Replace all http code in epi/eframe/egui_glium/egui_web with ehttp (#697)

I've extracted all the http request code and turned it
into its own crate at <https://github.com/emilk/ehttp>.

There was never a reason for the HTTP request library to be part of
`eframe`. Much better to have it as its own crate!

egui_demo_lib/src/apps/demo/code_editor.rs

@@ -65,7 +65,7 @@ impl super::View for CodeEditor {
         } else {
             ui.horizontal_wrapped(|ui|{
                 ui.spacing_mut().item_spacing.x = 0.0;
-                ui.label("Compile the demo with the 'syntect' feature to enable much nicer syntax highlighting using ");
+                ui.label("Compile the demo with the 'syntax_highlighting' feature to enable much nicer syntax highlighting using ");
                 ui.hyperlink_to("syntect", "https://github.com/trishume/syntect");
                 ui.label(".");
             });

egui_demo_lib/src/apps/http_app.rs

@@ -1,9 +1,8 @@
-use epi::http::{Request, Response};
 use std::sync::mpsc::Receiver;
 
 struct Resource {
     /// HTTP response
-    response: Response,
+    response: ehttp::Response,
 
     text: Option<String>,
 
@@ -15,7 +14,7 @@ struct Resource {
 }
 
 impl Resource {
-    fn from_response(response: Response) -> Self {
+    fn from_response(response: ehttp::Response) -> Self {
         let content_type = response.content_type().unwrap_or_default();
         let image = if content_type.starts_with("image/") {
             Image::decode(&response.bytes)
@@ -54,7 +53,7 @@ pub struct HttpApp {
     request_body: String,
 
     #[cfg_attr(feature = "persistence", serde(skip))]
-    in_progress: Option<Receiver<Result<Response, String>>>,
+    in_progress: Option<Receiver<Result<ehttp::Response, String>>>,
 
     #[cfg_attr(feature = "persistence", serde(skip))]
     result: Option<Result<Resource, String>>,
@@ -94,9 +93,15 @@ impl epi::App for HttpApp {
 
         egui::CentralPanel::default().show(ctx, |ui| {
             ui.heading("HTTP Fetch Example");
+            ui.horizontal(|ui| {
+                ui.spacing_mut().item_spacing.x = 0.0;
+                ui.label("HTTP requests made using ");
+                ui.hyperlink_to("ehttp", "https://www.github.com/emilk/ehttp");
+                ui.label(".");
+            });
             ui.add(egui::github_link_file!(
                 "https://github.com/emilk/egui/blob/master/",
-                "(source code)"
+                "(demo source code)"
             ));
 
             if let Some(request) = ui_url(
@@ -110,7 +115,7 @@ impl epi::App for HttpApp {
                 let (sender, receiver) = std::sync::mpsc::channel();
                 self.in_progress = Some(receiver);
 
-                frame.http_fetch(request, move |response| {
+                ehttp::fetch(request, move |response| {
                     sender.send(response).ok();
                     repaint_signal.request_repaint();
                 });
@@ -144,7 +149,7 @@ fn ui_url(
     url: &mut String,
     method: &mut Method,
     request_body: &mut String,
-) -> Option<Request> {
+) -> Option<ehttp::Request> {
     let mut trigger_fetch = false;
 
     egui::Grid::new("request_params").show(ui, |ui| {
@@ -202,8 +207,8 @@ fn ui_url(
 
     if trigger_fetch {
         Some(match *method {
-            Method::Get => Request::get(url),
-            Method::Post => Request::post(url, request_body),
+            Method::Get => ehttp::Request::get(url),
+            Method::Post => ehttp::Request::post(url, request_body),
         })
     } else {
         None
@@ -284,7 +289,7 @@ fn ui_resource(
 // Syntax highlighting:
 
 #[cfg(feature = "syntect")]
-fn syntax_highlighting(response: &Response, text: &str) -> Option<ColoredText> {
+fn syntax_highlighting(response: &ehttp::Response, text: &str) -> Option<ColoredText> {
     let extension_and_rest: Vec<&str> = response.url.rsplitn(2, '.').collect();
     let extension = extension_and_rest.get(0)?;
     ColoredText::text_with_extension(text, extension)
@@ -361,6 +366,7 @@ impl ColoredText {
     }
 }
 
+#[cfg(feature = "syntect")]
 fn as_byte_range(whole: &str, range: &str) -> std::ops::Range<usize> {
     let whole_start = whole.as_ptr() as usize;
     let range_start = range.as_ptr() as usize;
@@ -371,7 +377,7 @@ fn as_byte_range(whole: &str, range: &str) -> std::ops::Range<usize> {
 }
 
 #[cfg(not(feature = "syntect"))]
-fn syntax_highlighting(_: &Response, _: &str) -> Option<ColoredText> {
+fn syntax_highlighting(_: &ehttp::Response, _: &str) -> Option<ColoredText> {
     None
 }
 #[cfg(not(feature = "syntect"))]