Initial revision

Lib/lib-stdwin/rect.py

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+# Module 'rect'.
+#
+# Operations on rectangles.
+# There is some normalization: all results return the object 'empty'
+# if their result would contain no points.
+
+
+# Exception.
+#
+error = 'rect.error'
+
+
+# The empty rectangle.
+#
+empty = (0, 0), (0, 0)
+
+
+# Check if a rectangle is empty.
+#
+def is_empty((left, top), (right, bottom)):
+	return left >= right or top >= bottom
+
+
+# Compute the intersection or two or more rectangles.
+# This works with a list or tuple argument.
+#
+def intersect(list):
+	if not list: raise error, 'intersect called with empty list'
+	if is_empty(list[0]): return empty
+	(left, top), (right, bottom) = list[0]
+	for rect in list[1:]:
+		if not is_empty(rect):
+			(l, t), (r, b) = rect
+			if left < l: left = l
+			if top < t: top = t
+			if right > r: right = r
+			if bottom > b: bottom = b
+			if is_empty((left, top), (right, bottom)):
+				return empty
+	return (left, top), (right, bottom)
+
+
+# Compute the smallest rectangle containing all given rectangles.
+# This works with a list or tuple argument.
+#
+def union(list):
+	(left, top), (right, bottom) = empty
+	for (l, t), (r, b) in list[1:]:
+		if not is_empty((l, t), (r, b)):
+			if l < left: left = l
+			if t < top: top = t
+			if r > right: right = r
+			if b > bottom: bottom = b
+	res = (left, top), (right, bottom)
+	if is_empty(res):
+		return empty
+	return res
+
+
+# Check if a point is in a rectangle.
+#
+def pointinrect((h, v), ((left, top), (right, bottom))):
+	return left <= h < right and top <= v < bottom
+
+
+# Return a rectangle that is dh, dv inside another
+#
+def inset(((left, top), (right, bottom)), (dh, dv)):
+	left = left + dh
+	top = top + dv
+	right = right - dh
+	bottom = bottom - dv
+	r = (left, top), (right, bottom)
+	if is_empty(r):
+		return empty
+	else:
+		return r
+
+
+# Conversions between rectangles and 'geometry tuples',
+# given as origin (h, v) and dimensions (width, height).
+#
+def rect2geom((left, top), (right, bottom)):
+	return (left, top), (right-left, bottom-top)
+
+def geom2rect((h, v), (width, height)):
+	return (h, v), (h+width, v+height)