svg_tetraflexagon_editor: draw also the backface

[flexagon-toolkit.git] / src / flexagon / tetraflexagon_diagram.py

diff --git a/src/flexagon/tetraflexagon_diagram.py b/src/flexagon/tetraflexagon_diagram.py
index 8045c23..a79a7a0 100755 (executable)
--- a/src/flexagon/tetraflexagon_diagram.py
+++ b/src/flexagon/tetraflexagon_diagram.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python
 #
-# An class to draw tetraflexagons
+# A class to draw tetraflexagons
 #
 # Copyright (C) 2018  Antonio Ospite <ao2@ao2.it>
 #
@@ -17,7 +17,6 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from math import sin, cos
 from .tritetraflexagon import TriTetraflexagon
 
 
@@ -40,6 +39,9 @@ class TetraflexagonDiagram(object):
         self.plan_origin = ((self.backend.width - self.tile_side * 5) / 2,
                             self.x_border)
 
+        self.backfaces_origin = (self.squares_centers[0][0] - self.tile_side,
+                                 self.squares_centers[0][1] + self.x_border * 2 + self.tile_side)
+
         self.squares_color_map = [(1, 0, 0), (0, 1, 0), (0, 0, 1)]
 
     def _init_centers(self):
@@ -55,9 +57,8 @@ class TetraflexagonDiagram(object):
 
             for tile in square.tiles:
                 # offset by 1 or -1 times the tile radius
-                tile_cx = cx + self.tile_radius * ((tile.index % 2) * 2 - 1)
-                tile_cy = cy + self.tile_radius * ((tile.index > 1) * 2 - 1)
-                self.tiles_centers[square.index][tile.index] = (tile_cx, tile_cy)
+                tile_xoffset, tile_yoffset = tile.calc_offset_in_square(self.tile_side)
+                self.tiles_centers[square.index][tile.index] = (cx + tile_xoffset, cy + tile_yoffset)
 
     def get_square_center(self, square):
         return self.squares_centers[square.index]
@@ -71,6 +72,16 @@ class TetraflexagonDiagram(object):
         x, y = tile.calc_plan_coordinates(self.tile_side, i, j)
         return x0 + x, y0 + y
 
+    def get_backface_tile_transform(self, tile):
+        src_x, src_y = self.get_tile_center(tile)
+        tile_xoffset, tile_yoffset = tile.calc_offset_in_square(self.tile_side)
+        # When calculating dest_x the minus in the formula switches the columns.
+        dest_x = self.backfaces_origin[0] + self.tile_side - tile_xoffset
+        dest_y = self.backfaces_origin[1] + self.tile_side + tile_yoffset
+
+        return self.backend.calc_rotate_translate_transform(src_x, src_y,
+                                                            dest_x, dest_y, 0)
+
     def get_tile_transform(self, tile):
         """Calculate the transformation matrix from a tile in an square to
         the correspondent tile in the plan.
@@ -83,59 +94,8 @@ class TetraflexagonDiagram(object):
         i, j = self.tetraflexagon.get_tile_plan_position(tile)
         theta = tile.calc_angle_in_plan(i, j)
 
-        # The transformation from a tile in the square to the correspondent
-        # tile in the plan is composed by these steps:
-        #
-        #   1. rotate by 'theta' around (src_x, src_y);
-        #   2. move to (dest_x, dest_y).
-        #
-        # Step 1 can be expressed by these sub-steps:
-        #
-        #  1a. translate by (-src_x, -src_y)
-        #  1b. rotate by 'theta'
-        #  1c. translate by (src_x, src_y)
-        #
-        # Step 2. can be expressed by a translation like:
-        #
-        #  2a. translate by (dest_x - src_x, dest_y - src_y)
-        #
-        # The consecutive translations 1c and 2a can be easily combined, so
-        # the final steps are:
-        #
-        #  T1 -> translate by (-src_x, -src_y)
-        #  R  -> rotate by 'theta'
-        #  T2 -> translate by (dest_x, dest_y)
-        #
-        # Using affine transformations these are expressed as:
-        #
-        #      | 1  0  -src_x |
-        # T1 = | 0  1  -src_y |
-        #      | 0  0       1 |
-        #
-        #      | cos(theta)  -sin(theta)  0 |
-        # R  = | sin(theta)   con(theta)  0 |
-        #      |          0            0  1 |
-        #
-        #      | 1  0  dest_x |
-        # T2 = | 0  1  dest_y |
-        #      | 0  0       1 |
-        #
-        # Composing these transformations into one is achieved by multiplying
-        # the matrices from right to left:
-        #
-        #   T = T2 * R * T1
-        #
-        # NOTE: To remember this think about composing functions: T2(R(T1())),
-        # the inner one is performed first.
-        #
-        # The resulting  T matrix is the one below.
-        matrix = [
-            cos(theta), -sin(theta), -src_x * cos(theta) + src_y * sin(theta) + dest_x,
-            sin(theta),  cos(theta), -src_x * sin(theta) - src_y * cos(theta) + dest_y,
-                     0,           0,                                                 1
-        ]
-
-        return matrix
+        return self.backend.calc_rotate_translate_transform(src_x, src_y,
+                                                            dest_x, dest_y, theta)
 
     def draw_square_template(self, square):
         for tile in square.tiles:
@@ -146,7 +106,9 @@ class TetraflexagonDiagram(object):
         side = self.tile_side
         color = self.squares_color_map[tile.square.index]
 
-        self.backend.draw_rect_from_center(cx, cy, side, side, theta, color)
+        self.backend.draw_rect_from_center(cx, cy, side, side, theta,
+                                           stroke_color=color,
+                                           fill_color=None)
 
         corners_labels = "ABC"
         corner_text = corners_labels[tile.square.index] + str(tile.index + 1)