October 2018 | Page 2 of 3 | The Old New Thing

What does the “Ae” stand for in AeDebug?

Raymond ChenOctober 17, 2018Oct 17, 201810/17/18

The name of the registry key for configuring automatic debugging of application crashes is AeDebug. Okay, so it's obvious what "Debug" stands for, but what does "Ae" stand for? I can't prove it, but circumstantial evidence points to AE standing for "Application Error". The title of the dialog box was originally "Application Error". And there'

Why does Windows ask me to pick a program with which to open a file, even when I already specified which program I want to use to open the file?

Raymond ChenOctober 16, 2018Oct 16, 201810/16/18

So you're working at your computer, everything is humming along just fine, and then when you double-click a file, instead of launching the associated application, Windows asks you what program you want to use to launch the document. Why doesn't it just follow the instructions you gave it already? A customer installed a new program that suppor

How can I programmatically inspect and manipulate a registry hive file without mounting it?

Raymond ChenOctober 15, 2018Oct 15, 201810/15/18

Say you have a registry hive file. One way to inspect and manipulate its contents is by calling the RegLoadKey function to mount it in the registry and then use the normal registry operations. This option may be undesirable for various reasons. First of all, the RegLoadKey function requires administrator privileges, so th

So, um, what are we looking at?

Raymond ChenOctober 12, 2018Oct 12, 201810/12/18

Some of my relatives from Vancouver, British Columbia enjoy going on cruises. During one cruise along the Alaska coast, they found a large number of passengers gathered on the viewing deck and gazing toward the shore in awe and amazement. My relatives looked out toward shore but couldn't identify what it was that drew everyone's attention. Wa

Why doesn’t GetTextExtentPoint return the correct extent for strings containing tabs?

Raymond ChenOctober 12, 2018Oct 12, 201810/12/18

A customer reported that the GetTextExtentPoint and GetTextExtentPoint32 functions do not return the correct extents for strings that contain tabs. The documentation does say that they do not support carriage return and linefeed, but nothing about tabs. The TextOut and GetTextExtentPoint funct

How can I include/exclude specific memory blocks in user-mode crash dumps?

Raymond ChenOctober 11, 2018Oct 11, 201810/11/18

You can tweak the information included in crash dumps created by Windows Error Reporting. To request that Windows Error Reporting include a dump of another process if the calling process crashes, use the WerRegisterAdditionalProcess function. This is useful if your program is split up into multiple processes. You can add addit

Notes on DrawText and tab stops

Raymond ChenOctober 10, 2018Oct 10, 201810/10/18

The DrawText function will recognize tab characters if you ask for DT_EXPANDTABS. And then things get weird. If you ask for DT_EXPANDTABS, then you cannot ask for any of the DT_*_ELLIPSIS features. The ellipsis code doesn't support tabs. Tab stops default to every eight average character widths. If you want to change the defa

The numerology of the sample directory listing in the Windows 95 font selector property sheet page

Raymond ChenOctober 9, 2018Oct 9, 201810/9/18

In Windows 95, it became tradition that if you modified the code that displays the font preview in the Windows 95 command prompt font chooser property sheet page, you also got to tweak the sample date and file sizes to be a value personally significant to you. By the time Windows 95 shipped, the values in the font preview were as follows:

When I call `CryptProtectData` with the same parameters, why aren’t the results identical?

Raymond ChenOctober 8, 2018Oct 8, 201810/8/18

If you call CryptProtectData twice in a row with the same parameters, you get different results. Why are the results inconsistent? The plaintext is the same. The entropy is the same. The key is the same. Shouldn't the result be the same? If those were the only inputs to the encryption algorithm, then the results should be the same.

How can I use `WS_CLIPCHILDREN` and still be able to draw a control with a transparent background?

Raymond ChenOctober 5, 2018Oct 5, 201810/5/18

A customer was using an MFC CHtmlDialog as a child dialog and found that they needed to add the WS_CLIPCHILDREN style to ensure that the contents appeared on the screen; otherwise, the parent dialog would paint its background over the child dialog, and the child dialog would consequently appear to vanish. On the other hand, they also had

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