+.PP
+Neither X/Open Curses nor the SVr4 manual pages give details about
+the way the rendition of characters on the screen is updated when
+\fBbkgd\fP or \fBwbkgd\fP is used to change the background character.
+.PP
+This implementation, like SVr4 curses, does not store the background
+and window attribute contributions to each cell separately.
+It updates the rendition by comparing the character, non-color attributes and
+colors contained in the background.
+For each cell in the window, whether or not it is blank:
+.bP
+The library first compares the \fIcharacter\fP,
+and if it matches the current character part of the background,
+it replaces that with the new background character.
+.bP
+The library then checks if the cell uses color,
+i.e., its color pair value is nonzero.
+If not, it simply replaces the attributes and color pair in the
+cell with those from the new background character.
+.bP
+If the cell uses color,
+and that matches the color in the current background,
+the library removes attributes
+which may have come from the current background
+and adds attributes from the new background.
+It finishes by setting the cell
+to use the color from the new background.
+.bP
+If the cell uses color,
+and that does not match the color in the current background,
+the library updates only the non-color attributes,
+first removing those which may have come from the current background,
+and then adding attributes from the new background.
+.PP
+If the background's character value is zero, a space is assumed.
+.PP
+If the terminal does not support color,
+or if color has not been started with \fBstart_color\fP,
+the new background character's color attribute will be ignored.
+.SS getbkgd
+.PP