wined3d: Implement VolumeTexture::UnLoad.

dlls/wined3d/volumetexture.c

@@ -136,7 +136,26 @@ static void WINAPI IWineD3DVolumeTextureImpl_PreLoad(IWineD3DVolumeTexture *ifac
 }
 
 static void WINAPI IWineD3DVolumeTextureImpl_UnLoad(IWineD3DVolumeTexture *iface) {
-    IWineD3DResourceImpl_UnLoad((IWineD3DResource *)iface);
+    unsigned int i;
+    IWineD3DVolumeTextureImpl *This = (IWineD3DVolumeTextureImpl *)iface;
+    IWineD3DDeviceImpl *device = This->resource.wineD3DDevice;
+    TRACE("(%p)\n", This);
+
+    /* Unload all the surfaces and reset the texture name. If UnLoad was called on the
+     * surface before, this one will be a NOP and vice versa. Unloading an unloaded
+     * surface is fine
+     */
+    for (i = 0; i < This->baseTexture.levels; i++) {
+        IWineD3DVolume_UnLoad(This->volumes[i]);
+    }
+
+    if(This->baseTexture.textureName) {
+        ActivateContext(device, device->lastActiveRenderTarget, CTXUSAGE_RESOURCELOAD);
+        ENTER_GL();
+        glDeleteTextures(1, &This->baseTexture.textureName);
+        This->baseTexture.textureName = 0;
+        LEAVE_GL();
+    }
 }
 
 static WINED3DRESOURCETYPE WINAPI IWineD3DVolumeTextureImpl_GetType(IWineD3DVolumeTexture *iface) {