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.NET Forum / Languages / Managed C++ / June 2005how to create a thread and a modal dialog from a regular dll?
Hi, there, I have a multi-threaded non-MFC program that will include a regular dll which would be part of the user interface, possibly a dialog based interface. I would prefer to have the user interface dll run on its own thread. How to do that? I can't find the answer from the msdn knowledge base. Thanks a lot in advance! Kate >Hi, there, > >I have a multi-threaded non-MFC program that will include a regular dll >which would be part of the user interface, possibly a dialog based interface. >I would prefer to have the user interface dll run on its own thread. How to >do that? I can't find the answer from the msdn knowledge base. Threads and DLLs are separate things; a DLL can start a thread, and a program can call DLL routines from different threads. If I understand what you want to do, it's probably to call a routine in the DLL -- StartMyDllUserInterface(), for instance -- and within that, begin the thread (_beginthreadex) to handle the UI for your DLL. Note that the thread will require its own message loop, and be careful not to update UI elements from multiple threads (this causes deadlocks). Communication back to the main program will depend on what it expects, and whether you're in control of how this works. I would need more details to give definite advice. Also, you may end up with a confusing interface if you expect things like keyboard focus, etc., to work well between the main program and your separate UI thread. -- Phillip Crews aka Severian Microsoft MVP, Windows SDK Posting email address is real, but please post replies on the newsgroup. Thank you very much for your prompt response. It is very helpful to me. Yes, my user interface dll will export a function to the application so that the application can call it to launch the interface. In the function, as you named, StartMyDllUserInterface(MyInterfaceClass*), the appplication will pass a pointer which contains all functions that the UI dll needs to communicate with the application. Most communications are one-way from the interface to the application. The application is like a database to the UI. The interface Dll will also export another function to allow the application to inform the UI of data changes. With the helpful information from your response, I think I need to create a user-interface thread from the exported function "StartMyDllUserInterface". I am going to look more to figure out the details. Any advice will be appreciated. Kate > >Hi, there, > > [quoted text clipped - 26 lines] > Microsoft MVP, Windows SDK > Posting email address is real, but please post replies on the newsgroup. >> >Hi, there, >> > [quoted text clipped - 23 lines] > >Thank you very much for your prompt response. It is very helpful to me. You're quite welcome. >Yes, my user interface dll will export a function to the application so that >the application can call it to launch the interface. In the function, as you >named, StartMyDllUserInterface(MyInterfaceClass*), the appplication will pass >a pointer which contains all functions that the UI dll needs to communicate >with the application. Most communications are one-way from the interface to >the application. The application is like a database to the UI. Be aware that callbacks to the application will be done in the context of your thread! This may have unusual consequences unless the application is carefully designed and written to handle calls from arbitrary threads. >The interface >Dll will also export another function to allow the application to inform the >UI of data changes. Since this function will be called from a different thread than the UI thread, it should only post messages to the UI thread or UI windows. It should not use SendMessage or any UI call that implies SendMessage (i.e., SetWindowText, SetDlgItemText). Otherwise, you could have two threads updating the same UI, which is dangerous and often causes deadlocks. >With the helpful information from your response, I think I need to create a >user-interface thread from the exported function "StartMyDllUserInterface". I >am going to look more to figure out the details. Any advice will be >appreciated. Your UI thread will probably look much like WinMain(); it will need to create a window (or dialog box) and start a message loop. If the main application also has a user interface, you may need to become familiar with such calls as AttachThreadInput(). Here are some articles that may help: http://support.microsoft.com/default.aspx?scid=kb;en-us;90975 http://support.microsoft.com/default.aspx?scid=kb;en-us;97925 and especially: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dndllpro/html/m sdn_winthr.asp -- Phillip Crews aka Severian Microsoft MVP, Windows SDK Posting email address is real, but please post replies on the newsgroup. Thank you! Those references are very good readings. I have learnt quite a lot today! And I have been able to display a dialog box already from the dll. Thanks again, Kate > >> >Hi, there, > >> > [quoted text clipped - 72 lines] > Microsoft MVP, Windows SDK > Posting email address is real, but please post replies on the newsgroup. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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