diff --git a/src/gx/CGxDevice.hpp b/src/gx/CGxDevice.hpp
index 8cdbcbc..5e1f76d 100644
--- a/src/gx/CGxDevice.hpp
+++ b/src/gx/CGxDevice.hpp
@@ -73,6 +73,7 @@ class CGxDevice {
         TSHashTable<CGxShader, HASHKEY_STRI> m_shaderList[GxShTargets_Last];
         int32_t m_context = 0;
         int32_t intF5C = 0;
+        int32_t m_windowVisible = 0;
         int32_t intF64 = 0;
         CBoundingBox m_viewport;
         C44Matrix m_projection;
diff --git a/src/gx/d3d/CGxDeviceD3d.cpp b/src/gx/d3d/CGxDeviceD3d.cpp
index 4bd3739..82f8207 100644
--- a/src/gx/d3d/CGxDeviceD3d.cpp
+++ b/src/gx/d3d/CGxDeviceD3d.cpp
@@ -408,7 +408,24 @@ int32_t CGxDeviceD3d::DeviceSetFormat(const CGxFormat& format) {
 }
 
 void CGxDeviceD3d::DeviceWM(EGxWM wm, uintptr_t param1, uintptr_t param2) {
-    // TODO
+    switch (wm) {
+    case GxWM_Size: {
+        if (param2 == 1 || param2 == 2) {
+            this->m_windowVisible = 0;
+        } else {
+            this->m_windowVisible = 1;
+
+            auto& windowRect = *reinterpret_cast<CRect*>(param1);
+            this->DeviceSetDefWindow(windowRect);
+
+            if (this->m_d3dDevice && this->m_context) {
+                // TODO
+            }
+        }
+
+        break;
+    }
+    }
 }
 
 void CGxDeviceD3d::Draw(CGxBatch* batch, int32_t indexed) {