From 91561e8c3585a00d8180c7080f1e1b5542785ab7 Mon Sep 17 00:00:00 2001
From: Nathan Adams <dinnerbone@dinnerbone.com>
Date: Sat, 24 Dec 2022 23:21:58 +0100
Subject: [PATCH] wgpu: Reduce gradient.ratios uniform memory by 4x

---
 render/wgpu/shaders/gradient_uniform.wgsl | 19 ++++++++-----------
 render/wgpu/src/lib.rs                    |  6 +++---
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/render/wgpu/shaders/gradient_uniform.wgsl b/render/wgpu/shaders/gradient_uniform.wgsl
index be1ff2840..5341678ee 100644
--- a/render/wgpu/shaders/gradient_uniform.wgsl
+++ b/render/wgpu/shaders/gradient_uniform.wgsl
@@ -1,15 +1,8 @@
 /// Shader used for drawing all flavors of gradients.
 
-struct wrapped_f32 {
-  elem: f32,
-  _padding1: f32,
-  _padding2: f32,
-  _padding3: f32,
-}
-
 struct Gradient {
     colors: array<vec4<f32>, 16>,
-    ratios: array<wrapped_f32,16u>,
+    ratios: array<vec4<f32>, 4u>, // secretly array<f32; 16> but this let's us squeeze it into alignment
     gradient_type: i32,
     num_colors: u32,
     repeat_mode: i32,
@@ -33,6 +26,10 @@ fn main_vertex(in: VertexInput) -> VertexOutput {
     return VertexOutput(pos, uv);
 }
 
+fn ratio(i: u32) -> f32 {
+    return gradient.ratios[i / 4u][i % 4u];
+}
+
 @fragment
 fn main_fragment(in: VertexOutput) -> @location(0) vec4<f32> {
     let last = gradient.num_colors - 1u;
@@ -91,17 +88,17 @@ fn main_fragment(in: VertexOutput) -> @location(0) vec4<f32> {
             break;
         }
     }
-    t = clamp(t, gradient.ratios[0].elem, gradient.ratios[last].elem);
+    t = clamp(t, ratio(0u), ratio(last));
 
     // Find the two gradient colors bordering our position.
     var j: u32;
-    for( j = 1u; t > gradient.ratios[j].elem; j = j + 1u) {
+    for( j = 1u; t > ratio(j); j = j + 1u) {
         // Noop
     }
     let i = j - 1u;
 
     // Lerp between the two colors.
-    let a = (t - gradient.ratios[i].elem) / (gradient.ratios[j].elem - gradient.ratios[i].elem);
+    let a = (t - ratio(i)) / (ratio(j) - ratio(i));
     var color: vec4<f32> = mix(gradient.colors[i], gradient.colors[j], a);
     if( gradient.interpolation != 0 ) {
         color = linear_to_srgb(color);
diff --git a/render/wgpu/src/lib.rs b/render/wgpu/src/lib.rs
index 58af6cc68..2e9c5ee43 100644
--- a/render/wgpu/src/lib.rs
+++ b/render/wgpu/src/lib.rs
@@ -108,7 +108,7 @@ impl From<TessVertex> for Vertex {
 #[derive(Copy, Clone, Debug, Pod, Zeroable)]
 struct GradientUniforms {
     colors: [[f32; 4]; 16],
-    ratios: [[f32; 4]; 16],
+    ratios: [f32; 16],
     gradient_type: i32,
     num_colors: u32,
     repeat_mode: i32,
@@ -119,11 +119,11 @@ struct GradientUniforms {
 
 impl From<TessGradient> for GradientUniforms {
     fn from(gradient: TessGradient) -> Self {
-        let mut ratios = [[0.0; 4]; 16];
+        let mut ratios = [0.0; 16];
         let mut colors = [[0.0; 4]; 16];
 
         for i in 0..gradient.num_colors {
-            ratios[i] = [gradient.ratios[i], 0.0, 0.0, 0.0];
+            ratios[i] = gradient.ratios[i];
             colors[i].copy_from_slice(&gradient.colors[i]);
         }