The Old New Thing

Code - The Old New Thing

The default error mode (SetErrorMode) is not zero

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

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

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

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

Displaying a property sheet for multiple files

June 17, 2013 Jun 17, 2013 06/17/13
Raymond Chen
Today's Little Program will show a property sheet that covers multiple files, just like the one you get from Explorer if you multi-select a bunch of files and right-click them all then select Properties. In fact, that description of how you do the operation interactively maps directly to how you do the operation programmatically! #define ...

A big little program: Monitoring Internet Explorer and Explorer windows, part 3: Tracking creation and destruction

June 14, 2013 Jun 14, 2013 06/14/13
Raymond Chen
Last time, we listener for window navigations. Today we'll learn about tracking window creation and destruction. The events to listen to are the DShell­Windows­Events. The Window­Registered event fires when a new window is created, and the Window­Revoked event fires when a window is destroyed. The bad news is that the ...

Dispatch interfaces as connection point interfaces

June 12, 2013 Jun 12, 2013 06/12/13
Raymond Chen
Last time, we learned about how connection points work. One special case of this is where the connection interface is a dispatch interface. Dispatch interfaces are, as the name suggests, COM interfaces based on IDispatch. The IDispatch interface is the base interface for OLE automation objects, and if you want your connection point ...

An introduction to COM connection points

June 11, 2013 Jun 11, 2013 06/11/13
Raymond Chen
Last time, we saw how to enumerate all the Internet Explorer and Explorer Windows and see what they are viewing. But that program printed static information. It didn't track the changes to the windows if the user clicked to another Web page or navigated to a different folder. In order to hook that up, we need to understand the connection ...