On Jun 8, 2010, at 9:03 AM, Bert Freudenberg wrote: > Thanks for inviting discussion! > > I recently started testing Etoys on the Apple iPad - not the least to get an > idea of what needs to be done to it for an XO tablet. Multi-touch is > definitely "cool", e.g. you can move around multiple Etoys objects > simultaneously. If you are interested, I can send you a test version (pm me). > > Etoys uses the Sugar tool bar on all platforms. That works very well, the > buttons are large enough even for my fingers. > > However, many other Etoys UI elements are much too small for touching. > They're finicky even on the XO screen, but with a pointer you can at least > hit them. That's rather hard with a finger (though the Apple touch screen is > amazingly precise). A stylus would be preferable, but then, two-finger > gestures are awkward with a stylus.
We aren't planning to provide a stylus (just something for the kids to loose), but with some touchscreens any pointed stick can be used as a stylus if needed. The projected capacitance touchscreens becoming popular (iPhone, iPad), on the other hand, don't support just any old stylus, it has to have a special tip. > It would help if the tablet had a 4:3 ratio. Ideally 1200x900 pixels just > like the XO, but at least preserve the ratio. The iPad has 1024x768 pixels > and I made Etoys use a virtual 1200x900 screen hw-scaled to the actual screen > size, looks very nice. The aspect ratio of a tablet device is the source of much debate these days. 16:9 displays are cheaper due to volume sales, but many (most ?) people around OLPC prefer 4:3. >> ----------------- >> 1) Number of simultaneous touches: >> The number of simultaneous touches that can be tracked. >> For W7, this is two. I believe OLPC is looking for more. > > IMHO multi-touch is almost essential on a tablet. Two would be enough IMHO, > more are nice. > > What's "W7"? Windows 7 I listed M$'s specifications as most vendors are trying to meet them. >> 2) Behavior when number of simultaneous touches is exceeded: >> If the number of simultaneous touches is exceeded, what happens ? >> I suggest that the "oldest" touch be forgotten and no longer tracked, >> but have seen other behaviors as well. > > I'd rather keep tracking the first touches and ignore additional ones. Then > accidental touches wouldn't interrupt the current interaction. Interesting point. >> 3) Palm rejection: >> A number of vendors include "palm rejection" algorithms in their >> controllers. I'm not sure how I feel about this --- I would prefer to >> push this information higher in the stack before discarding it... >> >> 4) "Sensor size": >> This applies to multizone resistive touchscreens, which may be >> thought about as a number of small touchscreens, each capable of >> a single touch. Two touches cannot be detected in any one zone, >> so this affects how close buttons which might be pressed simultaneously >> (think piano keys) can be placed to one another. W7 specs 1 in. x1 in. max. >> I believe this needs to be closer to 1 cm x 1cm max. > > I'm imagining to use a two-finger tap to invoke meta operations, like the > right touchpad button in Etoys on the XO. For this it would need to detect > two kid's fingers form one ... Getting closer than 1 cm x 1 cm would probably rule out multi-zone resistive. But a 1 cm^2 zone would probably work fine for two finger tap, even with kid's fingers. >> 5) Resolution: >> Do we need to have a touch resolution equal to the screen size ? > > I have no real experience with this yet, but it needs to be high enough to > allow drawing. I didn't list W7's specs for this: 2.5mm accuracy for single touches, and 5mm accuracy for multiple touches An interesting effect I've noticed is that with some touchscreen, you get smooth lines when moving your finger at a "normal speed", say 8 cm/s, but when you slow down (1 cm/s) the line wiggles around. >> 6) Scan rate: >> The number of times a second that the touch controller >> can identify and report a touch. W7 specifies 50 Hz minimum, >> which seems a little high. >> >> 7) Robustness: >> This is usually specified as the number of presses in one spot with a contact >> area of either 8mm (finger) or 0.8mm (stylus). Industry standard for >> resistive >> (single or multizone) seems to be around 80K, which is too low for our needs >> (we try to reach a 2000 day lifetime). But the one vendor supporting 250K >> touches was unusable by a bare finger (needed fingernail or stylus). >> >> 8) UV resistance: >> Since this touchscreen is on top of a sunlight readable display, it will need >> to be UV resistant. Our current standard (for the display) is no >> significant >> change (>5%) in optical properties after 4000 hours of full sunlight UV >> irradiation. >> >> 9) Humidity, temperature: >> Same as the XO: operation from 0 to 50C, in RH up to 95%. >> >> Regards, >> wad > > No opinion on these issues, yet ... Keep experimenting! Thanks, wad _______________________________________________ Devel mailing list [email protected] http://lists.laptop.org/listinfo/devel
