• The Old New Thing

    If you return from the main thread, does the process exit?


    If instead of calling ExitProcess you merely return from the main thread of a process, does the process terminate?

    No, but maybe yes.

    This is another one of the places where the C runtime behaves differently from raw Win32.

    Under raw Win32, a process exits when any thread chooses to exit the process explicitly (usually by calling ExitProcess) or when all threads have exited. Exiting the main thread will not result in the process exiting if there are any other threads still active. According to the old-fashioned model of how processes exit, a process was in control of all its threads and could mediate the shutdown of those threads, thereby controlling the shutdown of the process. (Of course, nowadays, with the thread pool, COM worker threads, and other threads doing random background work, the idea of being in control of all the threads in the process is now just a reminder of those simpler days.)

    On the other hand, the C runtime library automatically calls ExitProcess when you exit the main thread, regardless of whether there are any worker threads still active. This behavior for console programs is mandated by the C language, which says that ( "a return from the initial call to the main function is equivalent to calling the exit function with the value returned by the main function as its argument." The C++ language has an equivalent requirement (3.6.1). Presumably, the C runtime folks carried this behavior to WinMain for consistency.

    This also means that if you decide to exit your main thread by calling ExitThread directly, then you aren't returning from the main function. Instead, you've leapt into the Win32 world where the process will not exit until all threads are gone.

  • The Old New Thing

    How do I recover the window handle passed to ShellExecute?


    A customer had the following question:

    I'm using the ShellExecute function to launch a new process and am passing the handle to my application's main window as the hwnd parameter. From the new process, I want to get information from the old process, and to do that, I need the window handle. How can I recover that window handle from the new process?

    You can't.

    That window handle is used by the ShellExecute function only to host any user interface operations that occur as a result of the attempt to execute the program. For example, it is the owner window used for any error dialogs. The ShellExecute function does not pass the window handle to the launched process. (It couldn't even if it wanted to: There is nowhere to pass it. There is no window handle among the parameters to CreateProcess nor is there a window handle in the STARTUPINFO structure.)

    If you want to pass this information to the process being launched, you'll have to come up with your own mechanism for transferring this information. For example, you can pass it on the command line, or if you have a lot of information to pass, you can use a shared memory block.

  • The Old New Thing

    What young children do when they hear a foreign language


    My young nieces live in a Chinese-speaking household, which is great for them because it means that when they grow up, they will be fluent in two languages. But it makes things a bit tricky at the beginning.

    The niece who is the subject of this story had just turned two at the time this story takes place, so her language skills even in Chinese are pretty rudimentary. Her language skills in English are restricted to a collection of set phrases like Excuse me!, I'm sorry!, What'you doing?, I want ice cream!, and any catch phrase from the character Dora the Explorer.

    (I'm also fairly sure she doesn't know what What'you doing? actually means. She'll come into a room and say, What'you doing? and then appear completely uninterested in the answer. I think she believes it to be a form of greeting and not an actual question.)

    She also loves to answer the phone, and this usually isn't a problem since most callers are relatives who can speak Chinese. But occasionally, it'll be somebody who speaks only English. (In general, these are just telemarketers, since most members of the household use their mobile phones as their main number.)

    Sometimes she'll run to the phone, pick it up, say "喂" (Hello), listen for a few seconds, and then just hang up.

    — Who was that on the phone? we'll ask.

    "人" is her one-word reply.

    It's hard to explain why this is a funny answer.

    The word 人 means man, person, so her response was a casual "A person." The offhand way she says it expresses her attitude that "The purpose of the telephone is to amuse me, but this was just some guy who provided no entertainment at all."

    The 人 phase lasted for only a month or so. In the next phase, she still picked up the phone and hung up when there was somebody speaking English on the other end, but when we asked her who it was, she gave a more detailed reply:

    "有人說ＡＢＣ", which translates roughly as "It's some guy speaking A-B-C." ("A-B-C" being her word for the English language.)

  • The Old New Thing

    Why did the Explore option disappear from the context menu of folders in the second column of the Start menu?


    A customer noticed that when you right-click on Computer in the second column of the Start menu on Windows Vista, the first two options are Open and Explore. On the other hand, in Windows 7, the Explore option is gone, leaving just Open. The customer also noticed that in Windows Vista, the two commands had the same effect and wondered if Explore was removed because it was redundant.

    The response from the product team was a very simple "Yes."

    It's interesting when a customer notices a relatively insignificant UI change, figures out the likely reason for the change, and then asks for confirmation. It's not like the reason for the change affects anything. My guess is that the customer already paid for a support contract so they're just going to use it, even when the issue wouldn't normally be worth raising a support incident over.

  • The Old New Thing

    Windows 95: It sucks less


    Today marks the 15th anniversary of the public release of Windows 95.

    During the development of Windows 95, one of the team members attended a Mac conference. And not as a secret agent, either. He proudly wore a Windows 95 team T-shirt as he strolled among the booths.

    The rest of us back at the mother ship wished him well and started discussing how we could get access to his dental records so we could identify his remains when they were sent back to us from the conference.

    When he returned, we didn't kill a calf in his honor, but we did marvel at his survival skills and asked him how it went.

    I got a lot of funny looks. And one guy, upon confirming that I really did work on the Windows 95 project, said to me, "I have to commend you guys on Windows 95 so far. It sucks less."

    That backwards compliment tickled the team's funny bone, and it quickly became the unofficial team motto: Windows 95: It sucks less.

  • The Old New Thing

    Be careful that your splash screen doesn't squander the foreground love


    Commenter Erbi has a program which creates a splash screen on a background thread while the main thread initializes. "I create and then destroy this splash screen window just before creating and displaying the main window." The problem is that the main window fails to obtain foreground activation. Commenting out the code that creates the splash screen fixes the problem, but then there isn't a splash screen any more (obviously). "Is there an explanation for this behavior?"

    This behavior is explained by two earlier blog posts, plus a PDC talk. The first blog post came out years before this question was asked: The correct order for disabling and enabling windows. Destroying a window is a rather extreme case of disabling it, but the effect is the same. When you destroy the splash screen, foreground activation needs to move to some other window, and since your main window isn't around to inherit it, foreground activation leaves your program. When the main window appears, it's too late.

    The PDC talk came next, followed shortly thereafter by a blog post version of the same talk. As marketing folks like to remind you, "You get only one chance to make a first impression." Similarly, you get only one chance to use your foreground activation permission, and you decided to blow it on a splash screen. That's fine as far as it goes, but if you want to transfer that permission to another window, you have to manage it yourself. The recommended way is to establish an owner/owned relationship between them; that's the case that the "disabling and enabling windows" article focuses on.

  • The Old New Thing

    Miss France, she has the Eiffel Tower on her head, because France has the Eiffel Tower, and no other country does, so she put it on her head, that's why


    Miss Universe 2010 National Costumes, Part 1
    Miss Universe 2010 National Costumes, Part 2

    Commentary in parts NSFW but they so deserve it.

  • The Old New Thing

    Why does the primary monitor have (0,0) as its upper left coordinate?


    By definition, the primary monitor is the monitor that has (0,0) as its upper left corner. Why can't the primary monitor be positioned somewhere else?

    Well, sure you could do that, but then you'd have to invent a new name for the monitor whose upper left corner is at (0,0), and then you're back where you started.

    In other words, it's just a name. You could ask, "Why can't starboard be on the left-hand side of the boat?" Well, sure you could do that, but then you'd have to come up with a new name for the right-hand side of the boat, and then things are pretty much the same as they were, just with different names.

    Perhaps a more descriptive (but clumsier) name for the primary monitor would be the backward-compatibility monitor (for applications which do not support multiple monitors), because that's what the primary monitor is. If an application is not multiple-monitor aware, then any time it asks for properties of "the" monitor, it gets information about the backward-compatibility monitor. A call to GetSystemMetrics(SM_CXSCREEN) gives the width of the backward-compatibility monitor, GetSystemMetrics(SM_CYMAXIMIZED) gives the height of a window maximized on the backward-compatibility monitor, and positioning a window at (0,0) puts it at the upper left corner of the backward-compatibility monitor.

    The window manager still respects window coordinates passed to functions like CreateWindow or SetWindowPos. If you pass coordinates that are on a secondary monitor—oops—a monitor different from the backward-compatibility monitor, then the window manager will happily put the window there. These coordinates might be the result of a program that is multiple-monitor aware, or possibly merely from a program which is multiple-monitor agnostic.

    Multiple-monitor agnosticism is a term I just made up which refers to programs which might not explicitly support multiple monitors, but at least were open to the possibility of multiple monitors by not making assumptions about the number of monitors but instead using functions like RectVisible to determine what the visible portions of the screen are. These techniques were hot topics many years ago when you wanted to write a program that ran both on single-monitor-only versions of Windows as well as multiple-monitor versions of windows; nowadays there are rather old-fashioned, like coming up with mnemonics for all your friends' telephone numbers so you didn't have to keep looking them up. (Today, you just go ahead and call the multiple monitor functions and use the address book function in your mobile phone to remember your friends' phone numbers.)

    It is not the case that the primary monitor is the applications show up here first monitor. As noted earlier, applications show up on whatever monitor they ask for, whether they asked for it explicitly (hunting around for a monitor and using it) or implicitly (restoring to the same coordinates they were on when they were last run).

    Of course, programs which pass CW_USEDEFAULT to the CreateWindow function explicitly abdicated the choice of the window position and therefore the monitor. In that case, the window manager tries to guess an appropriate monitor. If the new window has a parent or owner, then it is placed on the same monitor as that parent or owner; otherwise, the window manager just puts the window on the backward-compatible monitor, for lack of a better idea.

  • The Old New Thing

    I challenge you to come up with an even lamer physics pun


    The other day, I was in the office kitchenette, and two of my colleagues both named Paul happened to be there getting coffee. I quipped, "Oh no, is this legal? I think it's a violation of the Paul Exclusion Principle."

    It was a horrible physics pun, perhaps one of the worst I've made in a long time. My challenge to you is to come up with an even worse one that you've told.

    Note: You have to have actually made the pun to an appropriate audience. No fair just making one up for the purpose of the challenge.

  • The Old New Thing

    How do I get the Explorer navigation pane to highlight the current folder all the time?


    In Windows 7, the folder tree in the Explorer navigation pane by default no longer highlights the item in the view pane. This change was based on user testing and feedback, but if, like me, you prefer things the old way, you can play with two new check boxes on the Folder Options dialog. You can get to Folder Options in a variety of ways:

    • From the Control Panel, go to Appearance and Personalization → Folder Options. (Or just type Folder Options into the Control Panel search box or the Start menu search box to go straight there.)
    • From the Explorer menu bar, select Tools → Folder options.
    • From the Explorer command bar, select Organize → Folder and search options.
    • Or you can exercise your super élite status and just right-click on a blank space in the navigation pane.

    However you wind up there, the item you want to turn on is Automatically expand to current folder (or Expand to current folder if you use the super élite method).

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