wined3d: Allow retrieving the frontbuffer from a wined3d swapchain.

dlls/wined3d/swapchain.c

@@ -275,6 +275,13 @@ struct wined3d_texture * CDECL wined3d_swapchain_get_back_buffer(const struct wi
     return swapchain->back_buffers[back_buffer_idx];
 }
 
+struct wined3d_texture * CDECL wined3d_swapchain_get_front_buffer(const struct wined3d_swapchain *swapchain)
+{
+    TRACE("swapchain %p.\n", swapchain);
+
+    return swapchain->front_buffer;
+}
+
 struct wined3d_output * wined3d_swapchain_get_output(const struct wined3d_swapchain *swapchain)
 {
     TRACE("swapchain %p.\n", swapchain);

dlls/wined3d/wined3d.spec

@@ -270,6 +270,7 @@
 @ cdecl wined3d_swapchain_get_desc(ptr ptr)
 @ cdecl wined3d_swapchain_get_device(ptr)
 @ cdecl wined3d_swapchain_get_display_mode(ptr ptr ptr)
+@ cdecl wined3d_swapchain_get_front_buffer(ptr)
 @ cdecl wined3d_swapchain_get_front_buffer_data(ptr ptr long)
 @ cdecl wined3d_swapchain_get_gamma_ramp(ptr ptr)
 @ cdecl wined3d_swapchain_get_parent(ptr)

include/wine/wined3d.h

@@ -2809,6 +2809,7 @@ struct wined3d_texture * __cdecl wined3d_swapchain_get_back_buffer(const struct
 struct wined3d_device * __cdecl wined3d_swapchain_get_device(const struct wined3d_swapchain *swapchain);
 HRESULT __cdecl wined3d_swapchain_get_display_mode(const struct wined3d_swapchain *swapchain,
         struct wined3d_display_mode *mode, enum wined3d_display_rotation *rotation);
+struct wined3d_texture * __cdecl wined3d_swapchain_get_front_buffer(const struct wined3d_swapchain *swapchain);
 HRESULT __cdecl wined3d_swapchain_get_front_buffer_data(const struct wined3d_swapchain *swapchain,
         struct wined3d_texture *dst_texture, unsigned int sub_resource_idx);
 HRESULT __cdecl wined3d_swapchain_get_gamma_ramp(const struct wined3d_swapchain *swapchain,