1 files changed, 717 insertions, 0 deletions
diff --git a/gfx/src/nsDeviceContext.cpp b/gfx/src/nsDeviceContext.cpp
new file mode 100644
index 0000000000..daa592e1bf
--- /dev/null
+++ b/gfx/src/nsDeviceContext.cpp
@@ -0,0 +1,717 @@
+/* -*- 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();
+  }
+}