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/*
* Copyright (C) 2012 Canonical Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; version 3.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*!
\page resolution-independence.html resolution-independence
\title Resolution Independence
\nextpage {Lomiri User Interface Toolkit}
The objective of resolution independence is to make it easy for graphical
user interfaces in Lomiri to scale to all the form factors that Lomiri
targets: phones, tablets, laptops and desktops.
The approach taken combines simplicity for the designers and developers
with visual fidelity, quality and usability.
\part Measurement Units
A new measurement unit is defined called the grid unit, abbreviated \b{\e gu}.
1 grid unit translates to a given number of pixels depending on the type of
screen that the user interface is displayed on.
For example, on a laptop computer 1 grid unit will typically translate to 8 pixels.
The number of pixels per grid unit is chosen in order to preserve the perceived
visual size of UI elements and therefore depends on the density of the display
and the distance the user is to the screen. We also ensure that 1 grid unit is
always an integer number of pixel.
Examples:
\table
\header
\li Device
\li Conversion
\row
\li Most laptops
\li 1 gu = 8 px
\row
\li Retina laptops
\li 1 gu = 16 px
\row
\li Phone with 4 inch screen at HD resolution (around 720x1,280 pixels)
\li 1 gu = 18 px
\row
\li Tablet with 10 inch screen at HD resolution (around 720x1,280 pixels)
\li 1 gu = 10 px
\endtable
The grid unit defines a visual rhythm in Lomiri and should be used for all measurements.
Sizes of elements, spacing, margins, etc. should all use multiples of 1 gu.
It is available from QML as a method of the global object \b units, instance of \l Units.
Example Usage:
\code
import Lomiri.Components 1.2
Item {
width: units.gu(2)
height: units.gu(5)
}
\endcode
Exceptionally, in order to accommodate for the rare cases where measurements of less
than 1 gu are needed another unit is available: the density independent pixel,
abbreviated \b{\e dp}. 1 dp typically translates to 1 pixel on laptops and low
density mobile phones and tablets.
Example Usage:
\code
import Lomiri.Components 1.2
Rectangle {
height: units.dp(1)
}
\endcode
\part Bitmaps
Vector graphics, fonts and programmatically drawn elements will usually scale well
to the different devices. On the other hand, bitmaps will typically require a bit
more care.
The size of a bitmap needs to be adequate to render well on a given
device. The toolkit allows one to design multiple versions of a bitmap and choose
the appropriate one dynamically depending on the device the application is
being run on.
In order to know for what target device a given version of a bitmap was
produced, we define a file naming convention based on the number of pixel
per grid unit of the device.
Example:
If the target device the bitmap is produced for has 10 pixels per
grid unit, then the file name of the bitmap should be suffixed with @10:
\e my_bitmap.png should be renamed to \e my_bitmap@10.png.
In order to support the highest possible resolution devices on the market, we
recommend to always design bitmaps for a device that would have 30 pixels per
grid unit (@30 suffix). The system will perform a high quality downscaling of
the bitmap when needed on lower resolution screens.
Example:
If the destination size of the bitmap is 10 gu * 10 gu and the developer
targets a device that has 18 pixels per grid unit (1 gu = 18 px), the bitmap
should still be created as if 1 gu = 30 px which results in a 300 px * 300 px
bitmap. When testing on the device the bitmap will be downscaled by a factor
of 30 / 18 = 1.66667.
\part Fonts
It is critical for the font sizes to be consistent across Lomiri and to
have a rhythm defining them.
Instead of setting the font size in pixels or points, it is imperative to
define the font size in terms of literals:
\table
\row
\li \b x-large
\row
\li \b large
\row
\li \b medium
\row
\li \b small
\row
\li \b x-small
\endtable
Example Usage:
\code
import Lomiri.Components 1.2
Label {
fontSize: "small"
}
\endcode
For reference when designing, these sizes correspond to the following
pixel measurements:
\table
\header
\li Font Size
\li Desktop
\li Smart Phone with 4" HD screen
\li Tablet with 10" HD screen
\row
\li \b{\e x-large}
\li 34 px
\li 76 px
\li 42 px
\row
\li \b{\e large}
\li 20 px
\li 45 px
\li 25 px
\row
\li \b{\e medium}
\li 14 px
\li 31 px
\li 18 px
\row
\li \b{\e small}
\li 12 px
\li 27 px
\li 15 px
\row
\li \b{\e x-small}
\li 10 px
\li 22 px
\li 12 px
\endtable
*/
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