Refactor Windows DPI Point, Rect, and Size for Multiple Monitor DPI Awareness

ui/gfx/screen_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/screen_win.h"
 
 #include <windows.h>
 #include <stdint.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/hash.h"
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/win_util.h"
 #include "ui/gfx/display.h"
+#include "ui/gfx/geometry/insets.h"
+#include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/point_conversions.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/geometry/safe_integer_conversions.h"
+#include "ui/gfx/geometry/size.h"
+#include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/win/dpi.h"
+#include "ui/gfx/win/rect_util.h"
 
 namespace {
 
-MONITORINFOEX GetMonitorInfoForMonitor(HMONITOR monitor) {
-  MONITORINFOEX monitor_info;
-  ZeroMemory(&monitor_info, sizeof(MONITORINFOEX));
-  monitor_info.cbSize = sizeof(monitor_info);
-  GetMonitorInfo(monitor, &monitor_info);
-  return monitor_info;
-}
-
-gfx::Display GetDisplay(const MONITORINFOEX& monitor_info) {
-  int64_t id =
-      static_cast<int64_t>(base::Hash(base::WideToUTF8(monitor_info.szDevice)));
-  gfx::Rect bounds = gfx::Rect(monitor_info.rcMonitor);
-  gfx::Display display(id);
-  display.set_bounds(gfx::win::ScreenToDIPRect(bounds));
-  display.set_work_area(
-      gfx::win::ScreenToDIPRect(gfx::Rect(monitor_info.rcWork)));
-  display.SetScaleAndBounds(gfx::GetDPIScale(), bounds);
-
+gfx::Display::Rotation GetRotationForDevice(const wchar_t* device_name) {
   DEVMODE mode;
-  memset(&mode, 0, sizeof(DEVMODE));
+  ::ZeroMemory(&mode, sizeof(mode));
   mode.dmSize = sizeof(DEVMODE);
   mode.dmDriverExtra = 0;
-  if (EnumDisplaySettings(monitor_info.szDevice,
-                          ENUM_CURRENT_SETTINGS,
-                          &mode)) {
+  if (::EnumDisplaySettings(device_name, ENUM_CURRENT_SETTINGS, &mode)) {
     switch (mode.dmDisplayOrientation) {
     case DMDO_DEFAULT:
-      display.set_rotation(gfx::Display::ROTATE_0);
-      break;
+      return gfx::Display::ROTATE_0;
     case DMDO_90:
-      display.set_rotation(gfx::Display::ROTATE_90);
-      break;
+      return gfx::Display::ROTATE_90;
     case DMDO_180:
-      display.set_rotation(gfx::Display::ROTATE_180);
-      break;
+      return gfx::Display::ROTATE_180;
     case DMDO_270:
-      display.set_rotation(gfx::Display::ROTATE_270);
-      break;
+      return gfx::Display::ROTATE_270;
     default:
       NOTREACHED();
     }
   }
-
-  return display;
+  return gfx::Display::ROTATE_0;
 }
 
-BOOL CALLBACK EnumMonitorCallback(HMONITOR monitor,
-                                  HDC hdc,
-                                  LPRECT rect,
-                                  LPARAM data) {
-  std::vector<gfx::Display>* all_displays =
-      reinterpret_cast<std::vector<gfx::Display>*>(data);
-  DCHECK(all_displays);
-
-  MONITORINFOEX monitor_info = GetMonitorInfoForMonitor(monitor);
-  gfx::Display display = GetDisplay(monitor_info);
-  all_displays->push_back(display);
-  return TRUE;
+// Returns a point in |to_origin|'s coordinates and position scaled by
+// |scale_factor|.
+gfx::Point ScalePointRelative(const gfx::Point& from_origin,
+                              const gfx::Point& to_origin,
+                              const float scale_factor,
+                              const gfx::Point& point) {
+  gfx::Vector2d from_origin_vector(from_origin.x(), from_origin.y());
+  gfx::Vector2d to_origin_vector(to_origin.x(), to_origin.y());
+  return gfx::ScaleToFlooredPoint(point - from_origin_vector, scale_factor) +
+      to_origin_vector;
 }
 
-std::vector<gfx::Display> GetDisplays() {
-  std::vector<gfx::Display> displays;
-  EnumDisplayMonitors(NULL, NULL, EnumMonitorCallback,
-                      reinterpret_cast<LPARAM>(&displays));
-  return displays;
+// Returns the NativeScreen. For all intents and purposes, this screen provides
+// the source of truth for displays in Windows.
+gfx::ScreenWin* GetNativeScreenWin() {
+  return static_cast<gfx::ScreenWin*>(gfx::Screen::GetNativeScreen());
+}
+
+// static
+MONITORINFOEX MonitorInfoFromHMONITOR(HMONITOR monitor) {
+  MONITORINFOEX monitor_info;
+  ::ZeroMemory(&monitor_info, sizeof(monitor_info));
+  monitor_info.cbSize = sizeof(monitor_info);
+  ::GetMonitorInfo(monitor, &monitor_info);
+  return monitor_info;
 }
 
 }  // namespace
 
 namespace gfx {
 
+class ScreenWin::DisplayWin {
+ public:
+  explicit DisplayWin();
+  explicit DisplayWin(const DisplayInfo& display_info);
+  DisplayWin(const DisplayWin& ref, const DisplayInfo& display_info);
+
+  const Display& display() const { return display_; }
+  const Rect& physical_bounds() const { return pixel_bounds_; }
+
+ private:
+  Display display_;
+  Rect pixel_bounds_;
+};
+
 ScreenWin::ScreenWin()
     : singleton_hwnd_observer_(new SingletonHwndObserver(
           base::Bind(&ScreenWin::OnWndProc, base::Unretained(this)))),
-      displays_(GetDisplays()) {
+      display_wins_(GetDisplayWins()) {}
+
+ScreenWin::~ScreenWin() {}
+
+// static
+Point ScreenWin::ScreenToDIPPoint(const Point& pixel_point) {
+  DisplayWin display_win = GetDisplayNearestScreenPoint(pixel_point);
+  Display display = display_win.display();
+  return ScalePointRelative(display_win.physical_bounds().origin(),
+                            display.bounds().origin(),
+                            1.0f / display.device_scale_factor(),
+                            pixel_point);
 }
 
-ScreenWin::~ScreenWin() {}
+// static
+Point ScreenWin::DIPToScreenPoint(const Point& dip_point) {
+  DisplayWin display_win = GetDisplayNearestDIPPoint(dip_point);
+  Display display = display_win.display();
+  return ScalePointRelative(display.bounds().origin(),
+                            display_win.physical_bounds().origin(),
+                            display.device_scale_factor(),
+                            dip_point);
+}
+
+
+Point ScreenWin::ClientToDIPPoint(HWND hwnd, const Point& client_point) {
+  return ScaleToFlooredPoint(client_point, 1.0f / GetScaleFactorForHWND(hwnd));
+}
+
+Point ScreenWin::DIPToClientPoint(HWND hwnd, const Point& dip_point) {
+  return ScaleToFlooredPoint(dip_point, GetScaleFactorForHWND(hwnd));
+}
+
+// static
+Rect ScreenWin::ScreenToDIPRect(HWND hwnd, const Rect& pixel_bounds) {
+  // It's important we scale the origin and size separately. If we instead
+  // calculated the size from the floored origin and ceiled right the size could
+  // vary depending upon where the two points land. That would cause problems
+  // for the places this code is used (in particular mapping from native window
+  // bounds to DIPs).
+  if (hwnd) {
+    return Rect(ScreenToDIPPoint(pixel_bounds.origin()),
+                ScreenToDIPSize(hwnd, pixel_bounds.size()));
+  }
+  float scale_factor =
+      GetDisplayNearestScreenRect(pixel_bounds).display().device_scale_factor();
+  return Rect(ScreenToDIPPoint(pixel_bounds.origin()),
+              ScaleToCeiledSize(pixel_bounds.size(), 1.0f / scale_factor));
+}
+
+// static
+Rect ScreenWin::DIPToScreenRect(HWND hwnd, const Rect& dip_bounds) {
+  // See comment in ScreenToDIPRect for why we calculate size like this.
+  if (hwnd) {
+    return Rect(DIPToScreenPoint(dip_bounds.origin()),
+                DIPToScreenSize(hwnd, dip_bounds.size()));
+  }
+  // Because origins don't change for screen points and scaling factors are
+  // greater than 1, the monitor bounding rect always contains the DIP point.
+  float scale_factor =
+      GetDisplayNearestDIPRect(dip_bounds).display().device_scale_factor();
+  return Rect(DIPToScreenPoint(dip_bounds.origin()),
+              ScaleToCeiledSize(dip_bounds.size(), scale_factor));
+}
+
+// static
+Rect ScreenWin::ClientToDIPRect(HWND hwnd, const Rect& pixel_bounds) {
+  // See comment in ScreenToDIPRect for why we calculate size like this.
+  return Rect(ClientToDIPPoint(hwnd, pixel_bounds.origin()),
+              ScreenToDIPSize(hwnd, pixel_bounds.size()));
+}
+
+// static
+Rect ScreenWin::DIPToClientRect(HWND hwnd, const Rect& dip_bounds) {
+  // See comment in ScreenToDIPRect for why we calculate size like this.
+  return Rect(DIPToClientPoint(hwnd, dip_bounds.origin()),
+              DIPToScreenSize(hwnd, dip_bounds.size()));
+}
+
+// static
+Size ScreenWin::ScreenToDIPSize(HWND hwnd, const Size& size_in_pixels) {
+  // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
+  return ScaleToCeiledSize(size_in_pixels, 1.0f / GetScaleFactorForHWND(hwnd));
+}
+
+// static
+Size ScreenWin::DIPToScreenSize(HWND hwnd, const Size& dip_size) {
+  // Always ceil sizes. Otherwise we may be leaving off part of the bounds.
+  return ScaleToCeiledSize(dip_size, GetScaleFactorForHWND(hwnd));
+}
 
 HWND ScreenWin::GetHWNDFromNativeView(NativeView window) const {
   NOTREACHED();
   return NULL;
 }
 
 NativeWindow ScreenWin::GetNativeWindowFromHWND(HWND hwnd) const {
   NOTREACHED();
   return NULL;
 }
 
+ScreenWin::DisplayInfo::DisplayInfo(HMONITOR monitor,
+                                    float device_scale_factor) :
+    device_scale_factor_(device_scale_factor){
+  MONITORINFOEX monitor_info;
+  ::ZeroMemory(&monitor_info, sizeof(monitor_info));
+  monitor_info.cbSize = sizeof(monitor_info);
+  ::GetMonitorInfo(monitor, &monitor_info);
+  InitializeFromMonitorInfo(monitor_info);
+}
+
+ScreenWin::DisplayInfo::DisplayInfo(const MONITORINFOEX& monitor_info,
+                                    gfx::Display::Rotation rotation,
+                                    float device_scale_factor)
+    : rotation_(rotation),
+      device_scale_factor_(device_scale_factor) {
+  InitializeFromMonitorInfo(monitor_info);
+}
+
+void ScreenWin::DisplayInfo::InitializeFromMonitorInfo(
+    const MONITORINFOEX& monitor_info) {
+  id_ = ScreenWin::HashDeviceName(monitor_info.szDevice);
+  screen_rect_ = gfx::Rect(monitor_info.rcMonitor);
+  screen_work_rect_ = gfx::Rect(monitor_info.rcWork);
+  rotation_ = GetRotationForDevice(monitor_info.szDevice);
+}
+
+ScreenWin::ScreenWin(const std::vector<ScreenWin::DisplayInfo>& display_infos) {
+  display_wins_ = GetDisplaysFromDisplayInfos(display_infos);
+}
+
+int64_t ScreenWin::HashDeviceName(const wchar_t* device_name) {
+  return static_cast<int64_t>(base::Hash(base::WideToUTF8(device_name)));
+}
+
 gfx::Point ScreenWin::GetCursorScreenPoint() {
   POINT pt;
   GetCursorPos(&pt);
   gfx::Point cursor_pos_pixels(pt);
-  return gfx::win::ScreenToDIPPoint(cursor_pos_pixels);
+  return ScreenToDIPPoint(cursor_pos_pixels);
 }
 
 gfx::NativeWindow ScreenWin::GetWindowUnderCursor() {
   POINT cursor_loc;
   HWND hwnd = GetCursorPos(&cursor_loc) ? WindowFromPoint(cursor_loc) : NULL;
   return GetNativeWindowFromHWND(hwnd);
 }
 
 gfx::NativeWindow ScreenWin::GetWindowAtScreenPoint(const gfx::Point& point) {
-  gfx::Point point_in_pixels = gfx::win::DIPToScreenPoint(point);
+  gfx::Point point_in_pixels = DIPToScreenPoint(point);
   return GetNativeWindowFromHWND(WindowFromPoint(point_in_pixels.ToPOINT()));
 }
 
 int ScreenWin::GetNumDisplays() const {
   return GetSystemMetrics(SM_CMONITORS);
 }
 
 std::vector<gfx::Display> ScreenWin::GetAllDisplays() const {
-  return displays_;
+  std::vector<gfx::Display> displays;
+  for (const DisplayWin& display_win : display_wins_) {
+    displays.push_back(display_win.display());
+  }
+  return displays;
 }
 
 gfx::Display ScreenWin::GetDisplayNearestWindow(gfx::NativeView window) const {
   HWND window_hwnd = GetHWNDFromNativeView(window);
   if (!window_hwnd) {
     // When |window| isn't rooted to a display, we should just return the
     // default display so we get some correct display information like the
     // scaling factor.
     return GetPrimaryDisplay();
   }
-
-  MONITORINFOEX monitor_info;
-  monitor_info.cbSize = sizeof(monitor_info);
-  GetMonitorInfo(MonitorFromWindow(window_hwnd, MONITOR_DEFAULTTONEAREST),
-                 &monitor_info);
-  return GetDisplay(monitor_info);
+  return GetDisplayNearestHWND(window_hwnd).display();
 }
 
 gfx::Display ScreenWin::GetDisplayNearestPoint(const gfx::Point& point) const {
-  gfx::Point point_in_pixels = gfx::win::DIPToScreenPoint(point);
-  POINT initial_loc = { point_in_pixels.x(), point_in_pixels.y() };
-  HMONITOR monitor = MonitorFromPoint(initial_loc, MONITOR_DEFAULTTONEAREST);
-  MONITORINFOEX mi;
-  ZeroMemory(&mi, sizeof(MONITORINFOEX));
-  mi.cbSize = sizeof(mi);
-  if (monitor && GetMonitorInfo(monitor, &mi)) {
-    return GetDisplay(mi);
-  }
-  return gfx::Display();
+  return GetDisplayNearestScreenPoint(DIPToScreenPoint(point)).display();
 }
 
 gfx::Display ScreenWin::GetDisplayMatching(const gfx::Rect& match_rect) const {
-  RECT other_bounds_rect = match_rect.ToRECT();
-  MONITORINFOEX monitor_info = GetMonitorInfoForMonitor(MonitorFromRect(
-      &other_bounds_rect, MONITOR_DEFAULTTONEAREST));
-  return GetDisplay(monitor_info);
+  return GetDisplayNearestScreenRect(match_rect).display();
 }
 
 gfx::Display ScreenWin::GetPrimaryDisplay() const {
-  MONITORINFOEX mi = GetMonitorInfoForMonitor(
-      MonitorFromWindow(NULL, MONITOR_DEFAULTTOPRIMARY));
-  gfx::Display display = GetDisplay(mi);
+  Display display =
+      GetDisplayWin(MonitorInfoFromHMONITOR(MonitorFromWindow(
+          NULL, MONITOR_DEFAULTTOPRIMARY))).display();
   // TODO(kevers|girard): Test if these checks can be reintroduced for high-DIP
   // once more of the app is DIP-aware.
-  if (GetDPIScale() == 1.0) {
+  if (display.device_scale_factor() == 1.0) {
     DCHECK_EQ(GetSystemMetrics(SM_CXSCREEN), display.size().width());
     DCHECK_EQ(GetSystemMetrics(SM_CYSCREEN), display.size().height());
   }
   return display;
 }
 
 void ScreenWin::AddObserver(DisplayObserver* observer) {
   change_notifier_.AddObserver(observer);
 }
 
 void ScreenWin::RemoveObserver(DisplayObserver* observer) {
   change_notifier_.RemoveObserver(observer);
 }
 
+gfx::Rect ScreenWin::ScreenToDIPRectInWindow(
+    NativeView view, const gfx::Rect& screen_rect) const {
+  HWND hwnd = view ? GetHWNDFromNativeView(view) : NULL;
+  return ScreenWin::ScreenToDIPRect(hwnd, screen_rect);
+}
+
+gfx::Rect ScreenWin::DIPToScreenRectInWindow(NativeView view,
+                                             const gfx::Rect& dip_rect) const {
+  HWND hwnd = view ? GetHWNDFromNativeView(view) : NULL;
+  return ScreenWin::DIPToScreenRect(hwnd, dip_rect);
+}
+
+ScreenWin::DisplayWin::DisplayWin() = default;
+
+ScreenWin::DisplayWin::DisplayWin(const DisplayInfo& display_info)
+    : display_(display_info.id()),
+      pixel_bounds_(display_info.screen_rect()) {
+  float scale_factor = display_info.device_scale_factor();
+  display_.set_device_scale_factor(scale_factor);
+  display_.set_work_area(
+      gfx::ScaleToEnclosedRect(display_info.screen_work_rect(),
+                               1.0f / scale_factor));
+  display_.set_bounds(gfx::ScaleToEnclosedRect(display_info.screen_rect(),
+                                               1.0f / scale_factor));
+}
+
+ScreenWin::DisplayWin::DisplayWin(const DisplayWin& ref,
+                                  const DisplayInfo& display_info)
+    : display_(display_info.id()),
+      pixel_bounds_(display_info.screen_rect()) {
+  float scale_factor = display_info.device_scale_factor();
+  display_.set_device_scale_factor(scale_factor);
+  const gfx::Insets pixel_insets =
+      display_info.screen_rect().InsetsFrom(display_info.screen_work_rect());
+  const gfx::Insets scaled_insets = pixel_insets.Scale(1.0f / scale_factor,
+                                                       1.0f / scale_factor);
+  const gfx::Rect scaled_bounds =
+      gfx::win::ScaleAndPositionRect(ref.display_.bounds(),
+                                     ref.physical_bounds(),
+                                     display_info.screen_rect(),
+                                     scale_factor);
+  display_.set_bounds(scaled_bounds);
+  gfx::Rect scaled_work_area(scaled_bounds);
+  scaled_work_area.Inset(scaled_insets);
+  display_.set_work_area(scaled_work_area);
+}
+
+// static
+ScreenWin::DisplayWin ScreenWin::GetDisplayNearestHWND(HWND hwnd) {
+  ScreenWin* screen = GetNativeScreenWin();
+  return screen->GetDisplayWin(screen->MonitorInfoFromWindow(hwnd));
+}
+
+// static
+ScreenWin::DisplayWin ScreenWin::GetDisplayNearestScreenRect(
+    const Rect& screen_rect) {
+  ScreenWin* screen = GetNativeScreenWin();
+  return screen->GetDisplayWin(screen->MonitorInfoFromScreenRect(screen_rect));
+}
+
+// static
+ScreenWin::DisplayWin ScreenWin::GetDisplayNearestScreenPoint(
+    const Point& screen_point) {
+  ScreenWin* screen = GetNativeScreenWin();
+  return screen->GetDisplayWin(
+      screen->MonitorInfoFromScreenPoint(screen_point));
+}
+
+// static
+ScreenWin::DisplayWin ScreenWin::GetDisplayNearestDIPRect(
+    const Rect& dip_rect) {
+  ScreenWin* screen = GetNativeScreenWin();
+  DisplayWin closest_display_win;
+  int64_t closest_distance_squared = INT64_MAX;
+  for (const DisplayWin& display_win : screen->display_wins_) {
+    Display display = display_win.display();
+    gfx::Rect dip_bounds = display.bounds();
+    int64_t distance_squared =
+        gfx::win::SquaredDistanceBetweenRects(dip_rect, dip_bounds);
+    if (distance_squared == 0) {
+      return display_win;
+    } else if (distance_squared < closest_distance_squared) {
+      closest_distance_squared = distance_squared;
+      closest_display_win = display_win;
+    }
+  }
+  return closest_display_win;
+}
+
+// static
+ScreenWin::DisplayWin ScreenWin::GetDisplayNearestDIPPoint(
+    const Point& dip_point) {
+  ScreenWin* screen = GetNativeScreenWin();
+  DisplayWin primary_display_win;
+  for (const DisplayWin& display_win : screen->display_wins_) {
+    Display display = display_win.display();
+    gfx::Rect dip_bounds = display.bounds();
+    if (dip_bounds.Contains(dip_point))
+      return display_win;
+    else if (dip_bounds.origin().IsOrigin())
+      primary_display_win = display_win;
+  }
+  return primary_display_win;
+}
+
+// static
+float ScreenWin::GetScaleFactorForHWND(HWND hwnd) {
+  DCHECK(hwnd);
+  ScreenWin* screen = GetNativeScreenWin();
+  HWND rootHwnd = screen->GetRootWindow(hwnd);
+  return GetDisplayNearestHWND(rootHwnd).display().device_scale_factor();
+}
+
+// static
+float ScreenWin::GetScaleFactorForScreenPoint(const Point& screen_point) {
+  Display display = GetDisplayNearestScreenPoint(screen_point).display();
+  return display.device_scale_factor();
+}
+
+// static
+std::vector<ScreenWin::DisplayInfo>::const_iterator
+ScreenWin::FindTouchingDisplayInfo(
+    const DisplayWin& display_win,
+    const std::vector<DisplayInfo>& display_infos) {
+  auto end = display_infos.end();
+  for (auto display_info = display_infos.begin();
+       display_info != end;
+       display_info++) {
+    gfx::win::RectEdge edge = gfx::win::RectTouch(display_win.physical_bounds(),
+                                                  display_info->screen_rect());
+    if (edge != gfx::win::RectEdge::NONE) {
+      return display_info;
+    }
+  }
+  return end;
+}
+
+// static
+std::vector<ScreenWin::DisplayWin> ScreenWin::GetDisplaysFromDisplayInfos(
+    const std::vector<ScreenWin::DisplayInfo>& display_infos) {
+  std::vector<DisplayInfo> display_infos_remaining = display_infos;
+
+  // Seed the primary display to layout all the other displays.
+  std::vector<DisplayWin> display_wins;
+  for (auto current = display_infos_remaining.begin();
+       current != display_infos_remaining.end();
+       current++) {
+    if (current->screen_rect().origin().IsOrigin()) {
+      display_wins.push_back(DisplayWin(*current));
+      display_infos_remaining.erase(current);
+      break;
+    }
+  }
+
+  // Scale touching display_infos relative to each other.
+  size_t display_infos_at_cycle_start = 0;
+  while ((display_infos_remaining.size() > 0) &&
+         (display_infos_remaining.size() != display_infos_at_cycle_start)) {
+    display_infos_at_cycle_start = display_infos_remaining.size();
+    for (const DisplayWin& display_win : display_wins) {
+      auto display_info = FindTouchingDisplayInfo(display_win,
+                                                  display_infos_remaining);
+      if (display_info != display_infos_remaining.end()) {
+        display_wins.push_back(DisplayWin(display_win, *display_info));
+        display_infos_remaining.erase(display_info);
+        break;
+      }
+    }
+  }
+
+  // Under Windows DPI virtualization, not all display_infos touch, so scale
+  // the remaining display infos relative to the origin.
+  for (const DisplayInfo& display_info : display_infos_remaining) {
+    display_wins.push_back(DisplayWin(display_info));
+  }
+
+  return display_wins;
+}
+
+// static
+std::vector<ScreenWin::DisplayWin> ScreenWin::GetDisplayWins() {
+  std::vector<DisplayInfo> display_infos;
+  EnumDisplayMonitors(NULL, NULL, EnumMonitorCallback,
+                      reinterpret_cast<LPARAM>(&display_infos));
+  return GetDisplaysFromDisplayInfos(display_infos);
+}
+
+// static
+BOOL CALLBACK ScreenWin::EnumMonitorCallback(HMONITOR monitor,
+                                             HDC hdc,
+                                             LPRECT rect,
+                                             LPARAM data) {
+  std::vector<DisplayInfo>* display_infos =
+      reinterpret_cast<std::vector<DisplayInfo>*>(data);
+  DCHECK(display_infos);
+  display_infos->push_back(DisplayInfo(monitor, gfx::GetDPIScale()));
+  return TRUE;
+}
+
 void ScreenWin::OnWndProc(HWND hwnd,
                           UINT message,
                           WPARAM wparam,
                           LPARAM lparam) {
   if (message != WM_DISPLAYCHANGE)
     return;
 
-  std::vector<gfx::Display> old_displays = displays_;
-  displays_ = GetDisplays();
+  std::vector<gfx::Display> old_displays = GetAllDisplays();
+  display_wins_ = GetDisplayWins();
+  std::vector<gfx::Display> new_displays = GetAllDisplays();
 
-  change_notifier_.NotifyDisplaysChanged(old_displays, displays_);
+  change_notifier_.NotifyDisplaysChanged(old_displays, new_displays);
 }
 
-// static
-std::vector<gfx::Display> ScreenWin::GetDisplaysForMonitorInfos(
-    const std::vector<MONITORINFOEX>& monitor_infos) {
-  std::vector<gfx::Display> displays;
-  for (const MONITORINFOEX& monitor_info : monitor_infos)
-    displays.push_back(GetDisplay(monitor_info));
+MONITORINFOEX ScreenWin::MonitorInfoFromScreenPoint(
+    const gfx::Point& screen_point) const {
+  POINT initial_loc = { screen_point.x(), screen_point.y() };
+  return MonitorInfoFromHMONITOR(::MonitorFromPoint(initial_loc,
+                                                    MONITOR_DEFAULTTONEAREST));
+}
 
-  return displays;
+MONITORINFOEX ScreenWin::MonitorInfoFromScreenRect(const gfx::Rect& screen_rect)
+    const {
+  RECT win_rect = screen_rect.ToRECT();
+  return MonitorInfoFromHMONITOR(::MonitorFromRect(&win_rect,
+                                                   MONITOR_DEFAULTTONEAREST));
+}
+
+MONITORINFOEX ScreenWin::MonitorInfoFromWindow(HWND hwnd) const {
+  return MonitorInfoFromHMONITOR(::MonitorFromWindow(hwnd,
+                                                     MONITOR_DEFAULTTONEAREST));
+}
+
+HWND ScreenWin::GetRootWindow(HWND hwnd) const {
+  return GetAncestor(hwnd, GA_ROOT);
+}
+
+ScreenWin::DisplayWin ScreenWin::GetDisplayWin(
+    const MONITORINFOEX& monitor_info) const {
+  int64_t id = HashDeviceName(monitor_info.szDevice);
+  for (const DisplayWin& display_win : display_wins_) {
+    if (display_win.display().id() == id)
+      return display_win;
+  }
+  NOTREACHED();
+  return DisplayWin();
 }
 
 }  // namespace gfx