The Old New Thing

Code - The Old New Thing

Why is GetWindowLongPtr returning a garbage value on 64-bit Windows?

December 26, 2013 Dec 26, 2013 12/26/13
Raymond Chen
A customer was running into problems with their application on 64-bit Windows 8. They claimed that on Windows 8, the is returning a garbage pointer, which causes their program to crash. The same program works fine on 64-bit Windows 7. They asked the Windows team why they broke . An investigation of the customer's code ...

Creating custom tasks on a jump list

December 23, 2013 Dec 23, 2013 12/23/13
Raymond Chen
Today's Little Program adds a custom task to the application's jump list. Take the scratch program and make the following changes. (Remember, Little Programs do very little error checking because that's how they roll.) This helper function creates an in-memory shell link object with the specified title, command line arguments, and icon. ...

How do I display an RTL string in a notification balloon on an LTR system?

December 19, 2013 Dec 19, 2013 12/19/13
Raymond Chen
Suppose you have a program that is written in Arabic or Hebrew and you want to render some text. No problem. You just call and pass the flag to say, "Please render this string in an RTL context." Many other text-rendering functions have a similar flag, such as for . But what if you don't control the call to or or whatever other ...

Disabling the PrtSc key by blocking input

December 16, 2013 Dec 16, 2013 12/16/13
Raymond Chen
A customer asked how to disable the PrtSc key in the On-Screen Keyboard. There is no way to disable the PrtSc key in the On-Screen Keyboard. The On-Screen Keyboard shows a keyboard, and you can click any virtual key you like. There is no policy to remove specific keys from the On-Screen Keyboard. But this was a case of a customer breaking...

How do you intercept taskbar notification balloons?

December 12, 2013 Dec 12, 2013 12/12/13
Raymond Chen
A customer wanted to know how they could monitor and intercept taskbar notification balloons. In particular, they wanted to intercept the clicks on a particular balloon and take alternative action. There is no supported mechanism for intercepting taskbar notification balloons or redirecting clicks on them. Imagine if that were possible: ...

Destroying all child processes (and grandchildren) when the parent exits

December 9, 2013 Dec 9, 2013 12/9/13
Raymond Chen
Today's Little Program launches a child process and then just hangs around. If you terminate the parent process, then all the children (and grandchildren and great-grandchildren, you get the idea) are also terminated. The tool for this is the Job Object. Specifically, we mark the job as "kill on job close" which causes all processes in the...

What's the difference between the wParam of the WM_NOTIFY message and the idFrom in the NMHDR structure?

December 4, 2013 Dec 4, 2013 12/4/13
Raymond Chen
The message takes the following parameters: Notice that the identifier of the control sending the message appears in two places, once in the and again in the . What's the difference? There is no difference. It's just a convenience. The same value is passed in both places, and you can check whichever one is easier for you. You might use ...

Logging the foreground process as it changes

December 2, 2013 Dec 2, 2013 12/2/13
Raymond Chen
Today's Little Program simply logs all changes to the foreground window by recording the path to the application the user switched to. You might use this as part of a usability study to monitor what applications users spend most of their time in. Most of this code is just taking things we already know and snapping them together...