Add `TableBuilder::id_source` (#5022)

* Closes https://github.com/emilk/egui/issues/4982

crates/egui_extras/src/table.rs

@@ -5,7 +5,7 @@
 
 use egui::{
     scroll_area::{ScrollAreaOutput, ScrollBarVisibility},
-    Align, NumExt as _, Rangef, Rect, Response, ScrollArea, Ui, Vec2, Vec2b,
+    Align, Id, NumExt as _, Rangef, Rect, Response, ScrollArea, Ui, Vec2, Vec2b,
 };
 
 use crate::{
@@ -199,7 +199,7 @@ impl Default for TableScrollOptions {
 /// You must pre-allocate all columns with [`Self::column`]/[`Self::columns`].
 ///
 /// If you have multiple [`Table`]:s in the same [`Ui`]
-/// you will need to give them unique id:s by surrounding them with [`Ui::push_id`].
+/// you will need to give them unique id:s by with [`Self::id_source`].
 ///
 /// ### Example
 /// ```
@@ -230,6 +230,7 @@ impl Default for TableScrollOptions {
 /// ```
 pub struct TableBuilder<'a> {
     ui: &'a mut Ui,
+    id_source: Id,
     columns: Vec<Column>,
     striped: Option<bool>,
     resizable: bool,
@@ -243,6 +244,7 @@ impl<'a> TableBuilder<'a> {
         let cell_layout = *ui.layout();
         Self {
             ui,
+            id_source: Id::new("__table_state"),
             columns: Default::default(),
             striped: None,
             resizable: false,
@@ -252,6 +254,15 @@ impl<'a> TableBuilder<'a> {
         }
     }
 
+    /// Give this table a unique id within the parent [`Ui`].
+    ///
+    /// This is required if you have multiple tables in the same [`Ui`].
+    #[inline]
+    pub fn id_source(mut self, id_source: impl std::hash::Hash) -> Self {
+        self.id_source = Id::new(id_source);
+        self
+    }
+
     /// Enable striped row background for improved readability.
     ///
     /// Default is whatever is in [`egui::Visuals::striped`].
@@ -406,7 +417,7 @@ impl<'a> TableBuilder<'a> {
 
     /// Reset all column widths.
     pub fn reset(&mut self) {
-        let state_id = self.ui.id().with("__table_state");
+        let state_id = self.ui.id().with(self.id_source);
         TableState::reset(self.ui, state_id);
     }
 
@@ -416,6 +427,7 @@ impl<'a> TableBuilder<'a> {
 
         let Self {
             ui,
+            id_source,
             columns,
             striped,
             resizable,
@@ -426,7 +438,7 @@ impl<'a> TableBuilder<'a> {
 
         let striped = striped.unwrap_or(ui.visuals().striped);
 
-        let state_id = ui.id().with("__table_state");
+        let state_id = ui.id().with(id_source);
 
         let (is_sizing_pass, state) =
             TableState::load(ui, state_id, resizable, &columns, available_width);
@@ -482,6 +494,7 @@ impl<'a> TableBuilder<'a> {
 
         let Self {
             ui,
+            id_source,
             columns,
             striped,
             resizable,
@@ -492,7 +505,7 @@ impl<'a> TableBuilder<'a> {
 
         let striped = striped.unwrap_or(ui.visuals().striped);
 
-        let state_id = ui.id().with("__table_state");
+        let state_id = ui.id().with(id_source);
 
         let (is_sizing_pass, state) =
             TableState::load(ui, state_id, resizable, &columns, available_width);