From e1e4dfb6507fa90d18c24f7fcd8ec7d2b93415f1 Mon Sep 17 00:00:00 2001
From: CrispyPin <crispin@tasa.se>
Date: Fri, 25 Oct 2024 18:03:44 +0200
Subject: [PATCH] center zooming on mouse

---
 showimage.odin | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/showimage.odin b/showimage.odin
index b3c5463..16c8c35 100644
--- a/showimage.odin
+++ b/showimage.odin
@@ -26,9 +26,9 @@ main :: proc() {
 	for !rl.WindowShouldClose() {
 		scroll := rl.GetMouseWheelMove()
 		if scroll > 0 {
-			zoom *= 2
+			change_zoom(zoom)
 		} else if scroll < 0 {
-			zoom /= 2
+			change_zoom(-zoom / 2)
 		}
 		if rl.IsMouseButtonDown(rl.MouseButton.LEFT) {
 			offset += rl.GetMouseDelta()
@@ -47,6 +47,13 @@ main :: proc() {
 	rl.CloseWindow()
 }
 
+change_zoom :: proc(delta: f32) {
+	mouse_pos := rl.GetMousePosition()
+	zoom_pos := (mouse_pos - offset) / zoom
+	zoom += delta
+	offset = mouse_pos - zoom_pos * zoom
+}
+
 zoom_to_power :: proc(size: i32, max: i32) -> i32 {
 	fit: i32 = 2
 	for fit * size < max {