feat: crop history and fitting in the editor

src/editor/doc.rs

@@ -1,13 +1,22 @@
-//! The edit history: the shapes drawn so far, what undo took away, and
-//! what was last saved.
+//! The edit history: what was drawn and cropped so far, what undo took
+//! away, and what was last saved.
 
-use crate::editor::shape::Shape;
+use crate::editor::shape::{Shape, Tool};
+use crate::frame::PixelRect;
+
+/// One step of the history.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Item {
+    Shape(Shape),
+    /// Show and export only this part of the image (image pixels).
+    Crop(PixelRect),
+}
 
 #[derive(Debug, Default)]
 pub struct Doc {
-    shapes: Vec<Shape>,
-    redo: Vec<Shape>,
-    saved: Vec<Shape>,
+    items: Vec<Item>,
+    redo: Vec<Item>,
+    saved: Vec<Item>,
     revision: u64,
 }
 
@@ -16,54 +25,82 @@ impl Doc {
         Doc::default()
     }
 
-    pub fn shapes(&self) -> &[Shape] {
-        &self.shapes
+    pub fn shapes(&self) -> impl Iterator<Item = &Shape> {
+        self.items.iter().filter_map(|i| match i {
+            Item::Shape(s) => Some(s),
+            Item::Crop(_) => None,
+        })
+    }
+
+    /// The last crop, if any.
+    pub fn crop(&self) -> Option<PixelRect> {
+        self.items.iter().rev().find_map(|i| match i {
+            Item::Crop(r) => Some(*r),
+            Item::Shape(_) => None,
+        })
+    }
+
+    /// The number the next Number shape shows.
+    // Used by the editor from Task 4 of the 5b plan on; that task removes this.
+    #[allow(dead_code)]
+    pub fn next_number(&self) -> u32 {
+        1 + self.shapes().filter(|s| s.tool == Tool::Number).count() as u32
     }
 
     pub fn add(&mut self, shape: Shape) {
-        self.shapes.push(shape);
+        self.push(Item::Shape(shape));
+    }
+
+    // Used by the editor from Task 4 of the 5b plan on; that task removes this.
+    #[allow(dead_code)]
+    pub fn add_crop(&mut self, rect: PixelRect) {
+        self.push(Item::Crop(rect));
+    }
+
+    fn push(&mut self, item: Item) {
+        self.items.push(item);
         self.redo.clear();
         self.revision += 1;
     }
 
     pub fn undo(&mut self) -> bool {
-        let Some(shape) = self.shapes.pop() else {
+        let Some(item) = self.items.pop() else {
             return false;
         };
-        self.redo.push(shape);
+        self.redo.push(item);
         self.revision += 1;
         true
     }
 
     pub fn redo(&mut self) -> bool {
-        let Some(shape) = self.redo.pop() else {
+        let Some(item) = self.redo.pop() else {
             return false;
         };
-        self.shapes.push(shape);
+        self.items.push(item);
         self.revision += 1;
         true
     }
 
-    /// Changes whenever the drawn shapes do.
+    /// Changes whenever the drawn shapes or the crop do.
     pub fn revision(&self) -> u64 {
         self.revision
     }
 
     pub fn can_undo(&self) -> bool {
-        !self.shapes.is_empty()
+        !self.items.is_empty()
     }
 
     pub fn can_redo(&self) -> bool {
         !self.redo.is_empty()
     }
 
-    /// Whether the shapes differ from what was last saved.
+    /// Whether the history differs from what was last saved.
     pub fn is_dirty(&self) -> bool {
-        self.shapes != self.saved
+        self.items != self.saved
     }
 
     pub fn mark_saved(&mut self) {
-        self.saved = self.shapes.clone();
+        self.saved = self.items.clone();
     }
 }
 
@@ -71,6 +108,7 @@ impl Doc {
 mod tests {
     use super::*;
     use crate::editor::shape::{Style, Tool};
+    use crate::frame::PixelRect;
 
     fn line(x: f32) -> Shape {
         Shape {
@@ -91,9 +129,12 @@ mod tests {
         d.add(line(1.0));
         d.add(line(2.0));
         assert!(d.undo());
-        assert_eq!(d.shapes(), &[line(1.0)]);
+        assert_eq!(d.shapes().cloned().collect::<Vec<_>>(), [line(1.0)]);
         assert!(d.redo());
-        assert_eq!(d.shapes(), &[line(1.0), line(2.0)]);
+        assert_eq!(
+            d.shapes().cloned().collect::<Vec<_>>(),
+            [line(1.0), line(2.0)]
+        );
         assert!(!d.redo());
     }
 
@@ -122,7 +163,7 @@ mod tests {
         d.undo();
         d.add(line(3.0));
         assert!(!d.can_redo());
-        assert_eq!(d.shapes(), &[line(3.0)]);
+        assert_eq!(d.shapes().cloned().collect::<Vec<_>>(), [line(3.0)]);
     }
 
     #[test]
@@ -145,4 +186,66 @@ mod tests {
         d.redo();
         assert!(!d.is_dirty(), "back to the saved content");
     }
+
+    fn number(n: &str) -> Shape {
+        Shape {
+            tool: Tool::Number,
+            style: Style {
+                color: [0, 0, 0],
+                width: 4.0,
+            },
+            points: vec![(1.0, 1.0)],
+            text: n.into(),
+        }
+    }
+
+    const R: PixelRect = PixelRect {
+        x: 1,
+        y: 2,
+        width: 30,
+        height: 20,
+    };
+
+    #[test]
+    fn numbers_count_only_numbers_and_follow_undo() {
+        let mut d = Doc::new();
+        assert_eq!(d.next_number(), 1);
+        d.add(number("1"));
+        d.add(line(5.0));
+        d.add(number("2"));
+        assert_eq!(d.next_number(), 3);
+        d.undo();
+        assert_eq!(d.next_number(), 2);
+    }
+
+    #[test]
+    fn crops_are_undoable_and_nest() {
+        let mut d = Doc::new();
+        assert_eq!(d.crop(), None);
+        d.add_crop(R);
+        let inner = PixelRect {
+            x: 5,
+            y: 5,
+            width: 10,
+            height: 10,
+        };
+        d.add_crop(inner);
+        assert_eq!(d.crop(), Some(inner));
+        d.undo();
+        assert_eq!(d.crop(), Some(R));
+        d.undo();
+        assert_eq!(d.crop(), None);
+        d.redo();
+        assert_eq!(d.crop(), Some(R));
+    }
+
+    #[test]
+    fn crops_make_the_doc_dirty_and_skip_shapes() {
+        let mut d = Doc::new();
+        d.add(line(1.0));
+        d.mark_saved();
+        d.add_crop(R);
+        assert!(d.is_dirty());
+        assert_eq!(d.shapes().count(), 1);
+    }
 }

src/editor/export.rs

@@ -31,8 +31,6 @@ pub fn render<'a>(base: &RgbaImage, shapes: impl IntoIterator<Item = &'a Shape>)
 }
 
 /// The part of `image` inside the last crop, or all of it.
-// The editor calls this from Task 3 of the 5b plan on; that task removes this.
-#[allow(dead_code)]
 pub fn crop(image: RgbaImage, rect: Option<PixelRect>) -> RgbaImage {
     match rect {
         Some(r) => image::imageops::crop_imm(&image, r.x, r.y, r.width, r.height).to_image(),

src/editor/mod.rs

@@ -16,6 +16,8 @@ use eframe::egui::{
 };
 use image::RgbaImage;
 
+use crate::frame::PixelRect;
+
 use self::doc::Doc;
 use self::shape::{Drag, PALETTE, Prim, Style, Tool, WIDTHS, geometry};
 use self::view::Fit;
@@ -105,7 +107,8 @@ impl Editor {
     }
 
     fn png(&self) -> Result<Vec<u8>> {
-        crate::output::encode_png(&export::render(&self.base, self.doc.shapes()))
+        let image = export::render(&self.base, self.doc.shapes());
+        crate::output::encode_png(&export::crop(image, self.doc.crop()))
     }
 
     fn save(&mut self, copy: bool) -> bool {
@@ -293,8 +296,14 @@ impl Editor {
         let area = ui.max_rect();
         let (response, painter) = ui.allocate_painter(area.size(), Sense::drag());
         let size = self.base.dimensions();
-        let fit = Fit::new(
-            size,
+        let shown = self.doc.crop().unwrap_or(PixelRect {
+            x: 0,
+            y: 0,
+            width: size.0,
+            height: size.1,
+        });
+        let fit = Fit::with_crop(
+            shown,
             (area.min.x, area.min.y, area.width(), area.height()),
             ui.ctx().pixels_per_point(),
         );
@@ -302,12 +311,14 @@ impl Editor {
             let (x, y) = fit.to_screen(p);
             Pos2::new(x, y)
         };
-        let image_rect =
-            Rect::from_min_max(to_pos((0.0, 0.0)), to_pos((size.0 as f32, size.1 as f32)));
+        let (x0, y0) = (shown.x as f32, shown.y as f32);
+        let (x1, y1) = (x0 + shown.width as f32, y0 + shown.height as f32);
+        let image_rect = Rect::from_min_max(to_pos((x0, y0)), to_pos((x1, y1)));
+        let (w, h) = (size.0 as f32, size.1 as f32);
         painter.image(
             self.texture.id(),
             image_rect,
-            Rect::from_min_max(Pos2::ZERO, Pos2::new(1.0, 1.0)),
+            Rect::from_min_max(Pos2::new(x0 / w, y0 / h), Pos2::new(x1 / w, y1 / h)),
             Color32::WHITE,
         );
 
@@ -330,7 +341,7 @@ impl Editor {
             self.drag = Some(Drag::new(self.tool, self.style(), p));
         }
         if let (Some(drag), Some(p)) = (&mut self.drag, pointer) {
-            drag.move_to(view::clamp(p, size));
+            drag.move_to(view::clamp(p, shown));
         }
         if response.drag_stopped()
             && let Some(drag) = self.drag.take()

src/editor/view.rs

@@ -1,20 +1,36 @@
-//! Fitting the image into the canvas: image pixels ↔ egui points.
+//! Fitting the image (or its crop) into the canvas: image pixels ↔ egui
+//! points.
 
 use crate::editor::shape::P;
+use crate::frame::PixelRect;
 
 #[derive(Debug, Clone, Copy, PartialEq)]
 pub struct Fit {
     /// Points per image pixel.
     pub scale: f32,
-    /// Where the image's top-left corner is, in points.
+    /// Where `origin` is drawn, in points.
     pub offset: P,
+    /// The image pixel at the top-left of what is shown (the crop's corner).
+    pub origin: P,
 }
 
 impl Fit {
-    /// Fits `image` into `area` (x, y, w, h in points), centred, never
-    /// above 100 % (one image pixel per physical pixel).
+    /// Fits the whole image; see `with_crop`.
+    #[cfg(test)]
     pub fn new(image: (u32, u32), area: (f32, f32, f32, f32), pixels_per_point: f32) -> Fit {
-        let (iw, ih) = (image.0 as f32, image.1 as f32);
+        let whole = PixelRect {
+            x: 0,
+            y: 0,
+            width: image.0,
+            height: image.1,
+        };
+        Fit::with_crop(whole, area, pixels_per_point)
+    }
+
+    /// Fits `crop` into `area` (x, y, w, h in points), centred, never above
+    /// 100 % (one image pixel per physical pixel).
+    pub fn with_crop(crop: PixelRect, area: (f32, f32, f32, f32), pixels_per_point: f32) -> Fit {
+        let (iw, ih) = (crop.width as f32, crop.height as f32);
         let (x, y, w, h) = area;
         let scale = (w / iw).min(h / ih).min(1.0 / pixels_per_point);
         // Centred, then onto a physical pixel boundary so that at 100 % each
@@ -26,29 +42,30 @@ impl Fit {
                 snap(x + (w - iw * scale) / 2.0),
                 snap(y + (h - ih * scale) / 2.0),
             ),
+            origin: (crop.x as f32, crop.y as f32),
         }
     }
 
     pub fn to_screen(self, p: P) -> P {
         (
-            self.offset.0 + p.0 * self.scale,
-            self.offset.1 + p.1 * self.scale,
+            self.offset.0 + (p.0 - self.origin.0) * self.scale,
+            self.offset.1 + (p.1 - self.origin.1) * self.scale,
         )
     }
 
     pub fn to_image(self, p: P) -> P {
         (
-            (p.0 - self.offset.0) / self.scale,
-            (p.1 - self.offset.1) / self.scale,
+            (p.0 - self.offset.0) / self.scale + self.origin.0,
+            (p.1 - self.offset.1) / self.scale + self.origin.1,
         )
     }
 }
 
-/// `p` moved onto the image's area.
-pub fn clamp(p: P, image: (u32, u32)) -> P {
+/// `p` moved into `rect`.
+pub fn clamp(p: P, rect: PixelRect) -> P {
     (
-        p.0.clamp(0.0, image.0 as f32),
-        p.1.clamp(0.0, image.1 as f32),
+        p.0.clamp(rect.x as f32, (rect.x + rect.width) as f32),
+        p.1.clamp(rect.y as f32, (rect.y + rect.height) as f32),
     )
 }
 
@@ -103,7 +120,48 @@ mod tests {
 
     #[test]
     fn clamp_keeps_points_on_the_image() {
-        assert_eq!(clamp((-5.0, 50.0), (100, 80)), (0.0, 50.0));
-        assert_eq!(clamp((150.0, 90.0), (100, 80)), (100.0, 80.0));
+        let r = PixelRect {
+            x: 0,
+            y: 0,
+            width: 100,
+            height: 80,
+        };
+        assert_eq!(clamp((-5.0, 50.0), r), (0.0, 50.0));
+        assert_eq!(clamp((150.0, 90.0), r), (100.0, 80.0));
+    }
+
+    #[test]
+    fn a_crop_fills_the_area() {
+        let crop = PixelRect {
+            x: 100,
+            y: 50,
+            width: 200,
+            height: 100,
+        };
+        let f = Fit::with_crop(crop, (0.0, 0.0, 400.0, 400.0), 1.0);
+        assert_eq!(f.scale, 1.0);
+        assert_eq!(
+            f.to_screen((100.0, 50.0)),
+            (100.0, 150.0),
+            "the crop's corner is centred"
+        );
+    }
+
+    #[test]
+    fn round_trip_with_a_crop() {
+        let crop = PixelRect {
+            x: 640,
+            y: 360,
+            width: 640,
+            height: 360,
+        };
+        let f = Fit::with_crop(crop, (0.0, 30.0, 500.0, 400.0), 1.0);
+        for p in [(640.0, 360.0), (1279.0, 719.0), (800.5, 400.25)] {
+            let q = f.to_image(f.to_screen(p));
+            assert!(
+                (q.0 - p.0).abs() < 1e-3 && (q.1 - p.1).abs() < 1e-3,
+                "{p:?} {q:?}"
+            );
+        }
     }
 }