/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "LayersHelpers.h"

namespace mozilla {

namespace layers {

using namespace gfx;

gfx::IntRect

ComputeBackdropCopyRect(const gfx::Rect& aRect,

                        const gfx::IntRect& aClipRect,

                        const gfx::Matrix4x4& aTransform,

                        const gfx::IntRect& aRenderTargetRect,

                        gfx::Matrix4x4* aOutTransform,

                        gfx::Rect* aOutLayerQuad)

{

  // Compute the clip.

  IntPoint rtOffset = aRenderTargetRect.TopLeft();

  IntSize rtSize = aRenderTargetRect.Size();

  gfx::IntRect renderBounds(0, 0, rtSize.width, rtSize.height);

  renderBounds.IntersectRect(renderBounds, aClipRect);

  renderBounds.MoveBy(rtOffset);

  // Apply the layer transform.

  RectDouble dest = aTransform.TransformAndClipBounds(

    RectDouble(aRect.X(), aRect.Y(), aRect.Width(), aRect.Height()),

    RectDouble(renderBounds.X(), renderBounds.Y(), renderBounds.Width(), renderBounds.Height()));

  dest -= rtOffset;

  // Ensure we don't round out to -1, which trips up Direct3D.

  dest.IntersectRect(dest, RectDouble(0, 0, rtSize.width, rtSize.height));

  if (aOutLayerQuad) {

    *aOutLayerQuad = Rect(dest.X(), dest.Y(), dest.Width(), dest.Height());

  }

  // Round out to integer.

  IntRect result;

  dest.RoundOut();

  dest.ToIntRect(&result);

  // Create a transform from adjusted clip space to render target space,

  // translate it for the backdrop rect, then transform it into the backdrop's

  // uv-space.

  Matrix4x4 transform;

  transform.PostScale(rtSize.width, rtSize.height, 1.0);

  transform.PostTranslate(-result.X(), -result.Y(), 0.0);

  transform.PostScale(1 / float(result.Width()), 1 / float(result.Height()), 1.0);

  *aOutTransform = transform;

  return result;

}

} // namespace layers

} // namespace mozilla