Code cleanup

example_web/src/example_app.rs

@@ -1,28 +1,6 @@
 use egui_web::fetch::Response;
 use std::sync::mpsc::Receiver;
 
-struct Image {
-    size: (usize, usize),
-    pixels: Vec<egui::Srgba>,
-}
-
-impl Image {
-    fn decode(bytes: &[u8]) -> Option<Image> {
-        use image::GenericImageView;
-        let image = image::load_from_memory(&bytes).ok()?;
-        let image_buffer = image.to_rgba();
-        let size = (image.width() as usize, image.height() as usize);
-        let pixels = image_buffer.into_vec();
-        assert_eq!(size.0 * size.1 * 4, pixels.len());
-        let pixels = pixels
-            .chunks(4)
-            .map(|p| egui::Srgba::from_rgba_unmultiplied(p[0], p[1], p[2], p[3]))
-            .collect();
-
-        Some(Image { size, pixels })
-    }
-}
-
 struct Resource {
     /// HTTP response
     response: Response,
@@ -31,11 +9,22 @@ struct Resource {
     image: Option<Image>,
 }
 
+impl Resource {
+    fn from_response(response: Response) -> Self {
+        let image = if response.header_content_type.starts_with("image/") {
+            Image::decode(&response.bytes)
+        } else {
+            None
+        };
+        Self { response, image }
+    }
+}
+
 pub struct ExampleApp {
     url: String,
     in_progress: Option<Receiver<Result<Response, String>>>,
     result: Option<Result<Resource, String>>,
-    texture_id: Option<egui::TextureId>,
+    tex_mngr: TexMngr,
 }
 
 impl Default for ExampleApp {
@@ -44,7 +33,7 @@ impl Default for ExampleApp {
             url: "https://raw.githubusercontent.com/emilk/egui/master/README.md".to_owned(),
             in_progress: Default::default(),
             result: Default::default(),
-            texture_id: None,
+            tex_mngr: Default::default(),
         }
     }
 }
@@ -58,7 +47,7 @@ impl egui::app::App for ExampleApp {
         integration_context: &mut egui::app::IntegrationContext,
     ) {
         egui::CentralPanel::default().show(ctx, |ui| {
-            ui.heading("HTTP Get inside of Egui");
+            ui.heading("Egui Example App");
             ui.add(egui::github_link_file!(
                 "https://github.com/emilk/egui/blob/master/",
                 "(source code)"
@@ -81,7 +70,7 @@ impl egui::app::App for ExampleApp {
             } else if let Some(result) = &self.result {
                 match result {
                     Ok(resource) => {
-                        ui_resouce(ui, self.texture_id, resource);
+                        ui_resouce(ui, integration_context, &mut self.tex_mngr, resource);
                     }
                     Err(error) => {
                         // This should only happen if the fetch API isn't available or something similar.
@@ -91,40 +80,11 @@ impl egui::app::App for ExampleApp {
             }
         });
 
-        self.poll_receiver(integration_context);
-    }
-}
-
-impl ExampleApp {
-    fn load_image(
-        &mut self,
-        integration_context: &mut egui::app::IntegrationContext,
-        response: &Response,
-    ) -> Option<Image> {
-        let tex_allocator = integration_context.tex_allocator.as_mut()?;
-
-        if matches!(
-            response.header_content_type.as_str(),
-            "image/jpeg" | "image/png"
-        ) {
-            let image = Image::decode(&response.bytes)?;
-            let texture_id = self.texture_id.unwrap_or_else(|| tex_allocator.alloc());
-            self.texture_id = Some(texture_id);
-            tex_allocator.set_srgba_premultiplied(texture_id, image.size, &image.pixels);
-            return Some(image);
-        }
-        None
-    }
-
-    fn poll_receiver(&mut self, integration_context: &mut egui::app::IntegrationContext) {
         if let Some(receiver) = &mut self.in_progress {
             // Are we there yet?
             if let Ok(result) = receiver.try_recv() {
                 self.in_progress = None;
-                self.result = Some(result.map(|response| Resource {
-                    image: self.load_image(integration_context, &response),
-                    response,
-                }));
+                self.result = Some(result.map(Resource::from_response));
             }
         }
     }
@@ -136,7 +96,10 @@ fn ui_url(ui: &mut egui::Ui, url: &mut String) -> bool {
     ui.horizontal(|ui| {
         ui.label("URL:");
         trigger_fetch |= ui.text_edit_singleline(url).lost_kb_focus;
+        trigger_fetch |= ui.button("GET").clicked;
+    });
 
+    ui.horizontal(|ui| {
         if ui.button("Source code for this example").clicked {
             *url = format!(
                 "https://raw.githubusercontent.com/emilk/egui/master/{}",
@@ -152,12 +115,16 @@ fn ui_url(ui: &mut egui::Ui, url: &mut String) -> bool {
             trigger_fetch = true;
         }
     });
-    trigger_fetch |= ui.button("GET").clicked;
 
     trigger_fetch
 }
 
-fn ui_resouce(ui: &mut egui::Ui, texture_id: Option<egui::TextureId>, resource: &Resource) {
+fn ui_resouce(
+    ui: &mut egui::Ui,
+    integration_context: &mut egui::app::IntegrationContext,
+    tex_mngr: &mut TexMngr,
+    resource: &Resource,
+) {
     let Resource { response, image } = resource;
 
     ui.monospace(format!("url:          {}", response.url));
@@ -172,11 +139,9 @@ fn ui_resouce(ui: &mut egui::Ui, texture_id: Option<egui::TextureId>, resource:
     ));
 
     if let Some(image) = image {
-        if let Some(texture_id) = texture_id {
-            ui.image(
-                texture_id,
-                egui::Vec2::new(image.size.0 as f32, image.size.1 as f32),
-            );
+        if let Some(texture_id) = tex_mngr.texture(integration_context, &response.url, &image) {
+            let size = egui::Vec2::new(image.size.0 as f32, image.size.1 as f32);
+            ui.image(texture_id, size);
         }
     } else if let Some(text) = &response.text {
         ui.monospace("Body:");
@@ -188,3 +153,53 @@ fn ui_resouce(ui: &mut egui::Ui, texture_id: Option<egui::TextureId>, resource:
         ui.monospace("[binary]");
     }
 }
+
+// ----------------------------------------------------------------------------
+// Texture/image handling is very manual at the moment.
+
+/// Immediate mode texture managers that supports at most one texture at the time :)
+#[derive(Default)]
+struct TexMngr {
+    loaded_url: String,
+    texture_id: Option<egui::TextureId>,
+}
+
+impl TexMngr {
+    fn texture(
+        &mut self,
+        integration_context: &mut egui::app::IntegrationContext,
+        url: &str,
+        image: &Image,
+    ) -> Option<egui::TextureId> {
+        let tex_allocator = integration_context.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 {
+            self.loaded_url = url.to_owned();
+            tex_allocator.set_srgba_premultiplied(texture_id, image.size, &image.pixels);
+        }
+        Some(texture_id)
+    }
+}
+
+struct Image {
+    size: (usize, usize),
+    pixels: Vec<egui::Srgba>,
+}
+
+impl Image {
+    fn decode(bytes: &[u8]) -> Option<Image> {
+        use image::GenericImageView;
+        let image = image::load_from_memory(&bytes).ok()?;
+        let image_buffer = image.to_rgba();
+        let size = (image.width() as usize, image.height() as usize);
+        let pixels = image_buffer.into_vec();
+        assert_eq!(size.0 * size.1 * 4, pixels.len());
+        let pixels = pixels
+            .chunks(4)
+            .map(|p| egui::Srgba::from_rgba_unmultiplied(p[0], p[1], p[2], p[3]))
+            .collect();
+
+        Some(Image { size, pixels })
+    }
+}