March 2017

A survey of the various ways of creating GDI bitmaps with predefined data

Raymond Chen March 31, 2017 Mar 31, 2017 03/31/17

Suppose you have a buffer full of pixels and you want to create a GDI bitmap that contains those pixels. We'll start with the CreateBitmap function. This creates a device-dependent bitmap with the pixels you provide. The weird thing about this function is that it's a device-dependent bitmap, but there's no parameter that specifies the ...

For sale: One TARDIS, working (lights), you must pick up from Vancouver

Raymond Chen March 30, 2017 Mar 30, 2017 03/30/17

Ever wanted a full-size TARDIS that works? Well, at least the the lights work. For sale: TARDIS - FULL SIZE - $2500 (191 Alexander Street, Vancouver, BC, Canada) condition: excellent size / dimensions: approx 4x4 7 ft tall CALLING ALL DR. WHO FANS! WE have a full size, working (as in lighted, not time portal) Tardis that was used as...

The gradual erosion of the SEM_NOOPENFILEERRORBOX error mode

Raymond Chen March 30, 2017 Mar 30, 2017 03/30/17

The SEM_NOOPENFILEERRORBOX flag has a long history. It goes back to 16-bit Windows and the way modules were loaded from floppy disks. If the loader could not find the file it needed, it prompted you to insert the disk and gave you the option to retry or cancel. The SEM_NOOPENFILEERRORBOX flag lets you ...

A brief discussion on how best to respond to the end-session messages

Raymond Chen March 29, 2017 Mar 29, 2017 03/29/17

A customer discovered that their application's shutdown code sometimes deadlocked. To address the problem, they moved the bulk of their shutdown code to the WM_ENDSESSION message handler. The customer found my earlier discussion of the WM_ENDSESSION message and wondered if they were doing the right thing. Yes, it's okay to do ...

Explorer is a single-instance application, but you can find other ways to get the effect of running a separate instance

Raymond Chen March 28, 2017 Mar 28, 2017 03/28/17

Explorer is a single-instance application, which means that if you try to elevate it, or if you try to run the 32-bit version on a 64-bit system, you don't actually get an elevated Explorer or a 32-bit Explorer, because the second instance hands the request to the existing instance. This is a problem if, say, you have an old shell extension ...

How real-mode Windows loaded code from the disk, and how you could use that to minimize disk swapping

Raymond Chen March 27, 2017 Mar 27, 2017 03/27/17

Real-mode Windows was originally designed to run on a PC with 192KB of RAM and two 360KB floppy drives. We saw some time ago that code was loaded dynamically off the disk on demand. The same principle also applies to read-only data, like resources. Now, you might not have enough disk space on two floppies to hold the core operating system ...

When you submit a security vulnerability report, we go the extra mile and try to fix your typos

Raymond Chen March 24, 2017 Mar 24, 2017 03/24/17

A security vulnerability report arrived that went like this: Even though all access has been revoked to the two files, the following program deletes C:\Folder\foo: From reading this page, it seems that file deletion is related to the control on the file itself and not on the parent folder. And anyway, both have the same rights. There...

Responses to various ideas on how to get people to stop using that leaked build

Raymond Chen March 23, 2017 Mar 23, 2017 03/23/17

Some time ago, I told the story of how we used psychology to get people to stop using a leaked build and upgrade to a newer build. People had suggestsions for other ways this could have been done. One suggestion to avoid the problem in the first place was to have internal builds refuse to activate from an IP address that is not assigned ot ...

You can peek to see whether your delay-loaded function loaded successfully

Raymond Chen March 22, 2017 Mar 22, 2017 03/22/17

The QueryOptionalDelayLoadedAPI function lets you ask whether a function marked as delay-loaded was in fact found. Here's a tiny demonstration: This gives you function-by-function granularity on checking whether a delay-loaded function was successfully loaded, which is an improvement over being told whether all the imports...

Why does the volume control let me set the volume only to even numbers?

Raymond Chen March 21, 2017 Mar 21, 2017 03/21/17

When you use the hardware button or the dedicated multimedia keyboard button to increase or decrease the volume, the resulting volume is always an even number. If the volume was 22 and you increase the volume, it goes up to 24. But if the volume was 21 and you increase the volume, it also goes up to 24. Why can't it set the volume to an odd ...

The Old New Thing

March 2017 - The Old New Thing