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

ui/gfx/screen_win.cc

Index: ui/gfx/screen_win.cc
diff --git a/ui/gfx/screen_win.cc b/ui/gfx/screen_win.cc
index f01d40aa833d8a48a92e56ebe3311a8b784b3c40..c411f14d17e7fb05920da9c14385120e7655fe49 100644
--- a/ui/gfx/screen_win.cc
+++ b/ui/gfx/screen_win.cc
@@ -13,33 +13,33 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/win_util.h"
 #include "ui/gfx/display.h"
+#include "ui/gfx/geometry/point_conversions.h"
+#include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/win/dpi.h"
 
 namespace {
 
-MONITORINFOEX GetMonitorInfoForMonitor(HMONITOR monitor) {
+gfx::Display GetDisplay(HMONITOR monitor) {
   MONITORINFOEX monitor_info;
-  ZeroMemory(&monitor_info, sizeof(MONITORINFOEX));
+  ::ZeroMemory(&monitor_info, sizeof(monitor_info));
   monitor_info.cbSize = sizeof(monitor_info);
-  GetMonitorInfo(monitor, &monitor_info);
-  return monitor_info;
-}
+  ::GetMonitorInfo(monitor, &monitor_info);
 
-gfx::Display GetDisplay(MONITORINFOEX& monitor_info) {
   int64 id = static_cast<int64>(
       base::Hash(base::WideToUTF8(monitor_info.szDevice)));
   gfx::Rect bounds = gfx::Rect(monitor_info.rcMonitor);
   gfx::Display display(id, bounds);
   display.set_work_area(gfx::Rect(monitor_info.rcWork));
   display.SetScaleAndBounds(gfx::GetDPIScale(), bounds);
+  DCHECK(display.device_scale_factor() >= 1.0);
 
   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(monitor_info.szDevice,
+                            ENUM_CURRENT_SETTINGS,
+                            &mode)) {
     switch (mode.dmDisplayOrientation) {
     case DMDO_DEFAULT:
       display.set_rotation(gfx::Display::ROTATE_0);
@@ -69,8 +69,7 @@ BOOL CALLBACK EnumMonitorCallback(HMONITOR monitor,
       reinterpret_cast<std::vector<gfx::Display>*>(data);
   DCHECK(all_displays);
 
-  MONITORINFOEX monitor_info = GetMonitorInfoForMonitor(monitor);
-  gfx::Display display = GetDisplay(monitor_info);
+  gfx::Display display = GetDisplay(monitor);
   all_displays->push_back(display);
   return TRUE;
 }
@@ -94,11 +93,102 @@ ScreenWin::ScreenWin()
 
 ScreenWin::~ScreenWin() {}
 
+// static
+Point ScreenWin::ScreenToDIPPoint(const Point& pixel_point) {
+  gfx::Display display = GetDisplayNearestScreenPoint(pixel_point);
+  float device_scale_factor = display.device_scale_factor();
+  const Rect& monitor_bounds = display.bounds();
+  Vector2d origin(monitor_bounds.x(), monitor_bounds.y());
+
+  // Monitors are anchored to their physical coordinate regardless of DPI.
+  return ScaleToFlooredPoint(pixel_point - origin, 1.0f / device_scale_factor) +
+      origin;
+}
+
+// static
+Point ScreenWin::DIPToScreenPoint(const Point& dip_point) {
+  // Because origins don't change for screen points and scaling factors are
+  // greater than 1, the monitor bounding rect always contains the DIP point.
+  gfx::Display display = GetDisplayNearestScreenPoint(dip_point);
+  float device_scale_factor = display.device_scale_factor();
+  const Rect& monitor_bounds = display.bounds();
+  Vector2d origin(monitor_bounds.x(), monitor_bounds.y());
+
+  return ScaleToFlooredPoint(dip_point - origin, device_scale_factor) + origin;
+}
+
+// static
+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 =
+      GetDisplayNearestRect(pixel_bounds).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 =
+      GetDisplayNearestRect(dip_bounds).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));
+}
+
 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() {
@@ -108,7 +198,7 @@ gfx::NativeWindow ScreenWin::GetWindowUnderCursor() {
 }
 
 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()));
 }
 
@@ -129,40 +219,23 @@ gfx::Display ScreenWin::GetDisplayNearestWindow(gfx::NativeView window) const {
     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);
 }
 
 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));
 }
 
 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 GetDisplayNearestRect(match_rect);
 }
 
 gfx::Display ScreenWin::GetPrimaryDisplay() const {
-  MONITORINFOEX mi = GetMonitorInfoForMonitor(
-      MonitorFromWindow(NULL, MONITOR_DEFAULTTOPRIMARY));
-  gfx::Display display = GetDisplay(mi);
+  gfx::Display display =
+      GetDisplay(MonitorFromWindow(NULL, MONITOR_DEFAULTTOPRIMARY));
   // 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());
   }
@@ -177,6 +250,36 @@ void ScreenWin::RemoveObserver(DisplayObserver* observer) {
   change_notifier_.RemoveObserver(observer);
 }
 
+// static
+gfx::Display ScreenWin::GetDisplayNearestHWND(HWND hwnd) {
+  return GetDisplay(::MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST));
+}
+
+// static
+gfx::Display ScreenWin::GetDisplayNearestRect(const Rect& rect) {
+  RECT winRect = rect.ToRECT();
+  return GetDisplay(::MonitorFromRect(&winRect, MONITOR_DEFAULTTONEAREST));
+}
+
+// static
+gfx::Display ScreenWin::GetDisplayNearestScreenPoint(
+    const Point& screen_point) {
+  POINT initial_loc = { screen_point.x(), screen_point.y() };
+  return GetDisplay(::MonitorFromPoint(initial_loc, MONITOR_DEFAULTTONEAREST));
+}
+
+// static
+float ScreenWin::GetScaleFactorForHWND(HWND hwnd) {
+  DCHECK(hwnd);
+  HWND hwndTopLevel = GetAncestor(hwnd, GA_ROOT);
+  return GetDisplayNearestHWND(hwndTopLevel).device_scale_factor();
+}
+
+// static
+float ScreenWin::GetScaleFactorForScreenPoint(const Point& screen_point) {
+  return GetDisplayNearestScreenPoint(screen_point).device_scale_factor();
+}
+
 void ScreenWin::OnWndProc(HWND hwnd,
                           UINT message,
                           WPARAM wparam,