The Old New Thing

Using modular arithmetic to avoid timing overflow problems

May 31, 2005 May 31, 2005 05/31/05

Raymond Chen

In an earlier article, I presented a simple way of avoiding timing overflows which seemed to create a bit of confusion. The short version: Given a starting time start, an ending time end and an interval interval, the way to check whether the interval has elapsed is to use the expression end - start >= interval. The naive expression end &...

You can't simulate keyboard input with PostMessage

May 30, 2005 May 30, 2005 05/30/05

Raymond Chen

Some people attempt to simulate keyboard input to an application by posting keyboard input messages, but this is not reliable for many reasons. First of all, keyboard input is a more complicated matter than those who imprinted on the English keyboard realize. Languages with accent marks have dead keys, Far East languages have a variety of ...

When is x/2 different from x>>1?

May 27, 2005 May 27, 2005 05/27/05

Raymond Chen

Everyone "knows" that the following pairs of expressions are equivalent: Too bad they aren't. In the C language standard, there is no requirement that the internal representation of signed integers be two's complement. All the permissible representations agree for positive numbers, but negative numbers can have different representations. If...

The effect of SetCursor lasts only until the next SetCursor

May 25, 2005 May 25, 2005 05/25/05

Raymond Chen

Of course the effect of the SetCursor function for a thread lasts only until that thread changes the cursor to something else. Any moron knows that, right? The tricky part is that the SetCursor may come from an unexpected place. THe most common place people run into this is when they do something like this: This puts up the hourglass ...

Understanding ternary raster operations

May 24, 2005 May 24, 2005 05/24/05

Raymond Chen

It's perfectly logical, which doesn't mean that it's easy to understand. A ternary raster operation describes how three boolean values should combine to form an output boolean. I was going to write up a description but found that the existing documentation pretty much covers it, so I refer you to that. In particular, look at the table that ...