vo_gpu: d3d11: add RA caps for ra_d3d11

ra_d3d11 uses the SPIR-V compiler to translate GLSL to SPIR-V, which is
then translated to HLSL. This means it always exposes the same GLSL
version that the SPIR-V compiler supports (4.50 for shaderc/glslang.)

Despite claiming to support GLSL 4.50, some features that are tied to
the GLSL version in OpenGL are not supported by ra_d3d11 when targeting
legacy Direct3D feature levels.

This includes two features that mpv relies on:
- Reading from gl_FragCoord in the fragment shader (requires FL 10_0)
- textureGather from any texture component (requires FL 11_0)

These features have been exposed as new RA caps.

4 files changed, 20 insertions, 5 deletions

diff --git a/video/out/gpu/ra.h b/video/out/gpu/ra.h
index b10ab76124..934e5db844 100644
--- a/video/out/gpu/ra.h
+++ b/video/out/gpu/ra.h
@@ -51,6 +51,8 @@ enum {
     RA_CAP_BUF_RW         = 1 << 6, // supports RA_VARTYPE_BUF_RW
     RA_CAP_NESTED_ARRAY   = 1 << 7, // supports nested arrays
     RA_CAP_GLOBAL_UNIFORM = 1 << 8, // supports using "naked" uniforms (not UBO)
+    RA_CAP_GATHER         = 1 << 9, // supports textureGather in GLSL
+    RA_CAP_FRAGCOORD      = 1 << 10, // supports reading from gl_FragCoord
 };
 
 enum ra_ctype {
diff --git a/video/out/gpu/video.c b/video/out/gpu/video.c
index fd870a2ffc..9cc889b401 100644
--- a/video/out/gpu/video.c
+++ b/video/out/gpu/video.c
@@ -1719,7 +1719,8 @@ static void pass_dispatch_sample_polar(struct gl_video *p, struct scaler *scaler
 fallback:
     // Fall back to regular polar shader when compute shaders are unsupported
     // or the kernel is too big for shmem
-    pass_sample_polar(p->sc, scaler, img.components, p->ra->glsl_version);
+    pass_sample_polar(p->sc, scaler, img.components,
+                      p->ra->caps & RA_CAP_GATHER);
 }
 
 // Sample from image, with the src rectangle given by it.
@@ -3465,6 +3466,19 @@ static void check_gl_features(struct gl_video *p)
         p->opts.compute_hdr_peak = 0;
         MP_WARN(p, "Disabling HDR peak computation (no compute shaders).\n");
     }
+    if (!(ra->caps & RA_CAP_FRAGCOORD) && p->opts.dither_depth >= 0 &&
+        p->opts.dither_algo != DITHER_NONE)
+    {
+        p->opts.dither_algo = DITHER_NONE;
+        MP_WARN(p, "Disabling dithering (no gl_FragCoord).\n");
+    }
+    if (!(ra->caps & RA_CAP_FRAGCOORD) &&
+        p->opts.alpha_mode == ALPHA_BLEND_TILES)
+    {
+        p->opts.alpha_mode = ALPHA_BLEND;
+        // Verbose, since this is the default setting
+        MP_VERBOSE(p, "Disabling alpha checkerboard (no gl_FragCoord).\n");
+    }
 }
 
 static void init_gl(struct gl_video *p)
diff --git a/video/out/gpu/video_shaders.c b/video/out/gpu/video_shaders.c
index 02f27b1bdb..3e71c31369 100644
--- a/video/out/gpu/video_shaders.c
+++ b/video/out/gpu/video_shaders.c
@@ -143,7 +143,7 @@ static void polar_sample(struct gl_shader_cache *sc, struct scaler *scaler,
 }
 
 void pass_sample_polar(struct gl_shader_cache *sc, struct scaler *scaler,
-                       int components, int glsl_version)
+                       int components, bool sup_gather)
 {
     GLSL(color = vec4(0.0);)
     GLSLF("{\n");
@@ -167,8 +167,7 @@ void pass_sample_polar(struct gl_shader_cache *sc, struct scaler *scaler,
             // exactly when all four texels are within bounds
             bool use_gather = sqrt(x*x + y*y) < scaler->kernel->radius_cutoff;
 
-            // textureGather is only supported in GLSL 400+
-            if (glsl_version < 400)
+            if (!sup_gather)
                 use_gather = false;
 
             if (use_gather) {
diff --git a/video/out/gpu/video_shaders.h b/video/out/gpu/video_shaders.h
index 8345e4c598..2ae2ac3fa9 100644
--- a/video/out/gpu/video_shaders.h
+++ b/video/out/gpu/video_shaders.h
@@ -30,7 +30,7 @@ void sampler_prelude(struct gl_shader_cache *sc, int tex_num);
 void pass_sample_separated_gen(struct gl_shader_cache *sc, struct scaler *scaler,
                                int d_x, int d_y);
 void pass_sample_polar(struct gl_shader_cache *sc, struct scaler *scaler,
-                       int components, int glsl_version);
+                       int components, bool sup_gather);
 void pass_compute_polar(struct gl_shader_cache *sc, struct scaler *scaler,
                         int components, int bw, int bh, int iw, int ih);
 void pass_sample_bicubic_fast(struct gl_shader_cache *sc);