add wacom support on Windows

engine/wacom.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "WinTab/msgpack.h"
+#include "WinTab/wintab.h"
+#define PACKETDATA (PK_X | PK_Y | PK_BUTTONS | PK_NORMAL_PRESSURE)
+#define PACKETMODE PK_BUTTONS
+#include "WinTab/pktdef.h"
+#include "WinTab/Utils.h"
+
+class WacomTablet
+{
+    HCTX g_hCtx = NULL;
+    AXIS TabletPressure = { 0 };
+    LOGCONTEXTA glogContext = { 0 };
+    glm::vec2 m_pen_pos{ 0 };
+    float m_pen_pres{ 1 };
+    bool m_pen_down = false;
+    int m_pen_idle = 0;
+    bool m_mouse_down = false;
+
+    HCTX TabletInit(HWND hWnd);
+public:
+    static WacomTablet I;
+    bool init(HWND hWnd);
+    void terminate();
+    void handle_message(HWND hwnd, UINT Msg, WPARAM wParam, LPARAM lParam);
+    void set_focus(int activate);
+    float get_pressure() const;
+};