2016-05-08 16:19 GMT+02:00 Don Osborn <[email protected]>: > The flexibility of touchpad keyboards in theory gets beyond the > limitations of the physical keyboards - has anyone tried adding a row to > say a QWERY layout, which includes additional characters, rather than > sweating the issues about shoehorning them in other levels or key > sequences? Is that even possible? Still would be helpful to have standards, > but where something is visible, it is easy to use. >
It is technically possible, but the problem is to add distinctive hardware "scan codes" to keys in this row. See this table: https://msdn.microsoft.com/en-us/library/aa299374(v=vs.60).aspx You'll note that almost all scancodes in the 7-bit range are used. So you'd need "extended scancodes", i.e. prefixing the special virtual scancode 00 on Windows (or the hardware scancode E0) before the extended scan code for the actual key. (The special scancode "00" turns the 7-bit table into an equivalent 8-bit table, but note that keyboards use 7-bit scancodes only, as the 8th bit is used for the press/release flag) For that, you could then reuse the scancodes of the first row (those for digits). Note that the scancodes for the row of "standard" function keys (F1..F12) is already extended this way (for additional function keys). Bit note also this table: https://www.win.tue.nl/~aeb/linux/kbd/scancodes-10.html You'll see that the hardware scancodes E0-0A and E0-0B are already assigned on PC for special functions, and so cannot be used to "extend" the keys for digits 9 and 0 on the first row (whose scancodes are 0A and 0B respectively). This is not so critical: you can perfectly have additional keys assigend for a row using non-contiguous hardware scancodes (after all the alphabetic part of the keyboard is already using multiple ranges of hardware and virtual scancodes). But you'd need a new keyboard driver (and an extension to MSKLC on Windows) to allow mapping this supplementary row, and a industry agreement to assign new extended keys in non-conflicting ways (these days, it is the Microsoft hardware labs that centralize the extensions used on PC-compatible hardware, Apple used to have its own registry for its own keyboards, but now Macs are PC and can use the same keyboards not necessarily built by Apple, e.g. by Logitech). The connectors are compatible with the same USB interface. There are some differences in hardware scancodes used on the USB interface (Windows internally translated hardware scancodes for some interfaces into the same virtual scancodes before sending them to upper keyboard drivers and applications: this is where scancode E0 on the old PC-keyboard interface or the newer PS/2 interface or USB interface, or in the old BIOS interface is remapped into the same virtual scancode 00 for Windows drivers and apps). There's also an additional hardware extension code E1 for a few function keys (it is used for a few functions encoded on 3 bytes, for upward compatibility reasons, such as the "Pause" key). Various other vendors have used specific hardware scancodes, but today almost everyone agrees to the same PC standard.
