Holy cow, I wrote a book!
Marketing writes the big print; lawyers write the small print.
I bought some portable stereo headphones. The front of the box
says you can use it "while in-line skating, power walking, biking,
jogging, skiing, running, weightlifting, climbing and more."
The back of the box says that it should not be used "while driving or
Some people have noticed that there is no message that lets
you disable the Cancel button on a wizard.
This is on purpose.
Usability studies reveal that users find it extremely frustrating
when they get partway through a wizard and then decide they don't
want to perform the operation after all, but find that the wizard
doesn't give them a way to cancel.
Now the user feels trapped.
They can't back out of the operation;
they're being forced to finish something against their will.
Imagine if you went to an e-commerce site and started going through
the checkout procedure, then decide that you didn't want to buy
the item after all, yet the web page disabled the Back button
and didn't have a Cancel,
and when you clicked the "X" button to close the web browser,
the page put up a message box saying, "You cannot cancel this
operation once it has begun."
Not a very pleasant experience,
and I suspect you would avoid this web site in the future.
The same principle applies to wizards.
Users should always be given a way to cancel out of a wizard.
Wizards should, generally speaking, collect information in
stages, and apply them at the point the user clicks Finish.
This is not always practical, and wizards may have need to
commit partially-made decisions along the way,
but that's the general idea.
Under such circumstances, the wizard author should make it
clear to the user whether cancelling the operation will undo
the previously-committed decisions or leave them intact.
If you are clever, you can do this without an annoying
Instead, you can indicate this by the flow of the wizard itself.
For example, you might have a wizard that goes like this:
With this wizard flow,
clicking "Next" to go from page 2 to page 3
commits the initial XYZ setup, as indicated by
the text "Your XYZ is now ready to use."
If the user decides to cancel out of the customization,
you've made it clear that the XYZ has nevertheless been set up
and cancelling will not undo it.
Okay, so it's bad enough that
I write like a girl.
so does Betsy.)
a little get-together of some Microsoft bloggers,
and in the photograph you can see that I'm doing the "peace" sign,
just like young Japanese women do in photographs.
Apparently, boys are supposed to strike a superhero pose,
but the peace sign is so much more fun.
On occasion, you might notice that every window on the desktop
flickers and repaints itself.
One of the causes for this is a simple null handle bug.
The InvalidateRect function is one you're
probably well-familiar with.
It is used to indicate to the window manager that the pixels
of a particular window are no longer current and should be
(You can optionally pass a rectangle that specifies a subset
of the window's client area that you wish to mark invalid.)
This is typically done when the state of the data underlying
the window has changed and you want the window to repaint with
the new data.
If however you end up passing NULL as the window
handle to the InvalidateRect function,
this is treated as a special case for compatibility with
early versions of Windows: It invalidates
all the windows on the desktop
and repaints them.
Consequently, if you, say, try to invalidate a window
but get your error checking or timing wrong and end up
passing NULL by mistake,
the result will be that the entire screen flickers.
Even more strangely, passing NULL as the
first parameter ValidateRect
has the same behavior of invalidating
all the windows.
(Yes, it's the "Validate" function, yet it invalidates.)
This wacko behavior exists for the same compatibility reason.
Yet another example of how programs rely on bugs or undocumented
behavior, in this case, the peculiar way a NULL parameter
was treated by very early versions of Windows due to lax
Changing nearly anything in the window manager
raises a strong probability that there will be many programs
that were relying on the old behavior, perhaps entirely by accident,
and breaking those programs means an angry phone call from a
major corporation because their factory control software stopped
Today's theme is a quick one:
Other Microsofties explain what at first appear to be puzzling decisions.
The folks on the logon team wish me to remind you that
the ForceAutoLogon setting
does more than just log on an account automatically.
They've had to deal with large numbers of people who set the key
without really understanding what it does, and then getting into
trouble because what they get is not what they expected.
In addition to logging on an account automatically,
the ForceAutoLogon setting also
logs you back on after you log off.
It is designed for machines running as kiosks
or other publically-accessible scenarios
where you want the kiosk account to be the only account
Even if the user manages to fiddle with the machine and
log off the kiosk user,
the logon system will just log the kiosk user back on.
As a result, setting the ForceAutoLogon setting effectively
locks out all users aside from the one you are forcing.
If you do this to one of your machines,
you'd better have some other way of administering the machine.
(Typically, this is done via remote administration.)
Only a Game
interviewed the authors of
The Baseball Uncyclopedia,
an irreverent guide to our national pastime,
it was a blast to listen to.
The two authors clearly are huge baseball fans,
but they bring to it a fascination not with mind-numbing statistics
but with the deep history of the sport.
(Plus the fact that they disagree on many things, which leads
to really funny arguments.)
And who can't appreciate the theory that Kevin Costner
is responsible for Shoeless Joe Jackson not being in the Baseball
Hall of Fame?
I have not forgotten about the Chinese/English dictionary series,
but I simply haven't had the motivation to sit down and write up
descriptions and discussion for
the code that I wrote along the way, so instead of adding to the
program, I'm going to answer some questions that were asked back
when I started the series but which I didn't respond to at the
time since I was out of town.
More than one commenter
suggested using v.reserve()
to pre-allocate the vector memory.
First of all, the cost of vector reallocation really didn't factor
into the performance after the first few rounds of optimization,
so adding a reservation step ended up being unnecessary.
Furthermore, getting the correct value to pass to v.reserve()
would mean making two passes over the dictionary, one to get the
number of entries in the dictionary and set the vector reservation size,
and another to fill the dictionary itself.
The alternative would have been to make a guess as to the number
of entries in the dictionary based on the total file size and the
average length of each entry.
Fortunately, it never came to that.
suggested preprocessing the file.
That is also a valid technique,
but I intentionally avoided it partly for expository purposes
(it would have removed much of the challenge),
and partly because I wanted to be able to update the dictionary
by merely replacing the dict.b5 file.
suggested using the wcsrchr function as an alternative
to the missing std::rfind method.
Note, however, that the DirctionaryEntry::Parse
method takes a string in the form of a start and end;
it is not a null-terminated string.
Passing this to wcsrchr would have resulted in quite
Martha Stewart was in town this past weekend signing
her book on baking.
Although I'm a Martha fan, I didn't attend the signing because
I already have
a really awesome book on baking.
I've listed below some of the ground rules for the book signing,
mixed in with some stuff I just plain made up.
Your mission is to pick out which of these rules are for real
and which are fake.
You can check your score
on this web page.
I'm satisfied with the MSDN documentation for
the WM_COMMAND message,
but for the sake of mind-numbing completeness,
I'm going to state the obvious in the hope that you,
dear readers, can use this technique to
fill in the obvious in other parts of MSDN.
The one-line summary of the WM_COMMAND message
"The WM_COMMAND message is sent when the user selects
a command item from a menu,
when a control sends a notification message to its parent window,
or when an accelerator keystroke is translated."
In a nutshell, there are three scenarios that generate a
WM_COMMAND message, namely the three listed above.
You want to think of the menu and accelerator scenarios of the
WM_COMMAND message as special cases of the control scenario.
The high-order word of the wParam parameter
"specifies the notification code if the message is from a control".
What does "control" mean here?
Remember that you have to take things in context.
The WM_COMMAND message is being presented in the
context of Win32 in general, and in the context of the window manager
Windows such as edit boxes, push buttons, and list boxes
are commonly called "controls", as are all the window classes
in the "common controls library".
In the world of the window manager, a "control" is a window
whose purpose is to provide some degree of interactivity
(which, in the case of the static control, might be no interactivity at all)
in the service of its parent window.
The fact that the WM_COMMAND is used primarily
in the context of dialog boxes further emphasizes the point
that the term "control" here is just a synonym for "child window".
What does "notification code" mean here?
Control notification codes are arbitrary 16-bit values defined
by the control itself.
By convention, they are named xxN_xxxx, where the "N"
stands for "notification".
Be careful, however, not to confuse this with notification codes
associated with the WM_NOTIFY message.
Fortunately, every notification code specifies in its documentation
whether it arrives as a WM_COMMAND notification or
a WM_NOTIFY notification.
A modern control designer is more likely to use
WM_NOTIFY notifications since they allow
additional information to be passed with the notification.
The WM_COMMAND message, by comparison, passes
only the notification itself; the other parameters to
the WM_COMMAND message are forced, as we'll see below.
If WM_NOTIFY is superior to WM_COMMAND,
why do some controls use WM_COMMAND?
Because WM_NOTIFY wasn't available until
Controls that were written prior to Windows 95 had to
content themselves with the WM_COMMAND message.
"If the message is from an accelerator, this value [the high-order
word of the wParam parameter] is 1."
Remember, we're still in the context of the window manager,
and particular in the context of the WM_COMMAND
The accelerator here refers to messages generated by the call to
TranslateAccelerator in the message loop.
"If the message is from a menu, this value is zero."
If the WM_COMMAND mesage was triggered by
the user selecting an item from a menu, then the high-order
word of the wParam is zero.
The low-order word of the wParam parameter
"specifies the identifier of the menu item, control, or
The identifier of a menu item or accelerator
is the command code you associated
with it in your menu or accelerator template or (in the case of a menu item)
when you manually created the menu item with a function like
(You probably named your menu item identifiers and accelerator
The identifier of a control is determined by the creator of the
control; recall that the
hMenu parameter to the CreateWindow
and CreateWindowEx functions is treated as a child
window identifier if you're creating a child window.
It is that identifier that the control identifier.
(You can retrieve the identifier for a control by calling the
Finally, the lParam parameter is the
"handle to the control sending the message if the message is from a control.
Otherwise, this parameter is NULL."
If the notification is generated by a child window
(with a notification code appropriate for that child window, obviously),
then that child window handle is passed as the lParam.
If the notification is generated by an accelerator or a menu,
then the lParam is zero.
Notice that nearly all of the parameters to the
WM_COMMAND message are forced, once you've decided
what notification you're generating.
If you are generating a notification from a control,
you must pass the notification code in the high word of the
wParam, the control identifier in the low word
of the wParam, and the control handle as the
In other words, once you've decided that the
hwndC window wants to send a
CN_READY notification, you have no choice but
In other words, all control notifications take the form
where hwndC is the control generating the notification
and notificationCode is the notification code.
Of course, you can use PostMessage instead of
SendMessage if you would rather post the notification
rather than sending it.
The other two cases (accelerators and menus) are not cases you
would normally code up, since you typically let the
TranslateAccelerator function deal with accelerators
and let the menu system deal with menu identifiers.
But if for some reason, you wanted to pretend that the user
had typed an accelerator or selected a menu item, you can generate
the notification manually by following the rules set out in the
// simulate the accelerator IDM_WHATEVER
Here, hwnd is the window that you want to pretend was
the window passed to the TranslateAccelerator function,
and IDM_WHATEVER is the accelerator identifier.
Simulating a menu selection is exactly the same, except that
(according to the rules above), you set the high-order word of
the wParam to zero.
// simulate the menu item IDM_WHATEVER
Here, hwnd is the window associated with the menu.
A window can be associated with a menu either by being created
with the menu (having passed the menu handle to the
CreateWindow or CreateWindowEx function
explicitly, or having it done implicitly by including it with the
class registration) or by having been passed explicitly as
the window parameter to a function like
One significant difference between the accelerator/menu case
and the control notification case is that accelerator and menu
identifiers are defined by the calling application,
whereas control notifications are defined by the control.
You may have noticed the opportunity to "pun"
the control notification codes.
If a control defines a notification code as zero, then it will
"look like" a menu item selection, since the high-order word
of the wParam in the case of a menu item selection
The button control takes advantage of this pun:
#define BN_CLICKED 0
This means that when the user clicks a button control,
the WM_COMMAND message that is generated
"smells like" a menu selection notification.
You probably take advantage of this in your dialog procedure
without even realizing it.
(The static control also takes advantage of this pun:
#define STN_CLICKED 0
but in order for the static control to generate the
you have to set the SS_NOTIFY style.)
I stated at the start that the accelerator and menu scenarios
are just special cases of the control scenario.
If you take the pieces of the WM_COMMAND message
apart, you'll see that they fall into two categories:
In the case of a menu or an accelerator, the "What happened?"
is "The user clicked on the menu (0)" or
"The user typed the accelerator (1)".
The "Whom did it happen to?" is "This menu ID" or "This accelerator ID".
Since the notification is not coming from a control, the control
handle is NULL.
I apologize to all you Win32 programmers for whom
this is just stating the obvious.
Now that you're an expert on the WM_COMMAND message,
perhaps you can solve
this person's problem.