by Matt Campbell and Mike Calvo Introduction Screen readers often need to obtain detailed information about the contents of the display. For the past several years, these products have obtained such information by chaining their own code to the display driver, at least under Windows 2000, XP, and Server 2003. Today, the new display driver model introduced in Windows Vista does not support display driver chaining, so the currently dominant screen readers now install a mirror driver instead. However, Windows must disable significant functionality to make the mirror driver work. The results of disabling that functionality have the potential to adversely affect even users who are totally blind. To support mirror drivers as used by screen readers, Windows must also continue to support the antiquated Windows XP display driver model. Meanwhile, newer screen readers are using an alternative technique called API hooking to obtain essentially the same information about the contents of the display, without any crippling side effects, even under Windows Vista. API hooking has considerable advantages over display-driver-based techniques now, and the advantages will become more significant as Windows continues to evolve. This paper explains the history that has led to the use of mirror drivers, the problems introduced by mirror drivers, and the advantages of API hooking. History To understand why the currently dominant screen readers now use mirror drivers, it is important to understand the problem that mirror drivers are intended to solve and the techniques that these products have previously used to solve this problem. The Problem: Building an Off- Screen Model The primary problem that Windows screen reader developers face is that neither Windows nor the majority of applications were designed to be used by the blind. Screen reader developers must therefore retrofit accessibility.
I actually have Office 2013 Pro installed the correct one is used when the machine type is identified. I/ O devices are given as offsets from 0x50000000. Each device is mapped across 0x2000 bytes unless noted otherwise. VIA1 at offset 0. May also be mirrored at 0x20000 and 0x40000. VIA2 at offset 0x2000 on II, IIx, IIcx, and SE/30 SCC ( Z8530) at offset 0x4000 SCSI (pseudo- DMA w/ DRQ on II, handshake on SE/30) at offset 0x6000 SCSI (normal) at 0x10000 SCSI (pseudo- DMA, no DRQ) at offset 0x12000 ASC ( Apple Sound Chip) at 0x14000 IWM/ SWIM (floppy) at 0x16000 VDAC (palette) at 0x24000 ( IIci, IIsi, LC series, Color Classic) RBV/ V8/etc registers (partially emulates VIA2, also video registers) at 0x26000 ( IIci & IIsi, LC series, Color Classic) RBV VRAM at 0x1000000 ( IIci).
From: Soronel Haetir To: jfw@xxxxxxxxxxxxx Date: Wed, Also try running the Video intercept manager found under the jaws utilities menu. It's generally a pain but possible to use with a partially installed jaws. On, Farfar Carlson wrote: > Call Tech Support and have Narrator running so you can follow their steps. I > think you need to clean out some registry keys. > > > > Dave > Composed on a Dell Latitude 630 in the general vicinity of my Audio > Recording and Mixing Studios, San Francisco Bay Area. > - Original Message - > From: Carliss > To: jfw@xxxxxxxxxxxxx > Sent: Wednesday, May 25, 2011 3:31 > Subject: Help with the Jaws mirror display drivers. > > > Listers, > > Okay, I blew it this time > > I was having problems with Jaws so I uninstalled everything including the > mirror display drivers in device maniger. I reinstalled Jaws at least, > three times but I'm getting a message saying, some thing like, the mirror > display drivers need to be repaired. So, how is that done? I've rebooted > the computer as I was told by Jaws to fix the problem, but thatdidn't fix > it. That too, was done several times. This is Jaws12 I'm dealing with, and > I did a full repair by installing the latest build of Jaws, and still > nothing!. > > If anyone knows how to fix this, please, tell me. Jaws isn't quite right > with out those mirror drivers. > > Thanks to all! > > > > Carliss > > > - Soronel Haetir soronel.haetir@xxxxxxxxx - JFW related links: JFW homepage: Scripting mailing list: JFW List instructions: To post a message to the list, send it to jfw@xxxxxxxxxxxxx To unsubscribe from this mailing list, send a message to jfw-request@xxxxxxxxxxxxx with the word unsubscribe in.
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