From 25b8a8ebfdfcbf0edbdcaaf805a4fb728cd93c78 Mon Sep 17 00:00:00 2001
From: Emil Ernerfeldt <emilernerfeldt@gmail.com>
Date: Sun, 3 Jan 2021 00:12:15 +0100
Subject: [PATCH] =?UTF-8?q?Add=20window.id(=E2=80=A6)=20and=20area.id(?=
 =?UTF-8?q?=E2=80=A6)=20for=20overriding=20the=20default=20Id?=
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---
 CHANGELOG.md                  |  1 +
 egui/src/containers/area.rs   |  7 ++++++-
 egui/src/containers/window.rs | 15 +++++++++++----
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 941fdfe7..cf17892b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 ### Added ⭐
 
 * Add `ui.scroll_to_cursor` and `response.scroll_to_me` ([#81](https://github.com/emilk/egui/pull/81) by [lucaspoffo](https://github.com/lucaspoffo)).
+* Add `window.id(…)` and `area.id(…)` for overriding the default `Id`.
 
 ### Changed 🔧
 
diff --git a/egui/src/containers/area.rs b/egui/src/containers/area.rs
index 3dffabc4..6af447f6 100644
--- a/egui/src/containers/area.rs
+++ b/egui/src/containers/area.rs
@@ -42,7 +42,7 @@ impl State {
 ///     });
 #[derive(Clone, Copy, Debug)]
 pub struct Area {
-    id: Id,
+    pub(crate) id: Id,
     movable: bool,
     interactable: bool,
     order: Order,
@@ -62,6 +62,11 @@ impl Area {
         }
     }
 
+    pub fn id(mut self, id: Id) -> Self {
+        self.id = id;
+        self
+    }
+
     pub fn layer(&self) -> LayerId {
         LayerId::new(self.order, self.id)
     }
diff --git a/egui/src/containers/window.rs b/egui/src/containers/window.rs
index 41ea999a..32e30c79 100644
--- a/egui/src/containers/window.rs
+++ b/egui/src/containers/window.rs
@@ -34,6 +34,7 @@ pub struct Window<'open> {
 impl<'open> Window<'open> {
     /// The window title is used as a unique [`Id`] and must be unique, and should not change.
     /// This is true even if you disable the title bar with `.title_bar(false)`.
+    /// If you need a changing title, you must call `window.id(…)` with a fixed id.
     pub fn new(title: impl Into<String>) -> Self {
         let title = title.into();
         let area = Area::new(&title);
@@ -55,6 +56,12 @@ impl<'open> Window<'open> {
         }
     }
 
+    /// Assign a unique id to the Window. Required if the title changes, or is shared with another window.
+    pub fn id(mut self, id: Id) -> Self {
+        self.area = self.area.id(id);
+        self
+    }
+
     /// Call this to add a close-button to the window title bar.
     ///
     /// * If `*open == false`, the window will not be visible.
@@ -213,10 +220,10 @@ impl<'open> Window<'open> {
             return None;
         }
 
-        let window_id = Id::new(title_label.text());
+        let area_id = area.id;
         let area_layer_id = area.layer();
-        let resize_id = window_id.with("resize");
-        let collapsing_id = window_id.with("collapsing");
+        let resize_id = area_id.with("resize");
+        let collapsing_id = area_id.with("collapsing");
 
         let is_maximized = !with_title_bar
             || collapsing_header::State::is_open(ctx, collapsing_id).unwrap_or_default();
@@ -242,7 +249,7 @@ impl<'open> Window<'open> {
                 ctx,
                 possible,
                 area_layer_id,
-                window_id.with("frame_resize"),
+                area_id.with("frame_resize"),
                 last_frame_outer_rect,
             )
             .and_then(|window_interaction| {