Adjustment on the design of UI + new shaders

dist/post_shaders/Levels.fx

@@ -0,0 +1,74 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+texture BackBufferTex : COLOR;
+sampler BackBuffer { Texture = BackBufferTex; };
+
+uniform float InputBlack <
+    ui_type = "slider";
+    ui_label = "Input Black";
+    ui_tooltip = "Input level mapped to black. Raise it to deepen washed out shadows.";
+    ui_min = 0.0; ui_max = 0.5; ui_step = 0.005;
+> = 0.0;
+
+uniform float InputWhite <
+    ui_type = "slider";
+    ui_label = "Input White";
+    ui_min = 0.5; ui_max = 1.0; ui_step = 0.005;
+> = 1.0;
+
+uniform float Gamma <
+    ui_type = "slider";
+    ui_label = "Gamma";
+    ui_min = 0.2; ui_max = 3.0; ui_step = 0.01;
+> = 1.0;
+
+uniform float OutputBlack <
+    ui_type = "slider";
+    ui_label = "Output Black";
+    ui_tooltip = "Lifts crushed shadows so detail stops collapsing into one flat black.";
+    ui_min = 0.0; ui_max = 0.5; ui_step = 0.005;
+> = 0.0;
+
+uniform float OutputWhite <
+    ui_type = "slider";
+    ui_label = "Output White";
+    ui_min = 0.5; ui_max = 1.0; ui_step = 0.005;
+> = 1.0;
+
+void VS_PostProcess(in uint id : SV_VertexID, out float4 pos : SV_Position, out float2 uv : TEXCOORD)
+{
+    uv = float2(0.0, 0.0);
+    if (id == 2)
+    {
+        uv.x = 2.0;
+    }
+    if (id == 1)
+    {
+        uv.y = 2.0;
+    }
+    pos = float4(uv * float2(2.0, -2.0) + float2(-1.0, 1.0), 0.0, 1.0);
+}
+
+float4 PS_Levels(float4 pos : SV_Position, float2 uv : TEXCOORD) : SV_Target
+{
+    float3 rgb = tex2D(BackBuffer, uv).rgb;
+
+    rgb = saturate((rgb - InputBlack) / max(InputWhite - InputBlack, 0.001));
+    rgb = pow(max(rgb, 0.0), 1.0 / max(Gamma, 0.001));
+    rgb = lerp(OutputBlack, OutputWhite, rgb);
+
+    return float4(saturate(rgb), 1.0);
+}
+
+technique Levels <
+    ui_label = "Levels";
+    ui_tooltip = "Black point, white point, gamma and output range. Use it to fix crushed or washed out shadows.";
+>
+{
+    pass
+    {
+        VertexShader = VS_PostProcess;
+        PixelShader = PS_Levels;
+    }
+}