Fixed scanlines if the screen output is less than twice the size of the host source

hlsl/post.fx

@@ -98,7 +98,7 @@ VS_OUTPUT vs_main(VS_INPUT Input)
 
 	Output.TexCoord = Input.TexCoord;
 	Output.TexCoord += PrepareBloom
-		? 0.0f / TargetDims  // use half texel offset (DX9) to do the blur for first bloom layer
+		? 0.0f               // use half texel offset (DX9) to do the blur for first bloom layer
 		: 0.5f / TargetDims; // fix half texel offset (DX9)
 
 	Output.ScreenCoord = Input.Position.xy / ScreenDims;
@@ -252,7 +252,13 @@ float4 ps_main(PS_INPUT Input) : COLOR
 
 			float ColorBrightness = 0.299f * BaseColor.r + 0.587f * BaseColor.g + 0.114 * BaseColor.b;
 
-			float ScanlineCoord = SourceCoord.y * SourceDims.y * ScanlineScale * PI;
+			float ScanlineCoord = SourceCoord.y;
+			ScanlineCoord += QuadDims.y <= SourceDims.y * 2.0f
+				? 0.5f / QuadDims.y // uncenter scanlines if the quad is less than twice the size of the source
+				: 0.0f;
+
+			ScanlineCoord *= SourceDims.y * ScanlineScale * PI;
+
 			float ScanlineCoordJitter = ScanlineOffset * PHI;
 			float ScanlineSine = sin(ScanlineCoord + ScanlineCoordJitter);
 			float ScanlineWide = ScanlineHeight + ScanlineVariation * max(1.0f, ScanlineHeight) * (1.0f - ColorBrightness);

src/osd/modules/render/bgfx/shaders/chains/hlsl/fs_post.sc

@@ -148,7 +148,13 @@ void main()
 
 			float ColorBrightness = 0.299 * BaseColor.r + 0.587 * BaseColor.g + 0.114 * BaseColor.b;
 
-			float ScanCoord = BaseCoord.y * u_source_dims.y * u_scanline_scale.x * 3.1415927; // PI
+			float ScanCoord = BaseCoord.y;
+			ScanCoord += u_quad_dims.y <= u_source_dims.y * 2.0f
+				? 0.5f / u_quad_dims.y // uncenter scanlines if the quad is less than twice the size of the source
+				: 0.0f;
+
+			ScanCoord *= u_source_dims.y * u_scanline_scale.x * 3.1415927; // PI
+
 			float ScanCoordJitter = u_scanline_jitter.x * u_jitter_amount.x * 1.618034; // PHI
 			float ScanSine = sin(ScanCoord + ScanCoordJitter);
 			float ScanlineWide = u_scanline_height.x + u_scanline_variation.x * max(1.0, u_scanline_height.x) * (1.0 - ColorBrightness);