WIP: move 3d rendering example into egui_demo_lib

egui_demo_lib/Cargo.toml

@@ -36,10 +36,12 @@ syntax_highlighting = ["syntect"]
 [dependencies]
 egui = { version = "0.17.0", path = "../egui", default-features = false }
 epi = { version = "0.17.0", path = "../epi" }
+egui_glow = { version = "0.17.0", path = "../egui_glow" }                 # for custom_3d app
 
 chrono = { version = "0.4", optional = true, features = ["js-sys", "wasmbind"] }
 enum-map = { version = "2", features = ["serde"] }
 tracing = "0.1"
+parking_lot = "0.12"
 unicode_names2 = { version = "0.5.0", default-features = false }
 
 # feature "http":

egui_demo_lib/src/apps/custom_3d.rs

@@ -0,0 +1,190 @@
+//! This demo shows how to embed 3D rendering using [`glow`](https://github.com/grovesNL/glow) in `epi`.
+//!
+//! This is very advanced usage, and you need to be careful.
+//!
+//! If you want an easier way to show 3D graphics with egui, take a look at:
+//! * [`bevy_egui`](https://github.com/mvlabat/bevy_egui)
+//! * [`three-d`](https://github.com/asny/three-d)
+
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")] // hide console window on Windows in release
+
+use epi::{glow, Renderer as _};
+use parking_lot::Mutex;
+use std::sync::Arc;
+
+pub struct Custom3dApp {
+    /// Behind an `Arc<Mutex<…>>` so we can pass it to [`egui::PaintCallback`] and paint later.
+    rotating_triangle: Arc<Mutex<RotatingTriangle>>,
+    angle: f32,
+}
+
+impl Custom3dApp {
+    pub fn new(cc: &epi::CreationContext<'_>) -> Self {
+        Self {
+            rotating_triangle: Arc::new(Mutex::new(RotatingTriangle::new(&cc.gl))),
+            angle: 0.0,
+        }
+    }
+}
+
+impl epi::App for Custom3dApp {
+    fn update(&mut self, ctx: &egui::Context, _frame: &epi::Frame) {
+        egui::CentralPanel::default().show(ctx, |ui| {
+            ui.vertical_centered(|ui| {
+                ui.add(crate::__egui_github_link_file!());
+            });
+
+            ui.horizontal(|ui| {
+                ui.spacing_mut().item_spacing.x = 0.0;
+                ui.label("The triangle is being painted using ");
+                ui.hyperlink_to("glow", "https://github.com/grovesNL/glow");
+                ui.label(" (OpenGL).");
+            });
+
+            egui::ScrollArea::both().show(ui, |ui| {
+                egui::Frame::canvas(ui.style()).show(ui, |ui| {
+                    self.custom_painting(ui);
+                });
+                ui.label("Drag to rotate!");
+            });
+        });
+    }
+}
+
+impl Custom3dApp {
+    fn custom_painting(&mut self, ui: &mut egui::Ui) {
+        let (rect, response) =
+            ui.allocate_exact_size(egui::Vec2::splat(256.0), egui::Sense::drag());
+
+        self.angle += response.drag_delta().x * 0.01;
+
+        let angle = self.angle;
+        let rotating_triangle = self.rotating_triangle.clone();
+
+        let callback = egui::epaint::PaintCallback {
+            rect,
+            callback: std::sync::Arc::new(move |render_ctx| {
+                if let Some(painter) = render_ctx.downcast_ref::<egui_glow::Painter>() {
+                    rotating_triangle.lock().paint(painter.gl(), angle);
+                } else {
+                    eprintln!("Can't do custom painting because we are not using a glow context");
+                }
+            }),
+        };
+        ui.painter().add(callback);
+    }
+}
+
+struct RotatingTriangle {
+    program: glow::Program,
+    vertex_array: glow::VertexArray,
+}
+
+impl RotatingTriangle {
+    fn new(gl: &glow::Context) -> Self {
+        use glow::HasContext as _;
+
+        let shader_version = if cfg!(target_arch = "wasm32") {
+            "#version 300 es"
+        } else {
+            "#version 410"
+        };
+
+        unsafe {
+            let program = gl.create_program().expect("Cannot create program");
+
+            let (vertex_shader_source, fragment_shader_source) = (
+                r#"
+                    const vec2 verts[3] = vec2[3](
+                        vec2(0.0, 1.0),
+                        vec2(-1.0, -1.0),
+                        vec2(1.0, -1.0)
+                    );
+                    const vec4 colors[3] = vec4[3](
+                        vec4(1.0, 0.0, 0.0, 1.0),
+                        vec4(0.0, 1.0, 0.0, 1.0),
+                        vec4(0.0, 0.0, 1.0, 1.0)
+                    );
+                    out vec4 v_color;
+                    uniform float u_angle;
+                    void main() {
+                        v_color = colors[gl_VertexID];
+                        gl_Position = vec4(verts[gl_VertexID], 0.0, 1.0);
+                        gl_Position.x *= cos(u_angle);
+                    }
+                "#,
+                r#"
+                    precision mediump float;
+                    in vec4 v_color;
+                    out vec4 out_color;
+                    void main() {
+                        out_color = v_color;
+                    }
+                "#,
+            );
+
+            let shader_sources = [
+                (glow::VERTEX_SHADER, vertex_shader_source),
+                (glow::FRAGMENT_SHADER, fragment_shader_source),
+            ];
+
+            let shaders: Vec<_> = shader_sources
+                .iter()
+                .map(|(shader_type, shader_source)| {
+                    let shader = gl
+                        .create_shader(*shader_type)
+                        .expect("Cannot create shader");
+                    gl.shader_source(shader, &format!("{}\n{}", shader_version, shader_source));
+                    gl.compile_shader(shader);
+                    if !gl.get_shader_compile_status(shader) {
+                        panic!("{}", gl.get_shader_info_log(shader));
+                    }
+                    gl.attach_shader(program, shader);
+                    shader
+                })
+                .collect();
+
+            gl.link_program(program);
+            if !gl.get_program_link_status(program) {
+                panic!("{}", gl.get_program_info_log(program));
+            }
+
+            for shader in shaders {
+                gl.detach_shader(program, shader);
+                gl.delete_shader(shader);
+            }
+
+            let vertex_array = gl
+                .create_vertex_array()
+                .expect("Cannot create vertex array");
+
+            Self {
+                program,
+                vertex_array,
+            }
+        }
+    }
+
+    // TODO: figure out how to call this in a nice way
+    #[allow(unused)]
+    fn destroy(self, gl: &glow::Context) {
+        use glow::HasContext as _;
+        unsafe {
+            gl.delete_program(self.program);
+            gl.delete_vertex_array(self.vertex_array);
+        }
+    }
+
+    fn paint(&self, gl: &glow::Context, angle: f32) {
+        use glow::HasContext as _;
+        unsafe {
+            gl.use_program(Some(self.program));
+            gl.uniform_1_f32(
+                gl.get_uniform_location(self.program, "u_angle").as_ref(),
+                angle,
+            );
+            gl.bind_vertex_array(Some(self.vertex_array));
+            gl.draw_arrays(glow::TRIANGLES, 0, 3);
+        }
+    }
+}

egui_demo_lib/src/apps/mod.rs

@@ -1,10 +1,12 @@
 mod color_test;
+mod custom_3d;
 mod demo;
 mod fractal_clock;
 #[cfg(feature = "http")]
 mod http_app;
 
 pub use color_test::ColorTest;
+pub use custom_3d::Custom3dApp;
 pub use demo::DemoApp;
 pub use fractal_clock::FractalClock;
 #[cfg(feature = "http")]

egui_demo_lib/src/wrap_app.rs

@@ -1,7 +1,5 @@
 /// All the different demo apps.
-#[derive(Default)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
-#[cfg_attr(feature = "serde", serde(default))]
 pub struct Apps {
     demo: crate::apps::DemoApp,
     easy_mark_editor: crate::easy_mark::EasyMarkEditor,
@@ -9,9 +7,22 @@ pub struct Apps {
     http: crate::apps::HttpApp,
     clock: crate::apps::FractalClock,
     color_test: crate::apps::ColorTest,
+    custom_3d: crate::apps::Custom3dApp,
 }
 
 impl Apps {
+    fn new(cc: &epi::CreationContext<'_>) -> Self {
+        Self {
+            demo: Default::default(),
+            easy_mark_editor: Default::default(),
+            #[cfg(feature = "http")]
+            http: Default::default(),
+            clock: Default::default(),
+            color_test: Default::default(),
+            custom_3d: crate::apps::Custom3dApp::new(cc),
+        }
+    }
+
     fn iter_mut(&mut self) -> impl Iterator<Item = (&str, &str, &mut dyn epi::App)> {
         vec![
             ("✨ Demos", "demo", &mut self.demo as &mut dyn epi::App),
@@ -32,6 +43,11 @@ impl Apps {
                 "colors",
                 &mut self.color_test as &mut dyn epi::App,
             ),
+            (
+                "🔺 3D painting",
+                "custom_3d",
+                &mut self.custom_3d as &mut dyn epi::App,
+            ),
         ]
         .into_iter()
     }