Applications can call functions in both the graphics library and the Intuition library to render images, lines, text and other graphic elements in windows. The graphics library provides primitive operations such as area fill, line drawing, text and animation. The number of colors and the palette available in a window are defined by the screen in which the window opens. Applications should never change the palette of a screen unless the screen is a custom screen created by the application. Graphics rendered into the window should respect the drawing pens defined for the screen. See the section on "DrawInfo and the 3D Look" in the "Intuition Screens" chapter for more information. Default window fonts come from one of two places, depending on the screen on which the window opens. The window title font is always taken from the screen font. If the screen is opened with a font specified, either by specifying the tag SA_Font or the variable NewScreen.Font, then Window.RPort->Font is taken from the screen's font. Otherwise, the window's rastport's font is taken from GfxBase->DefaultFont. This information is available to the application if it opened the screen. If the application did not open the screen, it has no way of knowing which font has been used for the window. Applications that require to know the window's font before the window is open must explicitly set the font (using SetFont()) for that window after opening it. In this case, the application may use any font it desires. It is recommended that applications use the screen's font if they support proportional fonts, and GfxBase->DefaultFont otherwise, as these fonts are generally the user's preference. Intuition also provides a minimal high level interface to some of the functions in the Graphics library. This includes calls to draw lines, text and images. See the chapter entitled "Intuition Images, Line Drawing and Text," for more information about using Intuition to render graphics.