servo/components/gfx_traits/lib.rs

/* 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/. */

#![feature(custom_derive, plugin)]
#![plugin(heapsize_plugin, plugins, serde_macros)]

#![crate_name = "gfx_traits"]
#![crate_type = "rlib"]

#![deny(unsafe_code)]

extern crate azure;
extern crate euclid;
extern crate heapsize;
extern crate layers;
extern crate msg;
extern crate profile_traits;
#[macro_use]
extern crate range;
extern crate rustc_serialize;
extern crate serde;

pub mod color;
mod paint_listener;
pub mod print_tree;

pub use paint_listener::PaintListener;
use azure::azure_hl::Color;
use euclid::Matrix4D;
use euclid::rect::Rect;
use layers::layers::BufferRequest;
use msg::constellation_msg::PipelineId;
use profile_traits::mem::ReportsChan;
use range::RangeIndex;
use std::fmt::{self, Debug, Formatter};
use std::sync::atomic::{ATOMIC_USIZE_INIT, AtomicUsize, Ordering};

/// The next ID that will be used for a special stacking context.
///
/// A special stacking context is a stacking context that is one of (a) the outer stacking context
/// of an element with `overflow: scroll`; (b) generated content; (c) both (a) and (b).
static NEXT_SPECIAL_STACKING_CONTEXT_ID: AtomicUsize = ATOMIC_USIZE_INIT;

/// If none of the bits outside this mask are set, the stacking context is a special stacking
/// context.
///
/// Note that we assume that the top 16 bits of the address space are unused on the platform.
const SPECIAL_STACKING_CONTEXT_ID_MASK: usize = 0xffff;


#[derive(Clone, Copy, Debug, PartialEq)]
pub enum LayerKind {
    NoTransform,
    HasTransform,
}

#[derive(Clone, PartialEq, Eq, Copy, Hash, Deserialize, Serialize, HeapSizeOf)]
pub enum LayerType {
    /// A layer for the fragment body itself.
    FragmentBody,
    /// An extra layer created for a DOM fragments with overflow:scroll.
    OverflowScroll,
    /// A layer created to contain ::before pseudo-element content.
    BeforePseudoContent,
    /// A layer created to contain ::after pseudo-element content.
    AfterPseudoContent,
}

/// The scrolling policy of a layer.
#[derive(Clone, PartialEq, Eq, Copy, Deserialize, Serialize, Debug, HeapSizeOf)]
pub enum ScrollPolicy {
    /// These layers scroll when the parent receives a scrolling message.
    Scrollable,
    /// These layers do not scroll when the parent receives a scrolling message.
    FixedPosition,
}

#[derive(Clone, PartialEq, Eq, Copy, Hash, Deserialize, Serialize, HeapSizeOf)]
pub struct LayerId(
    /// The type of the layer. This serves to differentiate layers that share fragments.
    LayerType,
    /// The identifier for this layer's fragment, derived from the fragment memory address.
    usize,
    /// An index for identifying companion layers, synthesized to ensure that
    /// content on top of this layer's fragment has the proper rendering order.
    usize
);

impl Debug for LayerId {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        let LayerId(layer_type, id, companion) = *self;
        let type_string = match layer_type {
            LayerType::FragmentBody => "-FragmentBody",
            LayerType::OverflowScroll => "-OverflowScroll",
            LayerType::BeforePseudoContent => "-BeforePseudoContent",
            LayerType::AfterPseudoContent => "-AfterPseudoContent",
        };

        write!(f, "{}{}-{}", id, type_string, companion)
    }
}

impl LayerId {
    /// FIXME(#2011, pcwalton): This is unfortunate. Maybe remove this in the future.
    pub fn null() -> LayerId {
        LayerId(LayerType::FragmentBody, 0, 0)
    }

    pub fn new_of_type(layer_type: LayerType, fragment_id: usize) -> LayerId {
        LayerId(layer_type, fragment_id, 0)
    }

    pub fn companion_layer_id(&self) -> LayerId {
        let LayerId(layer_type, id, companion) = *self;
        LayerId(layer_type, id, companion + 1)
    }

    pub fn original(&self) -> LayerId {
        let LayerId(layer_type, id, _) = *self;
        LayerId(layer_type, id, 0)
    }

    pub fn kind(&self) -> LayerType {
        self.0
    }
}

/// All layer-specific information that the painting task sends to the compositor other than the
/// buffer contents of the layer itself.
#[derive(Copy, Clone, HeapSizeOf)]
pub struct LayerProperties {
    /// An opaque ID. This is usually the address of the flow and index of the box within it.
    pub id: LayerId,
    /// The id of the parent layer.
    pub parent_id: Option<LayerId>,
    /// The position and size of the layer in pixels.
    pub rect: Rect<f32>,
    /// The background color of the layer.
    pub background_color: Color,
    /// The scrolling policy of this layer.
    pub scroll_policy: ScrollPolicy,
    /// The transform for this layer
    pub transform: Matrix4D<f32>,
    /// The perspective transform for this layer
    pub perspective: Matrix4D<f32>,
    /// The subpage that this layer represents. If this is `Some`, this layer represents an
    /// iframe.
    pub subpage_pipeline_id: Option<PipelineId>,
    /// Whether this layer establishes a new 3d rendering context.
    pub establishes_3d_context: bool,
    /// Whether this layer scrolls its overflow area.
    pub scrolls_overflow_area: bool,
}

/// A newtype struct for denoting the age of messages; prevents race conditions.
#[derive(PartialEq, Eq, Debug, Copy, Clone, PartialOrd, Ord, Deserialize, Serialize)]
pub struct Epoch(pub u32);

impl Epoch {
    pub fn next(&mut self) {
        self.0 += 1;
    }
}

#[derive(PartialEq, Eq, Debug, Copy, Clone)]
pub struct FrameTreeId(pub u32);

impl FrameTreeId {
    pub fn next(&mut self) {
        self.0 += 1;
    }
}

/// A unique ID for every stacking context.
#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, HeapSizeOf, PartialEq, Serialize)]
pub struct StackingContextId(
    /// The identifier for this StackingContext, derived from the Flow's memory address
    /// and fragment type.  As a space optimization, these are combined into a single word.
    usize
);

impl StackingContextId {
    #[inline]
    pub fn new(id: usize) -> StackingContextId {
        StackingContextId::new_of_type(id, FragmentType::FragmentBody)
    }

    /// Returns a new stacking context ID for a special stacking context.
    fn next_special_id() -> usize {
        // We shift this left by 2 to make room for the fragment type ID.
        ((NEXT_SPECIAL_STACKING_CONTEXT_ID.fetch_add(1, Ordering::SeqCst) + 1) << 2) &
            SPECIAL_STACKING_CONTEXT_ID_MASK
    }

    #[inline]
    pub fn new_of_type(id: usize, fragment_type: FragmentType) -> StackingContextId {
        debug_assert_eq!(id & (fragment_type as usize), 0);
        if fragment_type == FragmentType::FragmentBody {
            StackingContextId(id)
        } else {
            StackingContextId(StackingContextId::next_special_id() | (fragment_type as usize))
        }
    }

    /// Returns an ID for the stacking context that forms the outer stacking context of an element
    /// with `overflow: scroll`.
    #[inline(always)]
    pub fn new_outer(fragment_type: FragmentType) -> StackingContextId {
        StackingContextId(StackingContextId::next_special_id() | (fragment_type as usize))
    }

    #[inline]
    pub fn fragment_type(&self) -> FragmentType {
        FragmentType::from_usize(self.0 & 3)
    }

    #[inline]
    pub fn id(&self) -> usize {
        self.0 & !3
    }

    /// Returns the stacking context ID for the outer document/layout root.
    #[inline]
    pub fn root() -> StackingContextId {
        StackingContextId(0)
    }

    /// Returns true if this is a special stacking context.
    ///
    /// A special stacking context is a stacking context that is one of (a) the outer stacking
    /// context of an element with `overflow: scroll`; (b) generated content; (c) both (a) and (b).
    #[inline]
    pub fn is_special(&self) -> bool {
        (self.0 & !SPECIAL_STACKING_CONTEXT_ID_MASK) == 0
    }
}

/// The type of fragment that a stacking context represents.
///
/// This can only ever grow to maximum 4 entries. That's because we cram the value of this enum
/// into the lower 2 bits of the `StackingContextId`, which otherwise contains a 32-bit-aligned
/// heap address.
#[derive(Clone, Debug, PartialEq, Eq, Copy, Hash, Deserialize, Serialize, HeapSizeOf)]
pub enum FragmentType {
    /// A StackingContext for the fragment body itself.
    FragmentBody,
    /// A StackingContext created to contain ::before pseudo-element content.
    BeforePseudoContent,
    /// A StackingContext created to contain ::after pseudo-element content.
    AfterPseudoContent,
}

impl FragmentType {
    #[inline]
    pub fn from_usize(n: usize) -> FragmentType {
        debug_assert!(n < 3);
        match n {
            0 => FragmentType::FragmentBody,
            1 => FragmentType::BeforePseudoContent,
            _ => FragmentType::AfterPseudoContent,
        }
    }
}

int_range_index! {
    #[derive(Deserialize, Serialize, RustcEncodable)]
    #[doc = "An index that refers to a byte offset in a text run. This could \
             point to the middle of a glyph."]
    #[derive(HeapSizeOf)]
    struct ByteIndex(isize)
}

pub struct PaintRequest {
    pub buffer_requests: Vec<BufferRequest>,
    pub scale: f32,
    pub layer_id: LayerId,
    pub epoch: Epoch,
    pub layer_kind: LayerKind,
}

pub enum ChromeToPaintMsg {
    Paint(Vec<PaintRequest>, FrameTreeId),
    PaintPermissionGranted,
    PaintPermissionRevoked,
    CollectReports(ReportsChan),
    Exit,
}