From b7887dd3264e6e0bb824566e4cc9eb7f26451a91 Mon Sep 17 00:00:00 2001
From: David Ludwig <dludwig@pobox.com>
Date: Tue, 2 Apr 2013 00:09:49 -0400
Subject: [PATCH] WinRT: added rotation support to SDL_RenderCopyEx via D3D
 11.1

---
 .../SDL_D3D11_VertexShader_Default.hlsl       |  6 ++-
 src/render/direct3d11/SDL_render_d3d11.cpp    | 47 ++++++++++++++-----
 src/render/direct3d11/SDL_render_d3d11_cpp.h  |  5 +-
 3 files changed, 41 insertions(+), 17 deletions(-)

diff --git a/src/render/direct3d11/SDL_D3D11_VertexShader_Default.hlsl b/src/render/direct3d11/SDL_D3D11_VertexShader_Default.hlsl
index c5131007a..b5cac4fa9 100644
--- a/src/render/direct3d11/SDL_D3D11_VertexShader_Default.hlsl
+++ b/src/render/direct3d11/SDL_D3D11_VertexShader_Default.hlsl
@@ -3,8 +3,9 @@
 
 cbuffer SDL_VertexShaderConstants : register(b0)
 {
-	matrix view;
-	matrix projection;
+    matrix model;
+    matrix view;
+    matrix projection;
 };
 
 struct VertexShaderInput
@@ -27,6 +28,7 @@ VertexShaderOutput main(VertexShaderInput input)
     float4 pos = float4(input.pos, 1.0f);
 
     // Transform the vertex position into projected space.
+    pos = mul(pos, model);
     pos = mul(pos, view);
     pos = mul(pos, projection);
     output.pos = pos;
diff --git a/src/render/direct3d11/SDL_render_d3d11.cpp b/src/render/direct3d11/SDL_render_d3d11.cpp
index 6ab401918..0aa1d3a96 100644
--- a/src/render/direct3d11/SDL_render_d3d11.cpp
+++ b/src/render/direct3d11/SDL_render_d3d11.cpp
@@ -1129,6 +1129,11 @@ D3D11_UpdateViewport(SDL_Renderer * renderer)
     data->vertexShaderConstantsData.view = XMMatrixIdentity();
 #endif
 
+    //
+    // Reset the model matrix
+    //
+    XMStoreFloat4x4(&data->vertexShaderConstantsData.model, XMMatrixIdentity());
+
     //
     // Update the Direct3D viewport, which seems to be aligned to the
     // swap buffer's coordinate space, which is always in landscape:
@@ -1250,15 +1255,6 @@ D3D11_RenderStartDrawOp(SDL_Renderer * renderer)
         rendererData->renderTargetView.GetAddressOf(),
         nullptr
         );
-
-    rendererData->d3dContext->UpdateSubresource(
-        rendererData->vertexShaderConstants.Get(),
-		0,
-		NULL,
-		&rendererData->vertexShaderConstantsData,
-		0,
-		0
-		);
 }
 
 static void
@@ -1299,6 +1295,16 @@ D3D11_RenderFinishDrawOp(SDL_Renderer * renderer,
                          UINT vertexCount)
 {
     D3D11_RenderData *rendererData = (D3D11_RenderData *) renderer->driverdata;
+
+    rendererData->d3dContext->UpdateSubresource(
+        rendererData->vertexShaderConstants.Get(),
+        0,
+        NULL,
+        &rendererData->vertexShaderConstantsData,
+        0,
+        0
+        );
+
     rendererData->d3dContext->IASetPrimitiveTopology(primitiveTopology);
     rendererData->d3dContext->IASetInputLayout(rendererData->inputLayout.Get());
     rendererData->d3dContext->VSSetShader(rendererData->vertexShader.Get(), nullptr, 0);
@@ -1504,12 +1510,25 @@ D3D11_RenderCopyEx(SDL_Renderer * renderer, SDL_Texture * texture,
         maxv = minv;
         minv = tmp;
     }
+
+    XMFLOAT4X4 oldModelMatrix = rendererData->vertexShaderConstantsData.model;
+    XMStoreFloat4x4(
+        &rendererData->vertexShaderConstantsData.model,
+        XMMatrixMultiply(
+            XMMatrixRotationZ((float)(XM_PI * (float) angle / 180.0f)),
+            XMMatrixTranslation(dstrect->x + center->x, dstrect->y + center->y, 0)
+            ));
+
+    const float minx = -center->x;
+    const float maxx = dstrect->w - center->x;
+    const float miny = -center->y;
+    const float maxy = dstrect->h - center->y;
 
     VertexPositionColor vertices[] = {
-        {XMFLOAT3(dstrect->x, dstrect->y, 0.0f),                           XMFLOAT2(minu, minv), XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f)},
-        {XMFLOAT3(dstrect->x, dstrect->y + dstrect->h, 0.0f),              XMFLOAT2(minu, maxv), XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f)},
-        {XMFLOAT3(dstrect->x + dstrect->w, dstrect->y, 0.0f),              XMFLOAT2(maxu, minv), XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f)},
-        {XMFLOAT3(dstrect->x + dstrect->w, dstrect->y + dstrect->h, 0.0f), XMFLOAT2(maxu, maxv), XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f)},
+        {XMFLOAT3(minx, miny, 0.0f), XMFLOAT2(minu, minv), XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f)},
+        {XMFLOAT3(minx, maxy, 0.0f), XMFLOAT2(minu, maxv), XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f)},
+        {XMFLOAT3(maxx, miny, 0.0f), XMFLOAT2(maxu, minv), XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f)},
+        {XMFLOAT3(maxx, maxy, 0.0f), XMFLOAT2(maxu, maxv), XMFLOAT4(1.0f, 1.0f, 1.0f, 1.0f)},
     };
     if (D3D11_UpdateVertexBuffer(renderer, vertices, sizeof(vertices)) != 0) {
         return -1;
@@ -1522,6 +1541,8 @@ D3D11_RenderCopyEx(SDL_Renderer * renderer, SDL_Texture * texture,
         rendererData->mainSampler.Get());
 
     D3D11_RenderFinishDrawOp(renderer, D3D11_PRIMITIVE_TOPOLOGY_TRIANGLESTRIP, sizeof(vertices) / sizeof(VertexPositionColor));
+
+    rendererData->vertexShaderConstantsData.model = oldModelMatrix;
 
     return 0;
 }
diff --git a/src/render/direct3d11/SDL_render_d3d11_cpp.h b/src/render/direct3d11/SDL_render_d3d11_cpp.h
index a879fdeba..be322832e 100644
--- a/src/render/direct3d11/SDL_render_d3d11_cpp.h
+++ b/src/render/direct3d11/SDL_render_d3d11_cpp.h
@@ -27,8 +27,9 @@
 
 struct SDL_VertexShaderConstants
 {
-	DirectX::XMFLOAT4X4 view;
-	DirectX::XMFLOAT4X4 projection;
+    DirectX::XMFLOAT4X4 model;
+    DirectX::XMFLOAT4X4 view;
+    DirectX::XMFLOAT4X4 projection;
 };
 
 typedef struct