ControllerInterface: devices population is now async so implement devices sorting priority

This helps us keeping the most important devices (e.g. Mouse and Keyboard) on the top
of the list of devices (they still are on all OSes supported by dolphin
and to make hotplug devices like DSU appear at the bottom.

Source/Core/InputCommon/ControllerInterface/ControllerInterface.cpp

@@ -319,6 +319,19 @@ bool ControllerInterface::AddDevice(std::shared_ptr<ciface::Core::Device> device
 
     NOTICE_LOG_FMT(CONTROLLERINTERFACE, "Added device: {}", device->GetQualifiedName());
     m_devices.emplace_back(std::move(device));
+
+    // We can't (and don't want) to control the order in which devices are added, but we
+    // need their order to be consistent, and we need the same one to always be the first, where
+    // present (the keyboard and mouse device usually). This is because when defaulting a
+    // controller profile, it will automatically select the first device in the list as its default.
+    std::stable_sort(m_devices.begin(), m_devices.end(),
+                     [](const std::shared_ptr<ciface::Core::Device>& a,
+                        const std::shared_ptr<ciface::Core::Device>& b) {
+                       // It would be nice to sort devices by Source then Name then ID but it's
+                       // better to leave them sorted by the add order, which also avoids breaking
+                       // the order on other platforms that are less tested.
+                       return a->GetSortPriority() > b->GetSortPriority();
+                     });
   }
 
   if (!m_populating_devices_counter)

Source/Core/InputCommon/ControllerInterface/CoreDevice.h

@@ -128,6 +128,11 @@ public:
   // (e.g. Xbox 360 controllers have controller number LEDs which should match the ID we use.)
   virtual std::optional<int> GetPreferredId() const;
 
+  // Use this to change the order in which devices are sorted in their list.
+  // A higher priority means it will be one of the first ones (smaller index), making it more
+  // likely to be index 0, which is automatically set as the default device when there isn't one.
+  virtual int GetSortPriority() const { return 0; }
+
   const std::vector<Input*>& Inputs() const { return m_inputs; }
   const std::vector<Output*>& Outputs() const { return m_outputs; }
 

Source/Core/InputCommon/ControllerInterface/DInput/DInputKeyboardMouse.cpp

@@ -230,6 +230,12 @@ std::string KeyboardMouse::GetSource() const
   return DINPUT_SOURCE_NAME;
 }
 
+// Give this device a higher priority to make sure it shows first
+int KeyboardMouse::GetSortPriority() const
+{
+  return 5;
+}
+
 // names
 std::string KeyboardMouse::Key::GetName() const
 {

Source/Core/InputCommon/ControllerInterface/DInput/DInputKeyboardMouse.h

@@ -102,6 +102,7 @@ public:
 
   std::string GetName() const override;
   std::string GetSource() const override;
+  int GetSortPriority() const override;
 
 private:
   void UpdateCursorInput();

Source/Core/InputCommon/ControllerInterface/DualShockUDPClient/DualShockUDPClient.cpp

@@ -136,6 +136,8 @@ public:
   std::string GetName() const final override;
   std::string GetSource() const final override;
   std::optional<int> GetPreferredId() const final override;
+  // Always add these at the end, given their hotplug nature
+  int GetSortPriority() const override { return -2; }
 
 private:
   void ResetPadData();

Source/Core/InputCommon/ControllerInterface/Wiimote/WiimoteController.cpp

@@ -321,6 +321,12 @@ std::string Device::GetSource() const
   return SOURCE_NAME;
 }
 
+// Always add these at the end, given their hotplug nature
+int Device::GetSortPriority() const
+{
+  return -1;
+}
+
 void Device::RunTasks()
 {
   if (IsPerformingTask())

Source/Core/InputCommon/ControllerInterface/Wiimote/WiimoteController.h

@@ -33,6 +33,7 @@ public:
 
   std::string GetName() const override;
   std::string GetSource() const override;
+  int GetSortPriority() const override;
 
   void UpdateInput() override;