The Old New Thing

Code - The Old New Thing

What does LockWindowUpdate do?

February 19, 2007 Feb 19, 2007 02/19/07
Raymond Chen
Poor misunderstood . This is the first in a series on , what it does, what it's for and (perhaps most important) what it's not for. What does is pretty simple. When a window is locked, all attempt to draw into it or its children fail. Instead of drawing, the window manager remembers which parts of the window the application tried to draw...

Why don't I use any class libraries in my sample code?

February 16, 2007 Feb 16, 2007 02/16/07
Raymond Chen
As a general rule, I avoid using any class libraries in my sample code. This isn't because I'm opposed to class libraries, but rather because I don't want to narrow my audience to "people who use MFC" (to choose one popular class library). If I were to start using MFC for all of my samples, I'd probably lose all the people who don't use MFC...

Why does my property sheet blink and the immediately disappear?

February 8, 2007 Feb 8, 2007 02/8/07
Raymond Chen
Occasionally, a customer will ask, "I'm trying to display a property sheet, but when I call the function, the property sheet blinks onto the screen and then immediately disappears. What is wrong?" Recall that displaying a property sheet entails filling out a structure, which in turn contains a pointer to either an array of s, or more often...

Why can't I create my dialog box? Rookie mistake #2

February 7, 2007 Feb 7, 2007 02/7/07
Raymond Chen
Another class of rookie mistake is less obvious from looking at the code. The problem with this code is that we forgot to call to register the listview class. More generally, the problem is that one of the controls on the dialog uses a window class that was not registered. (For example, maybe there's a rich edit control on the dialog, but...

Why can't I create my dialog box? Rookie mistake #1

February 6, 2007 Feb 6, 2007 02/6/07
Raymond Chen
Each dialog box resource is specified either by an integer ordinal or by a string name. But a simple typo will turn one into the other. Do you see the two "classic rookie mistakes"? It may be easier to spot if you take the resource file and send it through the preprocessor first: The first call to passes as the resource name. But ...

If vertical strips are better, why do toolbars use horizontal strips?

January 29, 2007 Jan 29, 2007 01/29/07
Raymond Chen
If vertical strips are better, why do toolbars use horizontal strips? An early version of the toolbar control first made its appearance in Windows 3.0, and in those days, screen resolutions were low and toolbar buttons were small. Horizontal or vertical didn't really matter. Ten bitmaps, each 16 × 16, at 4-bit color, comes out to...

The cost of continuously-visible affordances with dynamic states

January 22, 2007 Jan 22, 2007 01/22/07
Raymond Chen
Serge Wautier asks, "Why are the copy/cut/paste buttons not disabled when there's nothing to copy/cut/paste?", noting that the back/forward buttons do disable themselves when navigation is not possible in that direction. To get to this question, we'll first go back in time a bit to a world without toolbars. In those early days, these dynamic ...

EnumChildWindows already enumerates recursively

January 16, 2007 Jan 16, 2007 01/16/07
Raymond Chen
I often see people write code that goes something like this: The intent here was to perform the operation on all the windows in a window tree by operating on the root, then operating on each of the children. Operating on the children is in turn performed recursively, so that we eventually see every window in the tree. Except that if you ...