add ClippingRect type

src/sdl2/render.rs

@@ -406,6 +406,15 @@ impl RenderTarget for Window {
     type Context = WindowContext;
 }
 
+pub enum ClippingRect {
+    /// a non-zero area clipping rect
+    Some(Rect),
+    /// a clipping rect with zero area
+    Zero,
+    /// the absence of a clipping rect
+    None,
+}
+
 /// Methods for the `WindowCanvas`.
 impl Canvas<Window> {
     /// Gets a reference to the associated window of the Canvas
@@ -1099,31 +1108,47 @@ impl<T: RenderTarget> Canvas<T> {
     }
 
     /// Sets the clip rectangle for rendering on the specified target.
-    ///
-    /// If the rectangle is `None`, clipping will be disabled.
     #[doc(alias = "SDL_RenderSetClipRect")]
-    pub fn set_clip_rect<R: Into<Option<Rect>>>(&mut self, rect: R) {
-        let rect = rect.into();
-        // as_ref is important because we need rect to live until the end of the FFI call, but map_or consumes an Option<T>
-        let ptr = rect.as_ref().map_or(ptr::null(), |rect| rect.raw());
-        let ret = unsafe { sys::SDL_RenderSetClipRect(self.context.raw, ptr) };
+    pub fn set_clip_rect(&mut self, arg: ClippingRect) {
+        let ret = match arg {
+            ClippingRect::Some(r) => {
+                unsafe { sys::SDL_RenderSetClipRect(self.context.raw, r.raw()) }
+            }
+            ClippingRect::Zero => {
+                let r = sys::SDL_Rect {
+                    x: 0,
+                    y: 0,
+                    w: 0,
+                    h: 0,
+                };
+                let r: *const sys::SDL_Rect = &r;
+                unsafe { sys::SDL_RenderSetClipRect(self.context.raw, r) }
+            }
+            ClippingRect::None => {
+                unsafe { sys::SDL_RenderSetClipRect(self.context.raw, ptr::null()) }
+            }
+        };
         if ret != 0 {
             panic!("Could not set clip rect: {}", get_error())
         }
     }
 
     /// Gets the clip rectangle for the current target.
-    ///
-    /// Returns `None` if clipping is disabled.
     #[doc(alias = "SDL_RenderGetClipRect")]
-    pub fn clip_rect(&self) -> Option<Rect> {
+    pub fn clip_rect(&self) -> ClippingRect {
+        let clip_enabled = unsafe { sys::SDL_RenderIsClipEnabled(self.context.raw) };
+
+        if let sys::SDL_bool::SDL_FALSE = clip_enabled {
+            return ClippingRect::None;
+        }
+
         let mut raw = mem::MaybeUninit::uninit();
         unsafe { sys::SDL_RenderGetClipRect(self.context.raw, raw.as_mut_ptr()) };
         let raw = unsafe { raw.assume_init() };
         if raw.w == 0 || raw.h == 0 {
-            None
+            ClippingRect::Zero
         } else {
-            Some(Rect::from_ll(raw))
+            ClippingRect::Some(Rect::from_ll(raw))
         }
     }