Change set_cursor_position to return Result<(), String> (#562)

* Change set_cursor_position to return Result<(), String>

This is now consistent with `grab_cursor`, and
enables `window.set_cursor_position(x, y)?` in functions
that return `Result<_, Box<Error>>`.

* Adjust error handling of unimplemented cusor opertions in wayland

* The final nitpick

* Actually one more

src/platform/linux/mod.rs

@@ -251,7 +251,7 @@ impl Window {
     pub fn grab_cursor(&self, grab: bool) -> Result<(), String> {
         match self {
             &Window::X(ref window) => window.grab_cursor(grab),
-            &Window::Wayland(ref _window) => Err("Cursor grabbing is not yet possible on Wayland.".to_owned()),
+            &Window::Wayland(ref window) => window.grab_cursor(grab),
         }
     }
 
@@ -259,7 +259,7 @@ impl Window {
     pub fn hide_cursor(&self, hide: bool) {
         match self {
             &Window::X(ref window) => window.hide_cursor(hide),
-            &Window::Wayland(ref _window) => unimplemented!(),
+            &Window::Wayland(ref window) => window.hide_cursor(hide),
         }
     }
 
@@ -272,7 +272,7 @@ impl Window {
     }
 
     #[inline]
-    pub fn set_cursor_position(&self, position: LogicalPosition) -> Result<(), ()> {
+    pub fn set_cursor_position(&self, position: LogicalPosition) -> Result<(), String> {
         match self {
             &Window::X(ref w) => w.set_cursor_position(position),
             &Window::Wayland(ref w) => w.set_cursor_position(position),

src/platform/linux/wayland/window.rs

@@ -235,11 +235,6 @@ impl Window {
         self.frame.lock().unwrap().set_resizable(resizable);
     }
 
-    #[inline]
-    pub fn set_cursor(&self, _cursor: MouseCursor) {
-        // TODO
-    }
-
     #[inline]
     pub fn hidpi_factor(&self) -> i32 {
         self.monitors.lock().unwrap().compute_hidpi_factor()
@@ -273,9 +268,23 @@ impl Window {
     }
 
     #[inline]
-    pub fn set_cursor_position(&self, _pos: LogicalPosition) -> Result<(), ()> {
-        // TODO: not yet possible on wayland
-        Err(())
+    pub fn set_cursor(&self, _cursor: MouseCursor) {
+        // TODO
+    }
+
+    #[inline]
+    pub fn hide_cursor(&self, _hide: bool) {
+        // TODO: This isn't possible on Wayland yet
+    }
+
+    #[inline]
+    pub fn grab_cursor(&self, _grab: bool) -> Result<(), String> {
+        Err("Cursor grabbing is not yet possible on Wayland.".to_owned())
+    }
+
+    #[inline]
+    pub fn set_cursor_position(&self, _pos: LogicalPosition) -> Result<(), String> {
+        Err("Setting the cursor position is not yet possible on Wayland.".to_owned())
     }
 
     pub fn get_display(&self) -> &Display {

src/platform/linux/x11/window.rs

@@ -1113,7 +1113,7 @@ impl UnownedWindow {
         self.get_current_monitor().hidpi_factor
     }
 
-    pub(crate) fn set_cursor_position_physical(&self, x: i32, y: i32) -> Result<(), ()> {
+    pub fn set_cursor_position_physical(&self, x: i32, y: i32) -> Result<(), String> {
         unsafe {
             (self.xconn.xlib.XWarpPointer)(
                 self.xconn.display,
@@ -1126,12 +1126,12 @@ impl UnownedWindow {
                 x,
                 y,
             );
-            self.xconn.flush_requests().map_err(|_| ())
+            self.xconn.flush_requests().map_err(|e| format!("`XWarpPointer` failed: {:?}", e))
         }
     }
 
     #[inline]
-    pub fn set_cursor_position(&self, logical_position: LogicalPosition) -> Result<(), ()> {
+    pub fn set_cursor_position(&self, logical_position: LogicalPosition) -> Result<(), String> {
         let (x, y) = logical_position.to_physical(self.get_hidpi_factor()).into();
         self.set_cursor_position_physical(x, y)
     }