Difference between revisions of "KDE Visual Design Group/HIG/Units"

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== Purpose ==
This pages gives an overview about different units used in KDE and Plasma
== Pixel ==
{{Note|This page is now on [[https://hig.kde.org/layout/units.html https://hig.kde.org/]]}}
A (physical) pixel or dot is a physical point in a raster image, or the smallest addressable element in an all points addressable display device. <span style="color: red">Be careful not to confuse it with DPI independent pixels</span>
== DPI - pixels per inch ==
Pixel density is the number of (physical) pixels or dots that fit into an inch. Different screens have different DPI.
<b>screen density = screen width (or height) in pixels / screen width (or height) in inches</b>
|[[Image:Pixel.qml.png|Different DPIs on desktop and mobile]]
DPI is often used interchangeably with PPI, pixel per inch.
== PPI / DPI independent pixels ==
A DPI independet pixel is scaled to look uniform on any screen regardless of the DPI. A lot of platforms, eg iOS, Android, the Web, replaced the old (physical) px with a DPI px. So most the time you read about pixel/px they actually talk about DPI independent pixels. Qt (and QML) support DPI independent pixels in newer versions, but because KDE and Plasma support older versions of Qt too, one can not assume that pixels used in Qt or QML apps are DPI independent.
|[[Image:Dpi.qml.png|Different DPIs on desktop and mobile]]
A rectangle defined with <span style="color: #da4453">physical pixels</span> and <span style="color: #27ae60">DPI independent pixels</span>.
<span style="color: red">Note to developers: Except explicilty stated otherwise, all HIG pages, draft, mockups, ... pixels/px are always DPI independent pixels.</span>
=== Fonts ===
Since KDE allows the user to change the font settings any dimensions defined with px, no matter if they are DPI independent or not, make problems together with text.
|[[Image:Font.qml.png|Using DPI independet pixel with different font setting]]
== base units in plasma ==
There are two special base units in plasma:
* units.smallSpacing
* units.largeSpacing
These two are not only DPI independent but scale according to the font settings too.
|[[Image:Units.qml.png|Using units.smallSpacing with different font setting]]
A rectangle defined with <span style="color: #3daee9">units.smallSpacing</span>

Latest revision as of 19:55, 5 February 2019

This page is now on [https://hig.kde.org/]

This page was last edited on 5 February 2019, at 19:55. Content is available under Creative Commons License SA 4.0 unless otherwise noted.