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-rw-r--r--components/util/geometry.rs304
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diff --git a/components/util/geometry.rs b/components/util/geometry.rs
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use geom::length::Length;
+use geom::point::Point2D;
+use geom::rect::Rect;
+use geom::size::Size2D;
+
+use serialize::{Encodable, Encoder};
+use std::default::Default;
+use std::num::{NumCast, One, Zero};
+use std::fmt;
+
+// Units for use with geom::length and geom::scale_factor.
+
+/// A normalized "pixel" at the default resolution for the display.
+///
+/// Like the CSS "px" unit, the exact physical size of this unit may vary between devices, but it
+/// should approximate a device-independent reference length. This unit corresponds to Android's
+/// "density-independent pixel" (dip), Mac OS X's "point", and Windows "device-independent pixel."
+///
+/// The relationship between DevicePixel and ScreenPx is defined by the OS. On most low-dpi
+/// screens, one ScreenPx is equal to one DevicePixel. But on high-density screens it can be
+/// some larger number. For example, by default on Apple "retina" displays, one ScreenPx equals
+/// two DevicePixels. On Android "MDPI" displays, one ScreenPx equals 1.5 device pixels.
+///
+/// The ratio between ScreenPx and DevicePixel for a given display be found by calling
+/// `servo::windowing::WindowMethods::hidpi_factor`.
+pub enum ScreenPx {}
+
+/// One CSS "px" in the coordinate system of the "initial viewport":
+/// http://www.w3.org/TR/css-device-adapt/#initial-viewport
+///
+/// ViewportPx is equal to ScreenPx times a "page zoom" factor controlled by the user. This is
+/// the desktop-style "full page" zoom that enlarges content but then reflows the layout viewport
+/// so it still exactly fits the visible area.
+///
+/// At the default zoom level of 100%, one PagePx is equal to one ScreenPx. However, if the
+/// document is zoomed in or out then this scale may be larger or smaller.
+#[deriving(Encodable)]
+pub enum ViewportPx {}
+
+/// One CSS "px" in the root coordinate system for the content document.
+///
+/// PagePx is equal to ViewportPx multiplied by a "viewport zoom" factor controlled by the user.
+/// This is the mobile-style "pinch zoom" that enlarges content without reflowing it. When the
+/// viewport zoom is not equal to 1.0, then the layout viewport is no longer the same physical size
+/// as the viewable area.
+#[deriving(Encodable)]
+pub enum PagePx {}
+
+// In summary, the hierarchy of pixel units and the factors to convert from one to the next:
+//
+// DevicePixel
+// / hidpi_ratio => ScreenPx
+// / desktop_zoom => ViewportPx
+// / pinch_zoom => PagePx
+
+// An Au is an "App Unit" and represents 1/60th of a CSS pixel. It was
+// originally proposed in 2002 as a standard unit of measure in Gecko.
+// See https://bugzilla.mozilla.org/show_bug.cgi?id=177805 for more info.
+//
+// FIXME: Implement Au using Length and ScaleFactor instead of a custom type.
+#[deriving(Clone, PartialEq, PartialOrd, Eq, Ord, Zero)]
+pub struct Au(pub i32);
+
+impl Default for Au {
+ #[inline]
+ fn default() -> Au {
+ Au(0)
+ }
+}
+
+impl<E, S: Encoder<E>> Encodable<S, E> for Au {
+ fn encode(&self, e: &mut S) -> Result<(), E> {
+ e.emit_f64(to_frac_px(*self))
+ }
+}
+
+impl fmt::Show for Au {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ write!(f, "{}px", to_frac_px(*self))
+ }}
+
+impl Add<Au,Au> for Au {
+ #[inline]
+ fn add(&self, other: &Au) -> Au {
+ let Au(s) = *self;
+ let Au(o) = *other;
+ Au(s + o)
+ }
+}
+
+impl Sub<Au,Au> for Au {
+ #[inline]
+ fn sub(&self, other: &Au) -> Au {
+ let Au(s) = *self;
+ let Au(o) = *other;
+ Au(s - o)
+ }
+
+}
+
+impl Mul<Au,Au> for Au {
+ #[inline]
+ fn mul(&self, other: &Au) -> Au {
+ let Au(s) = *self;
+ let Au(o) = *other;
+ Au(s * o)
+ }
+}
+
+impl Div<Au,Au> for Au {
+ #[inline]
+ fn div(&self, other: &Au) -> Au {
+ let Au(s) = *self;
+ let Au(o) = *other;
+ Au(s / o)
+ }
+}
+
+impl Rem<Au,Au> for Au {
+ #[inline]
+ fn rem(&self, other: &Au) -> Au {
+ let Au(s) = *self;
+ let Au(o) = *other;
+ Au(s % o)
+ }
+}
+
+impl Neg<Au> for Au {
+ #[inline]
+ fn neg(&self) -> Au {
+ let Au(s) = *self;
+ Au(-s)
+ }
+}
+
+impl One for Au {
+ #[inline]
+ fn one() -> Au { Au(1) }
+}
+
+impl Num for Au {}
+
+#[inline]
+pub fn min(x: Au, y: Au) -> Au { if x < y { x } else { y } }
+#[inline]
+pub fn max(x: Au, y: Au) -> Au { if x > y { x } else { y } }
+
+impl NumCast for Au {
+ #[inline]
+ fn from<T:ToPrimitive>(n: T) -> Option<Au> {
+ Some(Au(n.to_i32().unwrap()))
+ }
+}
+
+impl ToPrimitive for Au {
+ #[inline]
+ fn to_i64(&self) -> Option<i64> {
+ let Au(s) = *self;
+ Some(s as i64)
+ }
+
+ #[inline]
+ fn to_u64(&self) -> Option<u64> {
+ let Au(s) = *self;
+ Some(s as u64)
+ }
+
+ #[inline]
+ fn to_f32(&self) -> Option<f32> {
+ let Au(s) = *self;
+ s.to_f32()
+ }
+
+ #[inline]
+ fn to_f64(&self) -> Option<f64> {
+ let Au(s) = *self;
+ s.to_f64()
+ }
+}
+
+impl Au {
+ /// FIXME(pcwalton): Workaround for lack of cross crate inlining of newtype structs!
+ #[inline]
+ pub fn new(value: i32) -> Au {
+ Au(value)
+ }
+
+ #[inline]
+ pub fn scale_by(self, factor: f64) -> Au {
+ let Au(s) = self;
+ Au(((s as f64) * factor) as i32)
+ }
+
+ #[inline]
+ pub fn from_px(px: int) -> Au {
+ NumCast::from(px * 60).unwrap()
+ }
+
+ #[inline]
+ pub fn from_page_px(px: Length<PagePx, f32>) -> Au {
+ NumCast::from(px.get() * 60f32).unwrap()
+ }
+
+ #[inline]
+ pub fn to_nearest_px(&self) -> int {
+ let Au(s) = *self;
+ ((s as f64) / 60f64).round() as int
+ }
+
+ #[inline]
+ pub fn to_snapped(&self) -> Au {
+ let Au(s) = *self;
+ let res = s % 60i32;
+ return if res >= 30i32 { return Au(s - res + 60i32) }
+ else { return Au(s - res) };
+ }
+
+ #[inline]
+ pub fn from_frac32_px(px: f32) -> Au {
+ Au((px * 60f32) as i32)
+ }
+
+ #[inline]
+ pub fn from_pt(pt: f64) -> Au {
+ from_frac_px(pt_to_px(pt))
+ }
+
+ #[inline]
+ pub fn from_frac_px(px: f64) -> Au {
+ Au((px * 60f64) as i32)
+ }
+
+ #[inline]
+ pub fn min(x: Au, y: Au) -> Au {
+ let Au(xi) = x;
+ let Au(yi) = y;
+ if xi < yi { x } else { y }
+ }
+
+ #[inline]
+ pub fn max(x: Au, y: Au) -> Au {
+ let Au(xi) = x;
+ let Au(yi) = y;
+ if xi > yi { x } else { y }
+ }
+}
+
+// assumes 72 points per inch, and 96 px per inch
+pub fn pt_to_px(pt: f64) -> f64 {
+ pt / 72f64 * 96f64
+}
+
+// assumes 72 points per inch, and 96 px per inch
+pub fn px_to_pt(px: f64) -> f64 {
+ px / 96f64 * 72f64
+}
+
+pub fn from_frac_px(px: f64) -> Au {
+ Au((px * 60f64) as i32)
+}
+
+pub fn from_px(px: int) -> Au {
+ NumCast::from(px * 60).unwrap()
+}
+
+pub fn to_px(au: Au) -> int {
+ let Au(a) = au;
+ (a / 60) as int
+}
+
+pub fn to_frac_px(au: Au) -> f64 {
+ let Au(a) = au;
+ (a as f64) / 60f64
+}
+
+// assumes 72 points per inch, and 96 px per inch
+pub fn from_pt(pt: f64) -> Au {
+ from_px((pt / 72f64 * 96f64) as int)
+}
+
+// assumes 72 points per inch, and 96 px per inch
+pub fn to_pt(au: Au) -> f64 {
+ let Au(a) = au;
+ (a as f64) / 60f64 * 72f64 / 96f64
+}
+
+/// Returns true if the rect contains the given point. Points on the top or left sides of the rect
+/// are considered inside the rectangle, while points on the right or bottom sides of the rect are
+/// not considered inside the rectangle.
+pub fn rect_contains_point<T:PartialOrd + Add<T,T>>(rect: Rect<T>, point: Point2D<T>) -> bool {
+ point.x >= rect.origin.x && point.x < rect.origin.x + rect.size.width &&
+ point.y >= rect.origin.y && point.y < rect.origin.y + rect.size.height
+}
+
+/// A helper function to convert a rect of `f32` pixels to a rect of app units.
+pub fn f32_rect_to_au_rect(rect: Rect<f32>) -> Rect<Au> {
+ Rect(Point2D(Au::from_frac32_px(rect.origin.x), Au::from_frac32_px(rect.origin.y)),
+ Size2D(Au::from_frac32_px(rect.size.width), Au::from_frac32_px(rect.size.height)))
+}
+
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