Windows: Add CefEnableHighDPISupport function and fix high-dpi scaling issues (issue #1674)

include/capi/cef_app_capi.h

@@ -175,6 +175,13 @@ CEF_EXPORT void cef_quit_message_loop();
 ///
 CEF_EXPORT void cef_set_osmodal_loop(int osModalLoop);
 
+///
+// Call during process startup to enable High-DPI support on Windows 7 or newer.
+// Older versions of Windows should be left DPI-unaware because they do not
+// support DirectWrite and GDI fonts are kerned very badly.
+///
+CEF_EXPORT void cef_enable_highdpi_support();
+
 #ifdef __cplusplus
 }
 #endif

include/cef_app.h

@@ -124,6 +124,14 @@ void CefQuitMessageLoop();
 /*--cef()--*/
 void CefSetOSModalLoop(bool osModalLoop);
 
+///
+// Call during process startup to enable High-DPI support on Windows 7 or newer.
+// Older versions of Windows should be left DPI-unaware because they do not
+// support DirectWrite and GDI fonts are kerned very badly.
+///
+/*--cef(capi_name=cef_enable_highdpi_support)--*/
+void CefEnableHighDPISupport();
+
 ///
 // Implement this interface to provide handler implementations. Methods will be
 // called by the process and/or thread indicated.

libcef/browser/browser_host_impl_win.cc

@@ -37,6 +37,7 @@
 #include "ui/aura/window_tree_host.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/win/shell.h"
+#include "ui/gfx/screen.h"
 #include "ui/gfx/win/hwnd_util.h"
 #include "ui/views/widget/desktop_aura/desktop_window_tree_host_win.h"
 #include "ui/views/widget/widget.h"
@@ -809,11 +810,17 @@ bool CefBrowserHostImpl::PlatformCreateWindow() {
         CefColorGetB(settings.background_color));
   }
 
+  // Adjust for potential display scaling.
+  gfx::Point point = gfx::Point(cr.right, cr.bottom);
+  float scale = gfx::Screen::GetNativeScreen()->
+      GetDisplayNearestPoint(point).device_scale_factor();
+  point = gfx::ToFlooredPoint(gfx::ScalePoint(point, 1.0f / scale));
+
   CefWindowDelegateView* delegate_view =
       new CefWindowDelegateView(background_color);
   delegate_view->Init(window_info_.window,
                       web_contents(),
-                      gfx::Rect(0, 0, cr.right, cr.bottom));
+                      gfx::Rect(0, 0, point.x(), point.y()));
 
   window_widget_ = delegate_view->GetWidget();
   window_widget_->Show();

libcef/browser/menu_creator_runner_win.cc

@@ -8,6 +8,8 @@
 #include "base/message_loop/message_loop.h"
 #include "ui/aura/window.h"
 #include "ui/gfx/geometry/point.h"
+#include "ui/gfx/geometry/point_conversions.h"
+#include "ui/gfx/screen.h"
 #include "ui/views/controls/menu/menu_2.h"
 
 CefMenuCreatorRunnerWin::CefMenuCreatorRunnerWin() {
@@ -46,6 +48,11 @@ bool CefMenuCreatorRunnerWin::RunContextMenu(CefMenuCreator* manager) {
     const gfx::Rect& bounds_in_screen = window->GetBoundsInScreen();
     screen_point = gfx::Point(bounds_in_screen.x() + manager->params().x,
                               bounds_in_screen.y() + manager->params().y);
+
+    // Adjust for potential display scaling.
+    float scale = gfx::Screen::GetScreenFor(window)->
+        GetDisplayNearestWindow(window).device_scale_factor();
+    screen_point = gfx::ToFlooredPoint(gfx::ScalePoint(screen_point, scale));
   }
 
   // Show the menu. Blocks until the menu is dismissed.

libcef/common/base_impl.cc

@@ -1,6 +1,13 @@
-// Copyright (c) 2014 The Chromium Embedded Framework Authors. All rights
-// reserved. Use of this source code is governed by a BSD-style license that can
-// be found in the LICENSE file.
+// Copyright 2014 The Chromium Embedded Framework Authors. Portions copyright
+// 2011 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 "include/base/cef_build.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#include <shellscalingapi.h>
+#endif
 
 #include "include/internal/cef_trace_event_internal.h"
 #include "include/internal/cef_logging_internal.h"
@@ -10,6 +17,55 @@
 #include "base/threading/platform_thread.h"
 #include "base/trace_event/trace_event.h"
 
+#if defined(OS_WIN)
+#include "base/win/windows_version.h"
+
+namespace {
+
+// Implementation from chrome/app/chrome_exe_main_win.cc.
+
+// Win8.1 supports monitor-specific DPI scaling.
+bool SetProcessDpiAwarenessWrapper(PROCESS_DPI_AWARENESS value) {
+  typedef HRESULT(WINAPI *SetProcessDpiAwarenessPtr)(PROCESS_DPI_AWARENESS);
+  SetProcessDpiAwarenessPtr set_process_dpi_awareness_func =
+      reinterpret_cast<SetProcessDpiAwarenessPtr>(
+          GetProcAddress(GetModuleHandleA("user32.dll"),
+                         "SetProcessDpiAwarenessInternal"));
+  if (set_process_dpi_awareness_func) {
+    HRESULT hr = set_process_dpi_awareness_func(value);
+    if (SUCCEEDED(hr)) {
+      VLOG(1) << "SetProcessDpiAwareness succeeded.";
+      return true;
+    } else if (hr == E_ACCESSDENIED) {
+      LOG(ERROR) << "Access denied error from SetProcessDpiAwareness. "
+          "Function called twice, or manifest was used.";
+    }
+  }
+  return false;
+}
+
+// This function works for Windows Vista through Win8. Win8.1 must use
+// SetProcessDpiAwareness[Wrapper].
+BOOL SetProcessDPIAwareWrapper() {
+  typedef BOOL(WINAPI *SetProcessDPIAwarePtr)(VOID);
+  SetProcessDPIAwarePtr set_process_dpi_aware_func =
+      reinterpret_cast<SetProcessDPIAwarePtr>(
+      GetProcAddress(GetModuleHandleA("user32.dll"),
+                      "SetProcessDPIAware"));
+  return set_process_dpi_aware_func &&
+    set_process_dpi_aware_func();
+}
+
+void EnableHighDPISupport() {
+  if (!SetProcessDpiAwarenessWrapper(PROCESS_SYSTEM_DPI_AWARE)) {
+    SetProcessDPIAwareWrapper();
+  }
+}
+
+}  // namespace
+
+#endif  // defined(OS_WIN)
+
 // The contents of this file are a compilation unit that is not called by other
 // functions in the the library. Consiquently MSVS will exclude it during the
 // linker stage if we don't call a stub function.
@@ -343,3 +399,13 @@ CEF_EXPORT cef_platform_thread_handle_t
   return base::PlatformThread::CurrentHandle().platform_handle();
 #endif
 }
+
+void CefEnableHighDPISupport() {
+#if defined(OS_WIN)
+  // We don't want to set DPI awareness on pre-Win7 because we don't support
+  // DirectWrite there. GDI fonts are kerned very badly, so better to leave
+  // DPI-unaware and at effective 1.0. See also ShouldUseDirectWrite().
+  if (base::win::GetVersion() >= base::win::VERSION_WIN7)
+    EnableHighDPISupport();
+#endif
+}

libcef_dll/libcef_dll.cc

@@ -311,6 +311,13 @@ CEF_EXPORT void cef_set_osmodal_loop(int osModalLoop) {
       osModalLoop?true:false);
 }
 
+CEF_EXPORT void cef_enable_highdpi_support() {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  CefEnableHighDPISupport();
+}
+
 CEF_EXPORT int cef_get_geolocation(
     struct _cef_get_geolocation_callback_t* callback) {
   // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING

libcef_dll/wrapper/libcef_dll_wrapper.cc

@@ -303,6 +303,13 @@ CEF_GLOBAL void CefSetOSModalLoop(bool osModalLoop) {
       osModalLoop);
 }
 
+CEF_GLOBAL void CefEnableHighDPISupport() {
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  cef_enable_highdpi_support();
+}
+
 CEF_GLOBAL bool CefGetGeolocation(
     CefRefPtr<CefGetGeolocationCallback> callback) {
   // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING

tests/cefclient/cefclient_win.cc

@@ -32,6 +32,9 @@ namespace client {
 namespace {
 
 int RunMain(HINSTANCE hInstance, int nCmdShow) {
+  // Enable High-DPI support on Windows 7 or newer.
+  CefEnableHighDPISupport();
+
   CefMainArgs main_args(hInstance);
 
   void* sandbox_info = NULL;

tests/cefsimple/cefsimple_win.cc

@@ -29,6 +29,9 @@ int APIENTRY wWinMain(HINSTANCE hInstance,
   UNREFERENCED_PARAMETER(hPrevInstance);
   UNREFERENCED_PARAMETER(lpCmdLine);
 
+  // Enable High-DPI support on Windows 7 or newer.
+  CefEnableHighDPISupport();
+
   void* sandbox_info = NULL;
 
 #if defined(CEF_USE_SANDBOX)