Add anti-aliasing option for graph

shaders/graph.glsl

@@ -13,6 +13,13 @@
 #define DRAW_OUTLINE 0
 /* 1 to draw edge highlight, 0 to disable */
 #define DRAW_HIGHLIGHT 1
+/* Whether to anti-alias the border of the graph, creating a smoother curve.
+   This may have a small impact on performance. Note that this only anti-aliases
+   the border, so that the seams between the graph and the outline and/or the
+   highlight (if present) will not be aliased.
+   Note: This requires `xroot` transparency to be enabled since it
+   relies on alpha blending with the background. */
+#define ANTI_ALIAS 0
 /* outline color */
 #define OUTLINE #262626
 /* 1 to invert (vertically), 0 otherwise */

shaders/graph/3.frag

@@ -0,0 +1,76 @@
+
+in vec4 gl_FragCoord;
+
+#request uniform "screen" screen
+uniform ivec2 screen; /* screen dimensions */
+
+#request uniform "prev" tex
+uniform sampler2D tex;    /* screen texture    */
+
+out vec4 fragment; /* output */
+
+#include "@graph.glsl"
+#include ":graph.glsl"
+
+float get_col_height_up(float x, float oy) {
+    float y = oy;
+    while (y < screen.y) {
+        vec4 f = texelFetch(tex, ivec2(x, y), 0);
+        if (f.a <= 0) {
+            y -= 1;
+            break;
+        }
+        y += 1;
+    }
+
+    return y;
+}
+
+float get_col_height_down(float x, float oy) {
+    float y = oy;
+    while (y >= 0) {
+        vec4 f = texelFetch(tex, ivec2(x, y), 0);
+        if (f.a > 0) {
+            break;
+        }
+        y -= 1;
+    }
+
+    return y;
+}
+
+void main() {
+    fragment = texelFetch(tex, ivec2(gl_FragCoord.x, gl_FragCoord.y), 0);
+
+    #if ANTI_ALIAS > 0
+
+    if (fragment.a <= 0) {
+        bool left_done = false;
+        float h2;
+        float a_fact = 0;
+
+        if (texelFetch(tex, ivec2(gl_FragCoord.x - 1, gl_FragCoord.y), 0).a > 0) {
+            float h1 = get_col_height_up(gl_FragCoord.x - 1, gl_FragCoord.y);
+            h2 = get_col_height_down(gl_FragCoord.x, gl_FragCoord.y);
+            fragment = texelFetch(tex, ivec2(gl_FragCoord.x, h2), 0);
+
+            a_fact = clamp((h1 - gl_FragCoord.y) / abs(h2 - h1), 0.0, 1.0);
+
+            left_done = true;
+        }
+        if (texelFetch(tex, ivec2(gl_FragCoord.x + 1, gl_FragCoord.y), 0).a > 0) {
+            if (!left_done) {
+                h2 = get_col_height_down(gl_FragCoord.x, gl_FragCoord.y);
+                fragment = texelFetch(tex, ivec2(gl_FragCoord.x, h2), 0);
+            }
+            float h3 = get_col_height_up(gl_FragCoord.x + 1, gl_FragCoord.y);
+
+            a_fact = max(a_fact, clamp((h3 - gl_FragCoord.y) / abs(h2 - h3), 0.0, 1.0));
+        }
+
+        fragment.a *= a_fact;
+
+    }
+
+    #endif
+}