From aef777c95ddd75f596c6d18ab51dab085705e289 Mon Sep 17 00:00:00 2001
From: Jesse Natalie <jenatali@microsoft.com>
Date: Thu, 13 Jan 2022 12:37:10 -0800
Subject: [PATCH] d3d12: Report sample positions

Reviewed-by: Sil Vilerino <sivileri@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14624>
---
 src/gallium/drivers/d3d12/d3d12_context.cpp | 73 +++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/src/gallium/drivers/d3d12/d3d12_context.cpp b/src/gallium/drivers/d3d12/d3d12_context.cpp
index 95ec07abae6..43ba31794ef 100644
--- a/src/gallium/drivers/d3d12/d3d12_context.cpp
+++ b/src/gallium/drivers/d3d12/d3d12_context.cpp
@@ -2151,6 +2151,77 @@ d3d12_memory_barrier(struct pipe_context *pctx, unsigned flags)
    }
 }
 
+static void
+d3d12_get_sample_position(struct pipe_context *pctx, unsigned sample_count, unsigned sample_index,
+                          float *positions)
+{
+   /* Sample patterns transcribed from
+    * https://docs.microsoft.com/en-us/windows/win32/api/d3d11/ne-d3d11-d3d11_standard_multisample_quality_levels
+    */
+   static const int sample_pattern_1sample[2] = { 0, 0 };
+   static const int sample_pattern_2samples[2][2] = {
+      {  4,  4 },
+      { -4, -4 },
+   };
+   static const int sample_pattern_4samples[4][2] = {
+      { -2, -6 },
+      {  6, -2 },
+      { -6,  2 },
+      {  2,  6 },
+   };
+   static const int sample_pattern_8samples[8][2] = {
+      {  1, -3 },
+      { -1,  3 },
+      {  5,  1 },
+      { -3, -5 },
+      { -5,  5 },
+      { -7, -1 },
+      {  3,  7 },
+      {  7, -7 },
+   };
+   static const int sample_pattern_16samples[16][2] = {
+      {  1,  1 },
+      { -1, -3 },
+      { -3,  2 },
+      {  4, -1 },
+      { -5, -2 },
+      {  2,  5 },
+      {  5,  3 },
+      {  3, -5 },
+      { -2,  6 },
+      {  0, -7 },
+      { -4, -6 },
+      { -6,  4 },
+      { -8,  0 },
+      {  7, -4 },
+      {  6,  7 },
+      { -7, -8 },
+   };
+   const int *samples;
+   switch (sample_count) {
+   case 1:
+   default:
+      samples = sample_pattern_1sample;
+      break;
+   case 2:
+      samples = sample_pattern_2samples[sample_index];
+      break;
+   case 4:
+      samples = sample_pattern_4samples[sample_index];
+      break;
+   case 8:
+      samples = sample_pattern_8samples[sample_index];
+      break;
+   case 16:
+      samples = sample_pattern_16samples[sample_index];
+      break;
+   }
+
+   /* GL coords go from 0 -> 1, D3D from -0.5 -> 0.5 */
+   for (unsigned i = 0; i < 2; ++i)
+      positions[i] = (float)(samples[i] + 8) / 16.0f;
+}
+
 struct pipe_context *
 d3d12_context_create(struct pipe_screen *pscreen, void *priv, unsigned flags)
 {
@@ -2235,6 +2306,8 @@ d3d12_context_create(struct pipe_screen *pscreen, void *priv, unsigned flags)
 
    ctx->base.memory_barrier = d3d12_memory_barrier;
 
+   ctx->base.get_sample_position = d3d12_get_sample_position;
+
    ctx->gfx_pipeline_state.sample_mask = ~0;
 
    d3d12_context_surface_init(&ctx->base);