properly center editor view and make zoom follow mouse position

README.md

@@ -4,9 +4,6 @@
 logic mostly like https://git.crispypin.cc/CrispyPin/marble
 
 ## todo
-cleanup: unpowered texture names x_off -> x
-scroll output
-properly center view
 make marble movement not order-dependent (`>ooo <` does not behave symmetrically)
 blueprints
 scroll level list

src/editor.rs

@@ -17,6 +17,7 @@ use crate::{
 
 const HEADER_HEIGHT: i32 = 40;
 const FOOTER_HEIGHT: i32 = 95;
+const MAX_ZOOM_IN: i32 = 3;
 
 #[derive(Debug)]
 pub struct Editor {
@@ -212,6 +213,37 @@ impl Editor {
 		}
 	}
 
+	pub fn center_view(&mut self, d: &RaylibHandle) {
+		let tile_size = (16 << self.zoom) as f32;
+		let tile_x = self.source_board.width() as f32 / 2. * tile_size;
+		let tile_y = self.source_board.height() as f32 / 2. * tile_size;
+		let screen_x = d.get_screen_width() as f32 / 2.;
+		let screen_y = d.get_screen_height() as f32 / 2.;
+		self.view_offset.x = screen_x - tile_x;
+		self.view_offset.y = screen_y - tile_y;
+	}
+
+	fn change_zoom_level(&mut self, d: &RaylibHandle, delta: i32) {
+		let tile_size = (16 << self.zoom) as f32;
+		let mouse_pos = d.get_mouse_position();
+		let tile_pos_of_mouse = (mouse_pos - self.view_offset) / tile_size;
+		self.zoom += delta;
+		let tile_size = (16 << self.zoom) as f32;
+		self.view_offset = mouse_pos - tile_pos_of_mouse * tile_size;
+	}
+
+	fn zoom_in(&mut self, d: &RaylibHandle) {
+		if self.zoom < MAX_ZOOM_IN {
+			self.change_zoom_level(d, 1);
+		}
+	}
+
+	fn zoom_out(&mut self, d: &RaylibHandle) {
+		if self.zoom > 0 {
+			self.change_zoom_level(d, -1);
+		}
+	}
+
 	fn set_tile(&mut self, mut pos: Pos, tile: Tile) {
 		let tile_size = (16 << self.zoom) as f32;
 		let (x, y) = self.source_board.grow_to_include(pos);
@@ -271,17 +303,17 @@ impl Editor {
 			}
 		}
 
-		if rl.get_mouse_wheel_move() > 0. && self.zoom < 3 {
+		if rl.get_mouse_wheel_move() > 0. {
-			self.zoom += 1;
+			self.zoom_in(rl);
 		}
-		if rl.get_mouse_wheel_move() < 0. && self.zoom > 0 {
+		if rl.get_mouse_wheel_move() < 0. {
-			self.zoom -= 1;
+			self.zoom_out(rl);
 		}
 		if rl.is_mouse_button_down(MouseButton::MOUSE_BUTTON_MIDDLE) {
 			self.view_offset += rl.get_mouse_delta()
 		}
 		if rl.is_mouse_button_pressed(MouseButton::MOUSE_BUTTON_RIGHT) {
-			self.view_offset = Vector2::zero();
+			self.center_view(rl);
 		}
 
 		if rl.is_key_pressed(KeyboardKey::KEY_R) {

src/main.rs

@@ -213,7 +213,9 @@ impl Game {
 					d.draw_text(solution.id(), column_x, y + 35, 10, Color::GRAY);
 
 					if simple_button(d, column_x, y + 50, 220, 30) {
-						self.open_editor = Some(Editor::new(solution.clone(), level.clone()));
+						let mut editor = Editor::new(solution.clone(), level.clone());
+						editor.center_view(d);
+						self.open_editor = Some(editor);
 					}
 					d.draw_text("edit", column_x + 5, y + 55, 20, Color::WHITE);
 				}