Typing-friendly cursor trails

cursor_blaze.glsl

@@ -1,3 +1,4 @@
+// Based on https://gist.github.com/chardskarth/95874c54e29da6b5a36ab7b50ae2d088
 float ease(float x) {
     return pow(1.0 - x, 10.0);
 }
@@ -76,6 +77,12 @@ const vec4 PREVIOUS_CURSOR_COLOR = TRAIL_COLOR;
 const vec4 TRAIL_COLOR_ACCENT = vec4(1.0, 0., 0., 1.0); // red-orange
 const float DURATION = .5;
 const float OPACITY = .2;
+// Don't draw trail within that distance * cursor size.
+// This prevents trails from appearing when typing.
+const float DRAW_THRESHOLD = 1.5;
+// Don't draw trails within the same line: same line jumps are usually where
+// people expect them.
+const bool HIDE_TRAILS_ON_THE_SAME_LINE = false;
 
 void mainImage(out vec4 fragColor, in vec2 fragCoord)
 {
@@ -110,21 +117,26 @@ void mainImage(out vec4 fragColor, in vec2 fragCoord)
     //Distance between cursors determine the total length of the parallelogram;
     vec2 centerCC = getRectangleCenter(currentCursor);
     vec2 centerCP = getRectangleCenter(previousCursor);
+    float cursorSize = max(currentCursor.z, currentCursor.w);
+    float trailThreshold = DRAW_THRESHOLD * cursorSize;
     float lineLength = distance(centerCC, centerCP);
-    float distanceToEnd = distance(vu.xy, centerCC);
-    float alphaModifier = distanceToEnd / (lineLength * (easedProgress));
-
-    if (alphaModifier > 1.0) { // this change fixed it for me.
-      alphaModifier = 1.0;
+    //
+    bool isFarEnough = lineLength > trailThreshold;
+    bool isOnSeparateLine = HIDE_TRAILS_ON_THE_SAME_LINE ? currentCursor.y != previousCursor.y : true;
+    if (isFarEnough && isOnSeparateLine) {
+        float distanceToEnd = distance(vu.xy, centerCC);
+        float alphaModifier = distanceToEnd / (lineLength * (easedProgress));
+
+        if (alphaModifier > 1.0) { // this change fixed it for me.
+            alphaModifier = 1.0;
+        }
+
+        float sdfCursor = getSdfRectangle(vu, currentCursor.xy - (currentCursor.zw * offsetFactor), currentCursor.zw * 0.5);
+        float sdfTrail = getSdfParallelogram(vu, v0, v1, v2, v3);
+
+        newColor = mix(newColor, TRAIL_COLOR_ACCENT, 1.0 - smoothstep(sdfTrail, -0.01, 0.001));
+        newColor = mix(newColor, TRAIL_COLOR, antialising(sdfTrail));
+        newColor = mix(fragColor, newColor, 1.0 - alphaModifier);
+        fragColor = mix(newColor, fragColor, step(sdfCursor, 0));
     }
-
-    float sdfCursor = getSdfRectangle(vu, currentCursor.xy - (currentCursor.zw * offsetFactor), currentCursor.zw * 0.5);
-    float sdfTrail = getSdfParallelogram(vu, v0, v1, v2, v3);
-
-    newColor = mix(newColor, TRAIL_COLOR_ACCENT, 1.0 - smoothstep(sdfTrail, -0.01, 0.001));
-    newColor = mix(newColor, TRAIL_COLOR, antialising(sdfTrail));
-
-    newColor = mix(fragColor, newColor, 1.0 - alphaModifier);
-    fragColor = mix(newColor, fragColor, step(sdfCursor, 0));
-
 }