Support capturing rotated displays on Windows (#1602)

src_assets/windows/assets/shaders/directx/SceneVS.hlsl

@@ -1,22 +1,37 @@
 struct PS_INPUT
 {
-	float4 pos : SV_POSITION;
-	float2 tex : TEXCOORD;
+    float4 pos : SV_POSITION;
+    float2 tex : TEXCOORD;
+};
+
+cbuffer rotation_info : register(b1) {
+    int rotation;
 };
 
 PS_INPUT main_vs(uint vI : SV_VERTEXID)
 {
-	float idHigh = float(vI >> 1);
-	float idLow = float(vI & uint(1));
+    PS_INPUT output;
 
-	float x = idHigh * 4.0 - 1.0;
-	float y = idLow * 4.0 - 1.0;
+    if (vI == 0) {
+        output.pos = float4(-1, -1, 0, 1);
+        output.tex = float2(0, 1);
+    }
+    else if (vI == 1) {
+        output.pos = float4(-1, 3, 0, 1);
+        output.tex = float2(0, -1);
+    }
+    else if (vI == 2) {
+        output.pos = float4(3, -1, 0, 1);
+        output.tex = float2(2, 1);
+    }
 
-	float u = idHigh * 2.0;
-	float v = 1.0 - idLow * 2.0;
+    if (rotation != 0) {
+        float rotation_radians = radians(90 * rotation);
+        float2x2 rotation_matrix = { cos(rotation_radians), -sin(rotation_radians),
+                                     sin(rotation_radians), cos(rotation_radians) };
+        float2 rotation_center = { 0.5, 0.5 };
+        output.tex = round(rotation_center + mul(rotation_matrix, output.tex - rotation_center));
+    }
 
-	PS_INPUT vert_out;
-	vert_out.pos = float4(x, y, 0.0, 1.0);
-	vert_out.tex = float2(u, v);
-	return vert_out;
+    return output;
 }