From 227bd6a2027d2c0c3e52b42e7e2f93f0d8399d1b Mon Sep 17 00:00:00 2001
From: Francis Chua <fqchua@stanford.edu>
Date: Thu, 1 Feb 2024 09:56:08 -0800
Subject: [PATCH] add invert method for TSTransform

---
 crates/egui/src/context.rs                |  2 +-
 crates/egui_demo_lib/src/demo/pan_zoom.rs |  4 ++--
 crates/emath/src/ts_transform.rs          | 25 +++++------------------
 3 files changed, 8 insertions(+), 23 deletions(-)

diff --git a/crates/egui/src/context.rs b/crates/egui/src/context.rs
index 90e72ff2145..b9a233273aa 100644
--- a/crates/egui/src/context.rs
+++ b/crates/egui/src/context.rs
@@ -2181,7 +2181,7 @@ impl Context {
                 let pointer_pos = viewport.input.pointer.interact_pos();
                 if let Some(pointer_pos) = pointer_pos {
                     // Apply the inverse transformation of this layer to the pointer pos.
-                    let pointer_pos = transform.invert_pos(pointer_pos);
+                    let pointer_pos = transform.inverse() * pointer_pos;
                     if let Some(rects) = viewport.layer_rects_prev_frame.get(&layer_id) {
                         for blocking in rects.iter().rev() {
                             if blocking.id == id {
diff --git a/crates/egui_demo_lib/src/demo/pan_zoom.rs b/crates/egui_demo_lib/src/demo/pan_zoom.rs
index 7b1c83e45b7..224323194b7 100644
--- a/crates/egui_demo_lib/src/demo/pan_zoom.rs
+++ b/crates/egui_demo_lib/src/demo/pan_zoom.rs
@@ -42,7 +42,7 @@ impl super::View for PanZoom {
                 let original_zoom = self.transform.scaling;
                 let new_zoom = original_zoom * ui.ctx().input(|i| i.zoom_delta());
 
-                let layer_pos = self.transform.invert_pos(pointer);
+                let layer_pos = self.transform.inverse() * pointer;
                 let new_transform = TSTransform::new(self.transform.translation, new_zoom);
                 let new_pos = new_transform * layer_pos;
 
@@ -83,7 +83,7 @@ impl super::View for PanZoom {
                 // but may also cover over other windows.
                 .order(egui::Order::Foreground)
                 .show(ui.ctx(), |ui| {
-                    ui.set_clip_rect(self.transform.invert_rect(rect));
+                    ui.set_clip_rect(self.transform.inverse() * rect);
                     egui::Frame::default()
                         .rounding(egui::Rounding::same(4.0))
                         .inner_margin(egui::Margin::same(8.0))
diff --git a/crates/emath/src/ts_transform.rs b/crates/emath/src/ts_transform.rs
index 014b3f0060a..e6f02cfc4ca 100644
--- a/crates/emath/src/ts_transform.rs
+++ b/crates/emath/src/ts_transform.rs
@@ -57,28 +57,13 @@ impl TSTransform {
     /// let p1 = pos2(2.0, 3.0);
     /// let p2 = pos2(12.0, 5.0);
     /// let ts = TSTransform::new(vec2(2.0, 3.0), 2.0);
-    /// assert_eq!(ts.invert_pos(p1), pos2(0.0, 0.0));
-    /// assert_eq!(ts.invert_pos(p2), pos2(5.0, 1.0));
+    /// let inv = ts.inverse();
+    /// assert_eq!(inv.mul_pos(p1), pos2(0.0, 0.0));
+    /// assert_eq!(inv.mul_pos(p2), pos2(5.0, 1.0));
     /// ```
     #[inline]
-    pub fn invert_pos(&self, pos: Pos2) -> Pos2 {
-        // First, reverse translation, then reverse scaling.
-        (pos - self.translation) / self.scaling
-    }
-
-    /// Reverses the transformation from screen space to layer space.
-    ///
-    /// ```
-    /// # use emath::{pos2, vec2, Rect, TSTransform};
-    /// let rect = Rect::from_min_max(pos2(16.0, 15.0), pos2(46.0, 30.0));
-    /// let ts = TSTransform::new(vec2(1.0, 0.0), 3.0);
-    /// let inverted = ts.invert_rect(rect);
-    /// assert_eq!(inverted.min, pos2(5.0, 5.0));
-    /// assert_eq!(inverted.max, pos2(15.0, 10.0));
-    /// ```
-    #[inline]
-    pub fn invert_rect(&self, rect: Rect) -> Rect {
-        Rect::from_min_max(self.invert_pos(rect.min), self.invert_pos(rect.max))
+    pub fn inverse(&self) -> Self {
+        Self::new(-self.translation / self.scaling, 1.0 / self.scaling)
     }
 
     /// Transforms the given coordinate by translation then scaling.