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<concept id="GUID-5486EFD3-4660-4C19-A007-286DE48F6EEF" xml:lang="en"><title>Scaling

and positioning of controls</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-EF8CA4BE-130F-4117-9722-3F652DD1D244"> <p>Interface elements

a user has to select and manipulate should not be smaller than the smallest

average finger pad, that is, no smaller than 1 cm (0.4") in diameter or a

1 cm × 1 cm square.</p> <p>In the Symbian platform, UI style defines the minimum

sizes for a UI element considered as finger usable:</p><ul>

<li><p>7 x 7 mm with 1 mm gaps for index finger usage</p></li>

<li><p>8 x 8 mm with 2 mm gaps for thumb usage</p></li>

<li><p>List type of components should have minimum of 5 mm line spacing</p></li>

</ul><p>The width of a finger limits the density of items on screen. If the

items are too close, the user will not be able to choose a single one.</p><p>As

the probability of the user touching the higher end of the button (than on

the either side of the key) is high, button and icon sizes can be increased

vertically.</p><p>Essential information or features, such as a label, instructions,

or sub-controls should never be placed below an interface element that can

be touched, as it may be hidden by the user's finger.</p><fig id="GUID-6D8108A5-9009-443D-9DF9-FA7AEFE1AD43">

<image href="GUID-70FC2D13-493D-433F-9CFB-ACF9F512513F_d0e69973_href.png" placement="inline"/>

</fig>Following are some useful tips that can be used while placing essential

information or features on interface element:<ul>

<li><p>With interfaces having input devices, it makes sense to place targets

like menu items on the edges of screens because the cursor movement stops

at the edge of the screen. </p></li>

<li><p>When using a touch screen, a user seldom drags the finger across the

screen like a cursor. Instead, they most likely lift their finger and place

it on a new target. Users may have difficulties in reaching the objects located

on the edges of the screen, especially if the physical device has protruding

edges around the touch screen panel. Additionally, with some devices, the

screen edges may be less sensitive to register the touch input.</p></li>

</ul> </section>

<section id="GUID-8974B60A-15AA-49DD-BC40-04D31CBA5205"><title>Finger usable UI</title><p>Sylus can be used as

the input method with touch UI, but events apply to finger use also. However,

in some cases the components may not be finger optimized due to the size of

objects, for example, virtual keyboard or text field.</p><p>In Symbian, UI

style defines the target minimum sizes for a UI element considered as finger

usable:</p><ul>

<li><p>7 x 7 mm with 1 mm gaps for index finger usage </p></li>

<li><p>8 x 8 mm with 2 mm gaps for thumb usage </p></li>

<li><p>List type of components should have minimum of 5 mm line spacing</p></li>

</ul><p>Targets are general as in practice sizes can be use case dependent,

for example, due to frequency of use, efficiency vs. error criticality or

ease of error correction, location of the button (edge of screen vs. center).</p><p>The

visible area of the component and the component's active area should be identical.

There are exception cases to this rule though:</p><ul>

<li><p>When components are located near the edge of the display, the touchable

area should extend fully to the edge of the display (beyond the components

visible graphics). </p></li>

<li><p>Visible area is smaller than the active area in order to keep the balance

in look and feel of the UI. For example, scrollbar has wider touch area than

visible area. </p></li>

<li><p>Active area is smaller than the visible area in order to avoid unwanted

presses to contiguous active areas. In this case, there it should be graphically

indicated where the user should tap. Example: fixed toolbar buttons in landscape

layout.</p></li>

</ul></section>