OK so I have my main window procedure (simplified):
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_CREATE:
{
if(!loadFiles())
SendMessage(hwnd, WM_CLOSE, 0, 0);
}
break;
case WM_CLOSE:
DestroyWindow(hwnd);
return 0;
break;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
loadFiles() is a function to read some text files. If the files are missing, it posts an error message and then returns false. I handle this by sending the WM_CLOSE message, which sends WM_DESTROY? The program calls PostQuitMessage(0) and.. nothing. The process is still sitting in background, now using 100% CPU on core 1. Here is my message loop :
MSG Msg;
while(GetMessage(&Msg, NULL, 0, 0) > 0)
{
TranslateMessage(&Msg);
DispatchMessage(&Msg);
}
return Msg.wParam;
Very simple, I've looked around and seen people using all kinds of different loops, most with PeekMessage() function.. its worth noting I have several child windows containing different controls, I show and hide them when the user selects different tabs, but I don't think it matters because PostQuitMessage(0) is supposed to post WM_QUIT to the message queue, which destroys the child windows aswell right? Any help? Thanks
According to MSDN WM_CREATE is sent during CreateWindow. So you are destroying the window right during creation. I am not sure that this is supposed to work. Also, why so complicated? The documentation says
If an application processes this message, it should return zero to
continue creation of the window. If the application returns –1, the
window is destroyed and the CreateWindowEx or CreateWindow function
returns a NULL handle.
So just return -1 in case loadFiles() fails and handle CreateWindow returning NULL accordingly.
Related
i want to stop my win32 window to be minimized programatically , so I did below but its not working. please let me know any other solution or if i am doing something wrong here.
for testing I am minimizing my window after 2 sec& trying to catch that that and maximize my window again. but its not working as expected.
below is the code.
case WM_SYSCOMMAND:
if ((wParam & 0xFFF0) == SC_MINIMIZE)
{
ShowWindow(hWnd, SW_SHOWMAXIMIZED);
UpdateWindow(hWnd);
}
else
DefWindowProc(hWnd, message, wParam, lParam);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
//show & hide for every 2sec
VOID CALLBACK timerelapsed(HWND hWnd, UINT, UINT_PTR, DWORD)
{
ShowWindow(hWnd, SW_SHOWMINIMIZED);
}
Read the documentation for WM_WINDOWPOSCHANGING. In particular:
An application can prevent changes to the window by setting or clearing the appropriate bits in the flags member of WINDOWPOS.
I viewed many tutorials and posts on this subject, and they all say I pass the class instance pointer (this) in my CreateWindowEx() function, and then store it in the window procedure function, when the WM_NCCREATE message is sent. I guess this is because WM_NCCREATE is supposedly the first message that gets sent to the window procedure since a window is created.
A few questions/notes:
From debugging I came to know that actually WM_GETMINMAXINFO is the first sent message, before WM_NCCREATE (at least on my machine). Does this mean I should listen for this message instead of WM_NCCREATE?
According to this popular article, the reason everyone calls SetWindowLongPtr() after the message WM_NCCREATE is received is because
If the value does not exist by the time WM_NCCREATE is called then,
by some mysterious Windows behavior that I still don't understand, the
value never gets inserted.
I tried to do exactly that (that is, call SetWindowLongPtr() after CreateWindowEx()). It turns out to be just fine. The application runs okay. Below is my code, please tell me if there's something wrong with this approach.
void GLWin32::CreateWindow(...)
{
...
_hwnd = CreateWindowEx(NULL, _wndclassex.lpszClassName, title.c_str(), WS_OVERLAPPEDWINDOW, x, y, width, height, NULL, NULL, _hinstance, NULL);
SetWindowLongPtr(_hwnd, GWL_USERDATA, reinterpret_cast<LONG_PTR>(this));
...
}
//static window procedure for all instances of this class
LRESULT CALLBACK GLWin32::_msgRouter(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
LONG l = GetWindowLongPtr(hwnd, GWLP_USERDATA);
GLWin32* thisPtr = reinterpret_cast<GLWin32*>(l);
if (thisPtr)
return thisPtr->_winProc(msg, wparam, lparam);
else
return DefWindowProc(hwnd, msg, wparam, lparam);
}
LRESULT GLWin32::_winProc(UINT msg, WPARAM wparam, LPARAM lparam)
{
switch (msg)
{
case WM_CLOSE:
{
PostQuitMessage(0);
return 0;
}
}
return DefWindowProc(_hwnd, msg, wparam, lparam);
}
Why is my approach not used instead of the popular approach?
The problem with this approach is that if you want to use the instance when processing any of the window creation messages (including "ordinary" messages that are sent as part of the creation process), you won't have access to it.
Suppose you want to create a button when processing WM_CREATE (typical scenario) and you want to set the button text to some instance member value. You want something like:
LRESULT GLWin32::_winProc(UINT msg, WPARAM wparam, LPARAM lparam)
{
switch (msg)
{
case WM_CREATE:
{
CreateWindow("BUTTON", this->buttonText, WS_VISIBLE | WS_CHILD,
10, 10, 50, 30, this->hwnd, NULL, this->hInstance, NULL);
return 0;
}
}
return DefWindowProc(_hwnd, msg, wparam, lparam);
}
Problem is, when WM_CREATE is processed (before CreateWindowEx returns), SetWindowLongPtr wasn't called yet and the instance pointer is missing, so _winProc isn't being called at all.
This is excerpt from my code based on win32 api:
LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
void __fastcall TMyThread::Execute(void)
{
WNDCLASSEX wc = {0};
wc.cbSize = sizeof(WNDCLASSEX);
wc.lpfnWndProc = WindowProc;
wc.hInstance = GetModuleHandle(NULL);
wc.lpszClassName = class_name.c_str();
if (!RegisterClassEx(&wc))
{
MessageBox(NULL, L"Window Registration Failed!", L"Error", MB_ICONEXCLAMATION | MB_OK);
return;
}
hwnd = CreateWindowEx(0, class_name.c_str(), NULL, 0, 0, 0, 100, 100, HWND_MESSAGE, NULL, wc.hInstance, NULL);
if (hwnd == NULL)
{
MessageBox(NULL, L"Window Creation Failed!", L"Error", MB_ICONEXCLAMATION | MB_OK);
return;
}
MSG msg;
BOOL ret;
while ((ret = GetMessage(&msg, 0, 0, 0)) != 0)
{
if (ret != -1)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
}
My questions:
Is it required to do some resource cleanup after quitting message loop (like CloseHandle for example)? Quite often i am seeing code samples without any such things. Is it correct?
Can newly created window receive messages into thread queue before first call of GetMessage function (we suppose that window was successfully created i.e. function CreateWindowEx returned without errors)?
Please take in mind that TMyThread is not main thread of application. So it can be created and destroyed many times in one application run. Please don't pay attention to quite simplified window creation. This particular window is not meant to be visible on screen. It is created solely for purpose of receiving messages from another application. This is highlighted by using HWND_MESSAGE value of hWndParent parameter when calling CreateWindowEx function.
By creating, running and destroying thread in the above example again and again I have found out that two methods needs to be called after quitting from message loop. First is DestroyWindow and second is UnregisterClass. In regular application DestroyWindow function should be called in WM_CLOSE handler after the user confirms that he really wants to close the application. DestroyWindow function then sends WM_DESTROY and WM_NCDESTROY messages to window. In response to WM_DESTROY message application should call PostQuitMessage(0) function which results to immediately quitting message loop. So this part of code is not neccessary in all scenarios. I needed to call DestroyWindow function explicitly because I exit message loop by simply sending WM_QUIT message. When not doing it sometimes I received error 1412 (ERROR_CLASS_HAS_WINDOWS) when trying to unregister window class.
if (hwnd != NULL)
{
ret = DestroyWindow(hwnd);
if (ret == 0)
{
str.printf(L"Window destroying failed (GetLastError = %d)!", GetLastError());
ShowError(str);
}
hwnd = NULL;
}
ret = UnregisterClass(class_name.c_str(), wc.hInstance);
if (ret == 0)
{
str.printf(L"Window class unregistration failed (GetLastError = %d)!", GetLastError());
ShowError(str);
}
You must be very careful with resources in Win32. Make sure you've looked at the documentation carefully to determine what Windows itself will unload for you and what you have to unload yourself.
For examples, HWNDs will get destroyed as parent HWNDs get destroyed.
The best trick is to attempt to unload everything you've personally created. If you get an error returned from a particular function on unload, you likely should not unload it as it's been unloaded by Windows or some related resource.
It is important not to unload things when it is not necessary, as that could cause a crash.
So for example, an icon created with a window that's directly from a resource likely shouldn't be unloaded. But an HBITMAP you create that you draw to other windows, should most definitely be unloaded.
Your section question can be determined by a quick test with breakpoints. I do not know off the top of my head.
I'm working on a windows application where I'm implementing the whole event loop and everything like that myself (there's a reason for that). In one place, I need to execute some code AFTER a window is shown. Normally, when the window is created, I do some initialisation when WM_CREATE message is received. WM_SHOWWINDOW is sent just BEFORE the window is displayed. However I need to get some code executed right AFTER the window is displayed for the first time. I can't seem to find a notification message sent AFTER the window is shown. Could it be that there isn't one?
Of course, I can keep a boolean - FirstRun - indicating whether or not I had performed my logic, and then execute the code when WM_ACTIVATE is received, provided the boolean is TRUE, then set FirstRun to FALSE so that the code is not execute the next time I am receive WM_ACTIVATE, but this seems somewhat unnatural to me.
It's been ages since I did win32 programming on this level, so can't remember much of it. What is the best approach here?
There is no special notification, but in many cases you can use this trick:
LRESULT CALLBACK MainWndProc(
HWND hwnd, // handle to window
UINT uMsg, // message identifier
WPARAM wParam, // first message parameter
LPARAM lParam) // second message parameter
{
switch (uMsg)
{
case WM_USER + 100:
//window is just displayed, do some actions
return DefWindowProc(hwnd, uMsg, wParam, lParam);
case WM_CREATE:
PostMessage(hwnd, WM_USER + 100, 0, 0);
return DefWindowProc(hwnd, uMsg, wParam, lParam);
default:
return DefWindowProc(hwnd, uMsg, wParam, lParam);
}
return 0;
}
There isn't one because that's what WM_SHOWWINDOW is for. Once that mesage is passed to the default message handling procedure, the window will be shown. The best thing you could do is poll with IsWindowVisible via some sort of timer.
Your program design seems flawed though to have to rely on something like this. What are you trying to do?
As long as you are implementing the whole event loop and everything like that yourself, you can handle this directly in WinMain() like this:
HWND hWnd = CreateWindow(...);
if (!hWnd) return 0;
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
OnWindowJustDisplayed(); // here
MSG msg;
while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
I created a window with the following flags to overlay a d3d application:
WS_EX_TOPMOST | WS_EX_COMPOSITED | WS_EX_TRANSPARENT | WS_EX_LAYERED
I proceeded with colorkeying the window for transperacy and all worked well.
However once I began drawing on it using GDI an unforeseen problem occurred:
For some reason the mouse events (especially movement) are not passed correctly through the window when WM_PAINT is in progress, and so it appears as though the mouse and the keyboard for that matter lag. the FPS is fine, this is some API problem, I suspect that for some reason the keyboard/mouse messages are not handled as they should while the WM_PAINT is in progress, because the slower the timer is set to the less jerking there is.
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
switch(msg)
{
case WM_DESTROY:
{
KillTimer(hwnd, ID_TIMER);
PostQuitMessage(0);
break;
}
case WM_CREATE:
{
SetTimer(hwnd, ID_TIMER, 10, NULL);
break;
}
case WM_TIMER:
{
InvalidateRect(hwnd, 0, 1);
break;
}
case WM_PAINT:
{
paint(hwnd);
break;
}
}
return DefWindowProc(hwnd, msg, wParam, lParam);
}
and
void paint (HWND hwnd)
{
PAINTSTRUCT Ps;
HDC hdc = BeginPaint(hwnd, &Ps);
SetBkColor(hdc, RGB(0,0,0));
SetBkMode(hdc, TRANSPARENT);
LOGBRUSH log_brush;
log_brush.lbStyle = BS_NULL;
HBRUSH handle_brush = CreateBrushIndirect(&log_brush);
SelectObject(hdc, handle_brush);
..........................................
DeleteObject(font);
DeleteObject(pen);
DeleteObject(handle_brush);
EndPaint(hwnd, &Ps);
}
Thank you for any help you may be able to give.
WM_PAINT messages are never delivered to your window unless someone calls UpdateWindow or there are no keyboard or mouse messages in your input queue.
Once you begin processing WM_PAINT, if a keyboard or mouse message arrives, it just sits in your queue until you are done with WM_PAINT. So What you are describing isn't possible.
If your WM_PAINT code takes a long time to execute, that could cause jerkiness, but you say that's not a problem so perhaps it's your handling of WM_ERASEBKGND? I don't see that code, but I do see that when you InvalidateRect, you are passing TRUE as the last parameter which means that you want the background to be erased.
If you don't handle WM_ERASEBKGND, then DefWindowProc will do it for you erasing your entire window with the brush from from your window class. This could result in windows thinking that no part of your window is transparent.
If you want mouse messages to pass through your window, a more reliable way is to handle the WM_NCHITTEST message and return HTTRANSPARENT where you want the mouse to pass through.
This is basically what how the WS_EX_TRANSPARENT style works. like this
case WM_NCHITTEST:
{
lRet = DefWindowProc(hwnd, uMsg, wParam, lParam);
if (HTCLIENT == lRet)
lRet = HTTRANSPARENT;
}
If your window has no non-client area, then you can skip the call to DefWindowProc.
WndProc() is not always re-entrant. I believe with the main message pump, the mouse and keyboard messages are queued up and waiting for you to finish the prior WM_PAINT message. Conversely, if you were to call SendMessage() from WndProc(), then you are looking at re-entrace. The other case is PostMessage() which would add the message to the queue. Maybe look at using DirectInput for mouse and keyboard input if this is an issue. Otherwise, look for ways to speed up your drawing.