src/canvas.rs

@@ -0,0 +1,88 @@
+#[derive(Clone, druid::Data)]
+pub struct Path {
+    pub kurbo_path: druid::kurbo::BezPath,
+}
+
+#[derive(Clone, druid::Data)]
+pub enum CanvasElement {
+    Freehand { path: Path, thickness: f64 },
+}
+
+impl CanvasElement {
+    pub fn bounding_box(&self) -> druid::Rect {
+        match self {
+            CanvasElement::Freehand { path, thickness } => {
+                use druid::kurbo::Shape;
+                path.kurbo_path
+                    .bounding_box()
+                    .inflate(*thickness, *thickness)
+            }
+        }
+    }
+    pub fn draw(&self, ctx: &mut druid::PaintCtx) {
+        match self {
+            CanvasElement::Freehand { path, thickness } => {
+                use druid::RenderContext;
+                let stroke_color = druid::Color::rgb8(0, 128, 0);
+                ctx.stroke(&path.kurbo_path, &stroke_color, *thickness);
+            }
+        }
+    }
+
+    pub fn get_path_mut(&mut self) -> Option<&mut Path> {
+        match self {
+            CanvasElement::Freehand { path, .. } => Some(path),
+        }
+    }
+}
+
+// O(1) complexity
+fn segment_intersects_rect(segment: &druid::kurbo::PathSeg, rect: druid::Rect) -> bool {
+    match segment {
+        druid::kurbo::PathSeg::Line(line) => rect.contains(line.p0) || rect.contains(line.p1),
+
+        druid::kurbo::PathSeg::Quad(quad) => {
+            rect.contains(quad.p0) || rect.contains(quad.p1) || rect.contains(quad.p2)
+        }
+
+        druid::kurbo::PathSeg::Cubic(cubic) => {
+            rect.contains(cubic.p0) || rect.contains(cubic.p1) || rect.contains(cubic.p2)
+        }
+    }
+}
+
+// A canvas contains all elements to be drawn
+#[derive(Clone, druid::Data)]
+pub struct Canvas {
+    pub elements: im::Vector<CanvasElement>,
+}
+
+impl Canvas {
+    pub fn new() -> Canvas {
+        Canvas {
+            elements: im::vector![],
+        }
+    }
+    // O(n) complexity, where n is the number of segments belonging to paths
+    // that intersect the eraser rectangle
+    pub fn erase(&mut self, eraser_rect: druid::Rect) {
+        for elem in self.elements.iter_mut() {
+            if elem.bounding_box().intersect(eraser_rect).area() > 0.0 {
+                match elem {
+                    CanvasElement::Freehand { path, thickness: _ } => {
+                        // Remove segments intersecting the eraser
+                        let new_segments = (*path)
+                            .kurbo_path
+                            .segments()
+                            .filter(|path| !segment_intersects_rect(path, eraser_rect));
+                        path.kurbo_path = druid::kurbo::BezPath::from_path_segments(new_segments);
+                    }
+                }
+            }
+        }
+    }
+
+    pub fn push_back(&mut self, element: CanvasElement) {
+        self.elements.push_back(element);
+    }
+}

src/canvas_tools.rs

@@ -0,0 +1,118 @@
+use crate::canvas::*;
+use crate::versioned_canvas::VersionedCanvas;
+
+use druid::kurbo::BezPath;
+use druid::{Data, Event, Rect};
+
+// Tools that can be used to interact with the canvas
+#[derive(Clone, Data)]
+pub enum CanvasTool {
+    Pen {
+        current_element: Option<CanvasElement>,
+    },
+    Eraser {
+        eraser_rect: Option<Rect>,
+    },
+}
+
+impl CanvasTool {
+    pub fn new_pen() -> CanvasTool {
+        CanvasTool::Pen {
+            current_element: None,
+        }
+    }
+
+    pub fn new_eraser() -> CanvasTool {
+        CanvasTool::Eraser { eraser_rect: None }
+    }
+
+    pub fn handle_event(&mut self, event: &Event, canvas: &mut VersionedCanvas) {
+        match self {
+            CanvasTool::Pen { current_element } => {
+                CanvasTool::pen_handle_event(current_element, event, canvas)
+            }
+            CanvasTool::Eraser { eraser_rect } => {
+                CanvasTool::eraser_handle_event(eraser_rect, event, canvas)
+            }
+        }
+    }
+
+    fn pen_handle_event(
+        current_element: &mut Option<CanvasElement>,
+        event: &Event,
+        canvas: &mut VersionedCanvas,
+    ) {
+        match event {
+            Event::MouseDown(mouse_event) => {
+                let mut kurbo_path = BezPath::new();
+                kurbo_path.move_to((mouse_event.pos.x, mouse_event.pos.y));
+                *current_element = Some(CanvasElement::Freehand {
+                    path: Path { kurbo_path },
+                    thickness: 2.0,
+                });
+            }
+            Event::MouseMove(mouse_event) => {
+                if current_element.is_some() {
+                    if let Some(current_element) = current_element.as_mut() {
+                        current_element
+                            .get_path_mut()
+                            .unwrap()
+                            .kurbo_path
+                            .line_to((mouse_event.pos.x, mouse_event.pos.y));
+                    }
+                }
+            }
+            Event::MouseUp(_) => {
+                if current_element.is_some() {
+                    if let Some(current_element) = current_element.take() {
+                        canvas.update(move |canvas: &Canvas| -> Canvas {
+                            let mut new_canvas = canvas.clone();
+                            new_canvas.push_back(current_element);
+                            return new_canvas;
+                        });
+                    }
+                }
+            }
+            _ => {}
+        }
+    }
+
+    fn eraser_handle_event(
+        eraser_rect: &mut Option<Rect>,
+        event: &Event,
+        canvas: &mut VersionedCanvas,
+    ) {
+        match event {
+            Event::MouseDown(mouse_event) => {
+                let rect =
+                    druid::Rect::from_center_size(mouse_event.pos, druid::Size::new(10.0, 10.0));
+                *eraser_rect = Some(rect);
+                // Create a new undo version each time the mouse is down
+                canvas.update(|canvas: &Canvas| -> Canvas {
+                    let mut new_canvas = canvas.clone();
+                    new_canvas.erase(rect);
+                    return new_canvas;
+                });
+            }
+            Event::MouseMove(mouse_event) => {
+                if eraser_rect.is_some() {
+                    let rect = druid::Rect::from_center_size(
+                        mouse_event.pos,
+                        druid::Size::new(10.0, 10.0),
+                    );
+                    *eraser_rect = Some(rect);
+                    // We don't want too many levels of undoing
+                    // So we make irreversible changes as long as
+                    // the mouse is pressed.
+                    canvas.irreversible_update(|canvas: &mut Canvas| {
+                        canvas.erase(rect);
+                    });
+                }
+            }
+            Event::MouseUp(_) => {
+                *eraser_rect = None;
+            }
+            _ => {}
+        }
+    }
+}

src/lib.rs

@@ -1,160 +1,3 @@
-#[derive(Clone, druid::Data)]
-pub struct Path {
-    pub kurbo_path: druid::kurbo::BezPath,
-}
-
-#[derive(Clone, druid::Data)]
-pub enum CanvasElement {
-    Freehand { path: Path, thickness: f64 },
-}
-
-impl CanvasElement {
-    pub fn bounding_box(&self) -> druid::Rect {
-        match self {
-            CanvasElement::Freehand { path, thickness } => {
-                use druid::kurbo::Shape;
-                path.kurbo_path
-                    .bounding_box()
-                    .inflate(*thickness, *thickness)
-            }
-        }
-    }
-    pub fn draw(&self, ctx: &mut druid::PaintCtx) {
-        match self {
-            CanvasElement::Freehand { path, thickness } => {
-                use druid::RenderContext;
-                let stroke_color = druid::Color::rgb8(0, 128, 0);
-                ctx.stroke(&path.kurbo_path, &stroke_color, *thickness);
-            }
-        }
-    }
-
-    pub fn get_path_mut(&mut self) -> Option<&mut Path> {
-        match self {
-            CanvasElement::Freehand { path, .. } => Some(path),
-        }
-    }
-}
-
-// O(1) complexity
-fn segment_intersects_rect(segment: &druid::kurbo::PathSeg, rect: druid::Rect) -> bool {
-
-    match segment {
-        druid::kurbo::PathSeg::Line(line) => rect.contains(line.p0)
-                                          || rect.contains(line.p1),
-
-        druid::kurbo::PathSeg::Quad(quad) => rect.contains(quad.p0)
-                                          || rect.contains(quad.p1)
-                                          || rect.contains(quad.p2),
-
-        druid::kurbo::PathSeg::Cubic(cubic) => rect.contains(cubic.p0)
-                                            || rect.contains(cubic.p1)
-                                            || rect.contains(cubic.p2),
-    }
-}
-
-// A canvas contains all elements to be drawn
-#[derive(Clone, druid::Data)]
-pub struct Canvas {
-    pub elements: im::Vector<CanvasElement>,
-}
-
-impl Canvas {
-    pub fn new() -> Canvas {
-        Canvas {
-            elements: im::vector![],
-        }
-    }
-    // O(n) complexity, where n is the number of segments belonging to paths
-    // that intersect the eraser rectangle
-    pub fn erase(&mut self, eraser_rect: druid::Rect) {
-        for elem in self.elements.iter_mut() {
-            if elem.bounding_box().intersect(eraser_rect).area() > 0.0 {
-                match elem {
-                    CanvasElement::Freehand{path, thickness: _} => {
-                        // Remove segments intersecting the eraser
-                        let new_segments = (*path).kurbo_path.segments().filter(|path| ! segment_intersects_rect(path, eraser_rect));
-                        path.kurbo_path = druid::kurbo::BezPath::from_path_segments(new_segments);
-                    }
-                }
-            }
-        }
-    }
-
-    pub fn push_back(&mut self, element: CanvasElement) {
-        self.elements.push_back(element);
-    }
-}
-
-#[derive(Clone, druid::Data)]
-pub struct VersionedCanvas {
-    // We internally guarantee that this vector
-    // is never empty
-    versions: im::Vector<Canvas>,
-    curr_version: usize,
-}
-
-impl VersionedCanvas {
-    pub fn new(canvas: Canvas) -> VersionedCanvas {
-        VersionedCanvas {
-            versions: im::vector![canvas],
-            curr_version: 0,
-        }
-    }
-
-    // Get current canvas version
-    pub fn get(&self) -> &Canvas {
-        self.versions.get(self.curr_version).unwrap()
-    }
-
-    fn has_newer_versions(&self) -> bool {
-        self.curr_version + 1 < self.versions.len()
-    }
-
-    fn has_older_versions(&self) -> bool {
-        self.curr_version > 0
-    }
-
-    pub fn version(&self) -> usize {
-        self.curr_version
-    }
-
-    pub fn undo(&mut self) {
-        if self.has_older_versions() {
-            self.curr_version = self.curr_version - 1;
-        }
-    }
-
-    pub fn redo(&mut self) {
-        if self.has_newer_versions() {
-            self.curr_version = self.curr_version + 1;
-        }
-    }
-
-    pub fn update(&mut self, update_fn: impl FnOnce(&Canvas) -> Canvas) {
-        // This is a linear history,
-        // so we first check if there are newer versions, if so
-        // this means we are in the past, so a change in the past destroys the future
-        // and creates a new future.
-        if self.has_newer_versions() {
-            self.versions = self.versions.take(self.curr_version + 1);
-        }
-        let new_version = update_fn(self.get());
-        self.versions.push_back(new_version);
-        self.curr_version = self.curr_version + 1;
-    }
-
-    // Do inplace update, which will be irreversible
-    pub fn irreversible_update(&mut self, update_fn: impl FnOnce(&mut Canvas)) {
-        // This is a linear history,
-        // so we first check if there are newer versions, if so
-        // this means we are in the past, so a change in the past destroys the future
-        // and creates a new future.
-        if self.has_newer_versions() {
-            self.versions = self.versions.take(self.curr_version + 1);
-        }
-
-        update_fn(self.versions.back_mut().unwrap());
-    }
-}
-
+pub mod canvas;
+pub mod canvas_tools;
+pub mod versioned_canvas;

src/main.rs

@@ -14,74 +14,23 @@
 //  You should have received a copy of the GNU Affero General Public License
 //  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-use druid::kurbo::{BezPath, Rect};
 use druid::widget::prelude::*;
-use druid::{AppLauncher, Color, Data, Lens, Event, LocalizedString, WidgetExt, WindowDesc};
+use druid::{
+    AppLauncher, Color, Data, Event, Lens, LensExt, LocalizedString, WidgetExt, WindowDesc,
+};
 
-use stiletto::{CanvasElement, VersionedCanvas, Canvas};
+use stiletto::canvas::Canvas;
+use stiletto::canvas_tools::CanvasTool;
+use stiletto::versioned_canvas::VersionedCanvas;
 
-#[derive(Clone, Data, PartialEq)]
-enum CanvasToolType {
-    Pen,
-    Eraser
-}
-
-// Tools that can be used to interact with the canvas
-#[derive(Clone, Data)]
-enum CanvasTool {
-    Pen { current_element: Option<CanvasElement> },
-    Eraser { eraser_rect: Option<Rect> },
-}
-
-impl CanvasTool {
-    fn new_pen() -> CanvasTool {
-        CanvasTool::Pen { current_element: None }
-    }
-    fn new_eraser() -> CanvasTool {
-        CanvasTool::Eraser { eraser_rect: None }
-    }
-
-    fn tool_type(&self) -> CanvasToolType {
-        match self {
-            CanvasTool::Pen { current_element: _ } => CanvasToolType::Pen,
-            CanvasTool::Eraser { eraser_rect: _ } => CanvasToolType::Eraser,
-        }
-    }
-}
-
-struct CanvasToolLens;
-
-impl Lens<CanvasData, CanvasToolType> for CanvasToolLens {
-    fn with<R, F: FnOnce(&CanvasToolType) -> R>(&self, data: &CanvasData, f: F) -> R {
-        f(&data.current_tool.tool_type())
-    }
-
-    fn with_mut<R, F: FnOnce(&mut CanvasToolType) -> R>(&self, data: &mut CanvasData, f: F) -> R {
-        let mut curr_type = data.current_tool.tool_type();
-        let result = f(&mut curr_type);
-
-        match curr_type {
-            CanvasToolType::Pen    => data.current_tool = CanvasTool::new_pen(),
-            CanvasToolType::Eraser => data.current_tool = CanvasTool::new_eraser(),
-        }
-
-        result
-    }
-}
-
-#[derive(Clone, Data)]
+#[derive(Clone, Data, Lens)]
 struct CanvasData {
+    #[lens(name = "current_tool_lens")]
     current_tool: CanvasTool,
     elements: VersionedCanvas,
 }
 
 impl CanvasData {
-    /*fn is_drawing(&self) -> bool {
-        self.current_element.is_some()
-    }*/
-
-    const CURRENT_TOOL_LENS: CanvasToolLens = CanvasToolLens;
-
     fn perform_undo(&mut self) {
         self.elements.undo();
     }
@@ -91,85 +40,15 @@ impl CanvasData {
     }
 
     fn handle_tool_event(&mut self, event: &Event) {
-        match &mut self.current_tool {
-            CanvasTool::Pen { current_element } => {
-                match event {
-                    Event::MouseDown(mouse_event) => {
-                        let mut kurbo_path = BezPath::new();
-                        kurbo_path.move_to((mouse_event.pos.x, mouse_event.pos.y));
-                        *current_element = Some(CanvasElement::Freehand {
-                            path: stiletto::Path { kurbo_path },
-                            thickness: 2.0,
-                        });
-                    }
-                    Event::MouseMove(mouse_event) => {
-                        if current_element.is_some() {
-                            if let Some(current_element) = current_element.as_mut() {
-                                current_element
-                                    .get_path_mut()
-                                    .unwrap()
-                                    .kurbo_path
-                                    .line_to((mouse_event.pos.x, mouse_event.pos.y));
-                            }
-                        }
-                    }
-                    Event::MouseUp(_) => {
-                        if current_element.is_some() {
-                            if let Some(current_element) = current_element.take() {
-
-                                self.elements.update(move |canvas: &Canvas| -> Canvas {
-                                    let mut new_canvas = canvas.clone();
-                                    new_canvas.push_back(current_element);
-                                    return new_canvas;
-                                });
-
-                            }
-                        }
-                    }
-                    _ => {}
-                }
-            },
-            CanvasTool::Eraser { eraser_rect } => {
-               match event {
-                    Event::MouseDown(mouse_event) => {
-                        let rect = druid::Rect::from_center_size(mouse_event.pos, druid::Size::new(10.0, 10.0));
-                        *eraser_rect = Some(rect);
-                        // Create a new undo version each time the mouse is down
-                        self.elements.update(|canvas: &Canvas| -> Canvas {
-                            let mut new_canvas = canvas.clone();
-                            new_canvas.erase(rect);
-                            return new_canvas;
-                        });
-                    }
-                    Event::MouseMove(mouse_event) => {
-                        if eraser_rect.is_some() {
-                            let rect = druid::Rect::from_center_size(mouse_event.pos, druid::Size::new(10.0, 10.0));
-                            *eraser_rect = Some(rect);
-                            // We don't want too many levels of undoing
-                            // So we make irreversible changes as long as
-                            // the mouse is pressed.
-                            self.elements.irreversible_update(|canvas: &mut Canvas| {
-                                canvas.erase(rect);
-                            });
-                        }
-                    }
-                    Event::MouseUp(_) => {
-                        *eraser_rect = None;
-                    }
-                    _ => {}
-                }
-            },
-        }
+        self.current_tool.handle_event(event, &mut self.elements);
     }
 }
 
-
 struct CanvasWidget;
 
 impl Widget<CanvasData> for CanvasWidget {
     fn event(&mut self, _ctx: &mut EventCtx, event: &Event, data: &mut CanvasData, _env: &Env) {
         data.handle_tool_event(event);
-            
     }
 
     fn lifecycle(
@@ -188,12 +67,19 @@ impl Widget<CanvasData> for CanvasWidget {
         data: &CanvasData,
         _env: &Env,
     ) {
-
+        // TODO: Polish a bit this logic
         match (&old_data.current_tool, &data.current_tool) {
-            (CanvasTool::Pen{ current_element: old_element }, CanvasTool::Pen{ current_element: new_element }) => {
+            (
+                CanvasTool::Pen {
+                    current_element: old_element,
+                },
+                CanvasTool::Pen {
+                    current_element: new_element,
+                },
+            ) => {
                 // the current_element is moved to the elements array, no need to repaint
                 if old_element.is_some() && !new_element.is_some() {
-                    return
+                    return;
                 }
 
                 if new_element.is_some() {
@@ -204,7 +90,7 @@ impl Widget<CanvasData> for CanvasWidget {
                     ctx.request_paint();
                 }
             }
-            (CanvasTool::Eraser{ eraser_rect: _ }, CanvasTool::Eraser{ eraser_rect }) => {
+            (CanvasTool::Eraser { eraser_rect: _ }, CanvasTool::Eraser { eraser_rect }) => {
                 // We just stopped erasing, no need to repaint
                 if let Some(rect) = eraser_rect {
                     ctx.request_paint_rect(*rect);
@@ -261,18 +147,49 @@ impl Widget<CanvasData> for CanvasWidget {
     }
 }
 
-fn build_ui() -> impl Widget<CanvasData> {
-    use druid::widget::{Align, Button, RadioGroup, CrossAxisAlignment, Flex, SizedBox};
+// Enum containing an entry for each canvas tool
+// it is used to implement the radio group for selecting the tool
+#[derive(Clone, Data, PartialEq)]
+enum ToolType {
+    Pen,
+    Eraser,
+}
 
-    let radio_group = RadioGroup::new(vec![("Pen", CanvasToolType::Pen), ("Eraser", CanvasToolType::Eraser)]);
-        
+// Make a CanvasTool of a given type
+fn update_canvas_tool_from_type(tool: &mut CanvasTool, new_type: ToolType) {
+    match new_type {
+        ToolType::Pen => *tool = CanvasTool::new_pen(),
+        ToolType::Eraser => *tool = CanvasTool::new_eraser(),
+    }
+}
+
+// Get a ToolType from a CanvasTool
+fn canvas_tool_type(tool: &CanvasTool) -> ToolType {
+    match tool {
+        CanvasTool::Pen { .. } => ToolType::Pen,
+        CanvasTool::Eraser { .. } => ToolType::Eraser,
+    }
+}
+
+fn build_ui() -> impl Widget<CanvasData> {
+    use druid::widget::{Align, Button, CrossAxisAlignment, Flex, RadioGroup, SizedBox};
+
+    let radio_group = RadioGroup::new(vec![("Pen", ToolType::Pen), ("Eraser", ToolType::Eraser)])
+        .lens(CanvasData::current_tool_lens.map(canvas_tool_type, update_canvas_tool_from_type));
+    // ^ We use a lens to make the radiogroup act only on the tool portion of data.
+    // Actually we must also perform a conversion, between ToolType and CanvasTool,
+    // that's why we perform a map on the lens.
 
     let toolbar = Flex::row()
         .cross_axis_alignment(CrossAxisAlignment::Center)
         .with_spacer(30.0)
-        .with_child(Button::new("Undo").on_click(|_ctx, data: &mut CanvasData, _env| data.perform_undo()))
-        .with_child(Button::new("Redo").on_click(|_ctx, data: &mut CanvasData, _env| data.perform_redo()))
-        .with_child(radio_group.lens(CanvasData::CURRENT_TOOL_LENS));
+        .with_child(
+            Button::new("Undo").on_click(|_ctx, data: &mut CanvasData, _env| data.perform_undo()),
+        )
+        .with_child(
+            Button::new("Redo").on_click(|_ctx, data: &mut CanvasData, _env| data.perform_redo()),
+        )
+        .with_child(radio_group);
 
     Flex::column()
         .cross_axis_alignment(CrossAxisAlignment::Center)

src/versioned_canvas.rs

@@ -0,0 +1,73 @@
+use crate::canvas::Canvas;
+
+#[derive(Clone, druid::Data)]
+pub struct VersionedCanvas {
+    // We internally guarantee that this vector
+    // is never empty
+    versions: im::Vector<Canvas>,
+    curr_version: usize,
+}
+
+impl VersionedCanvas {
+    pub fn new(canvas: Canvas) -> VersionedCanvas {
+        VersionedCanvas {
+            versions: im::vector![canvas],
+            curr_version: 0,
+        }
+    }
+
+    // Get current canvas version
+    pub fn get(&self) -> &Canvas {
+        self.versions.get(self.curr_version).unwrap()
+    }
+
+    fn has_newer_versions(&self) -> bool {
+        self.curr_version + 1 < self.versions.len()
+    }
+
+    fn has_older_versions(&self) -> bool {
+        self.curr_version > 0
+    }
+
+    pub fn version(&self) -> usize {
+        self.curr_version
+    }
+
+    pub fn undo(&mut self) {
+        if self.has_older_versions() {
+            self.curr_version = self.curr_version - 1;
+        }
+    }
+
+    pub fn redo(&mut self) {
+        if self.has_newer_versions() {
+            self.curr_version = self.curr_version + 1;
+        }
+    }
+
+    pub fn update(&mut self, update_fn: impl FnOnce(&Canvas) -> Canvas) {
+        // This is a linear history,
+        // so we first check if there are newer versions, if so
+        // this means we are in the past, so a change in the past destroys the future
+        // and creates a new future.
+        if self.has_newer_versions() {
+            self.versions = self.versions.take(self.curr_version + 1);
+        }
+        let new_version = update_fn(self.get());
+        self.versions.push_back(new_version);
+        self.curr_version = self.curr_version + 1;
+    }
+
+    // Do inplace update, which will be irreversible
+    pub fn irreversible_update(&mut self, update_fn: impl FnOnce(&mut Canvas)) {
+        // This is a linear history,
+        // so we first check if there are newer versions, if so
+        // this means we are in the past, so a change in the past destroys the future
+        // and creates a new future.
+        if self.has_newer_versions() {
+            self.versions = self.versions.take(self.curr_version + 1);
+        }
+
+        update_fn(self.versions.back_mut().unwrap());
+    }
+}