size hints infrastructure

Operations.hs

@@ -482,3 +482,36 @@ mouseResizeWindow w = withDisplay $ \d -> do
 --     x  <- f d w wa
 --     mouseDrag $ \(_,_,_,ex,ey,_,_,_,_,_) -> g x ex ey d w wa
 --     float w
+
+
+------------------------------------------------------------------------
+-- size hints
+
+-- | Reduce the dimensions if needed to comply to the given SizeHints.
+applySizeHints :: SizeHints -> (Dimension, Dimension) -> (Dimension, Dimension)
+applySizeHints sh =
+    maybe id applyMaxSizeHint (sh_max_size sh) .
+    maybe id (\(bw, bh) (w, h) -> (w+bw, h+bh)) (sh_base_size sh) .
+    maybe id applyResizeIncHint (sh_resize_inc sh) .
+    maybe id applyAspectHint (sh_aspect sh) .
+    maybe id (\(bw, bh) (w, h) -> (w-bw, h-bh)) (sh_base_size sh)
+
+-- | Reduce the dimensions so their aspect ratio falls between the two given aspect ratios.
+applyAspectHint :: ((Dimension, Dimension), (Dimension, Dimension)) -> (Dimension, Dimension) -> (Dimension, Dimension)
+applyAspectHint ((minx, miny), (maxx, maxy)) (w, h)
+    | or [minx < 1, miny < 1, maxx < 1, maxy < 1] = (w, h)
+    | w * maxy > h * maxx = (h * maxx `div` maxy, h)
+    | w * miny < h * minx = (w, w * miny `div` minx)
+    | otherwise = (w, h)
+
+-- | Reduce the dimensions so they are a multiple of the size increments.
+applyResizeIncHint :: (Dimension, Dimension) -> (Dimension, Dimension) -> (Dimension, Dimension)
+applyResizeIncHint (iw, ih) (w, h)
+    | iw > 0 && ih > 0 = (w - w `mod` iw, h - h `mod` ih)
+    | otherwise = (w, h)
+
+-- | Reduce the dimensions if they exceed the given maximum dimensions.
+applyMaxSizeHint :: (Dimension, Dimension) -> (Dimension, Dimension) -> (Dimension, Dimension)
+applyMaxSizeHint (maxw, maxh) (w, h)
+    | maxw > 0 && maxh > 0 = (min w maxw, min h maxh)
+    | otherwise = (w, h)