Add Null backend to anyrender crate

Author: nicoburns

crates/anyrender/src/lib.rs

@@ -35,6 +35,8 @@ pub mod wasm_send_sync;
 pub use wasm_send_sync::*;
 pub mod types;
 pub use types::*;
+mod null_backend;
+pub use null_backend::*;
 
 /// Abstraction for rendering a scene to a window
 pub trait WindowRenderer {

crates/anyrender/src/null_backend.rs

@@ -0,0 +1,140 @@
+//! A dummy implementation of the AnyRender traits while simply ignores all commands
+
+use crate::{ImageRenderer, PaintScene, WindowHandle, WindowRenderer};
+use std::sync::Arc;
+
+#[derive(Copy, Clone, Default)]
+pub struct NullWindowRenderer {
+    is_active: bool,
+}
+
+impl NullWindowRenderer {
+    pub fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl WindowRenderer for NullWindowRenderer {
+    type ScenePainter<'a>
+        = NullScenePainter
+    where
+        Self: 'a;
+
+    fn resume(&mut self, _window: Arc<dyn WindowHandle>, _width: u32, _height: u32) {
+        self.is_active = true;
+    }
+
+    fn suspend(&mut self) {
+        self.is_active = false
+    }
+
+    fn is_active(&self) -> bool {
+        self.is_active
+    }
+
+    fn set_size(&mut self, _width: u32, _height: u32) {}
+
+    fn render<F: FnOnce(&mut Self::ScenePainter<'_>)>(&mut self, _draw_fn: F) {}
+}
+
+#[derive(Copy, Clone, Default)]
+pub struct NullImageRenderer;
+
+impl NullImageRenderer {
+    pub fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl ImageRenderer for NullImageRenderer {
+    type ScenePainter<'a>
+        = NullScenePainter
+    where
+        Self: 'a;
+
+    fn new(_width: u32, _height: u32) -> Self {
+        Self
+    }
+
+    fn resize(&mut self, _width: u32, _height: u32) {}
+
+    fn reset(&mut self) {}
+
+    fn render_to_vec<F: FnOnce(&mut Self::ScenePainter<'_>)>(
+        &mut self,
+        _draw_fn: F,
+        _vec: &mut Vec<u8>,
+    ) {
+    }
+
+    fn render<F: FnOnce(&mut Self::ScenePainter<'_>)>(&mut self, _draw_fn: F, _buffer: &mut [u8]) {}
+}
+
+#[derive(Copy, Clone, Default)]
+pub struct NullScenePainter;
+
+impl NullScenePainter {
+    pub fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl PaintScene for NullScenePainter {
+    fn reset(&mut self) {}
+
+    fn push_layer(
+        &mut self,
+        _blend: impl Into<peniko::BlendMode>,
+        _alpha: f32,
+        _transform: kurbo::Affine,
+        _clip: &impl kurbo::Shape,
+    ) {
+    }
+
+    fn pop_layer(&mut self) {}
+
+    fn stroke<'a>(
+        &mut self,
+        _style: &kurbo::Stroke,
+        _transform: kurbo::Affine,
+        _brush: impl Into<crate::PaintRef<'a>>,
+        _brush_transform: Option<kurbo::Affine>,
+        _shape: &impl kurbo::Shape,
+    ) {
+    }
+
+    fn fill<'a>(
+        &mut self,
+        _style: peniko::Fill,
+        _transform: kurbo::Affine,
+        _brush: impl Into<crate::PaintRef<'a>>,
+        _brush_transform: Option<kurbo::Affine>,
+        _shape: &impl kurbo::Shape,
+    ) {
+    }
+
+    fn draw_glyphs<'a, 's: 'a>(
+        &'s mut self,
+        _font: &'a peniko::FontData,
+        _font_size: f32,
+        _hint: bool,
+        _normalized_coords: &'a [crate::NormalizedCoord],
+        _style: impl Into<peniko::StyleRef<'a>>,
+        _brush: impl Into<crate::PaintRef<'a>>,
+        _brush_alpha: f32,
+        _transform: kurbo::Affine,
+        _glyph_transform: Option<kurbo::Affine>,
+        _glyphs: impl Iterator<Item = crate::Glyph>,
+    ) {
+    }
+
+    fn draw_box_shadow(
+        &mut self,
+        _transform: kurbo::Affine,
+        _rect: kurbo::Rect,
+        _brush: peniko::Color,
+        _radius: f64,
+        _std_dev: f64,
+    ) {
+    }
+}