xserver/mi/mizerclip.c

67 	M = # of steps in X direction
68 	N = # of steps in Y direction
69 	B = 0 to prefer diagonal steps in a given octant,
70 	    1 to prefer axial steps in a given octant
80 At the start of the line, we have taken 0 X steps and 0 Y steps,
89 At the end of the line, we have taken dx X steps and dy Y steps,
104 cases, we know the number of X steps (M) and we wish to find the
105 number of Y steps (N).  Thus, we will solve our error term equation.
108 end of the line, we will find the largest number of Y steps that
110 the Y steps as (dy - N), we will actually want to solve for the
113 Case 1:  X major, starting X coordinate moved by M steps
127 Case 1b: X major, ending X coordinate moved to M steps
134 Case 2: X major, ending X coordinate moved by M steps
143 Since we are trying to find the highest number of Y steps that
151 Case 2b: X major, starting X coordinate moved to M steps from end
154 steps, so we want the highest N, so we use the < inequality:
161 Case 3: Y major, starting X coordinate moved by M steps
175 Case 3b: Y major, ending X coordinate moved to M steps
185 Case 4: Y major, ending X coordinate moved by M steps
194 Since we are trying to find the highest number of Y steps that
200 Case 4b: Y major, starting X coordinate moved to M steps from end
202 Same analysis as Case 4, but we want the smallest number of Y steps
209 Case 5: X major, starting Y coordinate moved by N steps
222 Case 5b: X major, ending Y coordinate moved to N steps
232 Case 6: X major, ending Y coordinate moved by N steps
241 Largest # of X steps means smallest M, so use the > inequality:
245 Case 6b: X major, starting Y coordinate moved to N steps from end
247 Same derivations as Case 6, but we want the smallest # of X steps
252 Case 7: Y major, starting Y coordinate moved by N steps
265 Case 7b: Y major, ending Y coordinate moved to N steps
272 Case 8: Y major, ending Y coordinate moved by N steps
281 To find the highest X steps, find the smallest M, use the >= inequality:
287 Case 8b: Y major, starting Y coordinate moved to N steps from the end
290 steps which means the largest M, so we use the < inequality:
595             if (eqn & T_2NDX)   /* We are calculating X steps */  in miZeroClipLine()
597             else                /* else, Y steps */  in miZeroClipLine()