vo_gpu: d3d11: initial implementation

This is a new RA/vo_gpu backend that uses Direct3D 11. The GLSL
generated by vo_gpu is cross-compiled to HLSL with SPIRV-Cross.

What works:

- All of mpv's internal shaders should work, including compute shaders.

- Some external shaders have been tested and work, including RAVU and
  adaptive-sharpen.

- Non-dumb mode works, even on very old hardware. Most features work at
  feature level 9_3 and all features work at feature level 10_0. Some
  features also work at feature level 9_1 and 9_2, but without high-bit-
  depth FBOs, it's not very useful. (Hardware this old is probably not
  fast enough for advanced features anyway.)

  Note: This is more compatible than ANGLE, which requires 9_3 to work
  at all (GLES 2.0,) and 10_1 for non-dumb-mode (GLES 3.0.)

- Hardware decoding with D3D11VA, including decoding of 10-bit formats
  without truncation to 8-bit.

What doesn't work / can be improved:

- PBO upload and direct rendering does not work yet. Direct rendering
  requires persistent-mapped PBOs because the decoder needs to be able
  to read data from images that have already been decoded and uploaded.
  Unfortunately, it seems like persistent-mapped PBOs are fundamentally
  incompatible with D3D11, which requires all resources to use driver-
  managed memory and requires memory to be unmapped (and hence pointers
  to be invalidated) when a resource is used in a draw or copy
  operation.

  However it might be possible to use D3D11's limited multithreading
  capabilities to emulate some features of PBOs, like asynchronous
  texture uploading.

- The blit() and clear() operations don't have equivalents in the D3D11
  API that handle all cases, so in most cases, they have to be emulated
  with a shader. This is currently done inside ra_d3d11, but ideally it
  would be done in generic code, so it can take advantage of mpv's
  shader generation utilities.

- SPIRV-Cross is used through a NIH C-compatible wrapper library, since
  it does not expose a C interface itself.

  The library is available here: https://github.com/rossy/crossc

- The D3D11 context could be made to support more modern DXGI features
  in future. For example, it should be possible to add support for
  high-bit-depth and HDR output with DXGI 1.5/1.6.

1 files changed, 79 insertions, 0 deletions

diff --git a/video/out/gpu/d3d11_helpers.h b/video/out/gpu/d3d11_helpers.h
new file mode 100644
index 0000000000..6d99c62a51
--- /dev/null
+++ b/video/out/gpu/d3d11_helpers.h
@@ -0,0 +1,79 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * mpv is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef MP_D3D11_HELPERS_H_
+#define MP_D3D11_HELPERS_H_
+
+#include <stdbool.h>
+#include <windows.h>
+#include <d3d11.h>
+#include <dxgi1_2.h>
+
+#define D3D_FEATURE_LEVEL_12_0 (0xc000)
+#define D3D_FEATURE_LEVEL_12_1 (0xc100)
+
+struct d3d11_device_opts {
+    // Enable the debug layer (D3D11_CREATE_DEVICE_DEBUG)
+    bool debug;
+
+    // Allow a software (WARP) adapter. Note, sometimes a software adapter will
+    // be used even when allow_warp is false. This is because, on Windows 8 and
+    // up, if there are no hardware adapters, Windows will pretend the WARP
+    // adapter is the primary hardware adapter.
+    bool allow_warp;
+
+    // Always use a WARP adapter. This is mainly for testing purposes.
+    bool force_warp;
+
+    // The maximum number of pending frames allowed to be queued to a swapchain
+    int max_frame_latency;
+
+    // The maximum Direct3D 11 feature level to attempt to create
+    // If unset, defaults to D3D_FEATURE_LEVEL_11_0
+    int max_feature_level;
+
+    // The minimum Direct3D 11 feature level to attempt to create. If this is
+    // not supported, device creation will fail.
+    // If unset, defaults to D3D_FEATURE_LEVEL_9_1
+    int min_feature_level;
+};
+
+bool mp_d3d11_create_present_device(struct mp_log *log,
+                                    struct d3d11_device_opts *opts,
+                                    ID3D11Device **dev_out);
+
+struct d3d11_swapchain_opts {
+    HWND window;
+    int width;
+    int height;
+
+    // Use DXGI_SWAP_EFFECT_FLIP_SEQUENTIAL if possible
+    bool flip;
+
+    // Number of surfaces in the swapchain
+    int length;
+
+    // The BufferUsage value for swapchain surfaces. This should probably
+    // contain DXGI_USAGE_RENDER_TARGET_OUTPUT.
+    DXGI_USAGE usage;
+};
+
+bool mp_d3d11_create_swapchain(ID3D11Device *dev, struct mp_log *log,
+                               struct d3d11_swapchain_opts *opts,
+                               IDXGISwapChain **swapchain_out);
+
+#endif