Creating a shared memory block that can grow in size

Raymond Chen January 30, 2015 Jan 30, 2015 01/30/15

A little-known feature of shared memory blocks in Win32 is that it is possible to resize them, sort of. When you create a shared memory block, you can pass the SEC_RESERVE flag to Create­File­Mapping, then the size you pass to the function is treated as a maximum rather than an exact size. (Don't forget that Create­File­...

Color-aware ClearType requires access to fixed background pixels, which is a problem if you don't know what the background pixels are, or if they aren't fixed

Raymond Chen January 29, 2015 Jan 29, 2015 01/29/15

ClearType is a technology that blends text pixels with background pixels with the goal of reducing visual artifacts during text rendering.¹ If you go for the full-meal version of ClearType, it uses knowledge about the physical properties of LCD screens in order to carry out its work. Some time ago, I noted one catch with this model, which...

The compiler can make up its own calling conventions, within limits

Raymond Chen January 28, 2015 Jan 28, 2015 01/28/15

A customer was confused by what they were seeing when debugging. It is our understanding that the Windows x86-64 calling convention passes the first four parameters in registers rcx, rdx, r8, and r9. But we're seeing the parameters being passed some other way. Given the function prototype we would expect to see the parameters passed as rcx...

Customizing item enumeration with IShellItem

Raymond Chen January 26, 2015 Jan 26, 2015 01/26/15

If you are using the original IShell­Folder interface, then you can use SHCONTF values to customize how child items are enumerated. But what if you're using IShell­Item? Let's take it one step at a time. First, the basic program. (Remember, Little Programs do little to no error checking.) Run this program with the fully-qualified ...

Helper functions to make shell bind contexts slightly more manageable

Raymond Chen January 23, 2015 Jan 23, 2015 01/23/15

Last time, we learned about the wonderful world of shell bind context strings, and I promised some helper functions to make this slightly more manageable. Here are some helper functions which supplement the Create­Bind­Ctx­With­Opts function we created some time ago. The Ensure­Bind­Ctx­Property­Bag function ...

The wonderful world of shell bind context strings

Raymond Chen January 22, 2015 Jan 22, 2015 01/22/15

Some time ago, we saw how the IBindCtx parameter to IShell­Folder::Parse­Display­Name can be used to modify how the parse takes place. More generally, the IBindCtx parameter to a function is a catch-all miscellaneous options parameter. The interesting part of the bind context is all the stuff that has been added to it via the ...

Why does my synchronous overlapped ReadFile return FALSE when the end of the file is reached?

Raymond Chen January 21, 2015 Jan 21, 2015 01/21/15

A customer reported that the behavior of Read­File was not what they were expecting. We have a synchronous file handle (not created with FILE_FLAG_OVERLAPPED), but we issue reads against it with an OVERLAPPED structure. We find that when we read past the end of the file, the Read­File returns FALSE even though the documentation says ...