From af11d766fcfb1c5c90303b0e4f7f07734e450a19 Mon Sep 17 00:00:00 2001
From: Emil Ernerfeldt <emilernerfeldt@gmail.com>
Date: Sat, 7 Nov 2020 11:44:32 +0100
Subject: [PATCH] Split out tesselation from Context::end_frame()

---
 CHANGELOG.md                  |  1 +
 README.md                     |  3 ++-
 egui/benches/benchmark.rs     | 15 ++++++++++++++-
 egui/src/context.rs           | 34 +++++++++++++++++++---------------
 egui/src/lib.rs               |  6 ++++--
 egui/src/paint/mod.rs         |  4 +++-
 egui/src/paint/tessellator.rs | 19 ++++++++++++-------
 egui_glium/src/backend.rs     |  3 ++-
 egui_web/src/backend.rs       |  3 ++-
 9 files changed, 59 insertions(+), 29 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3135943f..1aab8513 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@
 * You can no longer throw windows
 * `Context::begin_frame()` no longer returns anything.
   * Put your widgets into a `SidePanel`, `TopPanel`, `CentralPanel`, `Window` or `Area`.
+* `Context::end_frame()` now returns "paint jobs" that need to be converted to triangles with `Context::tesselate()`.
 
 ## 0.2.0 - 2020-10-10
 
diff --git a/README.md b/README.md
index 5fd90c12..8593be9c 100644
--- a/README.md
+++ b/README.md
@@ -154,7 +154,8 @@ loop {
     let raw_input: egui::RawInput = my_integration.gather_input();
     egui_ctx.begin_frame(raw_input);
     my_app.ui(&mut egui_ctx); // add panels, windows and widgets to `egui_ctx` here
-    let (output, paint_jobs) = egui_ctx.end_frame();
+    let (output, paint_commands) = egui_ctx.end_frame();
+    let paint_jobs = self.ctx.tesselate(paint_commands); // create triangles to paint
     my_integration.paint(paint_jobs);
     my_integration.set_cursor_icon(output.cursor_icon);
     // Also see `egui::Output` for more
diff --git a/egui/benches/benchmark.rs b/egui/benches/benchmark.rs
index 763bab74..aa49a73a 100644
--- a/egui/benches/benchmark.rs
+++ b/egui/benches/benchmark.rs
@@ -33,6 +33,19 @@ pub fn criterion_benchmark(c: &mut Criterion) {
         });
     }
 
+    {
+        let mut ctx = egui::Context::new();
+        ctx.memory().all_collpasing_are_open = true; // expand the demo window with everything
+        let mut demo_windows = egui::demos::DemoWindows::default();
+        ctx.begin_frame(raw_input.clone());
+        demo_windows.ui(&ctx, &Default::default(), &mut None);
+        let (_, paint_commands) = ctx.end_frame();
+
+        c.bench_function("tesselate", |b| {
+            b.iter(|| ctx.tesselate(paint_commands.clone()))
+        });
+    }
+
     {
         let mut ctx = egui::Context::new();
         ctx.begin_frame(raw_input);
@@ -43,7 +56,7 @@ pub fn criterion_benchmark(c: &mut Criterion) {
                 })
             });
         });
-        // let _ = ctx.end_frame(); // skip, because tessellating all that text is slow
+        let _ = ctx.end_frame();
     }
 }
 
diff --git a/egui/src/context.rs b/egui/src/context.rs
index cbfd47c9..0ebcb07f 100644
--- a/egui/src/context.rs
+++ b/egui/src/context.rs
@@ -20,7 +20,7 @@ struct Options {
     /// The default style for new `Ui`:s.
     style: Arc<Style>,
     /// Controls the tessellator.
-    paint_options: paint::PaintOptions,
+    tesselation_options: paint::TesselationOptions,
     /// Font sizes etc.
     font_definitions: FontDefinitions,
 }
@@ -242,8 +242,10 @@ impl Context {
 
     /// Call at the end of each frame.
     /// Returns what has happened this frame (`Output`) as well as what you need to paint.
+    /// You can transform the returned paint commands into triangles with a call to
+    /// `Context::tesselate`.
     #[must_use]
-    pub fn end_frame(&self) -> (Output, PaintJobs) {
+    pub fn end_frame(&self) -> (Output, Vec<(Rect, PaintCmd)>) {
         if self.input.wants_repaint() {
             self.request_repaint();
         }
@@ -256,8 +258,8 @@ impl Context {
             output.needs_repaint = true;
         }
 
-        let paint_jobs = self.paint();
-        (output, paint_jobs)
+        let paint_commands = self.drain_paint_lists();
+        (output, paint_commands)
     }
 
     fn drain_paint_lists(&self) -> Vec<(Rect, PaintCmd)> {
@@ -265,15 +267,17 @@ impl Context {
         self.graphics().drain(memory.areas.order()).collect()
     }
 
-    fn paint(&self) -> PaintJobs {
-        let mut paint_options = self.options.lock().paint_options;
-        paint_options.aa_size = 1.0 / self.pixels_per_point();
-        let paint_commands = self.drain_paint_lists();
+    /// Tesselate the given paint commands into triangle meshes.
+    pub fn tesselate(&self, paint_commands: Vec<(Rect, PaintCmd)>) -> PaintJobs {
+        let mut tesselation_options = self.options.lock().tesselation_options;
+        tesselation_options.aa_size = 1.0 / self.pixels_per_point();
         let paint_stats = PaintStats::from_paint_commands(&paint_commands); // TODO: internal allocations
-        let paint_jobs =
-            tessellator::tessellate_paint_commands(paint_commands, paint_options, self.fonts());
+        let paint_jobs = tessellator::tessellate_paint_commands(
+            paint_commands,
+            tesselation_options,
+            self.fonts(),
+        );
         *self.paint_stats.lock() = paint_stats.with_paint_jobs(&paint_jobs);
-
         paint_jobs
     }
 
@@ -591,9 +595,9 @@ impl Context {
         CollapsingHeader::new("Painting")
             .default_open(true)
             .show(ui, |ui| {
-                let mut paint_options = self.options.lock().paint_options;
-                paint_options.ui(ui);
-                self.options.lock().paint_options = paint_options;
+                let mut tesselation_options = self.options.lock().tesselation_options;
+                tesselation_options.ui(ui);
+                self.options.lock().tesselation_options = tesselation_options;
             });
     }
 
@@ -708,7 +712,7 @@ impl Context {
     }
 }
 
-impl paint::PaintOptions {
+impl paint::TesselationOptions {
     pub fn ui(&mut self, ui: &mut Ui) {
         let Self {
             aa_size: _,
diff --git a/egui/src/lib.rs b/egui/src/lib.rs
index f31d1a12..682cd460 100644
--- a/egui/src/lib.rs
+++ b/egui/src/lib.rs
@@ -26,7 +26,8 @@
 //!     let raw_input: egui::RawInput = my_integration.gather_input();
 //!     egui_ctx.begin_frame(raw_input);
 //!     my_app.ui(&egui_ctx); // add panels, windows and widgets to `egui_ctx` here
-//!     let (output, paint_jobs) = egui_ctx.end_frame();
+//!     let (output, paint_commands) = egui_ctx.end_frame();
+//!     let paint_jobs = self.ctx.tesselate(paint_commands); // create triangles to paint
 //!     my_integration.paint(paint_jobs);
 //!     my_integration.set_cursor_icon(output.cursor_icon);
 //!     // Also see `egui::Output` for more
@@ -116,7 +117,8 @@ pub fn text_egui_e2e() {
     for _ in 0..NUM_FRAMES {
         ctx.begin_frame(raw_input.clone());
         demo_windows.ui(&ctx, &Default::default(), &mut None);
-        let (_output, paint_jobs) = ctx.end_frame();
+        let (_output, paint_commands) = ctx.end_frame();
+        let paint_jobs = ctx.tesselate(paint_commands);
         assert!(!paint_jobs.is_empty());
     }
 }
diff --git a/egui/src/paint/mod.rs b/egui/src/paint/mod.rs
index 39465431..6c87d7e8 100644
--- a/egui/src/paint/mod.rs
+++ b/egui/src/paint/mod.rs
@@ -15,6 +15,8 @@ pub use {
     command::{PaintCmd, Stroke},
     fonts::{FontDefinitions, FontFamily, Fonts, TextStyle},
     stats::PaintStats,
-    tessellator::{PaintJob, PaintJobs, PaintOptions, TextureId, Triangles, Vertex, WHITE_UV},
+    tessellator::{
+        PaintJob, PaintJobs, TesselationOptions, TextureId, Triangles, Vertex, WHITE_UV,
+    },
     texture_atlas::Texture,
 };
diff --git a/egui/src/paint/tessellator.rs b/egui/src/paint/tessellator.rs
index bb0ab574..4f3f6eef 100644
--- a/egui/src/paint/tessellator.rs
+++ b/egui/src/paint/tessellator.rs
@@ -446,7 +446,7 @@ use self::PathType::{Closed, Open};
 
 /// Tesselation quality options
 #[derive(Clone, Copy, Debug)]
-pub struct PaintOptions {
+pub struct TesselationOptions {
     /// Size of a pixel in points, e.g. 0.5
     pub aa_size: f32,
     /// Anti-aliasing makes shapes appear smoother, but requires more triangles and is therefore slower.
@@ -459,20 +459,25 @@ pub struct PaintOptions {
     pub debug_ignore_clip_rects: bool,
 }
 
-impl Default for PaintOptions {
+impl Default for TesselationOptions {
     fn default() -> Self {
         Self {
             aa_size: 1.0,
             anti_alias: true,
+            coarse_tessellation_culling: true,
             debug_paint_clip_rects: false,
             debug_ignore_clip_rects: false,
-            coarse_tessellation_culling: true,
         }
     }
 }
 
 /// Tesselate the given convex area into a polygon.
-fn fill_closed_path(path: &[PathPoint], color: Srgba, options: PaintOptions, out: &mut Triangles) {
+fn fill_closed_path(
+    path: &[PathPoint],
+    color: Srgba,
+    options: TesselationOptions,
+    out: &mut Triangles,
+) {
     if color == color::TRANSPARENT {
         return;
     }
@@ -516,7 +521,7 @@ fn stroke_path(
     path: &[PathPoint],
     path_type: PathType,
     stroke: Stroke,
-    options: PaintOptions,
+    options: TesselationOptions,
     out: &mut Triangles,
 ) {
     if stroke.width <= 0.0 || stroke.color == color::TRANSPARENT {
@@ -669,7 +674,7 @@ fn mul_color(color: Srgba, factor: f32) -> Srgba {
 fn tessellate_paint_command(
     clip_rect: Rect,
     command: PaintCmd,
-    options: PaintOptions,
+    options: TesselationOptions,
     fonts: &Fonts,
     out: &mut Triangles,
     scratchpad_points: &mut Vec<Pos2>,
@@ -833,7 +838,7 @@ fn tessellate_paint_command(
 /// A list of clip rectangles with matching `Triangles`.
 pub fn tessellate_paint_commands(
     commands: Vec<(Rect, PaintCmd)>,
-    options: PaintOptions,
+    options: TesselationOptions,
     fonts: &Fonts,
 ) -> Vec<(Rect, Triangles)> {
     let mut scratchpad_points = Vec::new();
diff --git a/egui_glium/src/backend.rs b/egui_glium/src/backend.rs
index e077bf4a..998273c6 100644
--- a/egui_glium/src/backend.rs
+++ b/egui_glium/src/backend.rs
@@ -89,7 +89,8 @@ pub fn run(
             };
             app.ui(&ctx, &mut integration_context);
             let app_output = integration_context.output;
-            let (egui_output, paint_jobs) = ctx.end_frame();
+            let (egui_output, paint_commands) = ctx.end_frame();
+            let paint_jobs = ctx.tesselate(paint_commands);
 
             let frame_time = (Instant::now() - egui_start).as_secs_f64() as f32;
             previous_frame_time = Some(frame_time);
diff --git a/egui_web/src/backend.rs b/egui_web/src/backend.rs
index 1e3bd7ae..8c8b1bb1 100644
--- a/egui_web/src/backend.rs
+++ b/egui_web/src/backend.rs
@@ -44,7 +44,8 @@ impl WebBackend {
             .take()
             .expect("unmatched calls to begin_frame/end_frame");
 
-        let (output, paint_jobs) = self.ctx.end_frame();
+        let (output, paint_commands) = self.ctx.end_frame();
+        let paint_jobs = self.ctx.tesselate(paint_commands);
 
         self.auto_save();