It’s the address space, stupid

Raymond ChenJune 28, 2013Jun 28, 201306/28/13

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”

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

Raymond ChenJune 27, 2013Jun 27, 201306/27/13

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,

The default error mode (SetErrorMode) is not zero

Raymond ChenJune 26, 2013Jun 26, 201306/26/13

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 zero.

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

Raymond ChenJune 24, 2013Jun 24, 201306/24/13

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.

Of what use is the RDW_INTERNALPAINT flag?

Raymond ChenJune 21, 2013Jun 21, 201306/21/13

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 ChenJune 19, 2013Jun 19, 201306/19/13

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 step over the
Attach­Thread­Input
call in the debugger,
both the debugger and the application being debugged will freeze.