From 6c616a1b69799dec7cf27e64e319422c837a42ec Mon Sep 17 00:00:00 2001
From: dvec <dvecend@gmail.com>
Date: Wed, 12 Jan 2022 13:33:06 +0300
Subject: [PATCH] egui_glow: Reduce memory allocations in Painter::set_texture
 (#1096)

Use bytemuck::cast_slice
---
 egui_glow/Cargo.toml     | 3 ++-
 egui_glow/src/painter.rs | 8 +++-----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/egui_glow/Cargo.toml b/egui_glow/Cargo.toml
index 8945b5f0..af53d9ac 100644
--- a/egui_glow/Cargo.toml
+++ b/egui_glow/Cargo.toml
@@ -23,8 +23,9 @@ include = [
 all-features = true
 
 [dependencies]
-egui = { version = "0.16.0", path = "../egui", default-features = false, features = ["single_threaded"] }
+egui = { version = "0.16.0", path = "../egui", default-features = false, features = ["single_threaded", "convert_bytemuck"] }
 
+bytemuck = "1.7"
 epi = { version = "0.16.0", path = "../epi", optional = true }
 glow = "0.11"
 memoffset = "0.6"
diff --git a/egui_glow/src/painter.rs b/egui_glow/src/painter.rs
index 0ba75f2e..5e087e63 100644
--- a/egui_glow/src/painter.rs
+++ b/egui_glow/src/painter.rs
@@ -2,6 +2,7 @@
 
 use std::collections::HashMap;
 
+use bytemuck::cast_slice;
 use egui::{
     emath::Rect,
     epaint::{Color32, Mesh, Vertex},
@@ -434,17 +435,14 @@ impl Painter {
             "Mismatch between texture size and texel count"
         );
 
-        let mut data = Vec::with_capacity(image.pixels.len() * 4);
-        for srgba in &image.pixels {
-            data.extend_from_slice(&srgba.to_array());
-        }
+        let data: &[u8] = cast_slice(image.pixels.as_ref());
 
         let gl_texture = srgb_texture2d(
             gl,
             self.is_webgl_1,
             self.srgb_support,
             self.texture_filter,
-            &data,
+            data,
             image.size[0],
             image.size[1],
         );