Add Shape::Callback to do custom rendering inside of an egui UI

eframe/Cargo.toml

@@ -73,9 +73,11 @@ egui_web = { version = "0.17.0", path = "../egui_web", default-features = false,
 # For examples:
 egui_extras = { path = "../egui_extras", features = ["image", "svg"] }
 ehttp = "0.2"
+glow = "0.11"
 image = { version = "0.24", default-features = false, features = [
   "jpeg",
   "png",
 ] }
+parking_lot = "0.12"
 poll-promise = "0.1"
 rfd = "0.8"

eframe/examples/custom_3d.rs

@@ -0,0 +1,182 @@
+//! This demo shows how to embed 3D rendering using [`glow`](https://github.com/grovesNL/glow) in `eframe`.
+//!
+//! 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 eframe::{egui, epi};
+
+use parking_lot::Mutex;
+use std::sync::Arc;
+
+#[derive(Default)]
+struct MyApp {
+    rotating_triangle: Arc<Mutex<Option<RotatingTriangle>>>,
+    angle: f32,
+}
+
+impl epi::App for MyApp {
+    fn name(&self) -> &str {
+        "Custom 3D painting inside an egui window"
+    }
+
+    fn update(&mut self, ctx: &egui::Context, _frame: &epi::Frame) {
+        egui::CentralPanel::default().show(ctx, |ui| {
+            ui.heading("Here is some 3D stuff:");
+
+            egui::ScrollArea::both().show(ui, |ui| {
+                egui::Frame::dark_canvas(ui.style()).show(ui, |ui| {
+                    self.custom_painting(ui);
+                });
+                ui.label("Drag to rotate!");
+            });
+        });
+
+        let mut frame = egui::Frame::window(&*ctx.style());
+        frame.fill = frame.fill.linear_multiply(0.5); // transparent
+        egui::Window::new("3D stuff in a window")
+            .frame(frame)
+            .show(ctx, |ui| {
+                self.custom_painting(ui);
+            });
+    }
+}
+
+impl MyApp {
+    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 shape = egui::shape::CallbackShape {
+            rect,
+            callback: std::sync::Arc::new(move |render_ctx| {
+                if let Some(gl) = render_ctx.downcast_ref::<glow::Context>() {
+                    let mut rotating_triangle = rotating_triangle.lock();
+                    let rotating_triangle =
+                        rotating_triangle.get_or_insert_with(|| RotatingTriangle::new(gl));
+                    rotating_triangle.paint(gl, angle);
+                } else {
+                    eprintln!("Can't do custom painting because we are not using a glow context");
+                }
+            }),
+        };
+        ui.painter().add(shape);
+    }
+}
+
+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 mut shaders = Vec::with_capacity(shader_sources.len());
+
+            for (shader_type, shader_source) in shader_sources.iter() {
+                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);
+                shaders.push(shader);
+            }
+
+            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,
+            }
+        }
+    }
+
+    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);
+        }
+    }
+}
+
+fn main() {
+    let options = eframe::NativeOptions::default();
+    eframe::run_native(Box::new(MyApp::default()), options);
+}

egui/src/context.rs

@@ -1246,3 +1246,10 @@ impl Context {
         self.set_style(style);
     }
 }
+
+#[cfg(test)]
+#[test]
+fn context_impl_send_sync() {
+    fn assert_send_sync<T: Send + Sync>() {}
+    assert_send_sync::<Context>();
+}

egui/src/introspection.rs

@@ -91,6 +91,7 @@ impl Widget for &epaint::stats::PaintStats {
                 shape_path,
                 shape_mesh,
                 shape_vec,
+                num_callbacks,
                 text_shape_vertices,
                 text_shape_indices,
                 clipped_meshes,
@@ -104,6 +105,7 @@ impl Widget for &epaint::stats::PaintStats {
             label(ui, shape_path, "paths");
             label(ui, shape_mesh, "nested meshes");
             label(ui, shape_vec, "nested shapes");
+            ui.label(format!("{} callbacks", num_callbacks));
             ui.add_space(10.0);
 
             ui.label("Text shapes:");

egui/src/lib.rs

@@ -383,7 +383,7 @@ pub use epaint::emath;
 
 pub use emath::{lerp, pos2, remap, remap_clamp, vec2, Align, Align2, NumExt, Pos2, Rect, Vec2};
 pub use epaint::{
-    color, mutex,
+    color, mutex, shape,
     text::{FontData, FontDefinitions, FontFamily, FontId, FontTweak},
     textures::TexturesDelta,
     AlphaImage, ClippedMesh, Color32, ColorImage, ImageData, Mesh, Rgba, Rounding, Shape, Stroke,

egui_glium/src/painter.rs

@@ -1,6 +1,8 @@
 #![allow(deprecated)] // legacy implement_vertex macro
 #![allow(semicolon_in_expressions_from_macros)] // glium::program! macro
 
+use egui::epaint::MeshOrCallback;
+
 use {
     ahash::AHashMap,
     egui::{emath::Rect, epaint::Mesh},
@@ -94,8 +96,19 @@ impl Painter {
         pixels_per_point: f32,
         clipped_meshes: Vec<egui::ClippedMesh>,
     ) {
-        for egui::ClippedMesh(clip_rect, mesh) in clipped_meshes {
-            self.paint_mesh(target, display, pixels_per_point, clip_rect, &mesh);
+        for egui::ClippedMesh {
+            clip_rect,
+            mesh_or_callback,
+        } in clipped_meshes
+        {
+            match mesh_or_callback {
+                MeshOrCallback::Mesh(mesh) => {
+                    self.paint_mesh(target, display, pixels_per_point, clip_rect, &mesh);
+                }
+                MeshOrCallback::Callback(_) => {
+                    panic!("Custom rendering callbacks are not implemented in egui_glium");
+                }
+            }
         }
     }