InputSystem: add IInputStackSystem interface

Interface is used in  commit fb8ef4f37964adf3d5128ccd98bff136af75e9bb.

src/public/inputsystem/iinputstacksystem.h

@@ -0,0 +1,73 @@
+//===== Copyright © 1996-2005, Valve Corporation, All rights reserved. ======//
+//
+// Purpose: This is input priority system, allowing various clients to
+// cause input messages / cursor control to be routed to them as opposed to
+// other clients.
+//
+//===========================================================================//
+
+#ifndef IINPUTCLIENTSTACK_H
+#define IINPUTCLIENTSTACK_H
+#ifdef _WIN32
+#pragma once
+#endif
+
+#include "appframework/iappsystem.h"
+#include "inputsystem/iinputsystem.h"
+
+
+///-----------------------------------------------------------------------------
+/// A handle to an input context. These are arranged in a priority-based
+/// stack; the top context on the stack which is also enabled wins.
+///-----------------------------------------------------------------------------
+DECLARE_POINTER_HANDLE( InputContextHandle_t );
+#define INPUT_CONTEXT_HANDLE_INVALID ( (InputContextHandle_t)0 )
+
+
+///-----------------------------------------------------------------------------
+/// Purpose: This is input priority system, allowing various clients to
+/// cause input messages / cursor control to be routed to them as opposed to
+/// other clients.
+///
+/// NOTE: For Source1, it would be a huge change to move all input (like 
+/// the code in engine/keys.cpp for example) to go through this interface. 
+/// Therefore, I'm going to stick with only dealing with cursor control, 
+/// which is necessary for Jen's new gameUI system to interoperate with VGui.
+///-----------------------------------------------------------------------------
+abstract_class IInputStackSystem : public IAppSystem
+{
+public:
+	/// Allocates an input context, pushing it on top of the input stack, 
+	/// thereby giving it top priority
+	virtual InputContextHandle_t PushInputContext() = 0;
+
+	/// Pops the top input context off the input stack, and destroys it.
+	virtual void PopInputContext( InputContextHandle_t hContext ) = 0;
+
+	/// Enables/disables an input context, allowing something lower on the
+	/// stack to have control of input. Disabling an input context which
+	/// owns mouse capture
+	virtual void EnableInputContext( InputContextHandle_t hContext, bool bEnable ) = 0;
+
+	/// Allows a context to make the cursor visible;
+	/// the topmost enabled context wins
+	virtual void SetCursorVisible( InputContextHandle_t hContext, bool bVisible ) = 0;
+
+	/// Allows a context to set the cursor icon;
+	/// the topmost enabled context wins
+	virtual void SetCursorIcon( InputContextHandle_t hContext, InputCursorHandle_t hCursor ) = 0;
+
+	/// Allows a context to enable mouse capture. Disabling an input context
+	/// deactivates mouse capture. Capture will occur if it happens on the
+	/// topmost enabled context
+	virtual void SetMouseCapture( InputContextHandle_t hContext, bool bEnable ) = 0;
+
+	/// Allows a context to set the mouse position. It only has any effect if the
+	/// specified context is the topmost enabled context
+	virtual void SetCursorPosition( InputContextHandle_t hContext, int x, int y ) = 0;
+
+	/// Returns true if the specified context is the topmost enabled context
+	virtual bool IsTopmostEnabledContext( InputContextHandle_t hContext ) const = 0;
+};
+
+#endif // IINPUTCLIENTSTACK_H