[epi] Simplify TextureAllocator interface

egui_demo_lib/src/apps/color_test.rs

@@ -394,9 +394,7 @@ impl TextureManager {
             let pixels = gradient.to_pixel_row();
             let width = pixels.len();
             let height = 1;
-            let id = tex_allocator.alloc();
-            tex_allocator.set_srgba_premultiplied(id, (width, height), &pixels);
-            id
+            tex_allocator.alloc_srgba_premultiplied((width, height), &pixels)
         })
     }
 }

egui_demo_lib/src/apps/http_app.rs

@@ -265,13 +265,16 @@ impl TexMngr {
         image: &Image,
     ) -> Option<egui::TextureId> {
         let tex_allocator = frame.tex_allocator().as_mut()?;
-        let texture_id = self.texture_id.unwrap_or_else(|| tex_allocator.alloc());
-        self.texture_id = Some(texture_id);
         if self.loaded_url != url {
+            if let Some(texture_id) = self.texture_id.take() {
+                tex_allocator.free(texture_id);
+            }
+
+            self.texture_id =
+                Some(tex_allocator.alloc_srgba_premultiplied(image.size, &image.pixels));
             self.loaded_url = url.to_owned();
-            tex_allocator.set_srgba_premultiplied(texture_id, image.size, &image.pixels);
         }
-        Some(texture_id)
+        self.texture_id
     }
 }
 

egui_glium/src/backend.rs

@@ -28,17 +28,14 @@ fn deserialize_memory(_: &Option<Box<dyn epi::Storage>>) -> Option<egui::Memory>
 }
 
 impl epi::TextureAllocator for Painter {
-    fn alloc(&mut self) -> egui::TextureId {
-        self.alloc_user_texture()
-    }
-
-    fn set_srgba_premultiplied(
+    fn alloc_srgba_premultiplied(
         &mut self,
-        id: egui::TextureId,
         size: (usize, usize),
         srgba_pixels: &[Color32],
-    ) {
+    ) -> egui::TextureId {
+        let id = self.alloc_user_texture();
         self.set_user_texture(id, size, srgba_pixels);
+        id
     }
 
     fn free(&mut self, id: egui::TextureId) {

egui_web/src/backend.rs

@@ -66,17 +66,14 @@ impl WebBackend {
 }
 
 impl epi::TextureAllocator for webgl::Painter {
-    fn alloc(&mut self) -> egui::TextureId {
-        self.alloc_user_texture()
-    }
-
-    fn set_srgba_premultiplied(
+    fn alloc_srgba_premultiplied(
         &mut self,
-        id: egui::TextureId,
         size: (usize, usize),
         srgba_pixels: &[Color32],
-    ) {
+    ) -> egui::TextureId {
+        let id = self.alloc_user_texture();
         self.set_user_texture(id, size, srgba_pixels);
+        id
     }
 
     fn free(&mut self, id: egui::TextureId) {

epi/CHANGELOG.md

@@ -7,6 +7,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased
 
+* Simplify `TextureAllocator` interface.
+
 
 ## 0.7.0 - 2021-01-04
 

epi/src/lib.rs

@@ -190,15 +190,11 @@ pub struct IntegrationInfo {
 /// How to allocate textures (images) to use in [`egui`].
 pub trait TextureAllocator {
     /// Allocate a new user texture.
-    fn alloc(&mut self) -> egui::TextureId;
-
-    /// Set or change the pixels of a user texture.
-    fn set_srgba_premultiplied(
+    fn alloc_srgba_premultiplied(
         &mut self,
-        id: egui::TextureId,
         size: (usize, usize),
         srgba_pixels: &[egui::Color32],
-    );
+    ) -> egui::TextureId;
 
     /// Free the given texture.
     fn free(&mut self, id: egui::TextureId);