Rename Rectangle::round to snap

Also use `ceil` instead of `round`.
Closes #380.

core/src/rectangle.rs

@@ -126,15 +126,15 @@ impl Rectangle<f32> {
         }
     }
 
-    /// Rounds the [`Rectangle`] to __unsigned__ integer coordinates.
+    /// Snaps the [`Rectangle`] to __unsigned__ integer coordinates.
     ///
     /// [`Rectangle`]: struct.Rectangle.html
-    pub fn round(self) -> Rectangle<u32> {
+    pub fn snap(self) -> Rectangle<u32> {
         Rectangle {
             x: self.x as u32,
             y: self.y as u32,
-            width: (self.width + 0.5).round() as u32,
+            width: self.width.ceil() as u32,
-            height: (self.height + 0.5).round() as u32,
+            height: self.height.ceil() as u32,
         }
     }
 }

glow/src/backend.rs

@@ -75,7 +75,7 @@ impl Backend {
         layer: &Layer<'_>,
         target_height: u32,
     ) {
-        let mut bounds = (layer.bounds * scale_factor).round();
+        let mut bounds = (layer.bounds * scale_factor).snap();
         bounds.height = bounds.height.min(target_height);
 
         if !layer.quads.is_empty() {

glow/src/triangle.rs

@@ -176,7 +176,7 @@ impl Pipeline {
             let transform =
                 transformation * Transformation::translate(origin.x, origin.y);
 
-            let clip_bounds = (*clip_bounds * scale_factor).round();
+            let clip_bounds = (*clip_bounds * scale_factor).snap();
 
             unsafe {
                 if self.current_transform != transform {

wgpu/src/backend.rs

@@ -105,7 +105,7 @@ impl Backend {
         target_width: u32,
         target_height: u32,
     ) {
-        let bounds = (layer.bounds * scale_factor).round();
+        let bounds = (layer.bounds * scale_factor).snap();
 
         if !layer.quads.is_empty() {
             self.quad_pipeline.draw(

wgpu/src/triangle.rs

@@ -326,8 +326,7 @@ impl Pipeline {
             for (i, (vertex_offset, index_offset, indices)) in
                 offsets.into_iter().enumerate()
             {
-                let clip_bounds =
+                let clip_bounds = (meshes[i].clip_bounds * scale_factor).snap();
-                    (meshes[i].clip_bounds * scale_factor).round();
 
                 render_pass.set_scissor_rect(
                     clip_bounds.x,