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sbcl/.quicklisp/dists/quicklisp/software/croatoan-20191227-git/src/bkgd.lisp

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+(in-package :de.anvi.croatoan)
+
+;; bkgd applies to every cell in the window.
+;; bkgdset applies only to new chars inserted after the call to bkgdset.
+;; i.e. with bkgd we manipulate the existing text, with bkgdset the new text.
+
+;; the attribute part of the background char is combined with any chars added.
+;; because of that, we cant use alternate chars as background chars, since
+;; :altcharset is an attribute.
+
+(defun set-background-char (winptr xchar &optional (apply t))
+  "Set a complex single-byte character as the background of a window.
+
+The attribute part of the background character is combined with
+simple characters in the window.
+
+If apply is t, the background setting is immediately applied to all cells
+in the window.
+
+Otherwise, it is applied only to newly added simple characters."
+  (let ((chtype (xchar2chtype xchar)))
+    (if apply
+        ;; the background char is applied to every cell in the window by default.
+        (%wbkgd    winptr chtype)
+        ;; if apply is nil, the background is combined only with new characters.
+        (%wbkgdset winptr chtype))))
+
+(defun get-background-char (window)
+  "Return the complex char that is the background character of the window."
+  (let* ((winptr (winptr window))
+         (chtype (%getbkgd winptr)))
+    (chtype2xchar chtype)))