Texture2D.GetData buggy for DXT textures

[Skeatwin]

I use MonoGame 3.4 on Windows (Windows DirectX project) with Visual Studio 2015.
I have this texture into DXT1 format:

When I use this code:

        Texture2D texture;
        SpriteBatch spriteBatch;

        protected override void LoadContent()
        {
            spriteBatch = new SpriteBatch(GraphicsDevice);

            // Load Dxt1 texture (256x256).
            texture = Content.Load<Texture2D>("t");
            byte[] data = new byte[texture.Width * texture.Height / 2]; // Dxt1 correct data size
            texture.GetData(data);
            texture.SetData(data); // Now texture is corrupted.
        }

        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.CornflowerBlue);
            spriteBatch.Begin();

            spriteBatch.Draw(texture, Vector2.Zero, Color.White);

            spriteBatch.End();
            base.Draw(gameTime);
        }

I get this result:

But, the same code with the texture into Color format (ARGB8) work fine.
I have also tried with DXT3 and DXT5 format and it's the same result as DXT1: texture is corrupted.

A previous issue thread #3590 suggest to change the type of struct to get texture data to avoid troubles, but no changes for DXT textures this time.

[tomspilman]

Looks like how we're stepping thru the height.

https://github.com/mono/MonoGame/blob/develop/MonoGame.Framework/Graphics/Texture2D.DirectX.cs#L168

My guess is that we should be incrementing the row more than we are for DXT surfaces.

[KonajuGames]

I had started looking at this. We will need to revise the process for compressed textures.

[Skeatwin]

I would like to help you but I don't think I am at the level... (off topic but great works for the 3.5 !)