Storage and frame refactor (#1418)

The purpose of this is to expose `frame.storage()` and `frame.storage_mut()` so users can save/load app state from the `App::update` function, without having to add another parameter to that function.

Changes:
* Added `Frame::storage()` and `Frame::storage_mut()`
* `App::update` now takes a `&mut Frame` rather than just `&Frame`
* `Frame` is no longer `Clone` or `Sync` (doesn't have to be since https://github.com/emilk/egui/pull/1366)

egui_demo_lib/src/apps/color_test.rs

@@ -30,7 +30,7 @@ impl Default for ColorTest {
 }
 
 impl epi::App for ColorTest {
-    fn update(&mut self, ctx: &egui::Context, frame: &epi::Frame) {
+    fn update(&mut self, ctx: &egui::Context, frame: &mut epi::Frame) {
         egui::CentralPanel::default().show(ctx, |ui| {
             if frame.is_web() {
                 ui.label(

egui_demo_lib/src/apps/demo/app.rs

@@ -6,7 +6,7 @@ pub struct DemoApp {
 }
 
 impl epi::App for DemoApp {
-    fn update(&mut self, ctx: &egui::Context, _frame: &epi::Frame) {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut epi::Frame) {
         self.demo_windows.ui(ctx);
     }
 }

egui_demo_lib/src/apps/fractal_clock.rs

@@ -33,7 +33,7 @@ impl Default for FractalClock {
 }
 
 impl epi::App for FractalClock {
-    fn update(&mut self, ctx: &egui::Context, _frame: &epi::Frame) {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut epi::Frame) {
         egui::CentralPanel::default()
             .frame(Frame::dark_canvas(&ctx.style()))
             .show(ctx, |ui| self.ui(ui, crate::seconds_since_midnight()));

egui_demo_lib/src/apps/http_app.rs

@@ -54,7 +54,7 @@ impl Default for HttpApp {
 }
 
 impl epi::App for HttpApp {
-    fn update(&mut self, ctx: &egui::Context, frame: &epi::Frame) {
+    fn update(&mut self, ctx: &egui::Context, frame: &mut epi::Frame) {
         egui::TopBottomPanel::bottom("http_bottom").show(ctx, |ui| {
             let layout = egui::Layout::top_down(egui::Align::Center).with_main_justify(true);
             ui.allocate_ui_with_layout(ui.available_size(), layout, |ui| {
@@ -108,7 +108,7 @@ impl epi::App for HttpApp {
     }
 }
 
-fn ui_url(ui: &mut egui::Ui, frame: &epi::Frame, url: &mut String) -> bool {
+fn ui_url(ui: &mut egui::Ui, frame: &mut epi::Frame, url: &mut String) -> bool {
     let mut trigger_fetch = false;
 
     ui.horizontal(|ui| {

egui_demo_lib/src/backend_panel.rs

@@ -73,7 +73,7 @@ impl Default for BackendPanel {
 }
 
 impl BackendPanel {
-    pub fn update(&mut self, ctx: &egui::Context, frame: &epi::Frame) {
+    pub fn update(&mut self, ctx: &egui::Context, frame: &mut epi::Frame) {
         self.frame_history
             .on_new_frame(ctx.input().time, frame.info().cpu_usage);
 
@@ -87,7 +87,7 @@ impl BackendPanel {
         self.egui_windows.windows(ctx);
     }
 
-    pub fn ui(&mut self, ui: &mut egui::Ui, frame: &epi::Frame) {
+    pub fn ui(&mut self, ui: &mut egui::Ui, frame: &mut epi::Frame) {
         egui::trace!(ui);
         ui.vertical_centered(|ui| {
             ui.heading("💻 Backend");
@@ -142,7 +142,7 @@ impl BackendPanel {
         }
     }
 
-    fn integration_ui(&mut self, ui: &mut egui::Ui, frame: &epi::Frame) {
+    fn integration_ui(&mut self, ui: &mut egui::Ui, frame: &mut epi::Frame) {
         if frame.is_web() {
             ui.label("egui is an immediate mode GUI written in Rust, compiled to WebAssembly, rendered with WebGL.");
             ui.label(

egui_demo_lib/src/easy_mark/easy_mark_editor.rs

@@ -30,7 +30,7 @@ impl Default for EasyMarkEditor {
 }
 
 impl epi::App for EasyMarkEditor {
-    fn update(&mut self, ctx: &egui::Context, _frame: &epi::Frame) {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut epi::Frame) {
         egui::TopBottomPanel::bottom("easy_mark_bottom").show(ctx, |ui| {
             let layout = egui::Layout::top_down(egui::Align::Center).with_main_justify(true);
             ui.allocate_ui_with_layout(ui.available_size(), layout, |ui| {

egui_demo_lib/src/wrap_app.rs

@@ -69,7 +69,7 @@ impl epi::App for WrapApp {
         egui::Rgba::TRANSPARENT // we set a `CentralPanel` fill color in `demo_windows.rs`
     }
 
-    fn update(&mut self, ctx: &egui::Context, frame: &epi::Frame) {
+    fn update(&mut self, ctx: &egui::Context, frame: &mut epi::Frame) {
         if let Some(web_info) = frame.info().web_info.as_ref() {
             if let Some(anchor) = web_info.location.hash.strip_prefix('#') {
                 self.selected_anchor = anchor.to_owned();
@@ -130,7 +130,7 @@ impl epi::App for WrapApp {
 }
 
 impl WrapApp {
-    fn bar_contents(&mut self, ui: &mut egui::Ui, frame: &epi::Frame) {
+    fn bar_contents(&mut self, ui: &mut egui::Ui, frame: &mut epi::Frame) {
         // A menu-bar is a horizontal layout with some special styles applied.
         // egui::menu::bar(ui, |ui| {
         ui.horizontal_wrapped(|ui| {