From 69d08c5ef491cd2fb43486d254cc4745faa997ba Mon Sep 17 00:00:00 2001
From: Okko Hakola <okkohakola@gmail.com>
Date: Wed, 21 Sep 2022 22:35:15 +0000
Subject: [PATCH] Reconfigure surface on present mode change (#6049)

# Objective

- Reconfigure surface after present mode changes. It seems that this is not done currently at runtime. It's pretty common for games to change such graphical settings at runtime.
- Fixes present mode issue in #5111

## Solution

- Exactly like resolution change gets tracked when extracting window, do the same for present mode.

Additionally, I added present mode (vsync) toggling to window settings example.
---
 crates/bevy_render/src/view/window.rs | 20 ++++++++++++++++++--
 examples/window/window_settings.rs    | 19 +++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/crates/bevy_render/src/view/window.rs b/crates/bevy_render/src/view/window.rs
index bba940680f..6fe1bc8627 100644
--- a/crates/bevy_render/src/view/window.rs
+++ b/crates/bevy_render/src/view/window.rs
@@ -46,6 +46,7 @@ pub struct ExtractedWindow {
     pub present_mode: PresentMode,
     pub swap_chain_texture: Option<TextureView>,
     pub size_changed: bool,
+    pub present_mode_changed: bool,
 }
 
 #[derive(Default, Resource)]
@@ -77,6 +78,7 @@ fn extract_windows(
             window.physical_width().max(1),
             window.physical_height().max(1),
         );
+        let new_present_mode = window.present_mode();
 
         let mut extracted_window =
             extracted_windows
@@ -89,12 +91,14 @@ fn extract_windows(
                     present_mode: window.present_mode(),
                     swap_chain_texture: None,
                     size_changed: false,
+                    present_mode_changed: false,
                 });
 
         // NOTE: Drop the swap chain frame here
         extracted_window.swap_chain_texture = None;
         extracted_window.size_changed = new_width != extracted_window.physical_width
             || new_height != extracted_window.physical_height;
+        extracted_window.present_mode_changed = new_present_mode != extracted_window.present_mode;
 
         if extracted_window.size_changed {
             debug!(
@@ -107,6 +111,14 @@ fn extract_windows(
             extracted_window.physical_width = new_width;
             extracted_window.physical_height = new_height;
         }
+
+        if extracted_window.present_mode_changed {
+            debug!(
+                "Window Present Mode changed from {:?} to {:?}",
+                extracted_window.present_mode, new_present_mode
+            );
+            extracted_window.present_mode = new_present_mode;
+        }
     }
     for closed_window in closed.iter() {
         extracted_windows.remove(&closed_window.id);
@@ -174,8 +186,12 @@ pub fn prepare_windows(
             },
         };
 
-        // Do the initial surface configuration if it hasn't been configured yet
-        if window_surfaces.configured_windows.insert(window.id) || window.size_changed {
+        // Do the initial surface configuration if it hasn't been configured yet. Or if size or
+        // present mode changed.
+        if window_surfaces.configured_windows.insert(window.id)
+            || window.size_changed
+            || window.present_mode_changed
+        {
             render_device.configure_surface(surface, &swap_chain_descriptor);
         }
 
diff --git a/examples/window/window_settings.rs b/examples/window/window_settings.rs
index 5bda8151b7..c06153ce15 100644
--- a/examples/window/window_settings.rs
+++ b/examples/window/window_settings.rs
@@ -2,6 +2,7 @@
 //! the mouse pointer in various ways.
 
 use bevy::{prelude::*, window::PresentMode};
+use bevy_internal::diagnostic::{FrameTimeDiagnosticsPlugin, LogDiagnosticsPlugin};
 
 fn main() {
     App::new()
@@ -13,12 +14,30 @@ fn main() {
             ..default()
         })
         .add_plugins(DefaultPlugins)
+        .add_plugin(LogDiagnosticsPlugin::default())
+        .add_plugin(FrameTimeDiagnosticsPlugin)
         .add_system(change_title)
         .add_system(toggle_cursor)
+        .add_system(toggle_vsync)
         .add_system(cycle_cursor_icon)
         .run();
 }
 
+/// This system toggles the vsync mode when pressing the button V.
+/// You'll see fps increase displayed in the console.
+fn toggle_vsync(input: Res<Input<KeyCode>>, mut windows: ResMut<Windows>) {
+    if input.just_pressed(KeyCode::V) {
+        let window = windows.primary_mut();
+
+        window.set_present_mode(if matches!(window.present_mode(), PresentMode::AutoVsync) {
+            PresentMode::AutoNoVsync
+        } else {
+            PresentMode::AutoVsync
+        });
+        info!("PRESENT_MODE: {:?}", window.present_mode());
+    }
+}
+
 /// This system will then change the title during execution
 fn change_title(time: Res<Time>, mut windows: ResMut<Windows>) {
     let window = windows.primary_mut();