From 5e94ec7f1de3e343b7a6128a2c331d9689fd915f Mon Sep 17 00:00:00 2001
From: Robbert van der Helm <mail@robbertvanderhelm.nl>
Date: Tue, 22 Mar 2022 19:44:40 +0100
Subject: [PATCH] Add an evenly distributed CurrentStep mode

---
 nih_plug_vizia/src/widgets/generic_ui.rs   |  8 ++++--
 nih_plug_vizia/src/widgets/param_slider.rs | 33 +++++++++++++++++-----
 2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/nih_plug_vizia/src/widgets/generic_ui.rs b/nih_plug_vizia/src/widgets/generic_ui.rs
index 446a980f..413ca94b 100644
--- a/nih_plug_vizia/src/widgets/generic_ui.rs
+++ b/nih_plug_vizia/src/widgets/generic_ui.rs
@@ -52,8 +52,12 @@ impl GenericUi {
                 .set_style(match unsafe { param_ptr.step_count() } {
                     // This looks nice for boolean values, but it's too crowded for anything beyond
                     // that without making the widget wider
-                    Some(step_count) if step_count <= 1 => ParamSliderStyle::CurrentStepLabeled,
-                    Some(step_count) if step_count <= 64 => ParamSliderStyle::CurrentStep,
+                    Some(step_count) if step_count <= 1 => {
+                        ParamSliderStyle::CurrentStepLabeled { even: true }
+                    }
+                    Some(step_count) if step_count <= 64 => {
+                        ParamSliderStyle::CurrentStep { even: true }
+                    }
                     Some(_) => ParamSliderStyle::FromLeft,
                     // This is already the default, but continuous parameters should be drawn from
                     // the center if the default is also centered, or from the left if it is not
diff --git a/nih_plug_vizia/src/widgets/param_slider.rs b/nih_plug_vizia/src/widgets/param_slider.rs
index 21045252..3cf18ff7 100644
--- a/nih_plug_vizia/src/widgets/param_slider.rs
+++ b/nih_plug_vizia/src/widgets/param_slider.rs
@@ -44,12 +44,15 @@ pub enum ParamSliderStyle {
     Centered,
     /// Always fill the bar starting from the left.
     FromLeft,
-    /// Show the current step instead of filling a portion fothe bar, useful for discrete
-    /// parameters.
-    CurrentStep,
+    /// Show the current step instead of filling a portion of the bar, useful for discrete
+    /// parameters. Set `even` to `true` to distribute the ticks evenly instead of following the
+    /// parameter's distribution. This can be desireable because discrete parameters have smaller
+    /// ranges near the edges (they'll span only half the range, which can make the display look
+    /// odd).
+    CurrentStep { even: bool },
     /// The same as `CurrentStep`, but overlay the labels over the steps instead of showing the
     /// active value. Only useful for discrete parameters with two, maybe three possible values.
-    CurrentStepLabeled,
+    CurrentStepLabeled { even: bool },
 }
 
 enum ParamSliderEvent {
@@ -205,8 +208,21 @@ impl ParamSlider {
                                             }
                                             ParamSliderStyle::Centered
                                             | ParamSliderStyle::FromLeft => (0.0, current_value),
-                                            ParamSliderStyle::CurrentStep
-                                            | ParamSliderStyle::CurrentStepLabeled => {
+                                            ParamSliderStyle::CurrentStep { even: true }
+                                            | ParamSliderStyle::CurrentStepLabeled { even: true }
+                                                if step_count.is_some() =>
+                                            {
+                                                // Assume the normalized value is distributed evenly
+                                                // across the range.
+                                                let step_count = step_count.unwrap() as f32;
+                                                let discrete_values = step_count + 1.0;
+                                                let previous_step = (current_value * step_count)
+                                                    .floor()
+                                                    / discrete_values;
+                                                (previous_step, discrete_values.recip())
+                                            }
+                                            ParamSliderStyle::CurrentStep { .. }
+                                            | ParamSliderStyle::CurrentStepLabeled { .. } => {
                                                 let previous_step = unsafe {
                                                     param_ptr
                                                         .previous_normalized_step(current_value)
@@ -237,7 +253,10 @@ impl ParamSlider {
                                 //       text overlapping the fill area slightly differently. We can
                                 //       set the cip region directly in vizia.
                                 match (style, step_count) {
-                                    (ParamSliderStyle::CurrentStepLabeled, Some(step_count)) => {
+                                    (
+                                        ParamSliderStyle::CurrentStepLabeled { .. },
+                                        Some(step_count),
+                                    ) => {
                                         HStack::new(cx, |cx| {
                                             // There are step_count + 1 possible values for a
                                             // discrete parameter