I have a problem.
I have a VCL application using a thread. This thread does some calculations and calls a MainForm's method through Synchronize(). It all works just fine, I have a "Start" button, which creates and runs the thread and a "Stop" button which stops and frees it. No errors, no nothing.
But for some reason when I close the application and I've run the thread I get a EOSError 1400 - Invalid window handle. I've breakpointed the OnClose procedure and the only thing I do there is saving an ini file, no error in that, when I trace further (using F7), I get to the very end (Application.Run; end.), after "calling" the end. I get the error, so there is no specific line of code raising it.
I hope the question is somewhat clear and I hope it's solvable, because just ignoring the error seems a bit unclean.
Thanks inb4
ANSWER
This error occured to me when the Execute method of a thread was called, it looked like this:
procedure TRunThread.Execute;
var (...)
begin
while not Terminated do begin
(...)
MainForm.Memo1.Lines.Add('Some text'); // Even though this call worked fine during
//the application running, it caused errors on shutting the app down.
// For acccessing GUI elements, it's necessary to use Synchronize()
(...)
end;
end;
A possible reason is some unsynchronized access to GUI from the thread. You said that the thread does not do it, but without seeing the TRunThread.Execute source code that looks like the best guess.
I had the same problem, error code 5 Access is denied. This turned out to related to a thread started to test an internet connection on an embedded panel (using BeginThread). If the user exits the form (which is testing the internet connection) immediately after displaying the form, the AV occurs.
On my development PC, the internet connection test was successful...and so fast I never saw the problem! After struggling for several hours, I finally tracked it down to this thread and reproduced it by disconnecting my network cable.
The solution was straightforward: When exiting the form (eg. in the FormDestroy event) ensure the thread is definitely not running before continuing.
Related
In my onDisbale() method in my Main class I have a loop which creates and starts new BukkitRunnables.
I'm getting a error in console: org.bukkit.plugin.IllegalPluginAccessException: Plugin attempted to register task while disabled I need to somehow wait in my onDisable() method until all the BukkitRunnables I create in the loop are finished. How to do that?
My code looks like this:
#Override
public void onDisable() {
for (Player p : Bukkit.getOnlinePlayers()) {
new PlayerDataSaverRunnable().runTaskAsynchronously(this);
}
}
The onDisable method is the very last thing that gets called before your plugin is disabled and the server shuts down. So, as the error message says, you unfortunately can't schedule any new tasks in the onDisable function.
You mentioned in a comment that you were trying to write to a file in the plugins folder, and under normal circumstances you'd want to do that asynchronously. But, because onDisable only ever gets called when the server is shut down (or when the entire server is reloaded with /reload), it's perfectly fine to run code here that blocks the main thread and could potentially take a few seconds to run — in the case of a shutdown, by the time this method gets called, all the players will have already been kicked off the server, and so there's no "lag" to complain about. If your plugin is super advanced and has to save a bunch of stuff, I don't think any server owners would complain even if it took 10 or so seconds to disable.
Of course, you would have to be saving something crazy for it to take a whole 10 seconds to save. More than likely, most files will save in just a few milliseconds.
If you're really dead-set on disabling the plugin as fast as possible, you might consider having some async task that runs every 5 minutes or so and auto-saves the files. Then, in onDisable, you could only save files that changed since the auto-saver was last run. That's a good practice anyways, just incase the server crashes or the power goes out and the onDisable method doesn't get a chance to run. But, then again, I would still recommend that you save everything in the onDisable method (that's what I do for all of my plugins, as well), even if it will take a few seconds and block the main thread, just so you can be 100% sure that everything gets saved correctly.
This is in response to dan's (dan^spotify on IRC) offer to take a look at my testcase, but I post it here in case anyone has encountered similar issues.
I'm experiencing a problem with libspotify where the application crashes (memory access violation) in both of these two scenarios:
the first sp_session_process_events (triggered by notify main thread callback) that's called after the sp_session_logout() function is called crashes the application
skipping logout and calling sp_session_release() crashes the application
I've applied sufficient synchronization from the session callbacks, and I'm otherwise operating on a single thread.
I've made a small testcase that does the following:
Creates session
Logs in
Waits 10 seconds
Attempts to logout, upon which it crashes (when calling sp_session_process_events())
If it were successful in logging out (which it isn't), would call sp_session_release()
I made a Gist for the testcase. It can be found here: https://gist.github.com/4496396
The test case is made using Qt (which is what I'm using for my project), so you'd need Qt 5 to compile it. I've also only written it with Windows and Linux in mind (don't have Mac). Assuming you have Qt 5 and Qt Creator installed, the instructions are as follows:
Download the gist
Copy the libspotify folder into the same folder as the .pro file
Copy your appkey.c file into the same folder
Edit main.cpp to login with your username and password
Edit line 38-39 in sessiontest.cpp and set the cache and settings path to your liking
Open up the .pro file and run from Qt Creator
I'd be very grateful if someone could tell me what I'm doing wrong, as I've spent so many hours trying anything I could think of or just staring at it, and I fear I've gone blind to my own mistakes by now.
I've tested it on both Windows 7 and Linux Ubuntu 12.10, and I've found some difference in behavior:
On Windows, the testcase crashes invariably regardless of settings and cache paths.
On Linux, if setting settings and cache to "" (empty string), logging out and releasing the session works fine.
On Linux, if paths are anything else, the first run (when folder does not already exist) logs out and releases session as it should, but on the next run (when folder already exists), it crashes in the exact same way as it does on Windows.
Also, I can report that sp_session_flush_caches() does not cause a crash.
EDIT: Also, hugo___ on IRC was kind enough to test it on OSX for me. He reported no crashes despite running the application several times in a row.
While you very well may be looking at a bug in libspotify, I'd like to point out a possibly redundant call to sp_session_process_events(), from what I gathered from looking at your code.
void SessionTest::processSpotifyEvents()
{
if (m_session == 0)
{
qDebug() << "Process: No session.";
return;
}
int interval = 0;
sp_session_process_events(m_session, &interval);
qDebug() << interval;
m_timerId = startTimer(interval);
}
It seems this code will pickup the interval value and start a timer on that to trigger a subsequent call to event(). However, this code will also call startTimer when interval is 0, which is strictly not necessary, or rather means that the app can go about doing other stuff until it gets a notify_main_thread callback. The docs on startTimer says "If interval is 0, then the timer event occurs once every time there are no more window system events to process.". I'm not sure what that means exactly but it seems like it can produce at least one redundant call to sp_session_process_events().
http://qt-project.org/doc/qt-4.8/qobject.html#startTimer
I notice that you will get a crash on sp_session_release if you have a track playing when you call it.
I have been chasing this issue today. Login/logout works just fine on Mac, but the issue was 100% repeatable as you described on Windows.
By registering empty callbacks for offline_status_updated and credentials_blob_updated, the crash went away. That was a pretty unsatisfying fix, and I wonder if any libspotify developers want to comment on it.
Callbacks registered in my app are:
logged_in
logged_out
notify_main_thread
log_message
offline_status_updated
credentials_blob_updated
I should explicitly point out that I did not try this on the code you supplied. It would be interesting to know if adding those two extra callbacks works for you. Note that the functions I supply do absolutely nothing. They just have to be there and be registered when you create the session.
Adding the following call in your "logged in" libspotify callback seems to fix this crash as detailed in this SO post:
sp_session_playlistcontainer(session);
is it possible to execute a crystal report (TCrpe component) from a Delphi non VCL main thread when Output = toWindow?
I execute reports from a background thread, and when Output is toPrinter or toExport, everything is fine.
I know that creating forms in a
Delphi non VCL main thread generally is a
bad idea.
When a Crystal
Report is executed, and Output=toWindow, the component creates the output
window on its own. So I cannot prevent that the window is created by the background thread.
So is there a clean way to
execute the report in a background
thread, and display the result in a
cleanly created form?
Version: Crystal11VCL7
The following code does not work:
procedure TMyThread.Execute;
var
cr: TCrpe;
begin
inherited;
cr:= TCrpe.Create(nil);
cr.ReportName:= 'C:\TestReport.rpt';
cr.Output:= toWindow;
cr.WindowParent:= Form1; //This is the main form
cr.Execute;
end;
It seems like the report will be created and immediately destroyed afterwards.
When I enter a message loop right after cr.Execute (while true do Application.ProcessMessages; - which is obviously a very bad idea), the report window is shown nicely.
Any idea, how to do it right? Or is it simply not possible? Thanks!
I haven't had any experience with Crystal for many years (thank goodness) but in the absence of any other reply I would consider approaching the problem from a different angle.
What I do is let the report form be created in the main thread - because, as you've said, it's not a good idea to do the VCL stuff in the background - but I generate all report /data/ in a background thread. Once the data is loaded then the thread signals the main form (or whatever) via a windows message and the report goes and connects up to the dataset/datasource.
Initially I display a blank label over the client area of the report window with a message saying something like 'Report loading...' then once the message is received it hides the label and attaches the data. Works really well here and keeps the UI responsive.
Background: I am using OmniThreadLibrary to load batch mode ADO stored procedures in the background. I am doing some slightly dodgy stuff by swapping the connection after opening the SP but that seems to be quite reliable. I'm using PostMessage to send messages back to the calling form and that works in my test applications. Primoz' comms channels work for me, I'm using those for inter-thread comms but for our main application I'm trying to avoid that dependency by using standard PostMessage calls as we do elsewhere in the app.
Problem: Unfortunately when I put this into our main application the PostMessage calls in the thread start failing with 1400:invalid window handle.
I have liberally added extra PostMessage calls and logging code to try to locate the problem, but I'm out of ideas now. The code is boilerplate:
const WM_PW_ADLQUEUEEMPTY = WM_USER + 11;
...
if PostMessage (OwnerHandle, WM_PW_ADLPROGRESS, QueueID, 10) then
pwDebugLog ('TADLQueue.Run WM_PW_ADLPROGRESS send to ' + IntToHex (OwnerHandle, 8) + ' (IsWindow '+BoolToStr(IsWindow(OwnerHandle),true)+') OK for Queue ' + IntToStr (QueueID))
else
pwDebugLog ('TADLQueue.Run WM_PW_ADLPROGRESS send to ' + IntToHex (OwnerHandle, 8) + ' (IsWindow '+BoolToStr(IsWindow(OwnerHandle),true)+') failed for Queue ' + IntToStr (QueueID));
But the log for a series of calls is not very revealing to me. note that the four hex digits after the time is the thread id from GetCurrentThreadID.
15:41:53.221 1614 TpwAsyncDataLoader.RunQueue WM_PW_ADLPROGRESS send to 00A5110C (IsWindow True) OK for Queue -6
15:41:53.265 13B4 TADLQueue.Run WM_PW_ADLPROGRESS send to 00A5110C (IsWindow True) OK for Queue -6
15:41:53.554 13B4 TADLQueueManager.WriteSysErrorMessageToDatabase Postmessage 00A5110C (IsWindow False) failed with 1400 Invalid window handle
Can anyone shed some light on this? I'm confused at how a window handle can become invalid while I'm looking at it, but that's what it looks like to me.
The one thing I can think of is that the form I'm showing here isn't processing messages and I'm seeing a "message queue full" failure rather than the IsWindow(handle) failure that it looks like. How can I test for that?
There are cases where a handle gets recreated, most notably when you change window flags. This might be what's happening in your application.
All I found so far about recreating windows handle is this post from Allen Bauer but I'm certain reading a more detailed one written by Peter Below. Unfortunatly I can't seem to find that one.
Finally, you need to be aware of cases
where your handle may need to get
recreated. This can happen if the
surrounding form or the parent
component's handle goes through a
recreate process. Up until more recent
releases of Windows, the only way to
change some window flags was to
destroy the handle and recreate with
new flags in the CreateWindowEx()
call. There are many components that
still do this. You know if you're in a
recreate situation by checking
(csRecreating in ControlState).
Edit
Not actually the posts from Peter I had in mind but it might give you some fresh ideas.
The form will not have a handle until
you show it the first time (unless
something in the form load sequence
request the handle) but the handle is
not destroyed when you hide the form
and unless you do something that
forces the form to recreate the
handle, e.g. change its border style
or border icons, or call RecreateWnd
yourself the handle will stay the
same.
It may not be desirable but it cannot
be avoided, at least not the way
Delphi drag&dock is currently
implemented. When you dock the dragged
form to another form it becomes a
control (with WS_CHILD window style)
and that means that its window handle
has to be destroyed and recreated with
the new style. And destroying the
window handle of a container control
automatically destroys the handles for
all child controls as well.
and
There is also the fact that the forms
window handle is destroyed and
recreated when you assign to its
Parent property. This also destroys
and recreates the handles for all
controls on the form.
I had a similar issue (but in VC++2010), and I did not find the solution on any forum, so I post it here, hope this will help:
Issue:
Creating a thread,
Passing the HWnd handle
In the thread, PostMessage
throws a 1400 error (invalid handle), although the pointer was equal
with the handle as seen from UI thread (with GetSafeHWnd()).
Solution:
Do not pass the handle, but the parent CDialog(Ex) class
This class has a m_hWnd member that will do the job
Here is a (Cpp) example, sorry for the cast mess.
// In the worker thread
ThreadParam *threadParam = (ThreadParam*)param
// This is ugly because my pointer is a void *, to avoid one more forward declaration
CCoreGenDlg *dlg = static_cast<CCoreGenDlg *>(threadParam->ptr);
// Post
bool b = PostMessage(dlg->m_hWnd ,1221,0,(LPARAM)message);
Cheers'
recently I started a project which can export some precalculated Grafix/Audio to files, for after processing.
All I was doing is to put a new Window (with progressindicator and an Abort Button) in my main xib and opened it using the following code:
[NSApp beginSheet: REC_Sheet modalForWindow: MOTHER_WINDOW modalDelegate: self didEndSelector: nil contextInfo: nil];
NSModalSession session=[NSApp beginModalSessionForWindow:REC_Sheet];
RECISNOTDONE=YES;
while (RECISNOTDONE) {
if ([NSApp runModalSession:session]!=NSRunContinuesResponse)
break;
usleep(100);
}
[NSApp endModalSession:session];
A Background Thread (pthread) was started earlier, to actually perform the work and save all the targas/wave file. Which worked great, but after an amount of time, it turned out that the main thread was not responding anymore and my memory footprint raised unstoppable. I tried to debug it with Instruments, and saw a lot of CFHash etc stuff growing to infinity.
By accident i clicked below the sheet, and temporary it helped, the main thread (AppKit ?) was releasing it's stuff, but just for a little time.
I can't explain it to me, first of all I thought it was the access from my thread to the Progressbar to update the Progress (intervalled at 0,5sec), so I cut it out. But even if I'm not updating anything and did nothing with the Progressbar, my Application eat up all the Memory, because of not releasing it's "Main-Event" or whatsoever Stuff.
Is there any possibility to "drain" this Main thread Memory stuff (Runloop / NSApp call?). And why the heck doesn't the Main thread respond anymore (after this simple task) ???
I don't have a clou anymore, please help !
Thanks in advance !
P.S. How do you guys implement "threaded long task" Stuff and updating your gui ???
while (RECISNOTDONE) {
if ([NSApp runModalSession:session]!=NSRunContinuesResponse)
break;
usleep(100);
}
Is there a reason you're doing that? A sheet will block its parent window without you having to do anything like this. You can prevent quit within your app delegate.
If you really do need the above code for something, try creating an autorelease pool before sending the runModalSession: message, then draining it after (but before you compare to NSRunContinuesResponse and break).