/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 ts=4 expandtab: */
/* 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 "nsDeviceContext.h"
#include <algorithm>      // for max
#include "gfxASurface.h"  // for gfxASurface, etc
#include "gfxContext.h"
#include "gfxImageSurface.h"     // for gfxImageSurface
#include "gfxPoint.h"            // for gfxSize
#include "gfxTextRun.h"          // for gfxFontGroup
#include "mozilla/Attributes.h"  // for final
#include "mozilla/gfx/PathHelpers.h"
#include "mozilla/gfx/PrintTarget.h"
#include "mozilla/Preferences.h"  // for Preferences
#include "mozilla/Services.h"     // for GetObserverService
#include "mozilla/mozalloc.h"     // for operator new
#include "nsCRT.h"                // for nsCRT
#include "nsDebug.h"              // for NS_ASSERTION, etc
#include "nsFont.h"               // for nsFont
#include "nsFontMetrics.h"        // for nsFontMetrics
#include "nsAtom.h"               // for nsAtom, NS_Atomize
#include "nsID.h"
#include "nsIDeviceContextSpec.h"   // for nsIDeviceContextSpec
#include "nsLanguageAtomService.h"  // for nsLanguageAtomService
#include "nsIObserver.h"            // for nsIObserver, etc
#include "nsIObserverService.h"     // for nsIObserverService
#include "nsIScreen.h"              // for nsIScreen
#include "nsISupportsImpl.h"        // for MOZ_COUNT_CTOR, etc
#include "nsISupportsUtils.h"       // for NS_ADDREF, NS_RELEASE
#include "nsIWidget.h"              // for nsIWidget, NS_NATIVE_WINDOW
#include "nsRect.h"                 // for nsRect
#include "nsServiceManagerUtils.h"  // for do_GetService
#include "nsString.h"               // for nsDependentString
#include "nsTArray.h"               // for nsTArray, nsTArray_Impl
#include "nsThreadUtils.h"          // for NS_IsMainThread
#include "mozilla/gfx/Logging.h"
#include "mozilla/widget/ScreenManager.h"  // for ScreenManager

using namespace mozilla;
using namespace mozilla::gfx;
using mozilla::services::GetObserverService;
using mozilla::widget::ScreenManager;

class nsFontCache final : public nsIObserver {
 public:
  nsFontCache() : mContext(nullptr) {}

  NS_DECL_THREADSAFE_ISUPPORTS
  NS_DECL_NSIOBSERVER

  void Init(nsDeviceContext* aContext);
  void Destroy();

  already_AddRefed<nsFontMetrics> GetMetricsFor(
      const nsFont& aFont, const nsFontMetrics::Params& aParams);

  void FontMetricsDeleted(const nsFontMetrics* aFontMetrics);
  void Compact();

  // Flush aFlushCount oldest entries, or all if aFlushCount is negative
  void Flush(int32_t aFlushCount = -1);

  void UpdateUserFonts(gfxUserFontSet* aUserFontSet);

 protected:
  // If the array of cached entries is about to exceed this threshold,
  // we'll discard the oldest ones so as to keep the size reasonable.
  // In practice, the great majority of cache hits are among the last
  // few entries; keeping thousands of older entries becomes counter-
  // productive because it can then take too long to scan the cache.
  static const int32_t kMaxCacheEntries = 128;

  ~nsFontCache() = default;

  nsDeviceContext* mContext;  // owner
  RefPtr<nsAtom> mLocaleLanguage;

  // We may not flush older entries immediately the array reaches
  // kMaxCacheEntries length, because this usually happens on a stylo
  // thread where we can't safely delete metrics objects. So we allocate an
  // oversized autoarray buffer here, so that we're unlikely to overflow
  // it and need separate heap allocation before the flush happens on the
  // main thread.
  AutoTArray<nsFontMetrics*, kMaxCacheEntries * 2> mFontMetrics;

  bool mFlushPending = false;

  class FlushFontMetricsTask : public mozilla::Runnable {
   public:
    explicit FlushFontMetricsTask(nsFontCache* aCache)
        : mozilla::Runnable("FlushFontMetricsTask"), mCache(aCache) {}
    NS_IMETHOD Run() override {
      // Partially flush the cache, leaving the kMaxCacheEntries/2 most
      // recent entries.
      mCache->Flush(mCache->mFontMetrics.Length() - kMaxCacheEntries / 2);
      mCache->mFlushPending = false;
      return NS_OK;
    }

   private:
    RefPtr<nsFontCache> mCache;
  };
};

NS_IMPL_ISUPPORTS(nsFontCache, nsIObserver)

// The Init and Destroy methods are necessary because it's not
// safe to call AddObserver from a constructor or RemoveObserver
// from a destructor.  That should be fixed.
void nsFontCache::Init(nsDeviceContext* aContext) {
  mContext = aContext;
  // register as a memory-pressure observer to free font resources
  // in low-memory situations.
  nsCOMPtr<nsIObserverService> obs = GetObserverService();
  if (obs) obs->AddObserver(this, "memory-pressure", false);

  mLocaleLanguage = nsLanguageAtomService::GetService()->GetLocaleLanguage();
  if (!mLocaleLanguage) {
    mLocaleLanguage = NS_Atomize("x-western");
  }
}

void nsFontCache::Destroy() {
  nsCOMPtr<nsIObserverService> obs = GetObserverService();
  if (obs) obs->RemoveObserver(this, "memory-pressure");
  Flush();
}

NS_IMETHODIMP
nsFontCache::Observe(nsISupports*, const char* aTopic, const char16_t*) {
  if (!nsCRT::strcmp(aTopic, "memory-pressure")) Compact();
  return NS_OK;
}

already_AddRefed<nsFontMetrics> nsFontCache::GetMetricsFor(
    const nsFont& aFont, const nsFontMetrics::Params& aParams) {
  nsAtom* language = aParams.language && !aParams.language->IsEmpty()
                         ? aParams.language
                         : mLocaleLanguage.get();

  // First check our cache
  // start from the end, which is where we put the most-recent-used element
  const int32_t n = mFontMetrics.Length() - 1;
  for (int32_t i = n; i >= 0; --i) {
    nsFontMetrics* fm = mFontMetrics[i];
    if (fm->Font().Equals(aFont) &&
        fm->GetUserFontSet() == aParams.userFontSet &&
        fm->Language() == language &&
        fm->Orientation() == aParams.orientation &&
        fm->ExplicitLanguage() == aParams.explicitLanguage) {
      if (i != n) {
        // promote it to the end of the cache
        mFontMetrics.RemoveElementAt(i);
        mFontMetrics.AppendElement(fm);
      }
      fm->GetThebesFontGroup()->UpdateUserFonts();
      return do_AddRef(fm);
    }
  }

  // It's not in the cache. Get font metrics and then cache them.
  // If the cache has reached its size limit, drop the older half of the
  // entries; but if we're on a stylo thread (the usual case), we have
  // to post a task back to the main thread to do the flush.
  if (n >= kMaxCacheEntries - 1 && !mFlushPending) {
    if (NS_IsMainThread()) {
      Flush(mFontMetrics.Length() - kMaxCacheEntries / 2);
    } else {
      mFlushPending = true;
      nsCOMPtr<nsIRunnable> flushTask = new FlushFontMetricsTask(this);
      MOZ_ALWAYS_SUCCEEDS(NS_DispatchToMainThread(flushTask));
    }
  }

  nsFontMetrics::Params params = aParams;
  params.language = language;
  RefPtr<nsFontMetrics> fm = new nsFontMetrics(aFont, params, mContext);
  // the mFontMetrics list has the "head" at the end, because append
  // is cheaper than insert
  mFontMetrics.AppendElement(do_AddRef(fm).take());
  return fm.forget();
}

void nsFontCache::UpdateUserFonts(gfxUserFontSet* aUserFontSet) {
  for (nsFontMetrics* fm : mFontMetrics) {
    gfxFontGroup* fg = fm->GetThebesFontGroup();
    if (fg->GetUserFontSet() == aUserFontSet) {
      fg->UpdateUserFonts();
    }
  }
}

void nsFontCache::FontMetricsDeleted(const nsFontMetrics* aFontMetrics) {
  mFontMetrics.RemoveElement(aFontMetrics);
}

void nsFontCache::Compact() {
  // Need to loop backward because the running element can be removed on
  // the way
  for (int32_t i = mFontMetrics.Length() - 1; i >= 0; --i) {
    nsFontMetrics* fm = mFontMetrics[i];
    nsFontMetrics* oldfm = fm;
    // Destroy() isn't here because we want our device context to be
    // notified
    NS_RELEASE(fm);  // this will reset fm to nullptr
    // if the font is really gone, it would have called back in
    // FontMetricsDeleted() and would have removed itself
    if (mFontMetrics.IndexOf(oldfm) != mFontMetrics.NoIndex) {
      // nope, the font is still there, so let's hold onto it too
      NS_ADDREF(oldfm);
    }
  }
}

// Flush the aFlushCount oldest entries, or all if (aFlushCount < 0)
void nsFontCache::Flush(int32_t aFlushCount) {
  int32_t n = aFlushCount < 0
                  ? mFontMetrics.Length()
                  : std::min<int32_t>(aFlushCount, mFontMetrics.Length());
  for (int32_t i = n - 1; i >= 0; --i) {
    nsFontMetrics* fm = mFontMetrics[i];
    // Destroy() will unhook our device context from the fm so that we
    // won't waste time in triggering the notification of
    // FontMetricsDeleted() in the subsequent release
    fm->Destroy();
    NS_RELEASE(fm);
  }
  mFontMetrics.RemoveElementsAt(0, n);
}

nsDeviceContext::nsDeviceContext()
    : mWidth(0),
      mHeight(0),
      mAppUnitsPerDevPixel(-1),
      mAppUnitsPerDevPixelAtUnitFullZoom(-1),
      mAppUnitsPerPhysicalInch(-1),
      mFullZoom(1.0f),
      mPrintingScale(1.0f),
      mPrintingTranslate(gfxPoint(0, 0)),
      mIsCurrentlyPrintingDoc(false)
#ifdef DEBUG
      ,
      mIsInitialized(false)
#endif
{
  MOZ_ASSERT(NS_IsMainThread(), "nsDeviceContext created off main thread");
}

nsDeviceContext::~nsDeviceContext() {
  if (mFontCache) {
    mFontCache->Destroy();
  }
}

void nsDeviceContext::InitFontCache() {
  if (!mFontCache) {
    mFontCache = new nsFontCache();
    mFontCache->Init(this);
  }
}

void nsDeviceContext::UpdateFontCacheUserFonts(gfxUserFontSet* aUserFontSet) {
  if (mFontCache) {
    mFontCache->UpdateUserFonts(aUserFontSet);
  }
}

already_AddRefed<nsFontMetrics> nsDeviceContext::GetMetricsFor(
    const nsFont& aFont, const nsFontMetrics::Params& aParams) {
  InitFontCache();
  return mFontCache->GetMetricsFor(aFont, aParams);
}

nsresult nsDeviceContext::FlushFontCache(void) {
  if (mFontCache) mFontCache->Flush();
  return NS_OK;
}

nsresult nsDeviceContext::FontMetricsDeleted(
    const nsFontMetrics* aFontMetrics) {
  if (mFontCache) {
    mFontCache->FontMetricsDeleted(aFontMetrics);
  }
  return NS_OK;
}

bool nsDeviceContext::IsPrinterContext() { return mPrintTarget != nullptr; }

void nsDeviceContext::SetDPI(double* aScale) {
  float dpi;

  // Use the printing DC to determine DPI values, if we have one.
  if (mDeviceContextSpec) {
    dpi = mDeviceContextSpec->GetDPI();
    mPrintingScale = mDeviceContextSpec->GetPrintingScale();
    mPrintingTranslate = mDeviceContextSpec->GetPrintingTranslate();
    mAppUnitsPerDevPixelAtUnitFullZoom =
        NS_lround((AppUnitsPerCSSPixel() * 96) / dpi);
  } else {
    nsCOMPtr<nsIScreen> primaryScreen;
    ScreenManager& screenManager = ScreenManager::GetSingleton();
    screenManager.GetPrimaryScreen(getter_AddRefs(primaryScreen));
    MOZ_ASSERT(primaryScreen);

    // A value of -1 means use the maximum of 96 and the system DPI.
    // A value of 0 means use the system DPI. A positive value is used as the
    // DPI. This sets the physical size of a device pixel and thus controls the
    // interpretation of physical units.
    int32_t prefDPI = Preferences::GetInt("layout.css.dpi", -1);

    if (prefDPI > 0) {
      dpi = prefDPI;
    } else if (mWidget) {
      // PuppetWidget could return -1 if the value's not available yet.
      dpi = mWidget->GetDPI();
      // In case that the widget returns -1, use the primary screen's
      // value as default.
      if (dpi < 0) {
        primaryScreen->GetDpi(&dpi);
      }
      if (prefDPI < 0) {
        dpi = std::max(96.0f, dpi);
      }
    } else {
      dpi = 96.0f;
    }

    double devPixelsPerCSSPixel;
    if (aScale && *aScale > 0.0) {
      // if caller provided a scale, we just use it
      devPixelsPerCSSPixel = *aScale;
    } else {
      // otherwise get from the widget, and return it in aScale for
      // the caller to pass to child contexts if needed
      CSSToLayoutDeviceScale scale =
          mWidget ? mWidget->GetDefaultScale() : CSSToLayoutDeviceScale(1.0);
      devPixelsPerCSSPixel = scale.scale;
      // In case that the widget returns -1, use the primary screen's
      // value as default.
      if (devPixelsPerCSSPixel < 0) {
        primaryScreen->GetDefaultCSSScaleFactor(&devPixelsPerCSSPixel);
      }
      if (aScale) {
        *aScale = devPixelsPerCSSPixel;
      }
    }

    mAppUnitsPerDevPixelAtUnitFullZoom =
        std::max(1, NS_lround(AppUnitsPerCSSPixel() / devPixelsPerCSSPixel));
  }

  NS_ASSERTION(dpi != -1.0, "no dpi set");

  mAppUnitsPerPhysicalInch =
      NS_lround(dpi * mAppUnitsPerDevPixelAtUnitFullZoom);
  UpdateAppUnitsForFullZoom();
}

nsresult nsDeviceContext::Init(nsIWidget* aWidget) {
#ifdef DEBUG
  // We can't assert |!mIsInitialized| here since EndSwapDocShellsForDocument
  // re-initializes nsDeviceContext objects.  We can only assert in
  // InitForPrinting (below).
  mIsInitialized = true;
#endif

  nsresult rv = NS_OK;
  if (mScreenManager && mWidget == aWidget) return rv;

  mWidget = aWidget;
  SetDPI();

  if (mScreenManager) return rv;

  mScreenManager = do_GetService("@mozilla.org/gfx/screenmanager;1", &rv);

  return rv;
}

// XXX This is only for printing. We should make that obvious in the name.
already_AddRefed<gfxContext> nsDeviceContext::CreateRenderingContext() {
  return CreateRenderingContextCommon(/* not a reference context */ false);
}

already_AddRefed<gfxContext>
nsDeviceContext::CreateReferenceRenderingContext() {
  return CreateRenderingContextCommon(/* a reference context */ true);
}

already_AddRefed<gfxContext> nsDeviceContext::CreateRenderingContextCommon(
    bool aWantReferenceContext) {
  MOZ_ASSERT(IsPrinterContext());
  MOZ_ASSERT(mWidth > 0 && mHeight > 0);

  RefPtr<gfx::DrawTarget> dt;
  if (aWantReferenceContext) {
    dt = mPrintTarget->GetReferenceDrawTarget();
  } else {
    // This will be null if e10s is disabled or print.print_via_parent=false.
    RefPtr<DrawEventRecorder> recorder;
    mDeviceContextSpec->GetDrawEventRecorder(getter_AddRefs(recorder));
    dt = mPrintTarget->MakeDrawTarget(gfx::IntSize(mWidth, mHeight), recorder);
  }

  if (!dt || !dt->IsValid()) {
    gfxCriticalNote << "Failed to create draw target in device context sized "
                    << mWidth << "x" << mHeight << " and pointer "
                    << hexa(mPrintTarget);
    return nullptr;
  }

#ifdef XP_MACOSX
  // The CGContextRef provided by PMSessionGetCGGraphicsContext is
  // write-only, so we need to prevent gfxContext::PushGroupAndCopyBackground
  // trying to read from it or else we'll crash.
  // XXXjwatt Consider adding a MakeDrawTarget override to PrintTargetCG and
  // moving this AddUserData call there.
  dt->AddUserData(&gfxContext::sDontUseAsSourceKey, dt, nullptr);
#endif
  dt->AddUserData(&sDisablePixelSnapping, (void*)0x1, nullptr);

  RefPtr<gfxContext> pContext = gfxContext::CreateOrNull(dt);
  MOZ_ASSERT(pContext);  // already checked draw target above

  gfxMatrix transform;
  transform.PreTranslate(mPrintingTranslate);
  if (mPrintTarget->RotateNeededForLandscape()) {
    // Rotate page 90 degrees to draw landscape page on portrait paper
    IntSize size = mPrintTarget->GetSize();
    transform.PreTranslate(gfxPoint(0, size.width));
    gfxMatrix rotate(0, -1, 1, 0, 0, 0);
    transform = rotate * transform;
  }
  transform.PreScale(mPrintingScale, mPrintingScale);

  pContext->SetMatrixDouble(transform);
  return pContext.forget();
}

nsresult nsDeviceContext::GetDepth(uint32_t& aDepth) {
  nsCOMPtr<nsIScreen> screen;
  FindScreen(getter_AddRefs(screen));
  if (!screen) {
    ScreenManager& screenManager = ScreenManager::GetSingleton();
    screenManager.GetPrimaryScreen(getter_AddRefs(screen));
    MOZ_ASSERT(screen);
  }
  screen->GetColorDepth(reinterpret_cast<int32_t*>(&aDepth));

  return NS_OK;
}

nsresult nsDeviceContext::GetDeviceSurfaceDimensions(nscoord& aWidth,
                                                     nscoord& aHeight) {
  if (IsPrinterContext()) {
    aWidth = mWidth;
    aHeight = mHeight;
  } else {
    nsRect area;
    ComputeFullAreaUsingScreen(&area);
    aWidth = area.Width();
    aHeight = area.Height();
  }

  return NS_OK;
}

nsresult nsDeviceContext::GetRect(nsRect& aRect) {
  if (IsPrinterContext()) {
    aRect.SetRect(0, 0, mWidth, mHeight);
  } else
    ComputeFullAreaUsingScreen(&aRect);

  return NS_OK;
}

nsresult nsDeviceContext::GetClientRect(nsRect& aRect) {
  if (IsPrinterContext()) {
    aRect.SetRect(0, 0, mWidth, mHeight);
  } else
    ComputeClientRectUsingScreen(&aRect);

  return NS_OK;
}

nsresult nsDeviceContext::InitForPrinting(nsIDeviceContextSpec* aDevice) {
  NS_ENSURE_ARG_POINTER(aDevice);

  MOZ_ASSERT(!mIsInitialized,
             "Only initialize once, immediately after construction");

  // We don't set mIsInitialized here. The Init() call below does that.

  mPrintTarget = aDevice->MakePrintTarget();
  if (!mPrintTarget) {
    return NS_ERROR_FAILURE;
  }

  mDeviceContextSpec = aDevice;

  Init(nullptr);

  if (!CalcPrintingSize()) {
    return NS_ERROR_FAILURE;
  }

  return NS_OK;
}

nsresult nsDeviceContext::BeginDocument(const nsAString& aTitle,
                                        const nsAString& aPrintToFileName,
                                        int32_t aStartPage, int32_t aEndPage) {
  MOZ_ASSERT(!mIsCurrentlyPrintingDoc,
             "Mismatched BeginDocument/EndDocument calls");

  nsresult rv = mPrintTarget->BeginPrinting(aTitle, aPrintToFileName,
                                            aStartPage, aEndPage);

  if (NS_SUCCEEDED(rv)) {
    if (mDeviceContextSpec) {
      rv = mDeviceContextSpec->BeginDocument(aTitle, aPrintToFileName,
                                             aStartPage, aEndPage);
    }
    mIsCurrentlyPrintingDoc = true;
  }

  // Warn about any failure (except user cancelling):
  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv) || rv == NS_ERROR_ABORT,
                       "nsDeviceContext::BeginDocument failed");

  return rv;
}

nsresult nsDeviceContext::EndDocument(void) {
  MOZ_ASSERT(mIsCurrentlyPrintingDoc,
             "Mismatched BeginDocument/EndDocument calls");

  mIsCurrentlyPrintingDoc = false;

  nsresult rv = mPrintTarget->EndPrinting();
  if (NS_SUCCEEDED(rv)) {
    mPrintTarget->Finish();
  }

  if (mDeviceContextSpec) mDeviceContextSpec->EndDocument();

  mPrintTarget = nullptr;

  return rv;
}

nsresult nsDeviceContext::AbortDocument(void) {
  MOZ_ASSERT(mIsCurrentlyPrintingDoc,
             "Mismatched BeginDocument/EndDocument calls");

  nsresult rv = mPrintTarget->AbortPrinting();

  mIsCurrentlyPrintingDoc = false;

  if (mDeviceContextSpec) mDeviceContextSpec->EndDocument();

  mPrintTarget = nullptr;

  return rv;
}

nsresult nsDeviceContext::BeginPage(void) {
  nsresult rv = NS_OK;

  if (mDeviceContextSpec) rv = mDeviceContextSpec->BeginPage();

  if (NS_FAILED(rv)) return rv;

  return mPrintTarget->BeginPage();
}

nsresult nsDeviceContext::EndPage(void) {
  nsresult rv = mPrintTarget->EndPage();

  if (mDeviceContextSpec) mDeviceContextSpec->EndPage();

  return rv;
}

void nsDeviceContext::ComputeClientRectUsingScreen(nsRect* outRect) {
  // we always need to recompute the clientRect
  // because the window may have moved onto a different screen. In the single
  // monitor case, we only need to do the computation if we haven't done it
  // once already, and remember that we have because we're assured it won't
  // change.
  nsCOMPtr<nsIScreen> screen;
  FindScreen(getter_AddRefs(screen));
  if (screen) {
    int32_t x, y, width, height;
    screen->GetAvailRect(&x, &y, &width, &height);

    // convert to device units
    outRect->SetRect(NSIntPixelsToAppUnits(x, AppUnitsPerDevPixel()),
                     NSIntPixelsToAppUnits(y, AppUnitsPerDevPixel()),
                     NSIntPixelsToAppUnits(width, AppUnitsPerDevPixel()),
                     NSIntPixelsToAppUnits(height, AppUnitsPerDevPixel()));
  }
}

void nsDeviceContext::ComputeFullAreaUsingScreen(nsRect* outRect) {
  // if we have more than one screen, we always need to recompute the clientRect
  // because the window may have moved onto a different screen. In the single
  // monitor case, we only need to do the computation if we haven't done it
  // once already, and remember that we have because we're assured it won't
  // change.
  nsCOMPtr<nsIScreen> screen;
  FindScreen(getter_AddRefs(screen));
  if (screen) {
    int32_t x, y, width, height;
    screen->GetRect(&x, &y, &width, &height);

    // convert to device units
    outRect->SetRect(NSIntPixelsToAppUnits(x, AppUnitsPerDevPixel()),
                     NSIntPixelsToAppUnits(y, AppUnitsPerDevPixel()),
                     NSIntPixelsToAppUnits(width, AppUnitsPerDevPixel()),
                     NSIntPixelsToAppUnits(height, AppUnitsPerDevPixel()));
    mWidth = outRect->Width();
    mHeight = outRect->Height();
  }
}

//
// FindScreen
//
// Determines which screen intersects the largest area of the given surface.
//
void nsDeviceContext::FindScreen(nsIScreen** outScreen) {
  if (!mWidget || !mScreenManager) {
    return;
  }

  CheckDPIChange();

  nsCOMPtr<nsIScreen> screen = mWidget->GetWidgetScreen();
  screen.forget(outScreen);

  if (!(*outScreen)) {
    mScreenManager->GetPrimaryScreen(outScreen);
  }
}

bool nsDeviceContext::CalcPrintingSize() {
  gfxSize size(mPrintTarget->GetSize());
  // For printing, CSS inches and physical inches are identical
  // so it doesn't matter which we use here
  mWidth = NSToCoordRound(size.width * AppUnitsPerPhysicalInch() /
                          POINTS_PER_INCH_FLOAT);
  mHeight = NSToCoordRound(size.height * AppUnitsPerPhysicalInch() /
                           POINTS_PER_INCH_FLOAT);

  return (mWidth > 0 && mHeight > 0);
}

bool nsDeviceContext::CheckDPIChange(double* aScale) {
  int32_t oldDevPixels = mAppUnitsPerDevPixelAtUnitFullZoom;
  int32_t oldInches = mAppUnitsPerPhysicalInch;

  SetDPI(aScale);

  return oldDevPixels != mAppUnitsPerDevPixelAtUnitFullZoom ||
         oldInches != mAppUnitsPerPhysicalInch;
}

bool nsDeviceContext::SetFullZoom(float aScale) {
  if (aScale <= 0) {
    MOZ_ASSERT_UNREACHABLE("Invalid full zoom value");
    return false;
  }
  int32_t oldAppUnitsPerDevPixel = mAppUnitsPerDevPixel;
  mFullZoom = aScale;
  UpdateAppUnitsForFullZoom();
  return oldAppUnitsPerDevPixel != mAppUnitsPerDevPixel;
}

void nsDeviceContext::UpdateAppUnitsForFullZoom() {
  mAppUnitsPerDevPixel = std::max(
      1, NSToIntRound(float(mAppUnitsPerDevPixelAtUnitFullZoom) / mFullZoom));
  // adjust mFullZoom to reflect appunit rounding
  mFullZoom = float(mAppUnitsPerDevPixelAtUnitFullZoom) / mAppUnitsPerDevPixel;
}

DesktopToLayoutDeviceScale nsDeviceContext::GetDesktopToDeviceScale() {
  nsCOMPtr<nsIScreen> screen;
  FindScreen(getter_AddRefs(screen));

  if (screen) {
    double scale;
    screen->GetContentsScaleFactor(&scale);
    return DesktopToLayoutDeviceScale(scale);
  }

  return DesktopToLayoutDeviceScale(1.0);
}

bool nsDeviceContext::IsSyncPagePrinting() const {
  MOZ_ASSERT(mPrintTarget);
  return mPrintTarget->IsSyncPagePrinting();
}

void nsDeviceContext::RegisterPageDoneCallback(
    PrintTarget::PageDoneCallback&& aCallback) {
  MOZ_ASSERT(mPrintTarget && aCallback && !IsSyncPagePrinting());
  mPrintTarget->RegisterPageDoneCallback(std::move(aCallback));
}
void nsDeviceContext::UnregisterPageDoneCallback() {
  if (mPrintTarget) {
    mPrintTarget->UnregisterPageDoneCallback();
  }
}