popn: fix subscreen redraw option causing graphical glitches (#854)

## Link to GitHub Issue or related Pull Request, if one exists
#0

## Description of change
Old behavior: Forced redraw presented the subscreen every main frame,
even when the game already presented it, causing duplicate presents and
tearing in popn (was fine in sdvx)

New behavior: Forced redraw acts as a fallback, presenting only when the
game skips or fails a subscreen update.

## Testing
Popn - no more glitching
Nabla - no regression

src/spice2x/hooks/graphics/backends/d3d9/d3d9_device.cpp

@@ -134,6 +134,10 @@ ULONG STDMETHODCALLTYPE WrappedIDirect3DDevice9::Release() {
             this->main_swapchain->Release();
             this->main_swapchain = nullptr;
         }
+        if (this->implicit_sub_swapchain) {
+            this->implicit_sub_swapchain->Release();
+            this->implicit_sub_swapchain = nullptr;
+        }
         for (auto &sc : this->sub_swapchain) {
             if (sc) {
                 sc->Release();
@@ -487,6 +491,24 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetSwapChain(
             fake_sub_swapchain[0]->AddRef();
             *ppSwapChain = static_cast<IDirect3DSwapChain9 *>(fake_sub_swapchain[0]);
 
+            graphics_screens_register(iSwapChain);
+            return D3D_OK;
+        } else if (SUBSCREEN_FORCE_REDRAW) {
+            // store implicit sub swap chain
+            if (!implicit_sub_swapchain) {
+                IDirect3DSwapChain9 *real_swapchain = nullptr;
+                HRESULT ret = pReal->GetSwapChain(iSwapChain, &real_swapchain);
+                if (FAILED(ret)) {
+                    return ret;
+                }
+
+                implicit_sub_swapchain = new WrappedIDirect3DSwapChain9(this, real_swapchain);
+                implicit_sub_swapchain->should_run_hooks = false;
+            }
+
+            implicit_sub_swapchain->AddRef();
+            *ppSwapChain = static_cast<IDirect3DSwapChain9 *>(implicit_sub_swapchain);
+
             graphics_screens_register(iSwapChain);
             return D3D_OK;
         }