From 0920572e703201368c9fbcc9108ce1888600ffa2 Mon Sep 17 00:00:00 2001
From: Vaxry <vaxry@vaxry.net>
Date: Tue, 5 Nov 2024 16:11:05 +0000
Subject: [PATCH] shaders: improve corner AA in borders shader

---
 src/render/shaders/Border.hpp       | 10 ++++++++--
 src/render/shaders/SharedValues.hpp |  3 +++
 src/render/shaders/Textures.hpp     |  6 +++++-
 3 files changed, 16 insertions(+), 3 deletions(-)
 create mode 100644 src/render/shaders/SharedValues.hpp

diff --git a/src/render/shaders/Border.hpp b/src/render/shaders/Border.hpp
index a33694a7..1f4a1d97 100644
--- a/src/render/shaders/Border.hpp
+++ b/src/render/shaders/Border.hpp
@@ -1,6 +1,8 @@
 #pragma once
 
 #include <string>
+#include <format>
+#include "SharedValues.hpp"
 
 // makes a stencil without corners
 inline const std::string FRAGBORDER1 = R"#(
@@ -72,18 +74,22 @@ void main() {
     pixCoordOuter += vec2(1.0, 1.0) / fullSize;
 
     if (min(pixCoord.x, pixCoord.y) > 0.0 && radius > 0.0) {
+        // smoothing constant for the edge: more = blurrier, but smoother
+        const float SMOOTHING_CONSTANT = )#" +
+    std::format("{:.7f}", SHADER_ROUNDED_SMOOTHING_FACTOR) + R"#(;
+
 	    float dist = length(pixCoord);
 	    float distOuter = length(pixCoordOuter);
         float h = (thick / 2.0);
 
 	    if (dist < radius - h) {
             // lower
-            float normalized = smoothstep(0.0, 1.0, dist - radius + thick + 0.5);
+            float normalized = smoothstep(0.0, 1.0, (dist - radius + thick + SMOOTHING_CONSTANT) / (SMOOTHING_CONSTANT * 2.0));
             additionalAlpha *= normalized;
             done = true;
         } else if (min(pixCoordOuter.x, pixCoordOuter.y) > 0.0) {
             // higher
-            float normalized = 1.0 - smoothstep(0.0, 1.0, distOuter - radiusOuter + 0.5);
+            float normalized = 1.0 - smoothstep(0.0, 1.0, (distOuter - radiusOuter + SMOOTHING_CONSTANT) / (SMOOTHING_CONSTANT * 2.0));
             additionalAlpha *= normalized;
             done = true;
         } else if (distOuter < radiusOuter - h) {
diff --git a/src/render/shaders/SharedValues.hpp b/src/render/shaders/SharedValues.hpp
new file mode 100644
index 00000000..9a74c892
--- /dev/null
+++ b/src/render/shaders/SharedValues.hpp
@@ -0,0 +1,3 @@
+#pragma once
+
+constexpr float SHADER_ROUNDED_SMOOTHING_FACTOR = M_PI / 5.34665792551;
\ No newline at end of file
diff --git a/src/render/shaders/Textures.hpp b/src/render/shaders/Textures.hpp
index e99d0a49..b203ad04 100644
--- a/src/render/shaders/Textures.hpp
+++ b/src/render/shaders/Textures.hpp
@@ -1,6 +1,8 @@
 #pragma once
 
 #include <string>
+#include <format>
+#include "SharedValues.hpp"
 
 inline static constexpr auto ROUNDED_SHADER_FUNC = [](const std::string colorVarName) -> std::string {
     return R"#(
@@ -13,7 +15,9 @@ inline static constexpr auto ROUNDED_SHADER_FUNC = [](const std::string colorVar
     pixCoord -= fullSize * 0.5 - radius;
     pixCoord += vec2(1.0, 1.0) / fullSize; // center the pix dont make it top-left
 
-    const float SMOOTHING_CONSTANT = 0.651724; // smoothing constant for the edge: more = blurrier, but smoother
+    // smoothing constant for the edge: more = blurrier, but smoother
+    const float SMOOTHING_CONSTANT = )#" +
+        std::format("{:.7f}", SHADER_ROUNDED_SMOOTHING_FACTOR) + R"#(;
 
     if (pixCoord.x + pixCoord.y > radius) {