libplasma provides the Theme class so Plasma elements and other applications, such as KRunner, that need to graphically hint or theme interface elements. This is not a replacement for QStyle, but rather provides standard elements for things such as box backgrounds.
This allows for easy re-theming of the desktop while also keeping elements on the desktop more consistent with each other.
See also Plasma widgets.
A theme is described by a .desktop file in share/apps/desktoptheme. The contents of which might look like this:
Comment=Theme done in the Oxygen style
X-KDE-PluginInfo-Author=The Oxygen Project
The X-KDE-PluginInfo-Name entry must contain the name of the subdirectory in share/apps/desktoptheme where the SVG files for this theme exist.
Theme elements are accessed by path. Whether this maps to literal paths on disk or not is not guaranteed and considered an implementation detail of Plasma::Theme.
Therefore, to access the dialog background, one might create an svg in this manner:
It is generally recommended to use Plasma::Svg instead of QSvgRenderer directly, however. Remember to call resize() on the Plasma::Svg before painting with it!
Reaction to Theme Changes
If you use Plasma::Svg, changes to the theme are automatically picked up. Otherwise, you can connect to the changed() signal in the Plasma::Theme class. This signal is emitted whenever the theme is changed.
Current Theme Elements
Themes get installed to share/apps/desktoptheme. Each theme is stored in a subdirectory with the following file structure
- /dialogs: elements for dialogs
- /background.svg: generic dialog background, used by the Run Command dialog, the sceensaver password dialog, etc
- /shutdowndlg.svg: background for the log out dialog
- /shutdowndlgbuttonglow.svg: an overlay for buttons on the log out dialog that is shown on mouse over
- /widgets: generic desktop widget background
- /background.svg: a background image for plasmoids
- /clock.svg: an analog clock face. it must have the following named elements:
- ClockFace: the background of the clock, usually containing the numbers, etc
- HourHand: the hour hand, pointing down in the svg
- MinuteHand: the minute hand, pointing down in the svg
- SecondHand: the second hand, pointing down in the svg
- HandCenterScrew: the "pin" that holds the hands together in the center
- Glass: a final overlay which allows for things such as the appearance of glass
- /iconbutton.svg: backgrounds and overlays for icons that are clickable. can have any of the following named elements, each of which should be the same size:
- background: the default background, painted beneath the icon
- background-hover: background when the mouse hovers the icon
- background-pressed: background when the icon is pressed
- foreground: the default foreground, painted on top of the icon
- foreground-hover: foreground when the mouse hovers the icon
- foreground-pressed: foreground when the icon is pressed
- /plot-background.svg: a background for plotter (graph) widgets, such as the plots in ksysguard
- /toolbox-button.svg: the background for the desktop configuration toolbox button that sites at the edge of the desktop