This is what I regard as ideal Qwert* keyboards:
- Slides out from the longer edge of Jolla (the phone is carried on rails above the keyboard), like on Nokia N810 and N900
- Keyboard width is determined by the width of the Jolla phone (in landscape orientation)
- Keys have a spherical shape, sufficiently outbowing: a bit more outbowing than on Nokia E7. Acceptable shapes of keys are found on Nokia N900 and E70.
- Key labels in 2 or 3 colors, background-illuminated
- At least one Shift, Ctrl, Fn and Sym key, perhaps also the Tab key
- Four arrow keys are a must. In language-localized variants their number must not be less than 4 (unfortunately on many localized N900 keyboards the ArrowUp is made with Sym+ArrowLeft and ArrowDown is made with Sym+ArrowRight, which is too impractical). Besides, the removal of the ArrowUp and ArrowDown keys ruin the use of keyboard shortcuts.
- When you slide the HW Qwerty in, you can continue using the virtual keyboard on touch screen, using practically the same key sequencies. To achieve this, there could be sticky Shift and Ctrl keys on the virtual keyboard. For easy text selection and cursor movements, 4 arrow keys are useful also on virtual keyboards. For example, if you have tapped on an arrow key after the Shift key, the Shift will remain sticky until you tap again on the Shift key, or make an operation which cancels the text-selection. Perhaps the arrow keys of the virtual keyboard can be omitted if the selection of text can be done easily, like with the Opera Mobile browser (but please do not mimic the miserable virtual keyboard of Opera!). I must admit, however, that beginners may regard the Editing Layer of the Swype keyboard as more user friendly than the shortcuts with sticky modifier keys - but keyboard shortcuts are quicker to use.
- To allow easy keyboard shortcuts like Ctrl + Shift + ArrowRight on HW Qwerty, please examine whether one or more of the Ctrl, Shift and Sym keys can be made to work as a sticky key (for keyboard shortcuts, the Sym key would have the same functionality as the Alt key on full-size Qwerty keyboards)
- To save space for other keys, spacebar should not be made wider than the sum of 2 or 3 adjacent keys.
- No excessively large keys. Yes, you can hit the Shift, Backspace and Enter keys with no problems even though they are not bigger than letter keys, if their shape is outbowing enough.
- Keys arranged like on chessboard. Although by tilting the key columns you can make the keyboard look more like a full-size keyboard, such a trick does not help: its use with two thumbs will remain totally different from how you enter text on a full-size Qwerty keyboard.
- Put Y-H-N (etc) keys in the same vertical key columns. It will help enormously those who are accustomed to 10-finger touch-typing on full-sized keyboards - they will know subconsciously where each key is located if columns are arranged correctly, even though naturally you cannot "10-finger touch-type" on two-thumb keyboards. This naturally applies to other key columns (T-G-B, U-J-M etc).
- The number of key rows depends on how much the keyboard slides from below the phone. I regard 4 rows as minimum. The Z X C V B N M keys should not be on the lowermost row of keys - it is best to use it for modifier keys like Shift, Fn, Sym etc. If there is not enough space for 5 rows, then numbers are entered as the combinations of the Fn and the topmost keys.