/src/wrappers/cairo/library/cairo_matrix.e

  1note
  2	description: "cairo_matrix_t -- Generic matrix operations."
  3	copyright: "[
  4					Copyright (C) 2007-2017: Paolo Redaelli,
  5					Soluciones Informaticas Libres S.A. (Except),
  6					Cairo team
  7					
  8					This library is free software; you can redistribute it and/or
  9					modify it under the terms of the GNU Lesser General Public License
 10					as published by the Free Software Foundation; either version 2.1 of
 11					the License, or (at your option) any later version.
 12					
 13					This library is distributed in the hope that it will be useful, but
 14					WITHOUT ANY WARRANTY; without even the implied warranty of
 15					MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 16					Lesser General Public License for more details.
 17
 18					You should have received a copy of the GNU Lesser General Public
 19					License along with this library; if not, write to the Free Software
 20					Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 21					02110-1301 USA
 22			]"
 23	date: "$Date:$"
 24	revision: "$Revision:$"
 25	wrapped_version: "1.2.4"
 26
 27class CAIRO_MATRIX
 28	-- CAIRO_MATRIX (cairo_matrix_t in C) is used throughout cairo to
 29	-- convert between different coordinate spaces. A cairo_matrix_t
 30	-- holds an affine transformation, such as a scale, rotation,
 31	-- shear, or a combination of these. The transformation of a point
 32	-- (x,y) is given by:
 33	
 34	--     x_new = xx * x + xy * y + x0;
 35	--     y_new = yx * x + yy * y + y0;
 36
 37	-- The current transformation matrix of a cairo_t, represented as a
 38	-- cairo_matrix_t, defines the transformation from user-space
 39	-- coordinates to device-space coordinates. See `matrix'() and
 40	-- `set_matrix' in CAIRO_CONTEXT.
 41
 42inherit C_STRUCT
 43
 44insert
 45	CAIRO_MATRIX_EXTERNALS
 46	CAIRO_STATUS
 47
 48create {ANY} make, allocate, from_external_pointer
 49
 50feature {} -- Creation
 51	make (an_xx, an_yx, an_xy, an_yy, an_x0, an_y0: REAL)
 52			-- Create matrix to be the affine transformation given by xx,
 53			-- yx, xy, yy, x0, y0. The transformation is given by:
 54
 55			--  x_new = xx * x + xy * y + x0;
 56			--  y_new = yx * x + yy * y + y0;
 57			
 58			--   xx :     xx component of the affine transformation
 59			--   yx :     yx component of the affine transformation
 60			--   xy :     xy component of the affine transformation
 61			--   yy :     yy component of the affine transformation
 62			--   x0 :     X translation component of the affine transformation
 63			--   y0 :     Y translation component of the affine transformation
 64		do
 65			allocate
 66			cairo_matrix_init(handle, xx, yx, xy, yy, x0, y0);
 67		end
 68
 69	identity
 70			-- Create a matrix for the identity transformation.
 71		do
 72			allocate
 73			cairo_matrix_init_identity (handle)
 74		end
 75
 76	translation (a_tx, a_ty: REAL)
 77			-- Initializes matrix to a transformation that translates by
 78			-- `a_tx' and `a_ty' in the X and Y dimensions, respectively.
 79		do
 80			allocate
 81			cairo_matrix_init_translate (handle, a_tx, a_ty)
 82		end
 83
 84	scaling (an_x_scale, an_y_scale: REAL)
 85			-- Create matrix to a transformation that scales by
 86			-- `an_x_scale' and `an_y_scale' in the X and Y dimensions,
 87			-- respectively.
 88		do
 89			allocate
 90			cairo_matrix_init_scale(handle,an_x_scale,an_y_scale)
 91		end
 92
 93	rotation (some_radians: REAL)
 94			-- Create matrix as a transformation that rotates by `some_radians'.
 95
 96			-- `some_radians': angle of rotation, in radians. The
 97			-- direction of rotation is defined such that positive angles
 98			-- rotate in the direction from the positive X axis toward
 99			-- the positive Y axis. With the default axis orientation of
100			-- cairo, positive angles rotate in a clockwise direction.
101		do
102			allocate
103			cairo_matrix_init_rotate(handle,some_radians)
104		end
105
106feature {ANY} -- Access
107	xx: REAL
108			-- xx component of the affine transformation
109		do
110			Result := cairo_matrix_get_xx(handle)
111		end
112
113	yx: REAL
114			-- yx component of the affine transformation
115		do
116			Result := cairo_matrix_get_yx(handle)
117		end
118
119	xy: REAL
120			-- xy component of the affine transformation
121		do
122			Result := cairo_matrix_get_xy(handle)
123		end
124
125	yy: REAL
126			-- yy component of the affine transformation
127		do
128			Result := cairo_matrix_get_yy(handle)
129		end
130
131	x0: REAL
132			-- x0 component of the affine transformation
133		do
134			Result := cairo_matrix_get_x0(handle)
135		end
136
137	y0: REAL
138			-- y0 component of the affine transformation
139		do
140			Result := cairo_matrix_get_y0(handle)
141		end
142
143feature {ANY}
144	translate (a_tx, a_ty: REAL)
145			-- Applies a translation by `a_tx', `a_ty' to the
146			-- transformation in matrix. The effect of the new
147			-- transformation is to first translate the coordinates by
148			-- `a_tx' and `a_ty', then apply the original transformation
149			-- to the coordinates.
150
151			-- `a_tx' :     amount to translate in the X direction
152			-- `a_ty' :     amount to translate in the Y direction		
153		do
154			cairo_matrix_translate(handle,a_tx,a_ty)
155		end			
156
157	scale (an_sx, an_sy: REAL)
158			-- Applies scaling by `an_sx', `an_sy' to the transformation
159			-- in matrix. The effect of the new transformation is to
160			-- first scale the coordinates by `an_sx' and `an_sy', then
161			-- apply the original transformation to the coordinates.
162		
163			-- `an_sx' :     scale factor in the X direction
164			-- `an_sy' :     scale factor in the Y direction
165		do
166			cairo_matrix_scale(handle,an_sx,an_sy)
167		end
168
169	rotate (some_radians: REAL)
170			-- Applies rotation by `some_radians' to the transformation
171			-- in matrix. The effect of the new transformation is to
172			-- first rotate the coordinates by radians, then apply the
173			-- original transformation to the coordinates.
174		
175			-- `some_radians': angle of rotation, in radians. The
176			-- direction of rotation is defined such that positive angles
177			-- rotate in the direction from the positive X axis toward
178			-- the positive Y axis. With the default axis orientation of
179			-- cairo, positive angles rotate in a clockwise direction.
180		do
181			cairo_matrix_rotate(handle,some_radians)
182		end
183
184	inverse: CAIRO_MATRIX
185			-- The inverse of Current value. Void if Current does not
186			-- have inverse, i.e.: if the matrix collapses points
187			-- together (it is degenerate), then it has no inverse and
188			-- this function will fail.
189		local a_status: INTEGER
190		do
191			Result := twin
192			a_status := cairo_matrix_invert (Result.handle)
193			-- cairo_matrix_invert returns: If matrix has an inverse,
194			-- modifies matrix to be the inverse matrix and returns
195			-- CAIRO_STATUS_SUCCESS. Otherwise,
196			if a_status = cairo_status_invalid_matrix then
197				Result := Void
198			end
199		end
200
201	inverted: BOOLEAN
202			-- True if matrix could be changed into the inverse of it's
203			-- original value.
204
205			-- Not all transformation matrices have inverses; if the
206			-- matrix collapses points together (it is degenerate), then
207			-- it has no inverse and this feature will be False and 
208			-- matrix will not be changed.
209		local a_status: INTEGER
210		do
211			Result:=(cairo_matrix_invert(handle) /= cairo_status_invalid_matrix)
212		end
213
214	infix "*" (another: like Current): like Current
215			-- A new matrix containing the multiplication of the affine
216			-- transformations of Current and `another' together. The
217			-- effect of the resulting transformation is to first apply
218			-- the transformation in Current to the coordinates and then
219			-- apply the transformation in `another' to the coordinates.
220		require another_not_void: another /= Void
221		do
222			create Result.allocate
223			cairo_matrix_multiply(Result.handle,handle,another.handle)
224			-- TODO: since it is allowable for result to be identical to either current or 
225			-- another, it is good to provide `multiply' and `square'.
226			ensure not_void: Result/=Void
227		end
228
229feature {ANY} -- Memory handling
230	dispose
231		do
232			free(handle)
233		end
234end -- class CAIRO_MATRIX