[app] Add demo app slider to change scale of all of Egui

CHANGELOG.md

@@ -5,6 +5,7 @@
 * `ui.horizontal(...)` etc returns `Response`
 * Add ability to override text color with `visuals.override_text_color`
 * Refactored the interface for `egui::app::App`
+* Demo App: Add slider to scale all of Egui
 
 ## 0.2.0 - 2020-10-10
 

egui/src/app.rs

@@ -24,12 +24,14 @@ pub trait App {
     fn on_exit(&mut self, _storage: &mut dyn Storage) {}
 }
 
+#[derive(Clone, Debug)]
 pub struct WebInfo {
     /// e.g. "#fragment" part of "www.example.com/index.html#fragment"
     pub web_location_hash: String,
 }
 
 /// Information about the backend passed to the use app each frame.
+#[derive(Clone, Debug)]
 pub struct BackendInfo {
     /// If the app is running in a Web context, this returns information about the environment.
     pub web_info: Option<WebInfo>,
@@ -41,14 +43,20 @@ pub struct BackendInfo {
     /// Local time. Used for the clock in the demo app.
     /// Set to `None` if you don't know.
     pub seconds_since_midnight: Option<f64>,
+
+    /// The OS native pixels-per-point
+    pub native_pixels_per_point: Option<f32>,
 }
 
 /// Action that can be taken by the user app.
-#[derive(Clone, Copy, Debug, Default)]
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
 pub struct AppOutput {
     /// Set to `true` to stop the app.
     /// This does nothing for web apps.
     pub quit: bool,
+
+    /// If the app sets this, change the `pixels_per_point` of Egui to this next frame.
+    pub pixels_per_point: Option<f32>,
 }
 
 pub trait TextureAllocator {

egui/src/demos/app.rs

@@ -188,6 +188,9 @@ pub struct DemoApp {
     demo_window: DemoWindow,
     fractal_clock: FractalClock,
 
+    /// current slider value for current gui scale (backend demo only)
+    pixels_per_point: Option<f32>,
+
     #[cfg_attr(feature = "serde", serde(skip))]
     frame_history: FrameHistory,
 
@@ -320,8 +323,6 @@ impl DemoApp {
 
         let is_web = info.web_info.is_some();
 
-        let mut options = app::AppOutput::default();
-
         if is_web {
             ui.label("Egui is an immediate mode GUI written in Rust, compiled to WebAssembly, rendered with WebGL.");
             ui.label(
@@ -332,23 +333,17 @@ impl DemoApp {
                 ui.label("Project home page:");
                 ui.hyperlink("https://github.com/emilk/egui");
             });
-        } else {
-            ui.heading("Egui");
-            options.quit |= ui.button("Quit").clicked;
+            ui.separator();
         }
 
+        self.run_mode_ui(ui);
+
         ui.separator();
 
-        self.run_mode_ui(ui);
+        let mut output = app::AppOutput::default();
+        output.pixels_per_point = self.pixels_per_point_ui(ui, info);
 
-        if self.run_mode == RunMode::Continuous {
-            ui.label(format!(
-                "Repainting the UI each frame. FPS: {:.1}",
-                self.frame_history.fps()
-            ));
-        } else {
-            ui.label("Only running UI code when there are animations or input");
-        }
+        ui.separator();
 
         ui.separator();
         self.frame_history.ui(ui);
@@ -359,7 +354,41 @@ impl DemoApp {
             "Show color blend test (debug backend painter)",
         );
 
-        options
+        if !is_web {
+            output.quit |= ui.button("Quit").clicked;
+        }
+
+        output
+    }
+
+    fn pixels_per_point_ui(&mut self, ui: &mut Ui, info: &app::BackendInfo) -> Option<f32> {
+        self.pixels_per_point = self
+            .pixels_per_point
+            .or(info.native_pixels_per_point)
+            .or_else(|| Some(ui.ctx().pixels_per_point()));
+        if let Some(pixels_per_point) = &mut self.pixels_per_point {
+            ui.add(
+                Slider::f32(pixels_per_point, 0.5..=5.0)
+                    .logarithmic(true)
+                    .text("Scale (physical pixels per point)"),
+            );
+            if let Some(native_pixels_per_point) = info.native_pixels_per_point {
+                if ui
+                    .button(format!(
+                        "Reset scale to native value ({:.1})",
+                        native_pixels_per_point
+                    ))
+                    .clicked
+                {
+                    *pixels_per_point = native_pixels_per_point;
+                }
+            }
+            if !ui.ctx().is_using_mouse() {
+                // We wait until mouse release to activate:
+                return Some(*pixels_per_point);
+            }
+        }
+        None
     }
 
     fn run_mode_ui(&mut self, ui: &mut Ui) {
@@ -371,6 +400,15 @@ impl DemoApp {
             ui.radio_value(run_mode, RunMode::Reactive, "Reactive")
                 .on_hover_text("Repaint when there are animations or input (e.g. mouse movement)");
         });
+
+        if self.run_mode == RunMode::Continuous {
+            ui.label(format!(
+                "Repainting the UI each frame. FPS: {:.1}",
+                self.frame_history.fps()
+            ));
+        } else {
+            ui.label("Only running UI code when there are animations or input");
+        }
     }
 }
 

egui/src/input.rs

@@ -388,7 +388,7 @@ impl InputState {
         ui.label(format!("scroll_delta: {:?} points", scroll_delta));
         ui.label(format!("screen_size: {:?} points", screen_size));
         ui.label(format!(
-            "{:?} points for each physical pixel (HDPI factor)",
+            "{:?} physical pixels for each logical point",
             pixels_per_point
         ));
         ui.label(format!("time: {:.3} s", time));

egui_glium/src/backend.rs

@@ -51,7 +51,10 @@ pub fn run(title: &str, mut storage: FileStorage, mut app: impl App + 'static) -
     let mut ctx = egui::Context::new();
     *ctx.memory() = egui::app::get_value(&storage, EGUI_MEMORY_KEY).unwrap_or_default();
 
-    let mut raw_input = make_raw_input(&display);
+    let mut raw_input = egui::RawInput {
+        pixels_per_point: Some(native_pixels_per_point(&display)),
+        ..Default::default()
+    };
 
     let start_time = Instant::now();
     let mut previous_frame_time = None;
@@ -62,11 +65,14 @@ pub fn run(title: &str, mut storage: FileStorage, mut app: impl App + 'static) -
         let mut redraw = || {
             let egui_start = Instant::now();
             raw_input.time = start_time.elapsed().as_nanos() as f64 * 1e-9;
+            raw_input.screen_size =
+                screen_size_in_pixels(&display) / raw_input.pixels_per_point.unwrap();
 
             let backend_info = egui::app::BackendInfo {
                 web_info: None,
                 cpu_usage: previous_frame_time,
                 seconds_since_midnight: Some(seconds_since_midnight()),
+                native_pixels_per_point: Some(native_pixels_per_point(&display)),
             };
 
             let mut ui = ctx.begin_frame(raw_input.take());
@@ -75,10 +81,17 @@ pub fn run(title: &str, mut storage: FileStorage, mut app: impl App + 'static) -
 
             let frame_time = (Instant::now() - egui_start).as_secs_f64() as f32;
             previous_frame_time = Some(frame_time);
-            painter.paint_jobs(&display, paint_jobs, &ctx.texture());
+            painter.paint_jobs(&display, ctx.pixels_per_point(), paint_jobs, &ctx.texture());
 
             {
-                let egui::app::AppOutput { quit } = app_output;
+                let egui::app::AppOutput {
+                    quit,
+                    pixels_per_point,
+                } = app_output;
+                if let Some(pixels_per_point) = pixels_per_point {
+                    // User changed GUI scale
+                    raw_input.pixels_per_point = Some(pixels_per_point);
+                }
 
                 *control_flow = if quit {
                     glutin::event_loop::ControlFlow::Exit

egui_glium/src/lib.rs

@@ -27,30 +27,16 @@ pub fn input_to_egui(
     use glutin::event::WindowEvent::*;
     match event {
         CloseRequested | Destroyed => *control_flow = ControlFlow::Exit,
-
-        Resized(physical_size) => {
-            raw_input.screen_size =
-                egui::vec2(physical_size.width as f32, physical_size.height as f32)
-                    / raw_input.pixels_per_point.unwrap();
-        }
-
-        ScaleFactorChanged {
-            scale_factor,
-            new_inner_size,
-        } => {
-            raw_input.pixels_per_point = Some(scale_factor as f32);
-            raw_input.screen_size =
-                egui::vec2(new_inner_size.width as f32, new_inner_size.height as f32)
-                    / (scale_factor as f32);
-        }
-
         MouseInput { state, .. } => {
             raw_input.mouse_down = state == glutin::event::ElementState::Pressed;
         }
-        CursorMoved { position, .. } => {
+        CursorMoved {
+            position: pos_in_pixels,
+            ..
+        } => {
             raw_input.mouse_pos = Some(pos2(
-                position.x as f32 / raw_input.pixels_per_point.unwrap(),
-                position.y as f32 / raw_input.pixels_per_point.unwrap(),
+                pos_in_pixels.x as f32 / raw_input.pixels_per_point.unwrap(),
+                pos_in_pixels.y as f32 / raw_input.pixels_per_point.unwrap(),
             ));
         }
         CursorLeft { .. } => {
@@ -213,14 +199,11 @@ pub fn seconds_since_midnight() -> f64 {
     time.num_seconds_from_midnight() as f64 + 1e-9 * (time.nanosecond() as f64)
 }
 
-pub fn make_raw_input(display: &glium::Display) -> egui::RawInput {
-    let pixels_per_point = display.gl_window().window().scale_factor() as f32;
-    egui::RawInput {
-        screen_size: {
-            let (width, height) = display.get_framebuffer_dimensions();
-            vec2(width as f32, height as f32) / pixels_per_point
-        },
-        pixels_per_point: Some(pixels_per_point),
-        ..Default::default()
-    }
+pub fn screen_size_in_pixels(display: &glium::Display) -> Vec2 {
+    let (width_in_pixels, height_in_pixels) = display.get_framebuffer_dimensions();
+    vec2(width_in_pixels as f32, height_in_pixels as f32)
+}
+
+pub fn native_pixels_per_point(display: &glium::Display) -> f32 {
+    display.gl_window().window().scale_factor() as f32
 }

egui_glium/src/painter.rs

@@ -152,16 +152,23 @@ impl Painter {
     pub fn paint_jobs(
         &mut self,
         display: &glium::Display,
+        pixels_per_point: f32,
         jobs: PaintJobs,
-        texture: &egui::Texture,
+        egui_texture: &egui::Texture,
     ) {
-        self.upload_egui_texture(display, texture);
+        self.upload_egui_texture(display, egui_texture);
         self.upload_pending_user_textures(display);
 
         let mut target = display.draw();
         target.clear_color(0.0, 0.0, 0.0, 0.0);
         for (clip_rect, triangles) in jobs {
-            self.paint_job(&mut target, display, clip_rect, &triangles)
+            self.paint_job(
+                &mut target,
+                display,
+                pixels_per_point,
+                clip_rect,
+                &triangles,
+            )
         }
         target.finish().unwrap();
     }
@@ -183,6 +190,7 @@ impl Painter {
         &mut self,
         target: &mut Frame,
         display: &glium::Display,
+        pixels_per_point: f32,
         clip_rect: Rect,
         triangles: &Triangles,
     ) {
@@ -217,15 +225,14 @@ impl Painter {
         let index_buffer =
             glium::IndexBuffer::new(display, PrimitiveType::TrianglesList, &indices).unwrap();
 
-        let pixels_per_point = display.gl_window().window().scale_factor() as f32;
-        let (width_pixels, height_pixels) = display.get_framebuffer_dimensions();
-        let width_points = width_pixels as f32 / pixels_per_point;
-        let height_points = height_pixels as f32 / pixels_per_point;
+        let (width_in_pixels, height_in_pixels) = display.get_framebuffer_dimensions();
+        let width_in_points = width_in_pixels as f32 / pixels_per_point;
+        let height_in_points = height_in_pixels as f32 / pixels_per_point;
 
         let texture = self.get_texture(triangles.texture_id);
 
         let uniforms = uniform! {
-            u_screen_size: [width_points, height_points],
+            u_screen_size: [width_in_points, height_in_points],
             u_sampler: texture.sampled().wrap_function(SamplerWrapFunction::Clamp),
         };
 
@@ -255,10 +262,10 @@ impl Painter {
         let clip_max_y = pixels_per_point * clip_rect.max.y;
 
         // Make sure clip rect can fit withing an `u32`:
-        let clip_min_x = clamp(clip_min_x, 0.0..=width_pixels as f32);
-        let clip_min_y = clamp(clip_min_y, 0.0..=height_pixels as f32);
-        let clip_max_x = clamp(clip_max_x, clip_min_x..=width_pixels as f32);
-        let clip_max_y = clamp(clip_max_y, clip_min_y..=height_pixels as f32);
+        let clip_min_x = clamp(clip_min_x, 0.0..=width_in_pixels as f32);
+        let clip_min_y = clamp(clip_min_y, 0.0..=height_in_pixels as f32);
+        let clip_max_x = clamp(clip_max_x, clip_min_x..=width_in_pixels as f32);
+        let clip_max_y = clamp(clip_max_y, clip_min_y..=height_in_pixels as f32);
 
         let clip_min_x = clip_min_x.round() as u32;
         let clip_min_y = clip_min_y.round() as u32;
@@ -269,7 +276,7 @@ impl Painter {
             blend,
             scissor: Some(glium::Rect {
                 left: clip_min_x,
-                bottom: height_pixels - clip_max_y,
+                bottom: height_in_pixels - clip_max_y,
                 width: clip_max_x - clip_min_x,
                 height: clip_max_y - clip_min_y,
             }),

egui_web/src/backend.rs

@@ -2,7 +2,7 @@ use crate::*;
 
 pub use egui::{
     app::{App, WebInfo},
-    Srgba,
+    pos2, Srgba,
 };
 
 // ----------------------------------------------------------------------------
@@ -105,13 +105,17 @@ pub struct WebInput {
 }
 
 impl WebInput {
-    pub fn new_frame(&mut self) -> egui::RawInput {
+    pub fn new_frame(&mut self, pixels_per_point: f32) -> egui::RawInput {
+        // Compensate for potential different scale of Egui compared to native.
+        let scale = native_pixels_per_point() / pixels_per_point;
+        let scroll_delta = std::mem::take(&mut self.scroll_delta) * scale;
+        let mouse_pos = self.mouse_pos.map(|mp| pos2(mp.x * scale, mp.y * scale));
         egui::RawInput {
             mouse_down: self.mouse_down,
-            mouse_pos: self.mouse_pos,
-            scroll_delta: std::mem::take(&mut self.scroll_delta),
-            screen_size: screen_size().unwrap(),
-            pixels_per_point: Some(pixels_per_point()),
+            mouse_pos,
+            scroll_delta,
+            screen_size: screen_size_in_native_points().unwrap() * scale,
+            pixels_per_point: Some(pixels_per_point),
             time: now_sec(),
             events: std::mem::take(&mut self.events),
         }
@@ -121,6 +125,7 @@ impl WebInput {
 // ----------------------------------------------------------------------------
 
 pub struct AppRunner {
+    pixels_per_point: f32,
     pub web_backend: WebBackend,
     pub web_input: WebInput,
     pub app: Box<dyn App>,
@@ -130,6 +135,7 @@ pub struct AppRunner {
 impl AppRunner {
     pub fn new(web_backend: WebBackend, app: Box<dyn App>) -> Result<Self, JsValue> {
         Ok(Self {
+            pixels_per_point: native_pixels_per_point(),
             web_backend,
             web_input: Default::default(),
             app,
@@ -142,9 +148,9 @@ impl AppRunner {
     }
 
     pub fn logic(&mut self) -> Result<(egui::Output, egui::PaintJobs), JsValue> {
-        resize_to_screen_size(self.web_backend.canvas_id());
+        resize_canvas_to_screen_size(self.web_backend.canvas_id());
 
-        let raw_input = self.web_input.new_frame();
+        let raw_input = self.web_input.new_frame(self.pixels_per_point);
 
         let backend_info = egui::app::BackendInfo {
             web_info: Some(WebInfo {
@@ -152,6 +158,7 @@ impl AppRunner {
             }),
             cpu_usage: self.web_backend.previous_frame_time,
             seconds_since_midnight: Some(seconds_since_midnight()),
+            native_pixels_per_point: Some(native_pixels_per_point()),
         };
 
         let mut ui = self.web_backend.begin_frame(raw_input);
@@ -162,7 +169,14 @@ impl AppRunner {
         handle_output(&egui_output);
 
         {
-            let egui::app::AppOutput { quit: _ } = app_output;
+            let egui::app::AppOutput {
+                quit: _,
+                pixels_per_point,
+            } = app_output;
+
+            if let Some(pixels_per_point) = pixels_per_point {
+                self.pixels_per_point = pixels_per_point;
+            }
         }
 
         Ok((egui_output, paint_jobs))

egui_web/src/lib.rs

@@ -17,14 +17,6 @@ pub fn console_log(s: String) {
     web_sys::console::log_1(&s.into());
 }
 
-pub fn screen_size() -> Option<egui::Vec2> {
-    let window = web_sys::window()?;
-    Some(egui::Vec2::new(
-        window.inner_width().ok()?.as_f64()? as f32,
-        window.inner_height().ok()?.as_f64()? as f32,
-    ))
-}
-
 pub fn now_sec() -> f64 {
     web_sys::window()
         .expect("should have a Window")
@@ -40,7 +32,15 @@ pub fn seconds_since_midnight() -> f64 {
     seconds as f64 + 1e-3 * (d.get_milliseconds() as f64)
 }
 
-pub fn pixels_per_point() -> f32 {
+pub fn screen_size_in_native_points() -> Option<egui::Vec2> {
+    let window = web_sys::window()?;
+    Some(egui::Vec2::new(
+        window.inner_width().ok()?.as_f64()? as f32,
+        window.inner_height().ok()?.as_f64()? as f32,
+    ))
+}
+
+pub fn native_pixels_per_point() -> f32 {
     let pixels_per_point = web_sys::window().unwrap().device_pixel_ratio() as f32;
     if pixels_per_point > 0.0 && pixels_per_point.is_finite() {
         pixels_per_point
@@ -78,11 +78,11 @@ pub fn pos_from_touch_event(event: &web_sys::TouchEvent) -> egui::Pos2 {
     }
 }
 
-pub fn resize_to_screen_size(canvas_id: &str) -> Option<()> {
+pub fn resize_canvas_to_screen_size(canvas_id: &str) -> Option<()> {
     let canvas = canvas_element(canvas_id)?;
 
-    let screen_size = screen_size()?;
-    let pixels_per_point = pixels_per_point();
+    let screen_size = screen_size_in_native_points()?;
+    let pixels_per_point = native_pixels_per_point();
     canvas
         .style()
         .set_property("width", &format!("{}px", screen_size.x))