From 4959f3512b361d5d44688db497f2ab9992a5cef7 Mon Sep 17 00:00:00 2001
From: Mikolaj Wielgus <wielgusmikolaj@gmail.com>
Date: Tue, 5 Mar 2024 18:51:17 +0000
Subject: [PATCH] egui: implement moving the canvas horizontally and vertically

---
 src/bin/topola-egui/app.rs     | 18 ++++++++----------
 src/bin/topola-egui/painter.rs |  9 ++++++---
 2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/src/bin/topola-egui/app.rs b/src/bin/topola-egui/app.rs
index ad9e700..52f82ef 100644
--- a/src/bin/topola-egui/app.rs
+++ b/src/bin/topola-egui/app.rs
@@ -26,7 +26,7 @@ pub struct App {
     design: Option<DsnDesign>,
 
     #[serde(skip)]
-    zoom_factor: f32,
+    from_rect: egui::emath::Rect,
 }
 
 impl Default for App {
@@ -36,7 +36,7 @@ impl Default for App {
             label: "Hello World!".to_owned(),
             file_handle_channel: channel(),
             design: None,
-            zoom_factor: 1.0,
+            from_rect: egui::Rect::from_x_y_ranges(0.0..=1000.0, 0.0..=500.0),
         }
     }
 }
@@ -111,25 +111,23 @@ impl eframe::App for App {
                 let desired_size = ui.available_width() * egui::vec2(1.0, 0.5);
                 let (_id, viewport_rect) = ui.allocate_space(desired_size);
 
-                self.zoom_factor = self.zoom_factor * ctx.input(|i| i.zoom_delta());
+                self.from_rect = self.from_rect.translate(ctx.input(|i| -i.raw_scroll_delta));
+                self.from_rect = self.from_rect / ctx.input(|i| i.zoom_delta());
 
-                let transform = egui::emath::RectTransform::from_to(
-                    egui::Rect::from_x_y_ranges(0.0..=1000.0, 0.0..=500.0) / self.zoom_factor,
-                    viewport_rect,
-                );
+                let transform = egui::emath::RectTransform::from_to(self.from_rect, viewport_rect);
                 let mut painter = Painter::new(ui, transform);
 
                 let dot_shape = Shape::Dot(DotShape {
                     c: Circle {
                         pos: [50.0, 100.0].into(),
-                        r: 10.0 * self.zoom_factor as f64,
+                        r: 10.0,
                     },
                 });
 
                 let seg_shape = Shape::Seg(SegShape {
                     from: [200.0, 25.0].into(),
                     to: [300.0, 300.0].into(),
-                    width: 5.0 * self.zoom_factor as f64,
+                    width: 5.0,
                 });
 
                 let bend_shape = Shape::Bend(BendShape {
@@ -139,7 +137,7 @@ impl eframe::App for App {
                         pos: [130.0, 130.0].into(),
                         r: 30.0,
                     },
-                    width: 12.0 * self.zoom_factor as f64,
+                    width: 12.0,
                 });
 
                 painter.paint_shape(&dot_shape, egui::Color32::from_rgb(255, 0, 0));
diff --git a/src/bin/topola-egui/painter.rs b/src/bin/topola-egui/painter.rs
index 2f2a8e7..5824c8d 100644
--- a/src/bin/topola-egui/painter.rs
+++ b/src/bin/topola-egui/painter.rs
@@ -17,7 +17,7 @@ impl<'a> Painter<'a> {
             Shape::Dot(dot) => epaint::Shape::circle_filled(
                 self.transform
                     .transform_pos([dot.c.pos.x() as f32, dot.c.pos.y() as f32].into()),
-                dot.c.r as f32,
+                dot.c.r as f32 * self.transform.scale().x,
                 color,
             ),
             Shape::Seg(seg) => epaint::Shape::line_segment(
@@ -27,7 +27,7 @@ impl<'a> Painter<'a> {
                     self.transform
                         .transform_pos([seg.to.x() as f32, seg.to.y() as f32].into()),
                 ],
-                egui::Stroke::new(seg.width as f32, color),
+                egui::Stroke::new(seg.width as f32 * self.transform.scale().x, color),
             ),
             Shape::Bend(bend) => {
                 let delta_from = bend.from - bend.c.pos;
@@ -45,7 +45,10 @@ impl<'a> Painter<'a> {
                     points.push(self.transform.transform_pos([x as f32, y as f32].into()));
                 }
 
-                epaint::Shape::line(points, egui::Stroke::new(bend.width as f32, color))
+                epaint::Shape::line(
+                    points,
+                    egui::Stroke::new(bend.width as f32 * self.transform.scale().x, color),
+                )
             }
         };