From 52fe997e286d84d4496748cb1002bc19b25e32b5 Mon Sep 17 00:00:00 2001
From: Alex Janka <alex@alexjanka.com>
Date: Thu, 9 Mar 2023 11:52:24 +1100
Subject: [PATCH] scale framebuffer in place

---
 gb-vst/src/ui.rs | 30 ++++++++++++++++++------------
 lib/src/util.rs  | 19 +++++++++++++++++++
 2 files changed, 37 insertions(+), 12 deletions(-)

diff --git a/gb-vst/src/ui.rs b/gb-vst/src/ui.rs
index f00f6b7..9be2fc0 100644
--- a/gb-vst/src/ui.rs
+++ b/gb-vst/src/ui.rs
@@ -8,7 +8,7 @@ use baseview::{
 };
 use gb_emu_lib::{
     connect::{JoypadButtons, JoypadState, Renderer, HEIGHT, WIDTH},
-    util::scale_buffer,
+    util::scale_buffer_in_place,
 };
 use keyboard_types::{Code, KeyState};
 use nih_plug::prelude::*;
@@ -74,6 +74,7 @@ impl Editor for Emulator {
 pub struct EmulatorWindow {
     pix: Pixels,
     scale: usize,
+    scaled_buf: Vec<[u8; 4]>,
     frame_receiver: Arc<FrameReceiver>,
     joypad_sender: Arc<JoypadSender>,
 }
@@ -86,20 +87,22 @@ impl EmulatorWindow {
     ) -> Self {
         let info = WindowInfo::from_logical_size(Size::new(WIDTH as f64, HEIGHT as f64), 1.);
 
-        let (pix, scale) = init_pixbuf(info, window);
+        let (pix, scale, scaled_buf) = init_pixbuf(info, window);
 
         Self {
             pix,
             scale,
+            scaled_buf,
             frame_receiver,
             joypad_sender,
         }
     }
 }
 
-fn init_pixbuf(info: WindowInfo, window: &mut Window) -> (Pixels, usize) {
+fn init_pixbuf(info: WindowInfo, window: &mut Window) -> (Pixels, usize, Vec<[u8; 4]>) {
     let physical_size = info.physical_size();
     let scale = (physical_size.width as usize / WIDTH).min(physical_size.height as usize / HEIGHT);
+    let scaled_buf = vec![[0, 0, 0, 0xFF]; WIDTH * scale * HEIGHT * scale];
     (
         pixels::Pixels::new(
             physical_size.width,
@@ -108,21 +111,24 @@ fn init_pixbuf(info: WindowInfo, window: &mut Window) -> (Pixels, usize) {
         )
         .unwrap(),
         scale,
+        scaled_buf,
     )
 }
 
 impl WindowHandler for EmulatorWindow {
     fn on_frame(&mut self, _window: &mut Window) {
         if let Some(ref mut receiver) = *self.frame_receiver.lock().expect("failed to lock mutex") {
-            if let Some(buf) = receiver.try_iter().last() {
-                let scaled_buf = if self.scale != 1 {
-                    scale_buffer(&buf, WIDTH, HEIGHT, self.scale)
-                } else {
-                    buf
-                };
-                for (pixel, source) in self.pix.get_frame_mut().chunks_exact_mut(4).zip(scaled_buf)
+            if let Some(ref buf) = receiver.try_iter().last() {
+                if self.scale != 1 {
+                    scale_buffer_in_place(buf, &mut self.scaled_buf, WIDTH, HEIGHT, self.scale);
+                }
+                for (pixel, source) in self
+                    .pix
+                    .get_frame_mut()
+                    .chunks_exact_mut(4)
+                    .zip(&self.scaled_buf)
                 {
-                    pixel.copy_from_slice(&source);
+                    pixel.copy_from_slice(source);
                 }
                 self.pix.render().unwrap();
             }
@@ -132,7 +138,7 @@ impl WindowHandler for EmulatorWindow {
     fn on_event(&mut self, window: &mut Window, event: baseview::Event) -> EventStatus {
         match event {
             Event::Window(WindowEvent::Resized(info)) => {
-                (self.pix, self.scale) = init_pixbuf(info, window);
+                (self.pix, self.scale, self.scaled_buf) = init_pixbuf(info, window);
                 EventStatus::Captured
             }
             Event::Keyboard(event) => {
diff --git a/lib/src/util.rs b/lib/src/util.rs
index eeda7bc..318df82 100644
--- a/lib/src/util.rs
+++ b/lib/src/util.rs
@@ -143,3 +143,22 @@ pub fn scale_buffer<T: From<Colour> + Copy>(
     }
     v
 }
+
+pub fn scale_buffer_in_place<T: From<Colour> + Copy>(
+    buffer: &[T],
+    target: &mut [T],
+    width: usize,
+    height: usize,
+    factor: usize,
+) {
+    for y in 0..height {
+        for y_2 in 0..factor {
+            for x in 0..width {
+                for x_2 in 0..factor {
+                    target[(((y * factor) + y_2) * (width * factor)) + (x * factor) + x_2] =
+                        buffer[(y * width) + x];
+                }
+            }
+        }
+    }
+}