From 0fdc73b9e4783343ad14a8f60e7c438a0530086b Mon Sep 17 00:00:00 2001
From: Enrico Lumetti <enrico.lumetti@gmail.com>
Date: Fri, 5 Mar 2021 02:15:36 +0100
Subject: [PATCH] Fix spurious drawing when mouse gets focus inside
 touch/stylus events

---
 src/widget/tool_ctx.rs | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/src/widget/tool_ctx.rs b/src/widget/tool_ctx.rs
index 5154866..2dc95f1 100644
--- a/src/widget/tool_ctx.rs
+++ b/src/widget/tool_ctx.rs
@@ -19,7 +19,7 @@ use crate::canvas::{Canvas, CanvasElement};
 use crate::history::VersionedCanvas;
 
 use druid::kurbo::BezPath;
-use druid::{Data, Env, Event, EventCtx, PaintCtx};
+use druid::{Data, Env, Event, EventCtx, MouseButton, MouseEvent, PaintCtx};
 
 #[derive(Clone, Data)]
 pub enum CanvasToolState {
@@ -46,6 +46,11 @@ impl CanvasToolParams {
     }
 }
 
+fn pressed(mouse_event: &MouseEvent) -> bool {
+    mouse_event.buttons.contains(MouseButton::Left)
+        || mouse_event.button == MouseButton::Left
+}
+
 impl CanvasToolCtx {
     pub fn new(params: CanvasToolParams) -> Self {
         CanvasToolCtx {
@@ -75,10 +80,10 @@ impl CanvasToolCtx {
         _env: &Env,
     ) {
         match (&mut self.state, event) {
-            (CanvasToolState::Idle, Event::MouseDown(_)) => {
+            (CanvasToolState::Idle, Event::MouseDown(mouse_event)) if pressed(mouse_event) => {
                 self.state = CanvasToolState::Erasing;
             }
-            (CanvasToolState::Erasing, Event::MouseMove(mouse_event)) => {
+            (CanvasToolState::Erasing, Event::MouseMove(mouse_event)) if pressed(mouse_event) => {
                 let eraser_rect = druid::Rect::from_center_size(mouse_event.pos, (5.0, 5.0));
                 let old_elements = vcanvas.get().elements();
                 let mut new_elements = old_elements.clone();
@@ -97,7 +102,7 @@ impl CanvasToolCtx {
                     });
                 }
             }
-            (CanvasToolState::Erasing, Event::MouseUp(_)) => {
+            (CanvasToolState::Erasing, Event::MouseUp(mouse_event)) if pressed(mouse_event) => {
                 self.state = CanvasToolState::Idle;
             }
             _ => {}
@@ -112,7 +117,7 @@ impl CanvasToolCtx {
         _env: &Env,
     ) {
         match (&mut self.state, event) {
-            (CanvasToolState::Idle, Event::MouseDown(mouse_event)) => {
+            (CanvasToolState::Idle, Event::MouseDown(mouse_event)) if pressed(mouse_event) => {
                 let mut kurbo_path = BezPath::new();
                 kurbo_path.move_to((mouse_event.pos.x, mouse_event.pos.y));
                 if let CanvasToolParams::Pen { thickness, color } = &self.initial_params {
@@ -132,13 +137,13 @@ impl CanvasToolCtx {
                     ..
                 },
                 Event::MouseMove(mouse_event),
-            ) => {
+            ) => if pressed(mouse_event) {
                 if let CanvasElement::Freehand { ref mut path, .. } = current_path {
                     path.kurbo_path
                         .line_to((mouse_event.pos.x, mouse_event.pos.y));
                 }
             }
-            (CanvasToolState::DrawingFreehand { .. }, Event::MouseUp(_)) => {
+            (CanvasToolState::DrawingFreehand { .. }, Event::MouseUp(mouse_event)) if pressed(mouse_event) => {
                 vcanvas.update(move |canvas: &mut Canvas| {
                     let current_state = std::mem::replace(&mut self.state, CanvasToolState::Idle);
                     if let CanvasToolState::DrawingFreehand { current_path, .. } = current_state {