lib/gamnit: intro `Sprite::invert_x`

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/gamnit/flat.nit b/lib/gamnit/flat.nit
index 6f9dea4..06ac8df 100644 (file)
--- a/lib/gamnit/flat.nit
+++ b/lib/gamnit/flat.nit
@@ -55,6 +55,9 @@ class Sprite
        # Rotation on the Z axis
        var rotation = 0.0 is writable
 
+       # Mirror `texture` horizontally, inverting each pixel on the X axis
+       var invert_x = false is writable
+
        # Scale applied to this sprite
        var scale = 1.0 is writable
 
@@ -86,7 +89,10 @@ class Sprite
 
                simple_2d_program.use_texture.uniform true
                simple_2d_program.texture.uniform 0
-               simple_2d_program.tex_coord.array(texture.texture_coords, 2)
+               simple_2d_program.tex_coord.array(
+                       if invert_x then
+                               texture.texture_coords_invert_x
+                       else texture.texture_coords, 2)
                simple_2d_program.coord.array(texture.vertices, 3)
 
                simple_2d_program.rotation.uniform new Matrix.rotation(rotation, 0.0, 0.0, 1.0)
@@ -295,6 +301,18 @@ redef class Texture
                for v in [c, d, a, b] do texture_coords.add_all v
                return texture_coords
        end
+
+       # Coordinates of this texture on the `root` texture, with the X axis inverted
+       private var texture_coords_invert_x: Array[Float] is lazy do
+               var a = [offset_left,  offset_bottom]
+               var b = [offset_right, offset_bottom]
+               var c = [offset_left,  offset_top]
+               var d = [offset_right, offset_top]
+
+               var texture_coords = new Array[Float]
+               for v in [d, c, b, a] do texture_coords.add_all v
+               return texture_coords
+       end
 end
 
 # Graphic program to display simple models with a texture, translation, rotation and scale