From 81b531aaec7ad12b138dbf1bd2c24d2bd4352024 Mon Sep 17 00:00:00 2001
From: Arne Dußin
Date: Mon, 2 Nov 2020 00:53:18 +0100
Subject: Tether on zoom

---
 src/transform.rs | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

(limited to 'src/transform.rs')

diff --git a/src/transform.rs b/src/transform.rs
index ca359f0..b0b0e0a 100644
--- a/src/transform.rs
+++ b/src/transform.rs
@@ -96,11 +96,17 @@ impl Transform {
 
     /// Attempts to zoom in a step and return true.
     /// If the maximum zoom is reached, this function changes nothing and returns false.
-    pub fn try_zoom_in(&mut self) -> bool {
-        // TODO: Zoom in on mouse pointer position
+    pub fn try_zoom_in(&mut self, mouse_pos_px: Vec2<f32>) -> bool {
         if self.pixels_per_m < MAX_PIXELS_PER_M {
+            // Save the absolute mouse position for tethering later
+            let mouse_pos_m = self.point_px_to_m(mouse_pos_px);
+
             self.pixels_per_m *= 1.2;
             self.normalise_zoom();
+
+            // Perform tethering (zoom in on mouse position)
+            self.translation_px += mouse_pos_px - self.point_m_to_px(mouse_pos_m);
+
             true
         } else {
             false
@@ -109,11 +115,18 @@ impl Transform {
 
     /// Attempts to zoom out a step and return true.
     /// If the minimum zoom is reached, this function changes nothing and returns false.
-    pub fn try_zoom_out(&mut self) -> bool {
+    pub fn try_zoom_out(&mut self, mouse_pos_px: Vec2<f32>) -> bool {
         // TODO: Zoom out at mouse pointer position
         if self.pixels_per_m > MIN_PIXELS_PER_M {
+            // Save the absolute mouse position for tethering later
+            let mouse_pos_m = self.point_px_to_m(mouse_pos_px);
+
             self.pixels_per_m /= 1.2;
             self.normalise_zoom();
+
+            // Perform tethering (zoom out at mouse position)
+            self.translation_px += mouse_pos_px - self.point_m_to_px(mouse_pos_m);
+
             true
         } else {
             false
-- 
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