The Old New Thing

Placebo setting: QoS bandwidth reservation

November 23, 2006 Nov 23, 2006 11/23/06
Raymond Chen
A placebo setting that has been getting a lot of play in recent years is that of QoS bandwidth reservation. The setting in question sets a maximum amount of bandwidth that can be reserved for QoS. I guess one thing people forgot to notice is the word "maximum". It doesn't set the amount of reserved bandwidth, just the maximum. Changing the ...

The quiet dream of placebo settings

November 22, 2006 Nov 22, 2006 11/22/06
Raymond Chen
Back in the Windows 95 days, people swore that increasing the value of in the file fixed application errors. People usually made up some pseudo-scientific explanation for why this fixed crashes. These explanations were complete rot. These breakpoints had nothing to do with Windows applications. They were used by 32-bit device drivers ...

What is the process by which the cursor gets set?

November 21, 2006 Nov 21, 2006 11/21/06
Raymond Chen
Commenter LittleHelper asked, "Why is the cursor associated with the class and not the window?" This question makes the implicit assumption that the cursor is associated with the class. While there is a cursor associated with each window class, it is the window that decides what cursor to use. The cursor-setting process is described in the ...

It takes only one program to foul an upgrade

November 20, 2006 Nov 20, 2006 11/20/06
Raymond Chen
"Worst software ever." That was Aaron Zupancic's cousin's reaction to the fact that Windows XP was incompatible with one program originally designed for Windows 98. Then again, commenter Aargh! says "The bad code should be fixed, period. If it can't be fixed, it breaks, too bad." Perhaps Aargh! can send a message to Aaron's ...

The window manager moves the mouse; applications choose the cursor

November 17, 2006 Nov 17, 2006 11/17/06
Raymond Chen
You can sometimes narrow down the source of a problem just by looking at the screen and moving the mouse. When you move the mouse, the cursor on the screen moves to match. This work is done in the window manager in kernel mode. The mouse hardware notifies the window manager, "Hey, I moved left twenty units." The window manager takes this ...

Using DIB sections to perform bulk color mapping

November 16, 2006 Nov 16, 2006 11/16/06
Raymond Chen
When doing dithering, one operation you have to do for every pixel is map it (more accurately, map a modified version of it) to the nearest color in your available palette. Since this is part of the dithering inner loop, you need this operation to be as fast as possible.¹ A common technique for this is to precompute the nearest palette ...

Manipulating the DIB color table for fun and profit

November 15, 2006 Nov 15, 2006 11/15/06
Raymond Chen
If you create a DIB section at 8bpp or lower, then it will come with a color table. Pixels in the bitmap are represented not by their red/blue/green component values, but are instead indices into the color table. For example, a 4bpp DIB section can have up to sixteen colors in its color table. Although displays that use 8bpp or lower are ...

Keeping classic hardware alive through emulation

November 14, 2006 Nov 14, 2006 11/14/06
Raymond Chen
At the Windows 2000 Conference and Expo which coincided with the operating system's launch, I paid a visit to the emulators.com booth, where they were excitedly showing off SoftMac 2000, a Mac emulator that ran on Windows 2000. Emulator trivia: MacOS booted in five seconds under Windows 2000, which was faster than the real ...

Blitting between color and monochrome DCs

November 14, 2006 Nov 14, 2006 11/14/06
Raymond Chen
When blitting between color and monochrome DCs, The text foreground and background colors play a role. We saw earlier that when blitting from a monochrome DC to a color DC, the color black in the source turns into the destination's text color, and the color white in the source turns into the destination's background color. This came in handy...