[Vulkan] Halve the viewport dimensions when viewport scaling is disabled (10240 -> 5120)

The negative part of the viewport is unused, so hijack the 2 unused parameters of the window scale to use as an offset

2 files changed, 19 insertions, 7 deletions

diff --git a/src/xenia/gpu/spirv_shader_translator.cc b/src/xenia/gpu/spirv_shader_translator.cc
index 6fd80c26e..384190124 100644
--- a/src/xenia/gpu/spirv_shader_translator.cc
+++ b/src/xenia/gpu/spirv_shader_translator.cc
@@ -532,8 +532,16 @@ std::vector<uint8_t> SpirvShaderTranslator::CompleteTranslation() {
     // pos.xy *= window_scale.xy
     auto p_scaled =
         b.createBinOp(spv::Op::OpFMul, vec4_float_type_, p, window_scale);
+
+    // Apply window offset
+    // pos.xy += window_scale.zw
+    auto window_offset = b.createOp(spv::Op::OpVectorShuffle, vec4_float_type_,
+                                    {window_scale, window_scale, 2, 3, 0, 1});
+    auto p_offset = b.createBinOp(spv::Op::OpFAdd, vec4_float_type_, p_scaled,
+                                  window_offset);
+
     p = b.createOp(spv::Op::OpVectorShuffle, vec4_float_type_,
-                   {p, p_scaled, 4, 5, 2, 3});
+                   {p, p_offset, 4, 5, 2, 3});
 
     b.createStore(p, pos_);
   } else {
diff --git a/src/xenia/gpu/vulkan/pipeline_cache.cc b/src/xenia/gpu/vulkan/pipeline_cache.cc
index b71b70c9d..b1eeec71e 100644
--- a/src/xenia/gpu/vulkan/pipeline_cache.cc
+++ b/src/xenia/gpu/vulkan/pipeline_cache.cc
@@ -674,10 +674,11 @@ bool PipelineCache::SetDynamicState(VkCommandBuffer command_buffer,
     vpx = window_width_scalar * vox - vpw / 2 + vtx_window_offset_x;
     vpy = window_height_scalar * voy - vph / 2 + vtx_window_offset_y;
   } else {
-    vpw = 2 * 2560.0f * window_width_scalar;
-    vph = 2 * 2560.0f * window_height_scalar;
-    vpx = -2560.0f * window_width_scalar + vtx_window_offset_x;
-    vpy = -2560.0f * window_height_scalar + vtx_window_offset_y;
+    // TODO(DrChat): This should be the width/height of the target picture
+    vpw = 2560.0f * window_width_scalar;
+    vph = 2560.0f * window_height_scalar;
+    vpx = vtx_window_offset_x;
+    vpy = vtx_window_offset_y;
   }
 
   if (viewport_state_dirty) {
@@ -776,12 +777,15 @@ bool PipelineCache::SetDynamicState(VkCommandBuffer command_buffer,
     if (vport_xscale_enable) {
       push_constants.window_scale[0] = 1.0f;
       push_constants.window_scale[1] = -1.0f;
+      push_constants.window_scale[2] = 0.f;
+      push_constants.window_scale[3] = 0.f;
     } else {
+      // 1 / unscaled viewport w/h
       push_constants.window_scale[0] = 1.0f / 2560.0f;
       push_constants.window_scale[1] = 1.0f / 2560.0f;
+      push_constants.window_scale[2] = -1.f;
+      push_constants.window_scale[3] = -1.f;
     }
-    push_constants.window_scale[2] = vpw;
-    push_constants.window_scale[3] = vph;
 
     // http://www.x.org/docs/AMD/old/evergreen_3D_registers_v2.pdf
     // VTX_XY_FMT = true: the incoming XY have already been multiplied by 1/W0.