From d431ca8aa645ded26833724f473577440fa73e88 Mon Sep 17 00:00:00 2001
From: Son Pham-Ba <son.phamba@epfl.ch>
Date: Tue, 3 Dec 2024 23:51:16 +0100
Subject: [PATCH] feat: more or less lagging intermediate points

---
 README.md                      | 13 +++++++++++++
 lua/smear_cursor/animation.lua |  4 ++--
 lua/smear_cursor/config.lua    |  6 +++++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 2fe713b..dc8343e 100644
--- a/README.md
+++ b/README.md
@@ -92,6 +92,19 @@ As an example of further configuration, you can tune the smear dynamics to be sn
   },
 ```
 
+
+> [!WARNING] Fire Hazard
+> Feel free to experiment with all the configuration options, but be aware that some combinations may cause your cursor to flicker or even **catch fire**. That can happen with the following settings:
+> ```lua
+>   opts = {
+>     cursor_color = "#ff8800",
+>     stiffness = 0.6,
+>     trailing_stiffness = 0.1,
+>     trailing_exponent = 5,
+>     gamma = 1,
+>   }
+> ```
+
 ### Transparent background
 
 Drawing the smear over a transparent background works better when using a font that supports legacy computing symbols, therefore setting the following option:
diff --git a/lua/smear_cursor/animation.lua b/lua/smear_cursor/animation.lua
index f91fcd5..975b8db 100644
--- a/lua/smear_cursor/animation.lua
+++ b/lua/smear_cursor/animation.lua
@@ -129,8 +129,8 @@ local function set_stiffnesses(head_stiffness, trailing_stiffness)
 	end
 
 	for i = 1, 4 do
-		local stiffness = head_stiffness
-			+ (trailing_stiffness - head_stiffness) * (distances[i] - min_distance) / (max_distance - min_distance)
+		local x = (distances[i] - min_distance) / (max_distance - min_distance)
+		local stiffness = head_stiffness + (trailing_stiffness - head_stiffness) * x ^ config.trailing_exponent
 		stiffnesses[i] = math.min(1, stiffness)
 	end
 end
diff --git a/lua/smear_cursor/config.lua b/lua/smear_cursor/config.lua
index 24163ea..2ce786a 100644
--- a/lua/smear_cursor/config.lua
+++ b/lua/smear_cursor/config.lua
@@ -27,7 +27,11 @@ M.stiffness = 0.6
 -- 0: no movement, 1: instantaneous
 M.trailing_stiffness = 0.25
 
--- How much the tail slows down when getting close to the head.
+-- Controls if middle points are closer to the head or the tail.
+-- < 1: closer to the tail, > 1: closer to the head
+M.trailing_exponent = 2
+
+-- How much the smear slows down when getting close to the target.
 -- 0: no slowdown, more: more slowdown
 M.slowdown_exponent = 0