1 files changed, 73 insertions, 0 deletions
diff --git a/mozglue/misc/WindowsDpiInitialization.cpp b/mozglue/misc/WindowsDpiInitialization.cpp
new file mode 100644
index 0000000000..2e957b5830
--- /dev/null
+++ b/mozglue/misc/WindowsDpiInitialization.cpp
@@ -0,0 +1,73 @@
+/* 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 "mozilla/WindowsDpiInitialization.h"
+
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/WindowsProcessMitigations.h"
+#include "mozilla/WindowsVersion.h"
+
+#include <shellscalingapi.h>
+#include <windows.h>
+
+namespace mozilla {
+
+typedef HRESULT(WINAPI* SetProcessDpiAwarenessType)(PROCESS_DPI_AWARENESS);
+typedef BOOL(WINAPI* SetProcessDpiAwarenessContextType)(DPI_AWARENESS_CONTEXT);
+
+WindowsDpiInitializationResult WindowsDpiInitialization() {
+  // DPI Awareness can't be used in a Win32k Lockdown process, so there's
+  // nothing to do
+  if (IsWin32kLockedDown()) {
+    return WindowsDpiInitializationResult::Success;
+  }
+
+  // From MSDN:
+  //  SetProcessDpiAwarenessContext() was added in the Win10 Anniversary Update
+  //  SetProcessDpiAwareness() was added in Windows 8.1
+  //  SetProcessDpiAware() was added in Windows Vista
+  //
+  //  DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2 wasn't added later until
+  //  the Creators Update, so if it fails we just fall back to
+  //  DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE
+  if (IsWin10AnniversaryUpdateOrLater()) {
+    DynamicallyLinkedFunctionPtr<SetProcessDpiAwarenessContextType>
+        setProcessDpiAwarenessContext(L"user32.dll",
+                                      "SetProcessDpiAwarenessContext");
+    if (!setProcessDpiAwarenessContext) {
+      return WindowsDpiInitializationResult::
+          FindSetProcessDpiAwarenessContextFailed;
+    }
+
+    if (!setProcessDpiAwarenessContext(
+            DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2) &&
+        !setProcessDpiAwarenessContext(
+            DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE)) {
+      return WindowsDpiInitializationResult::
+          SetProcessDpiAwarenessContextFailed;
+    }
+
+    return WindowsDpiInitializationResult::Success;
+  } else if (IsWin8Point1OrLater()) {
+    DynamicallyLinkedFunctionPtr<SetProcessDpiAwarenessType>
+        setProcessDpiAwareness(L"Shcore.dll", "SetProcessDpiAwareness");
+    if (!setProcessDpiAwareness) {
+      return WindowsDpiInitializationResult::FindSetProcessDpiAwarenessFailed;
+    }
+
+    if (FAILED(setProcessDpiAwareness(PROCESS_PER_MONITOR_DPI_AWARE))) {
+      return WindowsDpiInitializationResult::SetProcessDpiAwarenessFailed;
+    }
+
+    return WindowsDpiInitializationResult::Success;
+  } else {
+    if (!SetProcessDPIAware()) {
+      return WindowsDpiInitializationResult::SetProcessDPIAwareFailed;
+    }
+
+    return WindowsDpiInitializationResult::Success;
+  }
+}
+
+}  // namespace mozilla