It’s the address space, stupid

Raymond Chen June 28, 2013 Jun 28, 2013 06/28/13

Nowadays, computers have so much memory that running out of RAM is rarely the cause for an "out of memory" error. Actually, let's try that again. For over a decade, hard drive have been so large (and cheap) that running out of swap space is rarely the cause for an "out of memory" error. In user-mode, the term memory refers to virtual ...

Once you return from the WM_ENDSESSION message, your process can be terminated at any time

Raymond Chen June 27, 2013 Jun 27, 2013 06/27/13

A customer had a program which performed some final I/O operations as it exited. Various C++ objects deleted files or flushed buffers as part of their destructors. The customer found that if their program was left running when the user shut down Windows, then the files never got deleted, and the buffers were never flushed. On the other hand, ...

The default error mode (SetErrorMode) is not zero

Raymond Chen June 26, 2013 Jun 26, 2013 06/26/13

A customer put the following code at the start of their program: // If this assertion fires, then somebody else changed the error mode // and I just overwrote it with my error mode. ASSERT(SetErrorMode(SEM_FAILCRITICALERRORS) == 0); The customer wanted to know whether it was a valid assumption that the initial error mode for a process is ...

Drawing content at a fixed screen position, regardless of window position

Raymond Chen June 24, 2013 Jun 24, 2013 06/24/13

Today's Little Program draws content at a fixed screen position. The idea is that the window is really a viewport into some magical world. Unfortunately, our magical world just has a sign that says "Booga booga." Creating a more interesting magical world is left as an exercise. Start with our scratch program and make these changes: void ...

Of what use is the RDW_INTERNALPAINT flag?

Raymond Chen June 21, 2013 Jun 21, 2013 06/21/13

For motivational purposes, let's start with a program that displays a DWM thumbnail. Start with the scratch program and add the following: #include <dwmapi.h> HWND g_hwndThumbnail; HTHUMBNAIL g_hthumb; void UpdateThumbnail(HWND hwndFrame, HWND hwndTarget) { if (g_hwndThumbnail != hwndTarget) { g_hwndThumbnail = hwndTarget; ...

AttachThreadInput is like taking two threads and pooling their money into a joint bank account, where both parties need to be present in order to withdraw any money

Raymond Chen June 19, 2013 Jun 19, 2013 06/19/13

Consider this code: // Code in italics is wrong foregroundThreadId = ::GetWindowThreadProcessId(::GetForegroundWindow(), 0); myThreadId = GetCurrentThreadId(); if (foregroundThreadId != myThreadId) { AttachThreadInput(foregroundThreadId, myThreadId, TRUE); BringWindowToTop(myWindowHandle); If you try to ...