gamnit: add a subtexture with relative border coordinates

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

diff --git a/lib/gamnit/textures.nit b/lib/gamnit/textures.nit
index 4bc95cb..65f654b 100644 (file)
--- a/lib/gamnit/textures.nit
+++ b/lib/gamnit/textures.nit
@@ -80,9 +80,7 @@ abstract class Texture
        # Prepare a subtexture from this texture, from the given pixel offsets
        fun subtexture(left, top, width, height: Numeric): Subtexture
        do
-               # Setup the subtexture
-               var subtex = new Subtexture(root, self, left.to_f, top.to_f, width.to_f, height.to_f)
-               return subtex
+               return new AbsoluteSubtexture(self, left.to_f, top.to_f, width.to_f, height.to_f)
        end
 
        # Offset of the left border on `root` from 0.0 to 1.0
@@ -309,18 +307,25 @@ class TextureAsset
 end
 
 # Texture derived from another texture, does not own its pixels
-class Subtexture
+abstract class Subtexture
        super Texture
 
-       redef var root
-
        # Parent texture, from which this texture was created
        var parent: Texture
 
-       # Left border of this texture compared to `parent`
+       redef var root = parent.root is lateinit
+
+       redef fun load(force) do root.load(force)
+end
+
+# Subtexture created from pixel coordinates within `parent`
+class AbsoluteSubtexture
+       super Subtexture
+
+       # Left border of this texture relative to `parent`
        var left: Float
 
-       # Top border of this texture compared to `parent`
+       # Top border of this texture relative to `parent`
        var top: Float
 
        private fun set_wh(width, height: Float)
@@ -329,14 +334,25 @@ class Subtexture
                self.height = height
        end
 
-       redef fun load(force) do root.load(force)
-
        redef var offset_left = parent.offset_left + left / root.width is lazy
        redef var offset_top = parent.offset_top + top / root.height is lazy
        redef var offset_right = offset_left + width / root.width is lazy
        redef var offset_bottom = offset_top + height / root.height is lazy
 end
 
+# Subtexture created from relative coordinates ([0..1]) out of the `root` texture
+class RelativeSubtexture
+       super Subtexture
+
+       redef var offset_left
+       redef var offset_top
+       redef var offset_right
+       redef var offset_bottom
+
+       redef fun width do return root.width * (offset_right - offset_left)
+       redef fun height do return root.height * (offset_bottom - offset_top)
+end
+
 redef class Sys
        # All declared root textures
        var all_root_textures = new TextureSet