TONT 32703 『诱饵』控制面板



Last time, we saw one example of a “decoy” used in the service of application compatibility with respect to the Printers Control Panel. Today we’ll look at another decoy, this time for the Display Control Panel.


When support for multiple monitors was being developed, a major obstacle was that a large number of display drivers hacked the Display Control Panel directly instead of using the documented extension mechanism. For example, instead of adding a separate page to the Display Control Panel’s property sheet for, say, virtual desktops, they would just hack into the “Settings” page and add their button there. Some drivers were so adventuresome as to do what seemed like a total rewrite of the “Settings” page. They would take all the controls, move them around, resize them, hide some, show others, add new buttons of their own, and generally speaking treat the page as a lump of clay waiting to be molded into their own image. (Here’s a handy rule of thumb: If your technique works only if the user speaks English, you probably should consider the possibility that what you’re doing is relying on an implementation detail rather than something that will be officially supported going forward.)


In order to support multiple monitors, the Settings page on the Display Control Panel underwent a major overhaul. But when you tried to open the Display Control Panel on a system that had one of these aggressive drivers installed, it would crash because the driver ran around rearranging things like it always did, even though the things it was manipulating weren’t what the developers of the driver intended!


The solution was to create a “decoy” Settings page that looked exactly like the classic Windows 95 Settings page. The decoy page’s purpose in life was to act as bait for these aggressive display drivers and allow itself to be abused mercilessly, letting the driver have its way. Meanwhile, the real Settings page (which is the one that was shown to the user), by virtue of having been overlooked, remained safe and unharmed.

解决方案,则是创建一个『诱饵』设置页面,这个页面看上去与旧式的 Windows 95(显示控制面板的)设置页面完全一样,而它的一切目的就是为了诱使那个野心勃勃的显卡驱动对它毫无怜悯之心地一通乱改,让驱动能心满意足。而与此同时,真正的『设置』页面(展示给用户的),由于被(驱动)忽视掉了,得以岁月静好。

There was no attempt to make this decoy Settings page do anything interesting at all. Its sole job was to soak up mistreatment without complaining. As a result, those drivers lost whatever nifty features their shenanigans were trying to accomplish, but at least the Display Control Panel stayed alive and allowed the user to do what they were trying to do in the first place: Adjust their display settings.


TONT 32723 当应用程序认为系统永远都不会变的时候:第3章



One of the stranger application compatibility puzzles was solved by a colleague of mine who was trying to figure out why a particular program couldn’t open the Printers Control Panel. Upon closer investigation, the reason became clear. The program launched the Control Panel, used FindWindow to locate the window, then accessed that window’s “File” menu and extracted the strings from that menu looking for an item that contained the word “Printer”. It then posted a WM_COMMAND message to the Control Panel window with the menu identifier it found, thereby simulating the user clicking on the “Printers” menu option.

我的一位同事曾解决过的一桩诡异的应用程序兼容性问题,是找出为什么某个程序无法打开打印机控制面板的原因。在深入调查后,原因变得明朗起来。这个程序会打开控制面板,用 FindWindow 找到控制面板的窗口,然后去访问这个窗口的 File(文件)菜单,把这个菜单里的菜单项字符串解析出来,然后在其中找到带有 Printer(打印机)这个词的项目,然后向控制面板窗口发送 WM_COMMAND 窗体消息,以刚才找到的菜单项为参数。经过以上一通操作,便完成了模拟用户单击『打印机』菜单项这个操作。(译注:可自行参考 Windows 3.x 的控制面板长什么样子,以便更好理解上文描述的操作)

With Windows 95’s Control Panel, this method fell apart pretty badly. There is no “Printers” option on the Control Panel’s File menu. It never occurred to the authors of the program that this was a possibility. (Mind you, it was a possibility even in Windows 3.1: If you were running a non-English version of Windows, the name of the Printers option will be something like “Skrivare” or “Drucker”. Not that it mattered, because the “File” menu will be called something like “Arkiv” or “Datei”! The developers of this program simply assumed that everyone in the world speaks English.)

到了 Windows 95 的控制面板里,这种操作可谓一败涂地。控制面板的『文件』菜单里并没有『打印机』这一项,对软件的编写者来说,这是根本不可能发生的事情。(需要提醒的是,即便在 Windows 3.1 中,这也是一件有可能发生的事:如果你运行的 Windows 不是英语版本,那么『打印机』一项的名字可能叫做 Skrivare(译注:瑞典语的『打印机』)或者 Drucker(译注:德语的『打印机』),但这其实也不是最大的问题,因为与此同时『文件』菜单的名字可是会叫做 Arkiv 或者 Datei(译注:分别为瑞典语和德语的『文件』)呢!编写这个软件的开发者估计简单的认为这个世界上的所有人都是讲英语的吧。)(译注:也可能人家根本就没想在英语区之外发行?)

The code never checked for errors; it plowed ahead on the assumption that everything was going according to plan. The code eventually completed its rounds and sent a garbage WM_COMMAND message to the Control Panel window, which was of course ignored since it didn’t match any of the valid commands on that window’s menu.

程序的代码从来都没有对错误进行过检查,只是一味地勇往直前,假定一切都会按计划进行而已。代码做完了它的工作,向控制面板窗口发送了一个无效的 WM_COMMAND 窗体消息,而这个消息由于没有包含针对窗体菜单的任何有效指令,理所当然地被系统忽略了。

The punch line is that the mechanism for opening the Printers Control Panel was rather clearly spelled out on the very first page of the “Control Panel” chapter of the Windows 3.1 SDK:

笑点在于,打开打印机控制面板的方式,实际上在 Windows 3.1 SDK『控制面板』章节的第一页就清清楚楚地写着:

The following example shows how an application can start Control Panel and the Printers application from the command line by using the WinExec function:

以下案例说明如何使应用程序通过调用 WinExec 函数来打开控制面板以及打印机设置界面:

WinExec(“control.exe printers”, SW_SHOWNORMAL);

In other words, they didn’t even read past the first page.


The solution: Create a “decoy” Control Panel window with the same class name as Windows 3.1, so that this program would find it. The purpose of these “decoys” is to draw the attention of the offending program, taking the brunt of the mistreatment and doing what they can to mimic the original behavior enough to keep that program happy. In this case, it waited patiently for the garbage WM_COMMAND message to arrive and dutifully launched the Printers Control Panel.

至于解决方案,则是创建了一个用作『诱饵』的控制面板窗口,这个窗口的类名与 Windows 3.1 的控制面板窗口一致,以便让这个程序能找到它。这个诱饵的作用是吸引这个无礼的应用程序的注意力,首当其冲地模仿旧式控制面板的行为,来让这类应用程序心满意足。在这个案例中,它的作用是耐心等待那个无效的 WM_COMMAND 窗体消息的来临,然后尽职尽责地打开『打印机』控制面板。

Nowadays, this sort of problem would probably have been solved with the use of a shim. But this was back in Windows 95, where application compatibility technology was still comparatively immature. All that was available at the time were application compatibility flags and hot-patching of binaries, wherein the values are modified as they are loaded into memory. Using hot-patching technology was reserved for only the most extreme compatibility cases, because getting permission from the vendor to patch their program was a comparatively lengthy legal process. Patching was considered a “last resort” compatibility mechanism not only for the legal machinery necessary to permit it, but also because patching a program fixes only the versions of the program the patch was developed to address. If the vendor shipped ten versions of a program, ten different patches would have to be developed. And if the vendor shipped another version after Windows 95 was delivered to duplication, that version would be broken when Windows 95 hit the shelves.

现如今,这类问题一般会通过使用『楔子』一类的方式解决,但这个案例是在 Windows 95 的年代发生的,那时应用程序兼容性技术相对来说还不够成熟,而那时能用的办法就是应用程序兼容性标签,以及对二进制文件应用热修复补丁,在其加载入内存时对二进制数据进行修改。热修复补丁这一招只会被留待遇到最棘手的兼容性问题时才会使用,因为从软件发行商哪里获得对其程序进行修改的许可,是一个冗长的法律过程。打补丁被视为是实现兼容性问题解决的『最终手段』,不仅仅因为获得许可要经过机械繁复的法律流程,同时也是因为这样只能修复兼容性补丁所针对的该软件特定版本的问题。如果软件发行商发布了10个版本的应用程序,那就要开发10个不同的补丁。而如果软件发行商在 Windows 95 送厂之后又发布了新版本,那么这个新版本在 Windows 95 上架销售之后便仍存在兼容性问题。

It is important to understand the distinction between what is a documented and supported feature and what is an implementation detail. Documented and supported features are contracts between Windows and your program. Windows will uphold its end of the contract for as long as that feature exists. Implementation details, on the other hand, are ephemeral; they can change at any time, be it at the next major operating system release, at the next service pack, even with the next security hotfix. If your program relies on implementation details, you’re contributing to the compatibility cruft that Windows carries around from release to release.

理解文档中受支持的功能和部署细节的区别很重要。文档中受支持的功能是 Windows 和你的程序之间的契约,Windows 在这个功能的存续期间会信守承诺。而另一方面,部署细节则是稍纵即逝的,可能随时发生变化,变化可能发生在下一个系统大版本,下一个 Service Pack,甚至是下一个安全更新补丁。如果你的程序依赖部署细节,那你不过是在为 Windows 代代相传的、沉重的兼容性包袱添砖加瓦罢了。

Over the next few days, I’ll talk about other decoys that have been used in Windows.

接下来的几天里,我会讲一讲 Windows 中其它的一些兼容性『诱饵』。

TONT 33023 关于无法再支持已经无人再制造的硬件这件事


Windows Vista will not have support for really old DVD drives. (The information below was kindly provided to me by the optical storage driver team.)

Windows Vista 对于一些特别老型号的 DVD 光驱已经不再提供支持了。(以下信息由光存储驱动开发组友情提供。)

When PC DVD drives first came out in 1998, the drives themselves did not have support for region codes but instead relied on (and in fact the DVD specification required) the operating system to enforce region coding, with the further understanding that starting on January 1, 2000 all newly-manufactured drives would support region coding in hardware rather than relying on software enforcement. For the purpose of this discussion, I will call the two types of drives “old” (manufactured before 2000) and “new” (manufactured on or after January 1, 2000).

1998年,PC 上的 DVD 光驱刚刚出现的时候,光驱硬件自身并不支持区码限制,而是依赖操作系统来确保这个限制(实际上也是 DVD 标准所要求的),不过在后来更新的标准中,自2000年1月1日起,所有新生产的DVD光驱都应当在硬件、而不是在软件中确保区码限制。为了讨论方便,接下来我将这两种光驱称作『旧』光驱(2000年以前生产)和『新』光驱(2000年1月1日起生产)。

It is that software enforcement that is going away. Turns out that the enforcement of region coding in software had its own problems:


  • It was impossible for third-parties to compile their own CDROM.SYS from the source code in the DDK because the region code enforcement code was not included in the DDK.
    第三方开发者无法从DDK(驱动程序开发包)的源代码中编译他们自己的 CDROM.SYS,因为 DDK 中没有区码限制相关的代码。
  • The region code enforcement code would sometimes mistake a new drive for an old one, resulting in customers unable to play DVDs. Even worse, the driver test team could not reproduce the problem reliably, and the problem went away entirely once a debugger was attached to the system.
  • The code to support the older drives is complex, and the drives that the optical storage team purchased prior to January 1, 2000 are dead or dying. Consequently, testing the code that provides support for old drives has become increasingly difficult, and when the last old drive finally gives up the ghost, testing will become impossible altogether.

These were among the considerations which contributed to the decision to stop supporting these old drives.


What does this mean for you? Almost certainly, the answer is “absolutely nothing”.


First, there is no change to the way data is read from DVD drives, so data discs will still work the same way as they do today. Second, all new DVD drives will continue to run as they did before; the only change is that the risk of mis-identification as an old drive has been removed. Only if you have an old drive will you notice anything different, namely that encrypted/regionalized DVD movies will no longer play. And since the average drive lifetime is only three years, the number of such old drives that are still working is vanishingly small. Not even the optical drive test team can manage to keep their old drives alive that long.


TONT 33043 用实体物品作为提醒


On our team, we have a mailing list where people can report problems. Those people could be testers from our team or they could be people from elsewhere in the company. Everybody on the team is expected to keep an eye on the messages and debug problems in their area. The job of monitoring the mailing list to ensure that every issue is ultimately addressed rotates according to a predetermined schedule, and in addition to receiving a piece of reminder mail at 4pm the business day before it’s your turn, you will also find a Mickey Mouse ears hat on your desk when you arrive in the morning.


I bought this hat in Disneyland a few years ago and somehow managed to convince the person operating the sewing machine to stitch the name “Dev O’Day” on the back. “It’s an Irish name,” I explained, but it also stands for “Developer of the Day”, which is the title we use for the person who monitors the mailing list.

这顶帽子是几年前我去迪士尼乐园的时候买的,并且设法说服了操作缝纫机给帽子织上名字的人,让他在帽子背面织了『Dev O’Day』这个名字。『这是个爱尔兰名字』,我是这么跟他解释的,不过这个缩写也代表『今日开发者』,亦即我们给今天盯着邮件列表的人的头衔。

One of our team members went on vacation to Disneyland the following year and brought back a back-up hat, which sits in my office. The back-up hat is occasionally brought into service when the primary Dev O’Day hat goes missing, at which point a Search and Rescue mission is undertaken to locate the hat and restore it to circulation. (It’s usually just sitting in the office of someone who was Developer of the Day recently and merely forgot to hand the hat off at the end of the day.)


TONT 33083 当标记的含义中途发生变化的时候


The project leader for the initial version of Internet Explorer was well-known for wearing Hawaiian shirts. I’m told that the team managers decided to take one of those shirts and use it as an award to the team member who fixed the most bugs or some similar thing. What the team managers failed to take into account that nobody actually liked having a Hawaiian shirt hanging in their office, especially not one that was worn by somebody else. If you happened to be the person who fixed the most bugs, you sort of reluctantly accepted the shirt even though you really didn’t want it.

Internet Explorer 早期版本的项目领导人的夏威夷衫装束在公司内人尽皆知。团队管理者告诉我,他们决定拿其中一件衬衫当奖励,奖给修复了最多bug或者做了类似贡献的团队成员。但是团队管理者没有考虑到的是,并没有人喜欢在办公室里挂一件夏威夷衬衫,尤其是被别人穿过的那种。如果你碰巧修复了最多的bug,就得不怎么情愿地接受一件衬衫,即便是你并不怎么想要它。

And then a wonderful thing happened: The meaning of the shirt flipped.


I don’t know the details. I suspect at one point, somebody who “won” the shirt just left it in somebody else’s office as a way of getting rid of it. This simple gesture was the turning point. The shirt became a symbol of disapproval. I believe the unofficial rule was that in order to get rid of the shirt, you had to find somebody who messed up at least as bad as whatever you did to earn the shirt in the first place.


It took a while before the team managers even realized what happened to their “award”.