Fix the build failure from #13

Author: Feng23

src/backend.rs

@@ -15,6 +15,18 @@ pub struct CairoBackend<'a> {
  init_flag: bool,
 }
 
+
+#[derive(Debug)]
+pub struct CairoError;
+
+impl std::fmt::Display for CairoError {
+ fn fmt(&self, fmt: &mut std::fmt::Formatter) -> std::fmt::Result {
+ write!(fmt, "{:?}", self)
+ }
+}
+
+impl std::error::Error for CairoError {}
+
 impl<'a> CairoBackend<'a> {
  fn set_color(&self, color: &BackendColor) {
  self.context.set_source_rgba(
@@ -355,7 +367,9 @@ mod test {
  let buffer: Vec<u8> = vec![];
  let surface = cairo::PsSurface::for_stream(500.0, 500.0, buffer).unwrap();
  let cr = CairoContext::new(&surface).unwrap();
- let root = CairoBackend::new(&cr, (500, 500)).into_drawing_area();
+ let root = CairoBackend::new(&cr, (500, 500))
+ .unwrap()
+ .into_drawing_area();
 
  // Text could be rendered to different elements if has whitespaces
  let mut chart = ChartBuilder::on(&root)
@@ -396,7 +410,9 @@ mod test {
  let (width, height) = (1500, 800);
  let surface = cairo::PsSurface::for_stream(width.into(), height.into(), buffer).unwrap();
  let cr = CairoContext::new(&surface).unwrap();
- let root = CairoBackend::new(&cr, (width, height)).into_drawing_area();
+ let root = CairoBackend::new(&cr, (width, height))
+ .unwrap()
+ .into_drawing_area();
  let root = root
  .titled("Image Title", ("sans-serif", 60).into_font())
  .unwrap();
@@ -461,7 +477,9 @@ mod test {
  let (width, height) = (500_i32, 500_i32);
  let surface = cairo::PsSurface::for_stream(width.into(), height.into(), buffer).unwrap();
  let cr = CairoContext::new(&surface).unwrap();
- let root = CairoBackend::new(&cr, (width as u32, height as u32)).into_drawing_area();
+ let root = CairoBackend::new(&cr, (width as u32, height as u32))
+ .unwrap()
+ .into_drawing_area();
 
  let style = TextStyle::from(("sans-serif", 20).into_font())
  .pos(Pos::new(HPos::Center, VPos::Center));
@@ -492,7 +510,9 @@ mod test {
  let (width, height) = (500, 500);
  let surface = cairo::PsSurface::for_stream(width.into(), height.into(), buffer).unwrap();
  let cr = CairoContext::new(&surface).unwrap();
- let root = CairoBackend::new(&cr, (width, height)).into_drawing_area();
+ let root = CairoBackend::new(&cr, (width, height))
+ .unwrap()
+ .into_drawing_area();
 
  let mut chart = ChartBuilder::on(&root)
  .caption("All series label positions", ("sans-serif", 20))
@@ -552,7 +572,9 @@ mod test {
  let (width, height) = (100_i32, 100_i32);
  let surface = cairo::PsSurface::for_stream(width.into(), height.into(), buffer).unwrap();
  let cr = CairoContext::new(&surface).unwrap();
- let root = CairoBackend::new(&cr, (width as u32, height as u32)).into_drawing_area();
+ let root = CairoBackend::new(&cr, (width as u32, height as u32))
+ .unwrap()
+ .into_drawing_area();
 
  for i in -20..20 {
  let alpha = i as f64 * 0.1;