Implement a TopScreen3D type for 3d mode

This type sets 3d mode on construction, and unsets it on drop, while
keeping a copy of the RefCell to the top screen.

I don't think this is perfect, but it seems like a decent option that
should still prevent any concurrent access to the top screen's buffer.

ctru-rs/examples/camera-image.rs

@@ -1,9 +1,8 @@
 use ctru::console::Console;
-use ctru::gfx::{Screen, Side};
+use ctru::gfx::{Gfx, Screen};
 use ctru::services::cam::{Cam, CamOutputFormat, CamShutterSoundType, CamSize, Camera};
 use ctru::services::hid::KeyPad;
 use ctru::services::{Apt, Hid};
-use ctru::Gfx;
 use std::time::Duration;
 
 const WIDTH: usize = 400;
@@ -89,7 +88,7 @@ fn main() {
         unsafe {
             gfx.top_screen
                 .borrow_mut()
-                .get_raw_framebuffer(Side::Left)
+                .get_raw_framebuffer()
                 .ptr
                 .copy_from(img.as_ptr(), img.len());
         }

ctru-rs/examples/gfx-3d-mode.rs

@@ -0,0 +1,72 @@
+use ctru::gfx::TopScreen3D;
+use ctru::prelude::*;
+
+/// See `graphics-bitmap.rs` for details on how the image is generated.
+///
+/// WARNING: this example uses 3D mode in a rather unnatural way, and should
+/// probably not be viewed for too long or at all if you are photosensitive.
+
+const IMAGE: &[u8] = include_bytes!("assets/ferris.rgb");
+const ZERO: &[u8] = &[0; IMAGE.len()];
+
+fn main() {
+    ctru::init();
+    let gfx = Gfx::init().expect("Couldn't obtain GFX controller");
+    let hid = Hid::init().expect("Couldn't obtain HID controller");
+    let apt = Apt::init().expect("Couldn't obtain APT controller");
+    let _console = Console::init(gfx.bottom_screen.borrow_mut());
+
+    println!("Press Start to exit.\nPress A to switch which side is drawn to.");
+
+    let top_screen = TopScreen3D::from(&gfx.top_screen);
+
+    // TODO set double buffering for top screen
+
+    let mut left = top_screen.left_mut();
+    let left_buf = left.get_raw_framebuffer();
+    let mut right = top_screen.right_mut();
+    let right_buf = right.get_raw_framebuffer();
+
+    // We assume the image is the correct size already, so we ignore width + height.
+    let mut buf = left_buf.ptr;
+
+    // Copy the image into the left-side frame buffer
+    unsafe {
+        buf.copy_from(IMAGE.as_ptr(), IMAGE.len());
+    }
+
+    // Main loop
+    while apt.main_loop() {
+        //Scan all the inputs. This should be done once for each frame
+        hid.scan_input();
+
+        if hid.keys_down().contains(KeyPad::KEY_START) {
+            break;
+        }
+
+        if hid.keys_down().contains(KeyPad::KEY_A) {
+            // Clear the side we just drew to by zeroing it out
+            unsafe {
+                buf.copy_from(ZERO.as_ptr(), ZERO.len());
+            }
+
+            // flip which buffer we're writing to, and redraw the image
+            buf = if buf == left_buf.ptr {
+                right_buf.ptr
+            } else {
+                left_buf.ptr
+            };
+
+            unsafe {
+                buf.copy_from(IMAGE.as_ptr(), IMAGE.len());
+            }
+        }
+
+        // Flush and swap framebuffers
+        gfx.flush_buffers();
+        gfx.swap_buffers();
+
+        //Wait for VBlank
+        gfx.wait_for_vblank();
+    }
+}

ctru-rs/examples/hello-world.rs

@@ -1,4 +1,3 @@
-use ctru::gfx::Side;
 use ctru::prelude::*;
 
 use std::io::BufWriter;
@@ -8,7 +7,7 @@ fn main() {
     let gfx = Gfx::init().expect("Couldn't obtain GFX controller");
     let hid = Hid::init().expect("Couldn't obtain HID controller");
     let apt = Apt::init().expect("Couldn't obtain APT controller");
-    let _console = Console::init(gfx.top_screen.borrow_side_mut(Side::Left));
+    let _console = Console::init(gfx.top_screen.borrow_mut());
 
     let out = b"Hello fellow Rustaceans, I'm on the Nintendo 3DS!";
     let width = 24;

ctru-rs/src/gfx.rs

@@ -9,10 +9,20 @@ use crate::error::Result;
 use crate::services::gspgpu::{self, FramebufferFormat};
 use crate::services::ServiceReference;
 
+mod private {
+    use super::{BottomScreen, TopScreen, TopScreenRight};
+
+    pub trait Sealed {}
+
+    impl Sealed for TopScreen {}
+    impl Sealed for TopScreenRight {}
+    impl Sealed for BottomScreen {}
+}
+
 /// This trait is implemented by the screen structs for working with frame buffers and
 /// drawing to the screens. Graphics-related code can be made generic over this
 /// trait to work with any of the given screens.
-pub trait Screen {
+pub trait Screen: private::Sealed {
     /// Returns the libctru value for the Screen kind
     fn as_raw(&self) -> ctru_sys::gfxScreen_t;
 
@@ -41,23 +51,23 @@ pub trait Screen {
     }
 }
 
-// TODO: it might be nice to do `TopScreen<const SIDE: Side>` but it requires
-// #![feature(adt_const_params)] which is unstable, and doesn't seem worth it
-// just for this.
 #[non_exhaustive]
-pub struct TopLeftScreen;
-
-#[non_exhaustive]
-pub struct TopRightScreen;
+pub struct TopScreen;
 
 /// A helper container for both sides of the top screen.
-pub struct TopScreenInner {
-    left: TopLeftScreen,
-    right: TopRightScreen,
+pub struct TopScreen3D<'a> {
+    // morally, this should be &mut or RefMut, but if we do
+    // - &mut: it means gfx can no longer be borrowed immutably while this exists
+    // - RefMut: we don't have an easy way to obtain Ref<dyn Screen> for the left side.
+    //      maybe this one isn't as important since the use case is typically RefMut anyway.
+    //      we could just return &dyn Screen instead of Ref<dyn Screen> ?
+    left: &'a RefCell<TopScreen>,
+    right: RefCell<TopScreenRight>,
 }
 
-#[non_exhaustive]
-pub struct TopScreen(RefCell<TopScreenInner>);
+// TODO: it feels a little weird to have an asymmetric separate type like this,
+// but maybe if it's not `pub` it's not as weird...
+struct TopScreenRight;
 
 #[non_exhaustive]
 pub struct BottomScreen;
@@ -81,7 +91,7 @@ pub struct RawFrameBuffer<'screen> {
 /// Side of top screen framebuffer
 ///
 /// The top screen of the 3DS can have two separate sets of framebuffers to support its 3D functionality
-pub enum Side {
+enum Side {
     /// The left framebuffer. This framebuffer is also the one used when 3D is disabled
     Left,
     /// The right framebuffer
@@ -94,7 +104,7 @@ pub enum Side {
 /// The service exits when this struct is dropped.
 #[non_exhaustive]
 pub struct Gfx {
-    pub top_screen: TopScreen,
+    pub top_screen: RefCell<TopScreen>,
     pub bottom_screen: RefCell<BottomScreen>,
     _service_handler: ServiceReference,
 }
@@ -123,7 +133,7 @@ impl Gfx {
         )?;
 
         Ok(Self {
-            top_screen: TopScreen::new(TopLeftScreen, TopRightScreen),
+            top_screen: RefCell::new(TopScreen),
             bottom_screen: RefCell::new(BottomScreen),
             _service_handler,
         })
@@ -163,87 +173,73 @@ impl Gfx {
     }
 }
 
-impl TopScreen {
-    fn new(left: TopLeftScreen, right: TopRightScreen) -> Self {
-        Self(RefCell::new(TopScreenInner { left, right }))
+impl<'screen> RawFrameBuffer<'screen> {
+    fn for_screen_side(screen: &'screen mut dyn Screen, side: Side) -> Self {
+        let mut width = 0;
+        let mut height = 0;
+        let ptr = unsafe {
+            ctru_sys::gfxGetFramebuffer(screen.as_raw(), side.into(), &mut width, &mut height)
+        };
+        Self {
+            ptr,
+            width,
+            height,
+            screen: PhantomData,
+        }
     }
+}
 
-    pub fn borrow(&self) -> Ref<'_, TopScreenInner> {
-        self.0.borrow()
+impl TopScreen3D<'_> {
+    pub fn left(&self) -> Ref<dyn Screen> {
+        self.left.borrow()
     }
 
-    pub fn borrow_mut(&self) -> RefMut<'_, TopScreenInner> {
-        self.0.borrow_mut()
+    pub fn left_mut(&self) -> RefMut<dyn Screen> {
+        self.left.borrow_mut()
     }
 
-    pub fn borrow_side(&self, side: Side) -> Ref<'_, dyn Screen> {
-        let borrow = self.0.borrow();
-        match side {
-            Side::Left => Ref::map(borrow, |top| &top.left),
-            Side::Right => Ref::map(borrow, |top| &top.right),
-        }
+    pub fn right(&self) -> Ref<dyn Screen> {
+        self.right.borrow()
     }
 
-    pub fn borrow_side_mut(&self, side: Side) -> RefMut<'_, dyn Screen> {
-        let borrow = self.0.borrow_mut();
-        match side {
-            Side::Left => RefMut::map(borrow, |top| &mut top.left),
-            Side::Right => RefMut::map(borrow, |top| &mut top.right),
-        }
+    pub fn right_mut(&self) -> RefMut<dyn Screen> {
+        self.right.borrow_mut()
     }
 }
 
-impl TopScreenInner {
-    /// Enable or disable the 3D stereoscopic effect
-    pub fn set_3d_enabled(&mut self, enabled: bool) {
+impl<'a> From<&'a RefCell<TopScreen>> for TopScreen3D<'a> {
+    fn from(top_screen: &'a RefCell<TopScreen>) -> Self {
         unsafe {
-            ctru_sys::gfxSet3D(enabled);
+            ctru_sys::gfxSet3D(true);
         }
-    }
-
-    /// Enable or disable the wide screen mode (top screen).
-    /// This only works when 3D is disabled.
-    pub fn set_wide_mode(&mut self, enabled: bool) {
-        unsafe {
-            ctru_sys::gfxSetWide(enabled);
+        TopScreen3D {
+            left: top_screen,
+            right: RefCell::new(TopScreenRight),
         }
     }
-
-    /// Get the status of wide screen mode.
-    pub fn get_wide_mode(&self) -> bool {
-        unsafe { ctru_sys::gfxIsWide() }
-    }
 }
 
-impl<'screen> RawFrameBuffer<'screen> {
-    fn for_screen_side(screen: &'screen mut dyn Screen, side: Side) -> Self {
-        let mut width = 0;
-        let mut height = 0;
-        let ptr = unsafe {
-            ctru_sys::gfxGetFramebuffer(screen.as_raw(), side.into(), &mut width, &mut height)
-        };
-        Self {
-            ptr,
-            width,
-            height,
-            screen: PhantomData,
+impl Drop for TopScreen3D<'_> {
+    fn drop(&mut self) {
+        unsafe {
+            ctru_sys::gfxSet3D(false);
         }
     }
 }
 
-impl Screen for TopScreenInner {
-    fn as_raw(&self) -> ctru_sys::gfxScreen_t {
-        self.left.as_raw()
+impl TopScreen {
+    pub fn set_wide_mode(&mut self, enable: bool) {
+        unsafe {
+            ctru_sys::gfxSetWide(enable);
+        }
     }
 
-    fn get_raw_framebuffer(&mut self) -> RawFrameBuffer {
-        // When dealing with the "whole" top screen, the left framebuffer is the
-        // one used for writing pixel data.
-        self.left.get_raw_framebuffer()
+    pub fn get_wide_mode(&self) -> bool {
+        unsafe { ctru_sys::gfxIsWide() }
     }
 }
 
-impl Screen for TopLeftScreen {
+impl Screen for TopScreen {
     fn as_raw(&self) -> ctru_sys::gfxScreen_t {
         ctru_sys::GFX_TOP
     }
@@ -253,7 +249,7 @@ impl Screen for TopLeftScreen {
     }
 }
 
-impl Screen for TopRightScreen {
+impl Screen for TopScreenRight {
     fn as_raw(&self) -> ctru_sys::gfxScreen_t {
         ctru_sys::GFX_TOP
     }