The Old New Thing

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 ...

A big little program: Monitoring Internet Explorer and Explorer windows, part 2: Tracking navigations

June 13, 2013 Jun 13, 2013 06/13/13

Raymond Chen

Okay, it's been a while since we set aside our Little Program to learn a bit about connection points and using dispatch interfaces as connection point interfaces. Now we can put that knowledge to use. Internet Explorer and Explorer windows fire a group of events known as DWeb­Browser­Events, so we just need to listen on those ...

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 ...

A big little program: Monitoring Internet Explorer and Explorer windows, part 1: Enumeration

June 10, 2013 Jun 10, 2013 06/10/13

Raymond Chen

Normally, Monday is the day for Little Programs, but this time I'm going to spend a few days on a single Little Program. Now, this might very well disqualify it from the name Little Program, but the concepts are still little; all I'm doing is snapping blocks together. (Plus, it's my Web site, so you can just suck it.) The goal of our ...

Sharing an input queue takes what used to be asynchronous and makes it synchronous, like focus changes

June 7, 2013 Jun 7, 2013 06/7/13

Raymond Chen

As I noted earlier in the series, attaching input queues puts you back into the world of coöperative multitasking, where the two attached threads need to work together to get anything done. Back in the old 16-bit days, when input was synchronous, there was only one active window, only one focus window, only one window with capture, ...

A pathological program which ignores the keyboard, and understanding the resulting behavior based on what we know about the synchronous input

June 6, 2013 Jun 6, 2013 06/6/13

Raymond Chen

Today, we'll illustrate the consequences of the way the window manager synchronizes input when two or more threads decide to share an input queue. Since I need to keep separate state for the two windows, I'm going to start with the new scratch program and make the following changes: #include <strsafe.h> class RootWindow : public ...

When you share an input queue, you have to wait your turn

June 5, 2013 Jun 5, 2013 06/5/13

Raymond Chen

Now that we've had a quick introduction to asynchronous input, let's look at some of the details. Remember, this is a peek under the hood at how the sausage is made. The algorithm described here is not part of the API contract and it can change at any time, as long as it services the overall goal of serializing input. Let's start by ...