Bug 1493128 - Consider a single mouse type device queried by SetupDiEnumDeviceInterfaces on tablet or on system with a digitizer as COARSE type pointer device. r=masayuki

Unfortunately there is no realiable way to tell whether there is no mouse
connected or not.  So we are going to take a heuristic way here.  The way is
that;

1) Count mouse type devices with SetupDiEnumDeviceInterfaces [1]
2) If the count is 1 and if the system is used as tablet or has a touch device,
   the device should be COARSE

This way causes a misrecognition as if there is a mouse device in the case
where the touchscreen is disabled on the tablet even if there is no mouse
connected (i.e. the case where CountMouseDevices() returns 1 and the system
is on table mode).  We will try to fix the misrecognition in a later bug
(bug 1495938).

[1] https://docs.microsoft.com/en-us/windows/desktop/api/setupapi/nf-setupapi-setupdienumdeviceinterfaces

Differential Revision: https://phabricator.services.mozilla.com/D7565

--HG--
extra : moz-landing-system : lando

widget/windows/InputDeviceUtils.cpp

@@ -10,6 +10,7 @@
 #include <dbt.h>
 #include <hidclass.h>
 #include <ntddmou.h>
+#include <setupapi.h>
 
 namespace mozilla {
 namespace widget {
@@ -37,5 +38,32 @@ InputDeviceUtils::UnregisterNotification(HDEVNOTIFY aHandle)
   UnregisterDeviceNotification(aHandle);
 }
 
+DWORD
+InputDeviceUtils::CountMouseDevices()
+{
+  HDEVINFO hdev = SetupDiGetClassDevs(&GUID_DEVINTERFACE_MOUSE,
+                                      nullptr,
+                                      nullptr,
+                                      DIGCF_DEVICEINTERFACE | DIGCF_PRESENT);
+  if (hdev == INVALID_HANDLE_VALUE) {
+    return 0;
+  }
+
+  DWORD count = 0;
+  SP_INTERFACE_DEVICE_DATA info = {};
+  info.cbSize = sizeof(SP_INTERFACE_DEVICE_DATA);
+  while (SetupDiEnumDeviceInterfaces(hdev,
+                                     nullptr,
+                                     &GUID_DEVINTERFACE_MOUSE,
+                                     count,
+                                     &info)) {
+    if (info.Flags & SPINT_ACTIVE) {
+      count++;
+    }
+  }
+  SetupDiDestroyDeviceInfoList(hdev);
+  return count;
+}
+
 } // namespace widget
 } // namespace mozilla

widget/windows/InputDeviceUtils.h

@@ -16,6 +16,9 @@ class InputDeviceUtils {
 public:
   static HDEVNOTIFY RegisterNotification(HWND aHwnd);
   static void UnregisterNotification(HDEVNOTIFY aHandle);
+
+  // Returns the number of mouse type devices connected to this system.
+  static DWORD CountMouseDevices();
 };
 
 } // namespace widget

widget/windows/WinUtils.cpp

@@ -13,6 +13,7 @@
 #include "gfxUtils.h"
 #include "nsWindow.h"
 #include "nsWindowDefs.h"
+#include "InputDeviceUtils.h"
 #include "KeyboardLayout.h"
 #include "mozilla/ArrayUtils.h"
 #include "mozilla/BackgroundHangMonitor.h"
@@ -1900,7 +1901,26 @@ IsTabletDevice()
 static bool
 IsMousePresent()
 {
-  return ::GetSystemMetrics(SM_MOUSEPRESENT);
+  if (!::GetSystemMetrics(SM_MOUSEPRESENT)) {
+    return false;
+  }
+
+  DWORD count = InputDeviceUtils::CountMouseDevices();
+  if (!count) {
+    return false;
+  }
+
+  // If there is a mouse device and if this machine is a tablet or has a
+  // digitizer, that's counted as the mouse device.
+  // FIXME: Bug 1495938:  We should drop this heuristic way once we find out a
+  // reliable way to tell there is no mouse or not.
+  if (count == 1 &&
+      (WinUtils::IsTouchDeviceSupportPresent() ||
+       IsTabletDevice())) {
+    return false;
+  }
+
+  return true;
 }
 
 /* static */
@@ -1912,7 +1932,7 @@ WinUtils::GetPrimaryPointerCapabilities()
   }
 
   if (IsMousePresent()) {
-    return PointerCapabilities::Fine|
+    return PointerCapabilities::Fine |
            PointerCapabilities::Hover;
   }