Expose Control Expression variables to mappings UI

-add a way to reset their value (from the mappings UI)
-fix "memory leak" where they would never be cleaned,
one would be created every time you wrote a character after a "$"
-fix ability to create variables with an empty string by just writing "$" (+added error for it)
-Add $ operator to the UI operators list, to expose this functionality even more

2 files changed, 40 insertions, 9 deletions

diff --git a/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp b/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
index 1a7ca5a8ef..6948ff07ac 100644
--- a/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
+++ b/Source/Core/InputCommon/ControlReference/ExpressionParser.cpp
@@ -461,20 +461,24 @@ class VariableExpression : public Expression
 public:
   VariableExpression(std::string name) : m_name(name) {}
 
-  ControlState GetValue() const override { return *m_value_ptr; }
+  ControlState GetValue() const override { return m_variable_ptr ? *m_variable_ptr : 0; }
 
-  void SetValue(ControlState value) override { *m_value_ptr = value; }
+  void SetValue(ControlState value) override
+  {
+    if (m_variable_ptr)
+      *m_variable_ptr = value;
+  }
 
   int CountNumControls() const override { return 1; }
 
   void UpdateReferences(ControlEnvironment& env) override
   {
-    m_value_ptr = env.GetVariablePtr(m_name);
+    m_variable_ptr = env.GetVariablePtr(m_name);
   }
 
 protected:
   const std::string m_name;
-  ControlState* m_value_ptr{};
+  std::shared_ptr<ControlState> m_variable_ptr;
 };
 
 class HotkeyExpression : public Expression
@@ -621,9 +625,30 @@ Device::Output* ControlEnvironment::FindOutput(ControlQualifier qualifier) const
   return device->FindOutput(qualifier.control_name);
 }
 
-ControlState* ControlEnvironment::GetVariablePtr(const std::string& name)
+std::shared_ptr<ControlState> ControlEnvironment::GetVariablePtr(const std::string& name)
 {
-  return &m_variables[name];
+  // Do not accept an empty string as key, even if the expression parser already prevents this case.
+  if (name.empty())
+    return nullptr;
+  std::shared_ptr<ControlState>& variable = m_variables[name];
+  // If new, make a shared ptr
+  if (!variable)
+  {
+    variable = std::make_shared<ControlState>();
+  }
+  return variable;
+}
+
+void ControlEnvironment::CleanUnusedVariables()
+{
+  for (auto it = m_variables.begin(); it != m_variables.end();)
+  {
+    // Don't count ourselves as reference
+    if (it->second.use_count() <= 1)
+      m_variables.erase(it++);
+    else
+      ++it;
+  }
 }
 
 ParseResult ParseResult::MakeEmptyResult()
@@ -785,7 +810,10 @@ private:
     }
     case TOK_VARIABLE:
     {
-      return ParseResult::MakeSuccessfulResult(std::make_unique<VariableExpression>(tok.data));
+      if (tok.data.empty())
+        return ParseResult::MakeErrorResult(tok, _trans("Expected variable name."));
+      else
+        return ParseResult::MakeSuccessfulResult(std::make_unique<VariableExpression>(tok.data));
     }
     case TOK_LPAREN:
     {
diff --git a/Source/Core/InputCommon/ControlReference/ExpressionParser.h b/Source/Core/InputCommon/ControlReference/ExpressionParser.h
index 14670848ae..d36e00888f 100644
--- a/Source/Core/InputCommon/ControlReference/ExpressionParser.h
+++ b/Source/Core/InputCommon/ControlReference/ExpressionParser.h
@@ -143,7 +143,7 @@ public:
 class ControlEnvironment
 {
 public:
-  using VariableContainer = std::map<std::string, ControlState>;
+  using VariableContainer = std::map<std::string, std::shared_ptr<ControlState>>;
 
   ControlEnvironment(const Core::DeviceContainer& container_, const Core::DeviceQualifier& default_,
                      VariableContainer& vars)
@@ -154,7 +154,10 @@ public:
   std::shared_ptr<Core::Device> FindDevice(ControlQualifier qualifier) const;
   Core::Device::Input* FindInput(ControlQualifier qualifier) const;
   Core::Device::Output* FindOutput(ControlQualifier qualifier) const;
-  ControlState* GetVariablePtr(const std::string& name);
+  // Returns an existing variable by the specified name if already existing. Creates it otherwise.
+  std::shared_ptr<ControlState> GetVariablePtr(const std::string& name);
+
+  void CleanUnusedVariables();
 
 private:
   VariableContainer& m_variables;