From 3104abd4ad7d0595d8114c6d4066d20e20132f5b Mon Sep 17 00:00:00 2001
From: Filippo Scognamiglio <flscogna@gmail.com>
Date: Wed, 7 Jul 2021 00:09:10 +0200
Subject: [PATCH] Add subpixel rasterization.

---
 app/qml/ApplicationSettings.qml |  4 ++--
 app/qml/SettingsTerminalTab.qml |  2 +-
 app/qml/ShaderLibrary.qml       | 21 ++++++++++++---------
 3 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/app/qml/ApplicationSettings.qml b/app/qml/ApplicationSettings.qml
index 967e598..056a93f 100644
--- a/app/qml/ApplicationSettings.qml
+++ b/app/qml/ApplicationSettings.qml
@@ -104,7 +104,7 @@ QtObject {
     readonly property int no_rasterization: 0
     readonly property int scanline_rasterization: 1
     readonly property int pixel_rasterization: 2
-    readonly property int lcd_rasterization: 3
+    readonly property int subpixel_rasterization: 3
 
     property int rasterization: no_rasterization
 
@@ -148,7 +148,7 @@ QtObject {
                 }
             },
             State {
-                when: rasterization == lcd_rasterization
+                when: rasterization == subpixel_rasterization
                 PropertyChanges {
                     target: fontManager
                     source: "FontPixels.qml"
diff --git a/app/qml/SettingsTerminalTab.qml b/app/qml/SettingsTerminalTab.qml
index 80b1039..8e3a35c 100644
--- a/app/qml/SettingsTerminalTab.qml
+++ b/app/qml/SettingsTerminalTab.qml
@@ -41,7 +41,7 @@ ColumnLayout {
                 property string selectedElement: model[currentIndex]
 
                 Layout.fillWidth: true
-                model: [qsTr("Default"), qsTr("Scanlines"), qsTr("Pixels"), qsTr("LCD")]
+                model: [qsTr("Default"), qsTr("Scanlines"), qsTr("Pixels"), qsTr("Sub-Pixels")]
                 currentIndex: appSettings.rasterization
                 onCurrentIndexChanged: {
                     appSettings.rasterization = currentIndex
diff --git a/app/qml/ShaderLibrary.qml b/app/qml/ShaderLibrary.qml
index 56eae11..ae95f05 100644
--- a/app/qml/ShaderLibrary.qml
+++ b/app/qml/ShaderLibrary.qml
@@ -12,8 +12,6 @@ QtObject {
             #define BRIGHTBOOST 0.30
 
             lowp vec3 applyRasterization(vec2 screenCoords, lowp vec3 texel, vec2 virtualResolution, float intensity) {
-                lowp vec3 result = texel;
-
                 lowp vec3 pixelHigh = ((1.0 + BRIGHTBOOST) - (0.2 * texel)) * texel;
                 lowp vec3 pixelLow  = ((1.0 - INTENSITY) + (0.1 * texel)) * texel;
 
@@ -42,20 +40,25 @@ QtObject {
                 return mix(texel, rasterizationColor, intensity);
             }" : "") +
 
-        (appSettings.rasterization === appSettings.lcd_rasterization ? "
-            #define brighten_scanlines 16.0
-            #define brighten_lcd 4.0
+        (appSettings.rasterization === appSettings.subpixel_rasterization ? "
+            #define INTENSITY 0.30
+            #define BRIGHTBOOST 0.30
+            #define SUBPIXELS 3.0
             const vec3 offsets = vec3(3.141592654) * vec3(1.0/2.0,1.0/2.0 - 2.0/3.0,1.0/2.0-4.0/3.0);
 
             lowp vec3 applyRasterization(vec2 screenCoords, lowp vec3 texel, vec2 virtualResolution, float intensity) {
                 vec2 omega = vec2(3.141592654) * vec2(2.0) * virtualResolution;
-
                 vec2 angle = screenCoords * omega;
+                vec3 xfactors = (SUBPIXELS + sin(angle.x + offsets)) / (SUBPIXELS + 1.0);
 
-                float yfactor = (brighten_scanlines + sin(angle.y)) / (brighten_scanlines + 1.0);
-                vec3 xfactors = (brighten_lcd + sin(angle.x + offsets)) / (brighten_lcd + 1.0);
+                lowp vec3 result = texel * xfactors;
+                lowp vec3 pixelHigh = ((1.0 + BRIGHTBOOST) - (0.2 * result)) * result;
+                lowp vec3 pixelLow  = ((1.0 - INTENSITY) + (0.1 * result)) * result;
 
-                lowp vec3 rasterizationColor = yfactor * xfactors * texel;
+                vec2 coords = fract(screenCoords * virtualResolution) * 2.0 - vec2(1.0);
+                lowp float mask = 1.0 - abs(coords.y);
+
+                lowp vec3 rasterizationColor = mix(pixelLow, pixelHigh, mask);
                 return mix(texel, rasterizationColor, intensity);
             }" : "") +