Support capturing rotated displays on Windows (#1602)

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

@@ -1,10 +1,14 @@
 struct VertTexPosWide {
-	float3 uuv : TEXCOORD;
-	float4 pos : SV_POSITION;
+    float3 uuv : TEXCOORD;
+    float4 pos : SV_POSITION;
 };
 
 cbuffer info : register(b0) {
-	float width_i;
+    float width_i;
+};
+
+cbuffer rotation_info : register(b1) {
+    int rotation;
 };
 
 //--------------------------------------------------------------------------------------
@@ -12,18 +16,31 @@ cbuffer info : register(b0) {
 //--------------------------------------------------------------------------------------
 VertTexPosWide main_vs(uint vI : SV_VERTEXID)
 {
-	float idHigh = float(vI >> 1);
-	float idLow = float(vI & uint(1));
+    VertTexPosWide output;
+    float2 tex;
 
-	float x = idHigh * 4.0 - 1.0;
-	float y = idLow * 4.0 - 1.0;
+    if (vI == 0) {
+        output.pos = float4(-1, -1, 0, 1);
+        tex = float2(0, 1);
+    }
+    else if (vI == 1) {
+        output.pos = float4(-1, 3, 0, 1);
+        tex = float2(0, -1);
+    }
+    else if (vI == 2) {
+        output.pos = float4(3, -1, 0, 1);
+        tex = float2(2, 1);
+    }
 
-	float u_right = idHigh * 2.0;
-	float u_left = u_right - width_i;
-	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 };
+        tex = round(rotation_center + mul(rotation_matrix, tex - rotation_center));
+    }
 
-	VertTexPosWide vert_out;
-	vert_out.uuv = float3(u_left, u_right, v);
-	vert_out.pos = float4(x, y, 0.0, 1.0);
-	return vert_out;
-}
+    output.uuv = float3(tex.x, tex.x - width_i, tex.y);
+
+    return output;
+}