last_execution_time,121), 12,2)  + '|' ,              @Series = @Series + CAST( COUNT(1) as varchar) + ',' FROM sys.dm_exec_query_stats s     CROSS APPLY sys.dm_exec_sql_text(plan_handle) t WHERE last_execution_time > = getdate()-1 GROUP BY CONVERT(varchar(13),last_execution_time,121) ORDER BY CONVERT(varchar(13),last_execution_time,121) SET @Series = SUBSTRING(@Series,1,LEN(@Series)-1) SET @html = '<img src="http://chart.apis.google.com/chart?'+ 'chco=CA3D05,87CEEB&'+ 'chd=t:'+@Series+'&'+ 'chds=1,350&'+ 'chdl= Proc executions from cache&'+ 'chf=bg,s,1F1D1D|c,lg,0,363433,1.0,2E2B2A,0.0&'+ 'chg=25.0,25.0,3,2&'+ 'chls=3|3&'+ 'chm=d,CA3D05,0,-1,12,0|d,FFFFFF,0,-1,8,0|d,87CEEB,1,-1,12,0|d,FFFFFF,1,-1,8,0&'+ 'chs=600x450&'+ 'cht=lc&'+ 'chts=FFFFFF,14&'+ 'chtt=Executions for from' +(SELECT CONVERT(varchar(16),min(last_execution_time),121)          FROM sys.dm_exec_query_stats          WHERE last_execution_time > = getdate()-1) +' till '+ +(SELECT CONVERT(varchar(16),max(last_execution_time),121)     FROM sys.dm_exec_query_stats) + '&'+ 'chxp=1,50.0|4,50.0&'+ 'chxs=0,FFFFFF,12,0|1,FFFFFF,12,0|2,FFFFFF,12,0|3,FFFFFF,12,0|4,FFFFFF,14,0&'+ 'chxt=y,y,x,x,x&'+ 'chxl=0:|1|350|1:|N|2:|'+@HourList+'3:|Hour&'+ 'chma=55,120,0,0" alt="" />' EXEC msdb.dbo.sp_send_dbmail @recipients = '[email protected]', @subject ='Daily number of executions', @body = @html, @body_format = 'HTML' Chart parameters reference: chco    series colors chd        series data chds    scale format chdl    chart legend chf        background fills chg        grid line chls    line style chm        line fill chs        chart size cht        chart type chts    chart style chtt    chart title chxp    axis label positions chxs    axis label styles chxt    axis tick mark styles chxl    axis labels chma    chart margins If you don’t mind to get your charts as an email attachment, you can enjoy the Java based Google Charts which are even easier to configure, and have much more advanced graphics. In the example below, the sp_send_email procedure uses the parameter @query which will be executed at the time that sp_send_dbemail is executed and the HTML result of this execution will be attached to the email. DECLARE @html varchar(max),@query varchar(max) DECLARE @SeriesDBusers  varchar(800);     SET @SeriesDBusers = ''; SELECT @SeriesDBusers = @SeriesDBusers +  ' ["'+DB_NAME(r.database_id) +'", ' +cast(count(1) as varchar)+'],' FROM sys.dm_exec_requests r GROUP BY DB_NAME(database_id) ORDER BY count(1) desc; SET @SeriesDBusers = SUBSTRING(@SeriesDBusers,1,LEN(@SeriesDBusers)-1) SET @query = ' PRINT '' <html>   <head>     <script type="text/javascript" src="https://www.google.com/jsapi"></script>     <script type="text/javascript">       google.load("visualization", "1", {packages:["corechart"]});        google.setOnLoadCallback(drawChart);       function drawChart() {                      var data = google.visualization.arrayToDataTable([                        ["Database Name", "Active users"],                        '+@SeriesDBusers+'                      ]);                        var options = {                        title: "Active users",                        pieSliceText: "value"                      };                        var chart = new google.visualization.PieChart(document.getElementById("chart_div"));                      chart.draw(data, options);       };     </script>   </head>   <body>     <table>     <tr><td>         <div id="chart_div" style='width: 800px; height: 300px;'></div>         </td></tr>     </table>   </body> </html> ''' EXEC msdb.dbo.sp_send_dbmail    @recipients = '[email protected]',    @subject ='Active users',    @body = @html,    @body_format = 'HTML',    @query = @Query,     @attach_query_result_as_file = 1,     @query_attachment_filename = 'Results.htm' After opening the email attachment in the browser you are getting this kind of report: In fact, the above is not only for database alerts. It can be used for applicative reports if you need high levels of customization that you cannot achieve using standard methods like SSRS. If you need more information on how to customize the charts, you can try the following: Image Based Charts wizard https://google-developers.appspot.com/chart/image/docs/chart_wizard  Live Image Charts Playground https://google-developers.appspot.com/chart/image/docs/chart_playground Image Based Charts Parameters List https://google-developers.appspot.com/chart/image/docs/chart_params Java Script Charts Playground https://code.google.com/apis/ajax/playground/?type=visualization Use the above examples as a starting point for your procedures and I’d be more than happy to hear of your implementations of the above techniques. Yours, Maria

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  • PHP inserting Apostrophes where it shouldn't

    - by Jack W-H
    Hi folks Not too sure what's going on here as this doesn't seem like standard practise to me. But basically I have a basic database thingy going on that lets users submit code snippets. They can provide up to 5 tags for their submission. Now I'm still learning so please forgive me if this is obvious! Here's the PHP script that makes it all work (note there may be some CodeIgniter specific functions in there): function submitform() { $this->load->helper(array('form', 'url')); $this->load->library('form_validation'); $this->load->database(); $this->form_validation->set_error_delimiters('<p style="color:#FF0000;">', '</p>'); $this->form_validation->set_rules('title', 'Title', 'trim|required|min_length[5]|max_length[255]|xss_clean'); $this->form_validation->set_rules('summary', 'Summary', 'trim|required|min_length[5]|max_length[255]|xss_clean'); $this->form_validation->set_rules('bbcode', 'Code', 'required|min_length[5]'); // No XSS clean (or <script> tags etc. are gone) $this->form_validation->set_rules('tags', 'Tags', 'trim|xss_clean|required|max_length[254]'); if ($this->form_validation->run() == FALSE) { // Do some stuff if it fails } else { // User's input values $title = $this->db->escape(set_value('title')); $summary = $this->db->escape(set_value('summary')); $code = $this->db->escape(set_value('bbcode')); $tags = $this->db->escape(set_value('tags')); // Stop things like <script> tags working $codesanitised = htmlspecialchars($code); // Other values to be entered $author = $this->tank_auth->get_user_id(); $bi1 = ""; $bi2 = ""; // This long messy bit basically sees which browsers the code is compatible with. if (isset($_POST['IE6'])) {$bi1 .= "IE6, "; $bi2 .= "1, ";} else {$bi1 .= "IE6, "; $bi2 .= "NULL, ";} if (isset($_POST['IE7'])) {$bi1 .= "IE7, "; $bi2 .= "1, ";} else {$bi1 .= "IE7, "; $bi2 .= "NULL, ";} if (isset($_POST['IE8'])) {$bi1 .= "IE8, "; $bi2 .= "1, ";} else {$bi1 .= "IE8, "; $bi2 .= "NULL, ";} if (isset($_POST['FF2'])) {$bi1 .= "FF2, "; $bi2 .= "1, ";} else {$bi1 .= "FF2, "; $bi2 .= "NULL, ";} if (isset($_POST['FF3'])) {$bi1 .= "FF3, "; $bi2 .= "1, ";} else {$bi1 .= "FF3, "; $bi2 .= "NULL, ";} if (isset($_POST['SA3'])) {$bi1 .= "SA3, "; $bi2 .= "1, ";} else {$bi1 .= "SA3, "; $bi2 .= "NULL, ";} if (isset($_POST['SA4'])) {$bi1 .= "SA4, "; $bi2 .= "1, ";} else {$bi1 .= "SA4, "; $bi2 .= "NULL, ";} if (isset($_POST['CHR'])) {$bi1 .= "CHR, "; $bi2 .= "1, ";} else {$bi1 .= "CHR, "; $bi2 .= "NULL, ";} if (isset($_POST['OPE'])) {$bi1 .= "OPE, "; $bi2 .= "1, ";} else {$bi1 .= "OPE, "; $bi2 .= "NULL, ";} if (isset($_POST['OTH'])) {$bi1 .= "OTH, "; $bi2 .= "1, ";} else {$bi1 .= "OTH, "; $bi2 .= "NULL, ";} // $b1 is $bi1 without the last two characters (, ) which would cause a query error $b1 = substr($bi1, 0, -2); $b2 = substr($bi2, 0, -2); // :::::::::::THIS IS WHERE THE IMPORTANT STUFF IS, STACKOVERFLOW READERS:::::::::: // Split up all the words in $tags into individual variables - each tag is seperated with a space $pieces = explode(" ", $tags); // Usage: // echo $pieces[0]; // piece1 etc $ti1 = ""; $ti2 = ""; // Now we'll do similar to what we did with the compatible browsers to generate a bit of a query string if ($pieces[0]!=NULL) {$ti1 .= "tag1, "; $ti2 .= "$pieces[0], ";} else {$ti1 .= "tag1, "; $ti2 .= "NULL, ";} if ($pieces[1]!=NULL) {$ti1 .= "tag2, "; $ti2 .= "$pieces[1], ";} else {$ti1 .= "tag2, "; $ti2 .= "NULL, ";} if ($pieces[2]!=NULL) {$ti1 .= "tag3, "; $ti2 .= "$pieces[2], ";} else {$ti1 .= "tag3, "; $ti2 .= "NULL, ";} if ($pieces[3]!=NULL) {$ti1 .= "tag4, "; $ti2 .= "$pieces[3], ";} else {$ti1 .= "tag4, "; $ti2 .= "NULL, ";} if ($pieces[4]!=NULL) {$ti1 .= "tag5, "; $ti2 .= "$pieces[4], ";} else {$ti1 .= "tag5, "; $ti2 .= "NULL, ";} $t1 = substr($ti1, 0, -2); $t2 = substr($ti2, 0, -2); $sql = "INSERT INTO code (id, title, author, summary, code, date, $t1, $b1) VALUES ('', $title, $author, $summary, $codesanitised, NOW(), $t2, $b2)"; $this->db->query($sql); $this->load->view('subviews/template/headerview'); $this->load->view('subviews/template/menuview'); $this->load->view('subviews/template/sidebar'); $this->load->view('thanksforsubmission'); $this->load->view('subviews/template/footerview'); } } Sorry about that boring drivel of code there. I realise I probably have a few bad practises in there - please point them out if so. This is what the outputted query looks like (it results in an error and isn't queried at all): A Database Error Occurred Error Number: 1136 Column count doesn't match value count at row 1 INSERT INTO code (id, title, author, summary, code, date, tag1, tag2, tag3, tag4, tag5, IE6, IE7, IE8, FF2, FF3, SA3, SA4, CHR, OPE, OTH) VALUES ('', 'test2', 1, 'test2', 'test2 ', NOW(), 'test2, test2, test2, test2, test2', NULL, NULL, 1, 1, 1, 1, 1, 1, 1, NULL) You'll see at the bit after NOW(), 'test2, test2, test2, test2, test2' - I never asked it to put all that in apostrophes. Did I? What I could do is put each of those lines like this: if ($pieces[0]!=NULL) {$ti1 .= "tag1, "; $ti2 .= "'$pieces[0]', ";} else {$ti1 .= "tag1, "; $ti2 .= "NULL, ";} With single quotes around $pieces[0] etc. - but then my problem is that this kinda fails when the user only enters 4 tags, or 3, or whatever. Sorry if that's the worst phrased question in history, I tried, but my brain has turned to mush. Thanks for your help! Jack

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  • Dealing with external processes

    - by Jesse Aldridge
    I've been working on a gui app that needs to manage external processes. Working with external processes leads to a lot of issues that can make a programmer's life difficult. I feel like maintenence on this app is taking an unacceptably long time. I've been trying to list the things that make working with external processes difficult so that I can come up with ways of mitigating the pain. This kind of turned into a rant which I thought I'd post here in order to get some feedback and to provide some guidance to anybody thinking about sailing into these very murky waters. Here's what I've got so far: Output from the child can get mixed up with output from the parent. This can make both outputs misleading and hard to read. It can be hard to tell what came from where. It becomes harder to figure out what's going on when things are asynchronous. Here's a contrived example: import textwrap, os, time from subprocess import Popen test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) proc = Popen('python -B "%s"' % test_path) for i in range(3): print 'Hello %i' % i time.sleep(1) os.remove(test_path) I guess I could have the child process write its output to a file. But it can be annoying to have to open up a file every time I want to see the result of a print statement. If I have code for the child process I could add a label, something like print 'child: Hello %i', but it can be annoying to do that for every print. And it adds some noise to the output. And of course I can't do it if I don't have access to the code. I could manually manage the process output. But then you open up a huge can of worms with threads and polling and stuff like that. A simple solution is to treat processes like synchronous functions, that is, no further code executes until the process completes. In other words, make the process block. But that doesn't work if you're building a gui app. Which brings me to the next problem... Blocking processes cause the gui to become unresponsive. import textwrap, sys, os from subprocess import Popen from PyQt4.QtGui import * from PyQt4.QtCore import * test_path = 'test_file.py' with open(test_path, 'w') as file: file.write(textwrap.dedent(''' import time for i in range(3): print 'Hello %i' % i time.sleep(1)''')) app = QApplication(sys.argv) button = QPushButton('Launch process') def launch_proc(): # Can't move the window until process completes proc = Popen('python -B "%s"' % test_path) proc.communicate() button.connect(button, SIGNAL('clicked()'), launch_proc) button.show() app.exec_() os.remove(test_path) Qt provides a process wrapper of its own called QProcess which can help with this. You can connect functions to signals to capture output relatively easily. This is what I'm currently using. But I'm finding that all these signals behave suspiciously like goto statements and can lead to spaghetti code. I think I want to get sort-of blocking behavior by having the 'finished' signal from QProcess call a function containing all the code that comes after the process call. I think that should work but I'm still a bit fuzzy on the details... Stack traces get interrupted when you go from the child process back to the parent process. If a normal function screws up, you get a nice complete stack trace with filenames and line numbers. If a subprocess screws up, you'll be lucky if you get any output at all. You end up having to do a lot more detective work everytime something goes wrong. Speaking of which, output has a way of disappearing when dealing external processes. Like if you run something via the windows 'cmd' command, the console will pop up, execute the code, and then disappear before you have a chance to see the output. You have to pass the /k flag to make it stick around. Similar issues seem to crop up all the time. I suppose both problems 3 and 4 have the same root cause: no exception handling. Exception handling is meant to be used with functions, it doesn't work with processes. Maybe there's some way to get something like exception handling for processes? I guess that's what stderr is for? But dealing with two different streams can be annoying in itself. Maybe I should look into this more... Processes can hang and stick around in the background without you realizing it. So you end up yelling at your computer cuz it's going so slow until you finally bring up your task manager and see 30 instances of the same process hanging out in the background. Also, hanging background processes can interefere with other instances of the process in various fun ways, such as causing permissions errors by holding a handle to a file or someting like that. It seems like an easy solution to this would be to have the parent process kill the child process on exit if the child process didn't close itself. But if the parent process crashes, cleanup code might not get called and the child can be left hanging. Also, if the parent waits for the child to complete, and the child is in an infinite loop or something, you can end up with two hanging processes. This problem can tie in to problem 2 for extra fun, causing your gui to stop responding entirely and force you to kill everything with the task manager. F***ing quotes Parameters often need to be passed to processes. This is a headache in itself. Especially if you're dealing with file paths. Say... 'C:/My Documents/whatever/'. If you don't have quotes, the string will often be split at the space and interpreted as two arguments. If you need nested quotes you can use ' and ". But if you need to use more than two layers of quotes, you have to do some nasty escaping, for example: "cmd /k 'python \'path 1\' \'path 2\''". A good solution to this problem is passing parameters as a list rather than as a single string. Subprocess allows you to do this. Can't easily return data from a subprocess. You can use stdout of course. But what if you want to throw a print in there for debugging purposes? That's gonna screw up the parent if it's expecting output formatted a certain way. In functions you can print one string and return another and everything works just fine. Obscure command-line flags and a crappy terminal based help system. These are problems I often run into when using os level apps. Like the /k flag I mentioned, for holding a cmd window open, who's idea was that? Unix apps don't tend to be much friendlier in this regard. Hopefully you can use google or StackOverflow to find the answer you need. But if not, you've got a lot of boring reading and frusterating trial and error to do. External factors. This one's kind of fuzzy. But when you leave the relatively sheltered harbor of your own scripts to deal with external processes you find yourself having to deal with the "outside world" to a much greater extent. And that's a scary place. All sorts of things can go wrong. Just to give a random example: the cwd in which a process is run can modify it's behavior. There are probably other issues, but those are the ones I've written down so far. Any other snags you'd like to add? Any suggestions for dealing with these problems?

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  • Little more help with writing a o buffer with libjpeg

    - by Richard Knop
    So I have managed to find another question discussing how to use the libjpeg to compress an image to jpeg. I have found this code which is supposed to work: Compressing IplImage to JPEG using libjpeg in OpenCV Here's the code (it compiles ok): /* This a custom destination manager for jpeglib that enables the use of memory to memory compression. See IJG documentation for details. */ typedef struct { struct jpeg_destination_mgr pub; /* base class */ JOCTET* buffer; /* buffer start address */ int bufsize; /* size of buffer */ size_t datasize; /* final size of compressed data */ int* outsize; /* user pointer to datasize */ int errcount; /* counts up write errors due to buffer overruns */ } memory_destination_mgr; typedef memory_destination_mgr* mem_dest_ptr; /* ------------------------------------------------------------- */ /* MEMORY DESTINATION INTERFACE METHODS */ /* ------------------------------------------------------------- */ /* This function is called by the library before any data gets written */ METHODDEF(void) init_destination (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->pub.next_output_byte = dest->buffer; /* set destination buffer */ dest->pub.free_in_buffer = dest->bufsize; /* input buffer size */ dest->datasize = 0; /* reset output size */ dest->errcount = 0; /* reset error count */ } /* This function is called by the library if the buffer fills up I just reset destination pointer and buffer size here. Note that this behavior, while preventing seg faults will lead to invalid output streams as data is over- written. */ METHODDEF(boolean) empty_output_buffer (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->pub.next_output_byte = dest->buffer; dest->pub.free_in_buffer = dest->bufsize; ++dest->errcount; /* need to increase error count */ return TRUE; } /* Usually the library wants to flush output here. I will calculate output buffer size here. Note that results become incorrect, once empty_output_buffer was called. This situation is notified by errcount. */ METHODDEF(void) term_destination (j_compress_ptr cinfo) { mem_dest_ptr dest = (mem_dest_ptr)cinfo->dest; dest->datasize = dest->bufsize - dest->pub.free_in_buffer; if (dest->outsize) *dest->outsize += (int)dest->datasize; } /* Override the default destination manager initialization provided by jpeglib. Since we want to use memory-to-memory compression, we need to use our own destination manager. */ GLOBAL(void) jpeg_memory_dest (j_compress_ptr cinfo, JOCTET* buffer, int bufsize, int* outsize) { mem_dest_ptr dest; /* first call for this instance - need to setup */ if (cinfo->dest == 0) { cinfo->dest = (struct jpeg_destination_mgr *) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, sizeof (memory_destination_mgr)); } dest = (mem_dest_ptr) cinfo->dest; dest->bufsize = bufsize; dest->buffer = buffer; dest->outsize = outsize; /* set method callbacks */ dest->pub.init_destination = init_destination; dest->pub.empty_output_buffer = empty_output_buffer; dest->pub.term_destination = term_destination; } /* ------------------------------------------------------------- */ /* MEMORY SOURCE INTERFACE METHODS */ /* ------------------------------------------------------------- */ /* Called before data is read */ METHODDEF(void) init_source (j_decompress_ptr dinfo) { /* nothing to do here, really. I mean. I'm not lazy or something, but... we're actually through here. */ } /* Called if the decoder wants some bytes that we cannot provide... */ METHODDEF(boolean) fill_input_buffer (j_decompress_ptr dinfo) { /* we can't do anything about this. This might happen if the provided buffer is either invalid with regards to its content or just a to small bufsize has been given. */ /* fail. */ return FALSE; } /* From IJG docs: "it's not clear that being smart is worth much trouble" So I save myself some trouble by ignoring this bit. */ METHODDEF(void) skip_input_data (j_decompress_ptr dinfo, INT32 num_bytes) { /* There might be more data to skip than available in buffer. This clearly is an error, so screw this mess. */ if ((size_t)num_bytes > dinfo->src->bytes_in_buffer) { dinfo->src->next_input_byte = 0; /* no buffer byte */ dinfo->src->bytes_in_buffer = 0; /* no input left */ } else { dinfo->src->next_input_byte += num_bytes; dinfo->src->bytes_in_buffer -= num_bytes; } } /* Finished with decompression */ METHODDEF(void) term_source (j_decompress_ptr dinfo) { /* Again. Absolute laziness. Nothing to do here. Boring. */ } GLOBAL(void) jpeg_memory_src (j_decompress_ptr dinfo, unsigned char* buffer, size_t size) { struct jpeg_source_mgr* src; /* first call for this instance - need to setup */ if (dinfo->src == 0) { dinfo->src = (struct jpeg_source_mgr *) (*dinfo->mem->alloc_small) ((j_common_ptr) dinfo, JPOOL_PERMANENT, sizeof (struct jpeg_source_mgr)); } src = dinfo->src; src->next_input_byte = buffer; src->bytes_in_buffer = size; src->init_source = init_source; src->fill_input_buffer = fill_input_buffer; src->skip_input_data = skip_input_data; src->term_source = term_source; /* IJG recommend to use their function - as I don't know **** about how to do better, I follow this recommendation */ src->resync_to_restart = jpeg_resync_to_restart; } All I need to do is replace the jpeg_stdio_dest in my program with this code: int numBytes = 0; //size of jpeg after compression char * storage = new char[150000]; //storage buffer JOCTET *jpgbuff = (JOCTET*)storage; //JOCTET pointer to buffer jpeg_memory_dest(&cinfo,jpgbuff,150000,&numBytes); So I need some help to incorporate the above four lines into this function which now works but writes to a file instead of a memory: int write_jpeg_file( char *filename ) { struct jpeg_compress_struct cinfo; struct jpeg_error_mgr jerr; /* this is a pointer to one row of image data */ JSAMPROW row_pointer[1]; FILE *outfile = fopen( filename, "wb" ); if ( !outfile ) { printf("Error opening output jpeg file %s\n!", filename ); return -1; } cinfo.err = jpeg_std_error( &jerr ); jpeg_create_compress(&cinfo); jpeg_stdio_dest(&cinfo, outfile); /* Setting the parameters of the output file here */ cinfo.image_width = width; cinfo.image_height = height; cinfo.input_components = bytes_per_pixel; cinfo.in_color_space = color_space; /* default compression parameters, we shouldn't be worried about these */ jpeg_set_defaults( &cinfo ); /* Now do the compression .. */ jpeg_start_compress( &cinfo, TRUE ); /* like reading a file, this time write one row at a time */ while( cinfo.next_scanline < cinfo.image_height ) { row_pointer[0] = &raw_image[ cinfo.next_scanline * cinfo.image_width * cinfo.input_components]; jpeg_write_scanlines( &cinfo, row_pointer, 1 ); } /* similar to read file, clean up after we're done compressing */ jpeg_finish_compress( &cinfo ); jpeg_destroy_compress( &cinfo ); fclose( outfile ); /* success code is 1! */ return 1; } Anybody could help me out a bit with it? I've tried meddling with it but I am not sure how to do it. I I just replace this line: jpeg_stdio_dest(&cinfo, outfile); It's not going to work. There is more stuff that needs to be changed a bit in that function and I am being a little lost from all those pointers and memory management.

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  • Silverlight for Windows Embedded tutorial (step 4)

    - by Valter Minute
    I’m back with my Silverlight for Windows Embedded tutorial. Sorry for the long delay between step 3 and step 4, the MVP summit and some work related issue prevented me from working on the tutorial during the last weeks. In our first,  second and third tutorial steps we implemented some very simple applications, just to understand the basic structure of a Silverlight for Windows Embedded application, learn how to handle events and how to operate on images. In this third step our sample application will be slightly more complicated, to introduce two new topics: list boxes and custom control. We will also learn how to create controls at runtime. I choose to explain those topics together and provide a sample a bit more complicated than usual just to start to give the feeling of how a “real” Silverlight for Windows Embedded application is organized. As usual we can start using Expression Blend to define our main page. In this case we will have a listbox and a textblock. Here’s the XAML code: <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="ListDemo.Page" Width="640" Height="480" x:Name="ListPage" xmlns:ListDemo="clr-namespace:ListDemo">   <Grid x:Name="LayoutRoot" Background="White"> <ListBox Margin="19,57,19,66" x:Name="FileList" SelectionChanged="Filelist_SelectionChanged"/> <TextBlock Height="35" Margin="19,8,19,0" VerticalAlignment="Top" TextWrapping="Wrap" x:Name="CurrentDir" Text="TextBlock" FontSize="20"/> </Grid> </UserControl> In our listbox we will load a list of directories, starting from the filesystem root (there are no drives in Windows CE, the filesystem has a single root named “\”). When the user clicks on an item inside the list, the corresponding directory path will be displayed in the TextBlock object and the subdirectories of the selected branch will be shown inside the list. As you can see we declared an event handler for the SelectionChanged event of our listbox. We also used a different font size for the TextBlock, to make it more readable. XAML and Expression Blend allow you to customize your UI pretty heavily, experiment with the tools and discover how you can completely change the aspect of your application without changing a single line of code! Inside our ListBox we want to insert the directory presenting a nice icon and their name, just like you are used to see them inside Windows 7 file explorer, for example. To get this we will define a user control. This is a custom object that will behave like “regular” Silverlight for Windows Embedded objects inside our application. First of all we have to define the look of our custom control, named DirectoryItem, using XAML: <UserControl xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="ListDemo.DirectoryItem" Width="500" Height="80">   <StackPanel x:Name="LayoutRoot" Orientation="Horizontal"> <Canvas Width="31.6667" Height="45.9583" Margin="10,10,10,10" RenderTransformOrigin="0.5,0.5"> <Canvas.RenderTransform> <TransformGroup> <ScaleTransform/> <SkewTransform/> <RotateTransform Angle="-31.27"/> <TranslateTransform/> </TransformGroup> </Canvas.RenderTransform> <Rectangle Width="31.6667" Height="45.8414" Canvas.Left="0" Canvas.Top="0.116943" Stretch="Fill"> <Rectangle.Fill> <LinearGradientBrush StartPoint="0.142631,0.75344" EndPoint="1.01886,0.75344"> <LinearGradientBrush.RelativeTransform> <TransformGroup> <SkewTransform CenterX="0.142631" CenterY="0.75344" AngleX="19.3128" AngleY="0"/> <RotateTransform CenterX="0.142631" CenterY="0.75344" Angle="-35.3436"/> </TransformGroup> </LinearGradientBrush.RelativeTransform> <LinearGradientBrush.GradientStops> <GradientStop Color="#FF7B6802" Offset="0"/> <GradientStop Color="#FFF3D42C" Offset="1"/> </LinearGradientBrush.GradientStops> </LinearGradientBrush> </Rectangle.Fill> </Rectangle> <Rectangle Width="29.8441" Height="43.1517" Canvas.Left="0.569519" Canvas.Top="1.05249" Stretch="Fill"> <Rectangle.Fill> <LinearGradientBrush StartPoint="0.142632,0.753441" EndPoint="1.01886,0.753441"> <LinearGradientBrush.RelativeTransform> <TransformGroup> <SkewTransform CenterX="0.142632" CenterY="0.753441" AngleX="19.3127" AngleY="0"/> <RotateTransform CenterX="0.142632" CenterY="0.753441" Angle="-35.3437"/> </TransformGroup> </LinearGradientBrush.RelativeTransform> <LinearGradientBrush.GradientStops> <GradientStop Color="#FFCDCDCD" Offset="0.0833333"/> <GradientStop Color="#FFFFFFFF" Offset="1"/> </LinearGradientBrush.GradientStops> </LinearGradientBrush> </Rectangle.Fill> </Rectangle> <Rectangle Width="29.8441" Height="43.1517" Canvas.Left="0.455627" Canvas.Top="2.28036" Stretch="Fill"> <Rectangle.Fill> <LinearGradientBrush StartPoint="0.142631,0.75344" EndPoint="1.01886,0.75344"> <LinearGradientBrush.RelativeTransform> <TransformGroup> <SkewTransform CenterX="0.142631" CenterY="0.75344" AngleX="19.3128" AngleY="0"/> <RotateTransform CenterX="0.142631" CenterY="0.75344" Angle="-35.3436"/> </TransformGroup> </LinearGradientBrush.RelativeTransform> <LinearGradientBrush.GradientStops> <GradientStop Color="#FFCDCDCD" Offset="0.0833333"/> <GradientStop Color="#FFFFFFFF" Offset="1"/> </LinearGradientBrush.GradientStops> </LinearGradientBrush> </Rectangle.Fill> </Rectangle> <Rectangle Width="29.8441" Height="43.1517" Canvas.Left="0.455627" Canvas.Top="1.34485" Stretch="Fill"> <Rectangle.Fill> <LinearGradientBrush StartPoint="0.142631,0.75344" EndPoint="1.01886,0.75344"> <LinearGradientBrush.RelativeTransform> <TransformGroup> <SkewTransform CenterX="0.142631" CenterY="0.75344" AngleX="19.3128" AngleY="0"/> <RotateTransform CenterX="0.142631" CenterY="0.75344" Angle="-35.3436"/> </TransformGroup> </LinearGradientBrush.RelativeTransform> <LinearGradientBrush.GradientStops> <GradientStop Color="#FFCDCDCD" Offset="0.0833333"/> <GradientStop Color="#FFFFFFFF" Offset="1"/> </LinearGradientBrush.GradientStops> </LinearGradientBrush> </Rectangle.Fill> </Rectangle> <Rectangle Width="26.4269" Height="45.8414" Canvas.Left="0.227798" Canvas.Top="0" Stretch="Fill"> <Rectangle.Fill> <LinearGradientBrush StartPoint="0.142631,0.75344" EndPoint="1.01886,0.75344"> <LinearGradientBrush.RelativeTransform> <TransformGroup> <SkewTransform CenterX="0.142631" CenterY="0.75344" AngleX="19.3127" AngleY="0"/> <RotateTransform CenterX="0.142631" CenterY="0.75344" Angle="-35.3436"/> </TransformGroup> </LinearGradientBrush.RelativeTransform> <LinearGradientBrush.GradientStops> <GradientStop Color="#FF7B6802" Offset="0"/> <GradientStop Color="#FFF3D42C" Offset="1"/> </LinearGradientBrush.GradientStops> </LinearGradientBrush> </Rectangle.Fill> </Rectangle> <Rectangle Width="1.25301" Height="45.8414" Canvas.Left="1.70862" Canvas.Top="0.116943" Stretch="Fill" Fill="#FFEBFF07"/> </Canvas> <TextBlock Height="80" x:Name="Name" Width="448" TextWrapping="Wrap" VerticalAlignment="Center" FontSize="24" Text="Directory"/> </StackPanel> </UserControl> As you can see, this XAML contains many graphic elements. Those elements are used to design the folder icon. The original drawing has been designed in Expression Design and then exported as XAML. In Silverlight for Windows Embedded you can use vector images. This means that your images will look good even when scaled or rotated. In our DirectoryItem custom control we have a TextBlock named Name, that will be used to display….(suspense)…. the directory name (I’m too lazy to invent fancy names for controls, and using “boring” intuitive names will make code more readable, I hope!). Now that we have some XAML code, we may execute XAML2CPP to generate part of the aplication code for us. We should then add references to our XAML2CPP generated resource file and include in our code and add a reference to the XAML runtime library to our sources file (you can follow the instruction of the first tutorial step to do that), To generate the code used in this tutorial you need XAML2CPP ver 1.0.1.0, that is downloadable here: http://geekswithblogs.net/WindowsEmbeddedCookbook/archive/2010/03/08/xaml2cpp-1.0.1.0.aspx We can now create our usual simple Win32 application inside Platform Builder, using the same step described in the first chapter of this tutorial (http://geekswithblogs.net/WindowsEmbeddedCookbook/archive/2009/10/01/silverlight-for-embedded-tutorial.aspx). We can declare a class for our main page, deriving it from the template that XAML2CPP generated for us: class ListPage : public TListPage<ListPage> { ... } We will see the ListPage class code in a short time, but before we will see the code of our DirectoryItem user control. This object will be used to populate our list, one item for each directory. To declare a user control things are a bit more complicated (but also in this case XAML2CPP will write most of the “boilerplate” code for use. To interact with a user control you should declare an interface. An interface defines the functions of a user control that can be called inside the application code. Our custom control is currently quite simple and we just need some member functions to store and retrieve a full pathname inside our control. The control will display just the last part of the path inside the control. An interface is declared as a C++ class that has only abstract virtual members. It should also have an UUID associated with it. UUID means Universal Unique IDentifier and it’s a 128 bit number that will identify our interface without the need of specifying its fully qualified name. UUIDs are used to identify COM interfaces and, as we discovered in chapter one, Silverlight for Windows Embedded is based on COM or, at least, provides a COM-like Application Programming Interface (API). Here’s the declaration of the DirectoryItem interface: class __declspec(novtable,uuid("{D38C66E5-2725-4111-B422-D75B32AA8702}")) IDirectoryItem : public IXRCustomUserControl { public:   virtual HRESULT SetFullPath(BSTR fullpath) = 0; virtual HRESULT GetFullPath(BSTR* retval) = 0; }; The interface is derived from IXRCustomControl, this will allow us to add our object to a XAML tree. It declares the two functions needed to set and get the full path, but don’t implement them. Implementation will be done inside the control class. The interface only defines the functions of our control class that are accessible from the outside. It’s a sort of “contract” between our control and the applications that will use it. We must support what’s inside the contract and the application code should know nothing else about our own control. To reference our interface we will use the UUID, to make code more readable we can declare a #define in this way: #define IID_IDirectoryItem __uuidof(IDirectoryItem) Silverlight for Windows Embedded objects (like COM objects) use a reference counting mechanism to handle object destruction. Every time you store a pointer to an object you should call its AddRef function and every time you no longer need that pointer you should call Release. The object keeps an internal counter, incremented for each AddRef and decremented on Release. When the counter reaches 0, the object is destroyed. Managing reference counting in our code can be quite complicated and, since we are lazy (I am, at least!), we will use a great feature of Silverlight for Windows Embedded: smart pointers.A smart pointer can be connected to a Silverlight for Windows Embedded object and manages its reference counting. To declare a smart pointer we must use the XRPtr template: typedef XRPtr<IDirectoryItem> IDirectoryItemPtr; Now that we have defined our interface, it’s time to implement our user control class. XAML2CPP has implemented a class for us, and we have only to derive our class from it, defining the main class and interface of our new custom control: class DirectoryItem : public DirectoryItemUserControlRegister<DirectoryItem,IDirectoryItem> { ... } XAML2CPP has generated some code for us to support the user control, we don’t have to mind too much about that code, since it will be generated (or written by hand, if you like) always in the same way, for every user control. But knowing how does this works “under the hood” is still useful to understand the architecture of Silverlight for Windows Embedded. Our base class declaration is a bit more complex than the one we used for a simple page in the previous chapters: template <class A,class B> class DirectoryItemUserControlRegister : public XRCustomUserControlImpl<A,B>,public TDirectoryItem<A,XAML2CPPUserControl> { ... } This class derives from the XAML2CPP generated template class, like the ListPage class, but it uses XAML2CPPUserControl for the implementation of some features. This class shares the same ancestor of XAML2CPPPage (base class for “regular” XAML pages), XAML2CPPBase, implements binding of member variables and event handlers but, instead of loading and creating its own XAML tree, it attaches to an existing one. The XAML tree (and UI) of our custom control is created and loaded by the XRCustomUserControlImpl class. This class is part of the Silverlight for Windows Embedded framework and implements most of the functions needed to build-up a custom control in Silverlight (the guys that developed Silverlight for Windows Embedded seem to care about lazy programmers!). We have just to initialize it, providing our class (DirectoryItem) and interface (IDirectoryItem). Our user control class has also a static member: protected:   static HINSTANCE hInstance; This is used to store the HINSTANCE of the modules that contain our user control class. I don’t like this implementation, but I can’t find a better one, so if somebody has good ideas about how to handle the HINSTANCE object, I’ll be happy to hear suggestions! It also implements two static members required by XRCustomUserControlImpl. The first one is used to load the XAML UI of our custom control: static HRESULT GetXamlSource(XRXamlSource* pXamlSource) { pXamlSource->SetResource(hInstance,TEXT("XAML"),IDR_XAML_DirectoryItem); return S_OK; }   It initializes a XRXamlSource object, connecting it to the XAML resource that XAML2CPP has included in our resource script. The other method is used to register our custom control, allowing Silverlight for Windows Embedded to create it when it load some XAML or when an application creates a new control at runtime (more about this later): static HRESULT Register() { return XRCustomUserControlImpl<A,B>::Register(__uuidof(B), L"DirectoryItem", L"clr-namespace:DirectoryItemNamespace"); } To register our control we should provide its interface UUID, the name of the corresponding element in the XAML tree and its current namespace (namespaces compatible with Silverlight must use the “clr-namespace” prefix. We may also register additional properties for our objects, allowing them to be loaded and saved inside XAML. In this case we have no permanent properties and the Register method will just register our control. An additional static method is implemented to allow easy registration of our custom control inside our application WinMain function: static HRESULT RegisterUserControl(HINSTANCE hInstance) { DirectoryItemUserControlRegister::hInstance=hInstance; return DirectoryItemUserControlRegister<A,B>::Register(); } Now our control is registered and we will be able to create it using the Silverlight for Windows Embedded runtime functions. But we need to bind our members and event handlers to have them available like we are used to do for other XAML2CPP generated objects. To bind events and members we need to implement the On_Loaded function: virtual HRESULT OnLoaded(__in IXRDependencyObject* pRoot) { HRESULT retcode; IXRApplicationPtr app; if (FAILED(retcode=GetXRApplicationInstance(&app))) return retcode; return ((A*)this)->Init(pRoot,hInstance,app); } This function will call the XAML2CPPUserControl::Init member that will connect the “root” member with the XAML sub tree that has been created for our control and then calls BindObjects and BindEvents to bind members and events to our code. Now we can go back to our application code (the code that you’ll have to actually write) to see the contents of our DirectoryItem class: class DirectoryItem : public DirectoryItemUserControlRegister<DirectoryItem,IDirectoryItem> { protected:   WCHAR fullpath[_MAX_PATH+1];   public:   DirectoryItem() { *fullpath=0; }   virtual HRESULT SetFullPath(BSTR fullpath) { wcscpy_s(this->fullpath,fullpath);   WCHAR* p=fullpath;   for(WCHAR*q=wcsstr(p,L"\\");q;p=q+1,q=wcsstr(p,L"\\")) ;   Name->SetText(p); return S_OK; }   virtual HRESULT GetFullPath(BSTR* retval) { *retval=SysAllocString(fullpath); return S_OK; } }; It’s pretty easy and contains a fullpath member (used to store that path of the directory connected with the user control) and the implementation of the two interface members that can be used to set and retrieve the path. The SetFullPath member parses the full path and displays just the last branch directory name inside the “Name” TextBlock object. As you can see, implementing a user control in Silverlight for Windows Embedded is not too complex and using XAML also for the UI of the control allows us to re-use the same mechanisms that we learnt and used in the previous steps of our tutorial. Now let’s see how the main page is managed by the ListPage class. class ListPage : public TListPage<ListPage> { protected:   // current path TCHAR curpath[_MAX_PATH+1]; It has a member named “curpath” that is used to store the current directory. It’s initialized inside the constructor: ListPage() { *curpath=0; } And it’s value is displayed inside the “CurrentDir” TextBlock inside the initialization function: virtual HRESULT Init(HINSTANCE hInstance,IXRApplication* app) { HRESULT retcode;   if (FAILED(retcode=TListPage<ListPage>::Init(hInstance,app))) return retcode;   CurrentDir->SetText(L"\\"); return S_OK; } The FillFileList function is used to enumerate subdirectories of the current dir and add entries for each one inside the list box that fills most of the client area of our main page: HRESULT FillFileList() { HRESULT retcode; IXRItemCollectionPtr items; IXRApplicationPtr app;   if (FAILED(retcode=GetXRApplicationInstance(&app))) return retcode; // retrieves the items contained in the listbox if (FAILED(retcode=FileList->GetItems(&items))) return retcode;   // clears the list if (FAILED(retcode=items->Clear())) return retcode;   // enumerates files and directory in the current path WCHAR filemask[_MAX_PATH+1];   wcscpy_s(filemask,curpath); wcscat_s(filemask,L"\\*.*");   WIN32_FIND_DATA finddata; HANDLE findhandle;   findhandle=FindFirstFile(filemask,&finddata);   // the directory is empty? if (findhandle==INVALID_HANDLE_VALUE) return S_OK;   do { if (finddata.dwFileAttributes&=FILE_ATTRIBUTE_DIRECTORY) { IXRListBoxItemPtr listboxitem;   // add a new item to the listbox if (FAILED(retcode=app->CreateObject(IID_IXRListBoxItem,&listboxitem))) { FindClose(findhandle); return retcode; }   if (FAILED(retcode=items->Add(listboxitem,NULL))) { FindClose(findhandle); return retcode; }   IDirectoryItemPtr directoryitem;   if (FAILED(retcode=app->CreateObject(IID_IDirectoryItem,&directoryitem))) { FindClose(findhandle); return retcode; }   WCHAR fullpath[_MAX_PATH+1];   wcscpy_s(fullpath,curpath); wcscat_s(fullpath,L"\\"); wcscat_s(fullpath,finddata.cFileName);   if (FAILED(retcode=directoryitem->SetFullPath(fullpath))) { FindClose(findhandle); return retcode; }   XAML2CPPXRValue value((IXRDependencyObject*)directoryitem);   if (FAILED(retcode=listboxitem->SetContent(&value))) { FindClose(findhandle); return retcode; } } } while (FindNextFile(findhandle,&finddata));   FindClose(findhandle); return S_OK; } This functions retrieve a pointer to the collection of the items contained in the directory listbox. The IXRItemCollection interface is used by listboxes and comboboxes and allow you to clear the list (using Clear(), as our function does at the beginning) and change its contents by adding and removing elements. This function uses the FindFirstFile/FindNextFile functions to enumerate all the objects inside our current directory and for each subdirectory creates a IXRListBoxItem object. You can insert any kind of control inside a list box, you don’t need a IXRListBoxItem, but using it will allow you to handle the selected state of an item, highlighting it inside the list. The function creates a list box item using the CreateObject function of XRApplication. The same function is then used to create an instance of our custom control. The function returns a pointer to the control IDirectoryItem interface and we can use it to store the directory full path inside the object and add it as content of the IXRListBox item object, adding it to the listbox contents. The listbox generates an event (SelectionChanged) each time the user clicks on one of the items contained in the listbox. We implement an event handler for that event and use it to change our current directory and repopulate the listbox. The current directory full path will be displayed in the TextBlock: HRESULT Filelist_SelectionChanged(IXRDependencyObject* source,XRSelectionChangedEventArgs* args) { HRESULT retcode;   IXRListBoxItemPtr listboxitem;   if (!args->pAddedItem) return S_OK;   if (FAILED(retcode=args->pAddedItem->QueryInterface(IID_IXRListBoxItem,(void**)&listboxitem))) return retcode;   XRValue content; if (FAILED(retcode=listboxitem->GetContent(&content))) return retcode;   if (content.vType!=VTYPE_OBJECT) return E_FAIL;   IDirectoryItemPtr directoryitem;   if (FAILED(retcode=content.pObjectVal->QueryInterface(IID_IDirectoryItem,(void**)&directoryitem))) return retcode;   content.pObjectVal->Release(); content.pObjectVal=NULL;   BSTR fullpath=NULL;   if (FAILED(retcode=directoryitem->GetFullPath(&fullpath))) return retcode;   CurrentDir->SetText(fullpath);   wcscpy_s(curpath,fullpath); FillFileList(); SysFreeString(fullpath);     return S_OK; } }; The function uses the pAddedItem member of the XRSelectionChangedEventArgs object to retrieve the currently selected item, converts it to a IXRListBoxItem interface using QueryInterface, and then retrives its contents (IDirectoryItem object). Using the GetFullPath method we can get the full path of our selected directory and assing it to the curdir member. A call to FillFileList will update the listbox contents, displaying the list of subdirectories of the selected folder. To build our sample we just need to add code to our WinMain function: int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) { if (!XamlRuntimeInitialize()) return -1;   HRESULT retcode;   IXRApplicationPtr app; if (FAILED(retcode=GetXRApplicationInstance(&app))) return -1;   if (FAILED(retcode=DirectoryItem::RegisterUserControl(hInstance))) return retcode;   ListPage page;   if (FAILED(page.Init(hInstance,app))) return -1;   page.FillFileList();   UINT exitcode;   if (FAILED(page.GetVisualHost()->StartDialog(&exitcode))) return -1;   return 0; } This code is very similar to the one of the WinMains of our previous samples. The main differences are that we register our custom control (you should do that as soon as you have initialized the XAML runtime) and call FillFileList after the initialization of our ListPage object to load the contents of the root folder of our device inside the listbox. As usual you can download the full sample source code from here: http://cid-9b7b0aefe3514dc5.skydrive.live.com/self.aspx/.Public/ListBoxTest.zip

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