Automatically repaint if any widget changes

emilk · Feb 1, 2024 · af9aa56 · af9aa56
1 parent 97221a4
commit af9aa56
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Showing 2 changed files with 29 additions and 14 deletions.
diff --git a/crates/egui/src/context.rs b/crates/egui/src/context.rs
@@ -198,7 +198,7 @@ pub struct WidgetRect {
 /// Stores the positions of all widgets generated during a single egui update/frame.
 ///
 /// Acgtually, only those that are on screen.
-#[derive(Default, Clone)]
+#[derive(Default, Clone, PartialEq, Eq)]
 pub struct WidgetRects {
     /// All widgets, in painting order.
     pub by_layer: HashMap<LayerId, Vec<WidgetRect>>,
@@ -398,14 +398,6 @@ impl ContextImpl {
                 .native_pixels_per_point
                 .unwrap_or(1.0);
 
-        {
-            std::mem::swap(
-                &mut viewport.layer_rects_prev_frame,
-                &mut viewport.layer_rects_this_frame,
-            );
-            viewport.layer_rects_this_frame.clear();
-        }
-
         let all_viewport_ids: ViewportIdSet = self.all_viewport_ids();
 
         let viewport = self.viewports.entry(self.viewport_id()).or_default();
@@ -645,12 +637,12 @@ impl Default for Context {
 }
 
 impl Context {
-    // Do read-only (shared access) transaction on Context
+    /// Do read-only (shared access) transaction on Context
     fn read<R>(&self, reader: impl FnOnce(&ContextImpl) -> R) -> R {
         reader(&self.0.read())
     }
 
-    // Do read-write (exclusive access) transaction on Context
+    /// Do read-write (exclusive access) transaction on Context
     fn write<R>(&self, writer: impl FnOnce(&mut ContextImpl) -> R) -> R {
         writer(&mut self.0.write())
     }
@@ -1820,7 +1812,24 @@ impl ContextImpl {
 
         let shapes = viewport.graphics.drain(self.memory.areas().order());
 
-        if viewport.input.wants_repaint() {
+        let mut repaint_needed = false;
+
+        {
+            if self.memory.options.repaint_on_widget_change {
+                crate::profile_function!("compare-widget-rects");
+                if viewport.layer_rects_prev_frame != viewport.layer_rects_this_frame {
+                    repaint_needed = true; // Some widget has moved
+                }
+            }
+
+            std::mem::swap(
+                &mut viewport.layer_rects_prev_frame,
+                &mut viewport.layer_rects_this_frame,
+            );
+            viewport.layer_rects_this_frame.clear();
+        }
+
+        if repaint_needed || viewport.input.wants_repaint() {
             self.request_repaint(ended_viewport_id);
         }
 
@@ -2194,7 +2203,7 @@ impl Context {
 
             // We add all widgets here, even non-interactive ones,
             // because we need this list not only for checking for blocking widgets,
-            // but also to know when we have reach the widget we are checking for cover.
+            // but also to know when we have reached the widget we are checking for cover.
             viewport
                 .layer_rects_this_frame
                 .insert(layer_id, WidgetRect { id, rect, sense });

diff --git a/crates/egui/src/memory.rs b/crates/egui/src/memory.rs
@@ -154,7 +154,7 @@ impl FocusDirection {
 // ----------------------------------------------------------------------------
 
 /// Some global options that you can read and write.
-#[derive(Clone, Debug)]
+#[derive(Clone, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[cfg_attr(feature = "serde", serde(default))]
 pub struct Options {
@@ -184,6 +184,11 @@ pub struct Options {
     /// Controls the tessellator.
     pub tessellation_options: epaint::TessellationOptions,
 
+    /// If any widget moves or changes id, repaint everything.
+    ///
+    /// This is `true` by default.
+    pub repaint_on_widget_change: bool,
+
     /// This is a signal to any backend that we want the [`crate::PlatformOutput::events`] read out loud.
     ///
     /// The only change to egui is that labels can be focused by pressing tab.
@@ -216,6 +221,7 @@ impl Default for Options {
             zoom_factor: 1.0,
             zoom_with_keyboard: true,
             tessellation_options: Default::default(),
+            repaint_on_widget_change: true,
             screen_reader: false,
             preload_font_glyphs: true,
             warn_on_id_clash: cfg!(debug_assertions),