From 81f9b8e04007aa2289d865b48d6bae03b19f287a Mon Sep 17 00:00:00 2001
From: Aaron Fenyes <aaron.fenyes@fareycircles.ooo>
Date: Wed, 21 Aug 2024 22:36:56 -0700
Subject: [PATCH] Find vertex attribute indices in advance

---
 app-proto/inversive-display/src/main.rs | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/app-proto/inversive-display/src/main.rs b/app-proto/inversive-display/src/main.rs
index 6768864..ed8200c 100644
--- a/app-proto/inversive-display/src/main.rs
+++ b/app-proto/inversive-display/src/main.rs
@@ -26,8 +26,7 @@ fn compile_shader(
 // load the given data into the vertex input of the given name
 fn bind_vertex_attrib(
     context: &WebGl2RenderingContext,
-    program: &WebGlProgram,
-    name: &str,
+    index: u32,
     size: i32,
     data: &[f32]
 ) {
@@ -48,11 +47,8 @@ fn bind_vertex_attrib(
         );
     }
     
-    // find the target attribute in the program's attribute list
-    let attrib_index = context.get_attrib_location(&program, name);
-    
     // allow the target attribute to be used
-    context.enable_vertex_attrib_array(attrib_index as u32);
+    context.enable_vertex_attrib_array(index);
     
     // take whatever's bound to ARRAY_BUFFER---here, the data buffer created
     // above---and bind it to the target attribute
@@ -60,7 +56,7 @@ fn bind_vertex_attrib(
     //   https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/vertexAttribPointer
     //
     context.vertex_attrib_pointer_with_i32(
-        attrib_index as u32,
+        index,
         size,
         WebGl2RenderingContext::FLOAT,
         false, // don't normalize
@@ -150,6 +146,10 @@ fn main() {
             console::log_1(&JsValue::from(link_msg));
             ctx.use_program(Some(&program));
             
+            // find indices of vertex attributes
+            let position_index = ctx.get_attrib_location(&program, "position") as u32;
+            let color_index = ctx.get_attrib_location(&program, "color") as u32;
+            
             // create a vertex array and bind it to the graphics context
             let vertex_array = ctx.create_vertex_array().unwrap();
             ctx.bind_vertex_array(Some(&vertex_array));
@@ -174,7 +174,7 @@ fn main() {
                     -1.0, -1.0, -7.0,
                     1.0, -1.0, -7.0
                 ];
-                bind_vertex_attrib(&ctx, &program, "position", 3, &positions);
+                bind_vertex_attrib(&ctx, position_index, 3, &positions);
                 
                 // set the vertex colors
                 let colors: [f32; 3*VERTEX_CNT] = [
@@ -191,7 +191,7 @@ fn main() {
                     0.5, 0.0, 1.0,
                     0.5, 0.0, 1.0
                 ];
-                bind_vertex_attrib(&ctx, &program, "color", 3, &colors);
+                bind_vertex_attrib(&ctx, color_index, 3, &colors);
                 
                 // clear the screen and draw the scene
                 ctx.clear_color(0.0, 0.0, 0.0, 1.0);