vesad: Update redox_syscall

vesad/src/screen/graphic.rs

@@ -91,13 +91,13 @@ impl Screen for GraphicScreen {
         Ok(size * 4)
     }
 
-    fn seek(&mut self, pos: usize, whence: usize) -> Result<usize> {
+    fn seek(&mut self, pos: isize, whence: usize) -> Result<usize> {
         let size = self.display.offscreen.len();
 
         self.seek = match whence {
-            SEEK_SET => cmp::min(size, pos/4),
-            SEEK_CUR => cmp::max(0, cmp::min(size as isize, self.seek as isize + (pos/4) as isize)) as usize,
-            SEEK_END => cmp::max(0, cmp::min(size as isize, size as isize + (pos/4) as isize)) as usize,
+            SEEK_SET => cmp::min(size, (pos/4) as usize),
+            SEEK_CUR => cmp::max(0, cmp::min(size as isize, self.seek as isize + (pos/4))) as usize,
+            SEEK_END => cmp::max(0, cmp::min(size as isize, size as isize + (pos/4))) as usize,
             _ => return Err(Error::new(EINVAL))
         };
 

vesad/src/screen/mod.rs

@@ -24,7 +24,7 @@ pub trait Screen {
 
     fn write(&mut self, buf: &[u8], sync: bool) -> Result<usize>;
 
-    fn seek(&mut self, pos: usize, whence: usize) -> Result<usize>;
+    fn seek(&mut self, pos: isize, whence: usize) -> Result<usize>;
 
     fn sync(&mut self);
 

vesad/src/screen/text.rs

@@ -209,7 +209,7 @@ impl Screen for TextScreen {
         Ok(buf.len())
     }
 
-    fn seek(&mut self, _pos: usize, _whence: usize) -> Result<usize> {
+    fn seek(&mut self, _pos: isize, _whence: usize) -> Result<usize> {
         Ok(0)
     }