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diff --git a/src/common/Grid.h b/src/common/Grid.h
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+++ b/src/common/Grid.h
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+/*
+ * Copyright 2011  Alex Merry <dev@randomguy3.me.uk>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#import <Foundation/Foundation.h>
+#import "RenderContext.h"
+#import "Transformer.h"
+
+/*!
+ * Provides a grid, which can be use for snapping points
+ *
+ * The grid is divided into cells, and each cell is further subdivided.
+ * These subdivisions are the snap points for the grid.
+ */
+@interface Grid: NSObject {
+	Transformer *transformer;
+	float spacing;
+	int cellSubdivisions;
+}
+
+/*!
+ * The number of times to subdivide the edge of each cell
+ *
+ * Each cell will be divided into cellSubdivisions^2 squares.
+ */
+@property (assign) int cellSubdivisions;
+
+/*!
+ * The cell spacing
+ *
+ * Each cell will be @p cellSpacing wide and @p cellSpacing high.
+ */
+@property (assign) float cellSpacing;
+
+
+/*!
+ * Create a new grid object.
+ *
+ * @param sp    the cell spacing - this will be the width and height of each cell
+ * @param subs  the number of cell subdivisions; the cell will end up being
+ *              divided into subs*subs squares that are each sp/subs wide and high
+ * @param t     the transformer to be used when snapping screen points
+ */
++ (Grid*) gridWithSpacing:(float)sp subdivisions:(int)subs transformer:(Transformer*)t;
+/*!
+ * Initialize a grid object.
+ *
+ * @param sp    the cell spacing - this will be the width and height of each cell
+ * @param subs  the number of cell subdivisions; each cell will end up being
+ *              divided into subs*subs squares that are each sp/subs wide and high
+ * @param t     the transformer to be used when snapping screen points
+ */
+- (id) initWithSpacing:(float)sp subdivisions:(int)subs transformer:(Transformer*)t;
+
+/*!
+ * Snap a point in screen co-ordinates
+ *
+ * @param p  the point to snap, in screen co-ordinates
+ * @result   @p p aligned to the nearest corner of a cell subdivision
+ */
+- (NSPoint) snapScreenPoint:(NSPoint)p;
+/*!
+ * Snap a point in base co-ordinates
+ *
+ * @param p  the point to snap
+ * @result   @p p aligned to the nearest corner of a cell subdivision
+ */
+- (NSPoint) snapPoint:(NSPoint)p;
+
+/**
+ * Renders the grid
+ *
+ * The grid is rendered across the entire surface (subject to the context's
+ * clip).
+ *
+ * The internal transformer is used to convert between graph co-ordinates
+ * and graphics co-ordinates.
+ *
+ * @param cr  the context to render in
+ */
+- (void) renderGridInContext:(id<RenderContext>)cr;
+
+/**
+ * Renders the grid
+ *
+ * The grid is rendered across the entire surface (subject to the context's
+ * clip).
+ *
+ * @param cr  the context to render in
+ * @param t   a transformer that will be used to map graph co-ordinates
+ *            to graphics co-ordinates
+ */
+- (void) renderGridInContext:(id<RenderContext>)cr transformer:(Transformer*)t;
+
+@end
+
+// vi:ft=objc:noet:ts=4:sts=4:sw=4