From bb59509d44d2979e4b91bd0f998c047f16b89dd0 Mon Sep 17 00:00:00 2001
From: ira <JustTheCoolDude@gmail.com>
Date: Thu, 22 Jun 2023 05:01:24 +0200
Subject: [PATCH] Fix gizmos in WebGPU (#8910)

# Objective

Fix #8908.

## Solution

Assign the vertex buffers twice with a single item offset instead of
setting the array_stride lower than the vertex layout's size for
linestrips.
---
 crates/bevy_gizmos/src/lib.rs | 103 +++++++++++++++++++++-------------
 1 file changed, 63 insertions(+), 40 deletions(-)

diff --git a/crates/bevy_gizmos/src/lib.rs b/crates/bevy_gizmos/src/lib.rs
index 3a6b89f3e0e52..23c53c895d719 100644
--- a/crates/bevy_gizmos/src/lib.rs
+++ b/crates/bevy_gizmos/src/lib.rs
@@ -452,12 +452,22 @@ impl<P: PhaseItem> RenderCommand<P> for DrawLineGizmo {
             return RenderCommandResult::Failure;
         };
 
-        pass.set_vertex_buffer(0, line_gizmo.position_buffer.slice(..));
-        pass.set_vertex_buffer(1, line_gizmo.color_buffer.slice(..));
-
         let instances = if line_gizmo.strip {
+            let item_size = VertexFormat::Float32x3.size();
+            let buffer_size = line_gizmo.position_buffer.size() - item_size;
+            pass.set_vertex_buffer(0, line_gizmo.position_buffer.slice(..buffer_size));
+            pass.set_vertex_buffer(1, line_gizmo.position_buffer.slice(item_size..));
+
+            let item_size = VertexFormat::Float32x4.size();
+            let buffer_size = line_gizmo.color_buffer.size() - item_size;
+            pass.set_vertex_buffer(2, line_gizmo.color_buffer.slice(..buffer_size));
+            pass.set_vertex_buffer(3, line_gizmo.color_buffer.slice(item_size..));
+
             u32::max(line_gizmo.vertex_count, 1) - 1
         } else {
+            pass.set_vertex_buffer(0, line_gizmo.position_buffer.slice(..));
+            pass.set_vertex_buffer(1, line_gizmo.color_buffer.slice(..));
+
             line_gizmo.vertex_count / 2
         };
 
@@ -468,42 +478,55 @@ impl<P: PhaseItem> RenderCommand<P> for DrawLineGizmo {
 }
 
 fn line_gizmo_vertex_buffer_layouts(strip: bool) -> Vec<VertexBufferLayout> {
-    let stride_multiplier = if strip { 1 } else { 2 };
     use VertexFormat::*;
-    vec![
-        // Positions
-        VertexBufferLayout {
-            array_stride: Float32x3.size() * stride_multiplier,
-            step_mode: VertexStepMode::Instance,
-            attributes: vec![
-                VertexAttribute {
-                    format: Float32x3,
-                    offset: 0,
-                    shader_location: 0,
-                },
-                VertexAttribute {
-                    format: Float32x3,
-                    offset: Float32x3.size(),
-                    shader_location: 1,
-                },
-            ],
-        },
-        // Colors
-        VertexBufferLayout {
-            array_stride: Float32x4.size() * stride_multiplier,
-            step_mode: VertexStepMode::Instance,
-            attributes: vec![
-                VertexAttribute {
-                    format: Float32x4,
-                    offset: 0,
-                    shader_location: 2,
-                },
-                VertexAttribute {
-                    format: Float32x4,
-                    offset: Float32x4.size(),
-                    shader_location: 3,
-                },
-            ],
-        },
-    ]
+    let mut position_layout = VertexBufferLayout {
+        array_stride: Float32x3.size(),
+        step_mode: VertexStepMode::Instance,
+        attributes: vec![VertexAttribute {
+            format: Float32x3,
+            offset: 0,
+            shader_location: 0,
+        }],
+    };
+
+    let mut color_layout = VertexBufferLayout {
+        array_stride: Float32x4.size(),
+        step_mode: VertexStepMode::Instance,
+        attributes: vec![VertexAttribute {
+            format: Float32x4,
+            offset: 0,
+            shader_location: 2,
+        }],
+    };
+
+    if strip {
+        vec![
+            position_layout.clone(),
+            {
+                position_layout.attributes[0].shader_location = 1;
+                position_layout
+            },
+            color_layout.clone(),
+            {
+                color_layout.attributes[0].shader_location = 3;
+                color_layout
+            },
+        ]
+    } else {
+        position_layout.array_stride *= 2;
+        position_layout.attributes.push(VertexAttribute {
+            format: Float32x3,
+            offset: Float32x3.size(),
+            shader_location: 1,
+        });
+
+        color_layout.array_stride *= 2;
+        color_layout.attributes.push(VertexAttribute {
+            format: Float32x4,
+            offset: Float32x4.size(),
+            shader_location: 3,
+        });
+
+        vec![position_layout, color_layout]
+    }
 }