gfx/layers/LayersHelpers.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "LayersHelpers.h"
   8
   9 namespace mozilla {
  10 namespace layers {
  11
  12 using namespace gfx;
  13
  14 gfx::IntRect ComputeBackdropCopyRect(const gfx::Rect& aRect,
  15                                      const gfx::IntRect& aClipRect,
  16                                      const gfx::Matrix4x4& aTransform,
  17                                      const gfx::IntRect& aRenderTargetRect,
  18                                      gfx::Matrix4x4* aOutTransform,
  19                                      gfx::Rect* aOutLayerQuad) {
  20   // Compute the clip.
  21   IntPoint rtOffset = aRenderTargetRect.TopLeft();
  22   IntSize rtSize = aRenderTargetRect.Size();
  23
  24   gfx::IntRect renderBounds(0, 0, rtSize.width, rtSize.height);
  25   renderBounds.IntersectRect(renderBounds, aClipRect);
  26   renderBounds.MoveBy(rtOffset);
  27
  28   // Apply the layer transform.
  29   RectDouble dest = aTransform.TransformAndClipBounds(
  30       RectDouble(aRect.X(), aRect.Y(), aRect.Width(), aRect.Height()),
  31       RectDouble(renderBounds.X(), renderBounds.Y(), renderBounds.Width(),
  32                  renderBounds.Height()));
  33   dest -= rtOffset;
  34
  35   // Ensure we don't round out to -1, which trips up Direct3D.
  36   dest.IntersectRect(dest, RectDouble(0, 0, rtSize.width, rtSize.height));
  37
  38   if (aOutLayerQuad) {
  39     *aOutLayerQuad = Rect(dest.X(), dest.Y(), dest.Width(), dest.Height());
  40   }
  41
  42   // Round out to integer.
  43   IntRect result;
  44   dest.RoundOut();
  45   dest.ToIntRect(&result);
  46
  47   // Create a transform from adjusted clip space to render target space,
  48   // translate it for the backdrop rect, then transform it into the backdrop's
  49   // uv-space.
  50   Matrix4x4 transform;
  51   transform.PostScale(rtSize.width, rtSize.height, 1.0);
  52   transform.PostTranslate(-result.X(), -result.Y(), 0.0);
  53   transform.PostScale(1 / float(result.Width()), 1 / float(result.Height()),
  54                       1.0);
  55   *aOutTransform = transform;
  56   return result;
  57 }
  58
  59 }  // namespace layers
  60 }  // namespace mozilla