Use Rgba (4xf32) instead of Color32 in all interfaces

This simplifies a few things, but some benchmarks gets worse,
probably due to the increased memory use (and thus more cache misses).

I don't plan to merge this, but leave it here as an experiment

egui_web/src/shader/vertex_100es.glsl

@@ -2,30 +2,16 @@ precision mediump float;
 uniform vec2 u_screen_size;
 attribute vec2 a_pos;
 attribute vec2 a_tc;
-attribute vec4 a_srgba;
-varying vec4 v_rgba;
+attribute vec4 a_rgba; // 0-1
+varying vec4 v_rgba; // 0-1
 varying vec2 v_tc;
 
-// 0-1 linear  from  0-255 sRGB
-vec3 linear_from_srgb(vec3 srgb) {
-  bvec3 cutoff = lessThan(srgb, vec3(10.31475));
-  vec3 lower = srgb / vec3(3294.6);
-  vec3 higher = pow((srgb + vec3(14.025)) / vec3(269.025), vec3(2.4));
-  return mix(higher, lower, vec3(cutoff));
-}
-
-// 0-1 linear  from  0-255 sRGBA
-vec4 linear_from_srgba(vec4 srgba) {
-  return vec4(linear_from_srgb(srgba.rgb), srgba.a / 255.0);
-}
-
 void main() {
   gl_Position = vec4(
                      2.0 * a_pos.x / u_screen_size.x - 1.0,
                      1.0 - 2.0 * a_pos.y / u_screen_size.y,
                      0.0,
                      1.0);
-  // egui encodes vertex colors in gamma spaces, so we must decode the colors here:
-  v_rgba = linear_from_srgba(a_srgba);
+  v_rgba = a_rgba;
   v_tc = a_tc;
 }

egui_web/src/shader/vertex_300es.glsl

@@ -2,30 +2,16 @@ precision mediump float;
 uniform vec2 u_screen_size;
 attribute vec2 a_pos;
 attribute vec2 a_tc;
-attribute vec4 a_srgba;
-varying vec4 v_rgba;
+attribute vec4 a_rgba; // 0-1
+varying vec4 v_rgba; // 0-1
 varying vec2 v_tc;
 
-// 0-1 linear  from  0-255 sRGB
-vec3 linear_from_srgb(vec3 srgb) {
-  bvec3 cutoff = lessThan(srgb, vec3(10.31475));
-  vec3 lower = srgb / vec3(3294.6);
-  vec3 higher = pow((srgb + vec3(14.025)) / vec3(269.025), vec3(2.4));
-  return mix(higher, lower, vec3(cutoff));
-}
-
-// 0-1 linear  from  0-255 sRGBA
-vec4 linear_from_srgba(vec4 srgba) {
-  return vec4(linear_from_srgb(srgba.rgb), srgba.a / 255.0);
-}
-
 void main() {
   gl_Position = vec4(
                      2.0 * a_pos.x / u_screen_size.x - 1.0,
                      1.0 - 2.0 * a_pos.y / u_screen_size.y,
                      0.0,
                      1.0);
-  // egui encodes vertex colors in gamma spaces, so we must decode the colors here:
-  v_rgba = linear_from_srgba(a_srgba);
+  v_rgba = a_rgba;
   v_tc = a_tc;
 }

egui_web/src/webgl1.rs

@@ -210,7 +210,7 @@ impl WebGlPainter {
 
         let mut positions: Vec<f32> = Vec::with_capacity(2 * mesh.vertices.len());
         let mut tex_coords: Vec<f32> = Vec::with_capacity(2 * mesh.vertices.len());
-        let mut colors: Vec<u8> = Vec::with_capacity(4 * mesh.vertices.len());
+        let mut colors: Vec<f32> = Vec::with_capacity(4 * mesh.vertices.len());
         for v in &mesh.vertices {
             positions.push(v.pos.x);
             positions.push(v.pos.y);
@@ -289,29 +289,22 @@ impl WebGlPainter {
         let colors_memory_buffer = wasm_bindgen::memory()
             .dyn_into::<WebAssembly::Memory>()?
             .buffer();
-        let colors_ptr = colors.as_ptr() as u32;
+        let colors_ptr = colors.as_ptr() as u32 / 4;
         let colors_array = js_sys::Uint8Array::new(&colors_memory_buffer)
             .subarray(colors_ptr, colors_ptr + colors.len() as u32);
 
         gl.bind_buffer(Gl::ARRAY_BUFFER, Some(&self.color_buffer));
         gl.buffer_data_with_array_buffer_view(Gl::ARRAY_BUFFER, &colors_array, Gl::STREAM_DRAW);
 
-        let a_srgba_loc = gl.get_attrib_location(&self.program, "a_srgba");
-        assert!(a_srgba_loc >= 0);
-        let a_srgba_loc = a_srgba_loc as u32;
+        let a_rgba_loc = gl.get_attrib_location(&self.program, "a_rgba");
+        assert!(a_rgba_loc >= 0);
+        let a_rgba_loc = a_rgba_loc as u32;
 
         let normalize = false;
         let stride = 0;
         let offset = 0;
-        gl.vertex_attrib_pointer_with_i32(
-            a_srgba_loc,
-            4,
-            Gl::UNSIGNED_BYTE,
-            normalize,
-            stride,
-            offset,
-        );
-        gl.enable_vertex_attrib_array(a_srgba_loc);
+        gl.vertex_attrib_pointer_with_i32(a_rgba_loc, 4, Gl::FLOAT, normalize, stride, offset);
+        gl.enable_vertex_attrib_array(a_rgba_loc);
 
         // --------------------------------------------------------------------
 

egui_web/src/webgl2.rs

@@ -211,7 +211,7 @@ impl WebGl2Painter {
 
         let mut positions: Vec<f32> = Vec::with_capacity(2 * mesh.vertices.len());
         let mut tex_coords: Vec<f32> = Vec::with_capacity(2 * mesh.vertices.len());
-        let mut colors: Vec<u8> = Vec::with_capacity(4 * mesh.vertices.len());
+        let mut colors: Vec<f32> = Vec::with_capacity(4 * mesh.vertices.len());
         for v in &mesh.vertices {
             positions.push(v.pos.x);
             positions.push(v.pos.y);
@@ -290,29 +290,22 @@ impl WebGl2Painter {
         let colors_memory_buffer = wasm_bindgen::memory()
             .dyn_into::<WebAssembly::Memory>()?
             .buffer();
-        let colors_ptr = colors.as_ptr() as u32;
+        let colors_ptr = colors.as_ptr() as u32 / 4;
         let colors_array = js_sys::Uint8Array::new(&colors_memory_buffer)
             .subarray(colors_ptr, colors_ptr + colors.len() as u32);
 
         gl.bind_buffer(Gl::ARRAY_BUFFER, Some(&self.color_buffer));
         gl.buffer_data_with_array_buffer_view(Gl::ARRAY_BUFFER, &colors_array, Gl::STREAM_DRAW);
 
-        let a_srgba_loc = gl.get_attrib_location(&self.program, "a_srgba");
-        assert!(a_srgba_loc >= 0);
-        let a_srgba_loc = a_srgba_loc as u32;
+        let a_rgba_loc = gl.get_attrib_location(&self.program, "a_rgba");
+        assert!(a_rgba_loc >= 0);
+        let a_rgba_loc = a_rgba_loc as u32;
 
         let normalize = false;
         let stride = 0;
         let offset = 0;
-        gl.vertex_attrib_pointer_with_i32(
-            a_srgba_loc,
-            4,
-            Gl::UNSIGNED_BYTE,
-            normalize,
-            stride,
-            offset,
-        );
-        gl.enable_vertex_attrib_array(a_srgba_loc);
+        gl.vertex_attrib_pointer_with_i32(a_rgba_loc, 4, Gl::FLOAT, normalize, stride, offset);
+        gl.enable_vertex_attrib_array(a_rgba_loc);
 
         // --------------------------------------------------------------------