1 files changed, 82 insertions, 14 deletions

diff --git a/engine/src/opengl/texture.rs b/engine/src/opengl/texture.rs
index 68ac050..4186479 100644
--- a/engine/src/opengl/texture.rs
+++ b/engine/src/opengl/texture.rs
@@ -1,3 +1,5 @@
+use std::ptr::null;
+
 use crate::opengl::currently_bound::CurrentlyBound;
 use crate::vector::Vec2;
 
@@ -33,26 +35,15 @@ impl Texture
     }
 
     pub fn generate(
-        _: &CurrentlyBound<Self>,
+        curr_bound: &CurrentlyBound<Self>,
         dimens: &Vec2<u32>,
         data: &[u8],
         pixel_data_format: PixelDataFormat,
     )
     {
-        #[allow(clippy::cast_possible_wrap)]
-        unsafe {
-            gl::TexImage2D(
-                gl::TEXTURE_2D,
-                0,
-                pixel_data_format.to_gl() as i32,
-                dimens.x as i32,
-                dimens.y as i32,
-                0,
-                pixel_data_format.to_gl(),
-                gl::UNSIGNED_BYTE,
-                data.as_ptr().cast(),
-            );
+        Self::alloc_image(curr_bound, pixel_data_format, dimens, Some(data));
 
+        unsafe {
             gl::GenerateMipmap(gl::TEXTURE_2D);
         }
     }
@@ -95,6 +86,83 @@ impl Texture
             );
         }
     }
+
+    /// Creates a copy of the texture & the texture images.
+    ///
+    /// `src_offset` and `dst_offset` are source & destination offsets from the
+    /// bottom-left of the images.
+    ///
+    /// New mipmaps are generated using the largest mipmap.
+    pub fn copy(
+        &self,
+        dimensions: &Vec2<u32>,
+        pixel_data_format: PixelDataFormat,
+        src_offset: &Vec2<u32>,
+        dst_offset: &Vec2<u32>,
+    ) -> Self
+    {
+        let new_texture = Self::new();
+
+        new_texture.bind(|curr_bound| {
+            Self::alloc_image(&curr_bound, pixel_data_format, dimensions, None);
+
+            // Mipmap have to be generated since CopyImageSubData demands that the
+            // destination texture is completed
+            unsafe {
+                gl::GenerateMipmap(gl::TEXTURE_2D);
+            }
+        });
+
+        #[allow(clippy::cast_possible_wrap)]
+        unsafe {
+            gl::CopyImageSubData(
+                self.texture,
+                gl::TEXTURE_2D,
+                0,
+                src_offset.x as i32,
+                src_offset.y as i32,
+                0,
+                new_texture.texture,
+                gl::TEXTURE_2D,
+                0,
+                dst_offset.x as i32,
+                dst_offset.y as i32,
+                0,
+                dimensions.x as i32,
+                dimensions.y as i32,
+                1,
+            );
+        }
+
+        unsafe {
+            gl::GenerateMipmap(gl::TEXTURE_2D);
+        }
+
+        new_texture
+    }
+
+    fn alloc_image(
+        _: &CurrentlyBound<Self>,
+        pixel_data_format: PixelDataFormat,
+        dimens: &Vec2<u32>,
+        data: Option<&[u8]>,
+    )
+    {
+        unsafe {
+            #[allow(clippy::cast_possible_wrap)]
+            gl::TexImage2D(
+                gl::TEXTURE_2D,
+                0,
+                pixel_data_format.to_gl() as i32,
+                dimens.x as i32,
+                dimens.y as i32,
+                0,
+                pixel_data_format.to_gl(),
+                gl::UNSIGNED_BYTE,
+                data.map_or_else(null, |data| data.as_ptr().cast()),
+            );
+        }
+    }
 }
 
 impl Drop for Texture