store gfx::framerate::FPSmanager directly in FPSManager instead of on the heap (#1415)

* store gfx::framerate::FPSmanager directly in FPSManager instead of on the heap

* update changelog

Author: antonilol

changelog.md

@@ -3,6 +3,8 @@ when upgrading from a version of rust-sdl2 to another.
 
 ### Next
 
+[PR #1415](https://github.com/Rust-SDL2/rust-sdl2/pull/1415) Store `gfx::framerate::FPSmanager` directly in `FPSManager` instead of on the heap.
+
 [PR #1450](https://github.com/Rust-SDL2/rust-sdl2/pull/1450) **BREAKING CHANGE** Create ClippingRect type, to disambiguate between no and zero area clipping rect.
 
 [PR #1416](https://github.com/Rust-SDL2/rust-sdl2/pull/1416) Apply clippy fixes, fix deprecations and other code quality improvements.

src/sdl2/gfx/framerate.rs

@@ -1,30 +1,36 @@
 //! Framerate control
 
 use get_error;
-use libc;
-use libc::{c_void, size_t};
-use std::mem;
+use std::mem::MaybeUninit;
 use sys::gfx;
 
 /// Structure holding the state and timing information of the framerate controller.
+#[derive(Debug, Clone)]
 pub struct FPSManager {
-    raw: *mut gfx::framerate::FPSmanager,
+    raw: gfx::framerate::FPSmanager,
+}
+
+impl Default for FPSManager {
+    fn default() -> Self {
+        Self::new()
+    }
 }
 
 impl FPSManager {
     /// Create the framerate manager.
     pub fn new() -> FPSManager {
         unsafe {
-            let size = mem::size_of::<gfx::framerate::FPSmanager>() as size_t;
-            let raw = libc::malloc(size) as *mut gfx::framerate::FPSmanager;
-            gfx::framerate::SDL_initFramerate(raw);
-            FPSManager { raw }
+            let mut raw = MaybeUninit::uninit();
+            gfx::framerate::SDL_initFramerate(raw.as_mut_ptr());
+            FPSManager {
+                raw: raw.assume_init(),
+            }
         }
     }
 
     /// Set the framerate in Hz.
     pub fn set_framerate(&mut self, rate: u32) -> Result<(), String> {
-        let ret = unsafe { gfx::framerate::SDL_setFramerate(self.raw, rate) };
+        let ret = unsafe { gfx::framerate::SDL_setFramerate(&mut self.raw, rate) };
         match ret {
             0 => Ok(()),
             _ => Err(get_error()),
@@ -34,23 +40,19 @@ impl FPSManager {
     /// Return the current target framerate in Hz.
     pub fn get_framerate(&self) -> i32 {
         // will not get an error
-        unsafe { gfx::framerate::SDL_getFramerate(self.raw) as i32 }
+        // SAFETY: SDL_getFramerate will not mutate self.raw, even though it accepts *mut FPSmanager.
+        unsafe { gfx::framerate::SDL_getFramerate(&self.raw as *const _ as *mut _) as i32 }
     }
 
     /// Return the current framecount.
     pub fn get_frame_count(&self) -> i32 {
         // will not get an error
-        unsafe { gfx::framerate::SDL_getFramecount(self.raw) as i32 }
+        // SAFETY: SDL_getFramecount will not mutate self.raw, even though it accepts *mut FPSmanager.
+        unsafe { gfx::framerate::SDL_getFramecount(&self.raw as *const _ as *mut _) as i32 }
     }
 
     /// Delay execution to maintain a constant framerate and calculate fps.
     pub fn delay(&mut self) -> u32 {
-        unsafe { gfx::framerate::SDL_framerateDelay(self.raw) as u32 }
-    }
-}
-
-impl Drop for FPSManager {
-    fn drop(&mut self) {
-        unsafe { libc::free(self.raw as *mut c_void) }
+        unsafe { gfx::framerate::SDL_framerateDelay(&mut self.raw) as u32 }
     }
 }