I know Swing use Java2d which extends AWT to draw on screen but, what low level toolkit is used by swing to render? GTK or QT for example?
Concrete implementations of Graphics2D on each supported platform direct painting to a heavyweight peer component provided by the host, e.g. Quartz on Mac OS X, Graphics Device Interface on Windows, and Xlib/XCB, part of the X Window System often used on Linux.
来源：https://stackoverflow.com/questions/29440313/how-java-swing-draws-to-screen-from-different-operating-systems