XFillRectangle

XFillRectangle is a function in the X Window System protocol used for drawing filled rectangles on a display. It is part of the Xlib library, which provides a C language interface to the X protocol. The function takes a drawable (such as a window or pixmap), a GC (graphics context), and the coordinates and dimensions of the rectangle to be filled. The GC specifies drawing properties like color, line style, and fill mode. When XFillRectangle is called, the X server renders a solid rectangle of the specified color within the given coordinates onto the specified drawable. This is a fundamental operation for many graphical user interface elements and drawing applications. The function is efficient as it is handled directly by the server. It is important to note that XFillRectangle draws the rectangle using the foreground color defined in the graphics context. If the graphics context is set to use a pattern for filling, the rectangle will be filled with that pattern instead of a solid color.