Split Image handling from handwriting/mod.rs

src/handwriting/canvas_rasterizer.rs

@@ -0,0 +1,81 @@
+use std::sync::Arc;
+
+use egui::{
+    Color32, ColorImage, CornerRadius, Painter, Pos2, Rect, Stroke, StrokeKind, TextureHandle,
+    emath::TSTransform,
+    epaint::{Brush, RectShape, Vertex},
+    load::SizedTexture,
+};
+
+use crate::rasterizer::rasterize_onto;
+
+use super::StrokeBlendMode;
+
+/// Rasterize onto a resizeable canvas.
+#[derive(Default)]
+pub struct CanvasRasterizer {
+    image: ColorImage,
+    texture: Option<TextureHandle>,
+    texture_is_dirty: bool,
+}
+
+impl CanvasRasterizer {
+    //pub fn clear(&mut self) {
+    //    self.image = ColorImage::new(self.image.size, Color32::TRANSPARENT);
+    //    self.texture_is_dirty = true;
+    //}
+
+    //pub fn set_size(&mut self, width: usize, height: usize) {
+    //    if self.image.size != [width, height] {
+    //        self.image = ColorImage::new([width, height], Color32::TRANSPARENT);
+    //        self.texture_is_dirty = true;
+    //    }
+    //}
+
+    pub fn clear_and_set_size(&mut self, width: usize, height: usize) {
+        self.image = ColorImage::new([width, height], Color32::TRANSPARENT);
+        self.texture_is_dirty = true;
+    }
+
+    pub fn rasterize<'a>(
+        &mut self,
+        point_to_pixel: TSTransform,
+        triangles: impl Iterator<Item = [&'a Vertex; 3]>,
+    ) {
+        rasterize_onto::<StrokeBlendMode>(&mut self.image, point_to_pixel, triangles);
+        self.texture_is_dirty = true;
+    }
+
+    pub fn show(&mut self, ctx: &egui::Context, painter: &Painter, at: Rect) {
+        if self.texture_is_dirty {
+            self.texture_is_dirty = false;
+            let new_image = || {
+                let image = ColorImage::new(self.image.size, Color32::TRANSPARENT);
+                ctx.load_texture("handwriting", image, Default::default())
+            };
+            let texture = self.texture.get_or_insert_with(new_image);
+            texture.set(self.image.clone(), Default::default());
+        }
+
+        if let Some(texture) = &mut self.texture {
+            let texture = SizedTexture::new(texture.id(), texture.size_vec2());
+            let shape = RectShape {
+                rect: at,
+                corner_radius: CornerRadius::ZERO,
+                fill: Color32::WHITE,
+                stroke: Stroke::NONE,
+                stroke_kind: StrokeKind::Inside,
+                round_to_pixels: None,
+                blur_width: 0.0,
+                brush: Some(Arc::new(Brush {
+                    fill_texture_id: texture.id,
+                    uv: Rect {
+                        min: Pos2::ZERO,
+                        max: Pos2::new(1.0, 1.0),
+                    },
+                })),
+            };
+            painter.add(shape);
+        }
+    }
+}