No matter what, I can't get this stupid progress bar to update from a thread!
- by Synthetix
I have a Windows app written in C (using gcc/MinGW) that works pretty well except for a few UI problems. One, I simply cannot get the progress bar to update from a thread. In fact, I probably can't get ANY UI stuff to update.
Basically, I have a spawned thread that does some processing, and from that thread I attempt to update the progress bar in the main thread. I tried this by using PostMessage() to the main hwnd, but no luck even though I can do other things like open message boxes. However, it's unclear whether the message box is getting called within the thread or on the main thread.
Here's some code:
//in header/globally accessible
HWND wnd; //main application window
HWND progress_bar; //progress bar
typedef struct { //to pass to thread
DWORD mainThreadId;
HWND mainHwnd;
char *filename;
} THREADSTUFF;
//callback function
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam){
switch(msg){
case WM_CREATE:{
//create progress bar
progress_bar = CreateWindowEx(
0,
PROGRESS_CLASS,
(LPCTSTR)NULL,
WS_CHILD | WS_VISIBLE,
79,164,455,15,
hwnd,
(HMENU)20,
NULL,
NULL);
break;
}
case WM_COMMAND:{
if(LOWORD(wParam)==2){ //do some processing in a thread
//struct of stuff I need to pass to thread
THREADSTUFF *threadStuff;
threadStuff = (THREADSTUFF*)malloc(sizeof(*threadStuff));
threadStuff->mainThreadId = GetCurrentThreadId();
threadStuff->mainHwnd = hwnd;
threadStuff->filename = (void*)&filename;
hThread1 = CreateThread(NULL,0,convertFile (LPVOID)threadStuff,0,NULL);
}else if(LOWORD(wParam)==5){ //update progress bar
MessageBox(hwnd,"I got a message!", "Message", MB_OK | MB_ICONINFORMATION);
PostMessage(progress_bar,PBM_STEPIT,0,CLR_DEFAULT);
}
break;
}
}
}
This all seems to work okay. The problem is in the thread:
DWORD WINAPI convertFile(LPVOID params){
//get passed params, this works perfectly fine
THREADSTUFF *tData = (THREADSTUFF*)params;
MessageBox(tData->mainHwnd,tData->filename,"File name",MB_OK | MB_ICONINFORMATION); //yep
PostThreadMessage(tData->mainThreadId,WM_COMMAND,5,0); //only shows message
PostMessage(tData->mainHwnd,WM_COMMAND,5,0); //only shows message
}
When I say, "only shows message," that means the MessageBox() function in the callback works, but not the PostMessage() to update the position of the progress bar.
What am I missing?
