From 1474c17b0d436f0c39dbbbae1d59b7f872f9ac12 Mon Sep 17 00:00:00 2001
From: rustbasic <127506429+rustbasic@users.noreply.github.com>
Date: Wed, 18 Sep 2024 02:49:53 +0900
Subject: [PATCH] Fix: panic when dragging window between monitors of different
 pixels_per_point (#4868)

Fix: panic when dragging window between monitors of different
pixels_per_point

This will continue to help us as we develop `egui`.
I hope you agree with my defense of `panic`.

* Relate #3959
* Relate #4088

* Closes #4178
* Closes #4179


There is also a way to add log if necessary.
```
                log::debug!("Anti-panic behavior occurs");
```

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
---
 crates/egui/src/context.rs | 18 ++++++++++++------
 crates/egui/src/layers.rs  |  6 ++++++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/crates/egui/src/context.rs b/crates/egui/src/context.rs
index 53ce7661531..ec899461a19 100644
--- a/crates/egui/src/context.rs
+++ b/crates/egui/src/context.rs
@@ -2418,12 +2418,18 @@ impl Context {
 
         self.write(|ctx| {
             let tessellation_options = ctx.memory.options.tessellation_options;
-            let texture_atlas = ctx
-                .fonts
-                .get(&pixels_per_point.into())
-                .expect("tessellate called with a different pixels_per_point than the font atlas was created with. \
-                         You should use egui::FullOutput::pixels_per_point when tessellating.")
-                .texture_atlas();
+            let texture_atlas = if let Some(fonts) = ctx.fonts.get(&pixels_per_point.into()) {
+                fonts.texture_atlas()
+            } else {
+                #[cfg(feature = "log")]
+                log::warn!("No font size matching {pixels_per_point} pixels per point found.");
+                ctx.fonts
+                    .iter()
+                    .next()
+                    .expect("No fonts loaded")
+                    .1
+                    .texture_atlas()
+            };
             let (font_tex_size, prepared_discs) = {
                 let atlas = texture_atlas.lock();
                 (atlas.size(), atlas.prepared_discs())
diff --git a/crates/egui/src/layers.rs b/crates/egui/src/layers.rs
index 66bbd338387..9105ece2591 100644
--- a/crates/egui/src/layers.rs
+++ b/crates/egui/src/layers.rs
@@ -153,6 +153,12 @@ impl PaintList {
     /// and then later setting it using `paint_list.set(idx, cr, frame);`.
     #[inline(always)]
     pub fn set(&mut self, idx: ShapeIdx, clip_rect: Rect, shape: Shape) {
+        if self.0.len() <= idx.0 {
+            #[cfg(feature = "log")]
+            log::warn!("Index {} is out of bounds for PaintList", idx.0);
+            return;
+        }
+
         self.0[idx.0] = ClippedShape { clip_rect, shape };
     }