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Now that NativeDisplay can be shared between the compositor and the paint task, we can move the LayerBuffer cache to the compositor. This allows surfaces to be potentially reused between different paint tasks and will eventually allow OpenGL contexts to be preserved between instances of GL rasterization.
162 lines
5.2 KiB
Rust
162 lines
5.2 KiB
Rust
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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use std::collections::HashMap;
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use std::collections::hash_map::Entry::{Occupied, Vacant};
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use euclid::size::Size2D;
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use layers::platform::surface::NativeDisplay;
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use layers::layers::LayerBuffer;
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use std::hash::{Hash, Hasher};
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/// This is a struct used to store buffers when they are not in use.
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/// The paint task can quickly query for a particular size of buffer when it
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/// needs it.
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pub struct BufferMap {
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/// A HashMap that stores the Buffers.
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map: HashMap<BufferKey, BufferValue>,
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/// The current amount of memory stored by the BufferMap's buffers.
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mem: usize,
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/// The maximum allowed memory. Unused buffers will be deleted
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/// when this threshold is exceeded.
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max_mem: usize,
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/// A monotonically increasing counter to track how recently tile sizes were used.
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counter: usize,
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}
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/// A key with which to store buffers. It is based on the size of the buffer.
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#[derive(Eq, Copy, Clone)]
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struct BufferKey([usize; 2]);
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impl Hash for BufferKey {
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fn hash<H: Hasher>(&self, state: &mut H) {
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let BufferKey(ref bytes) = *self;
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bytes.hash(state);
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}
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}
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impl PartialEq for BufferKey {
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fn eq(&self, other: &BufferKey) -> bool {
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let BufferKey(s) = *self;
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let BufferKey(o) = *other;
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s[0] == o[0] && s[1] == o[1]
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}
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}
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/// Create a key from a given size
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impl BufferKey {
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fn get(input: Size2D<usize>) -> BufferKey {
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BufferKey([input.width, input.height])
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}
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}
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/// A helper struct to keep track of buffers in the HashMap
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struct BufferValue {
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/// An array of buffers, all the same size
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buffers: Vec<Box<LayerBuffer>>,
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/// The counter when this size was last requested
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last_action: usize,
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}
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impl BufferMap {
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// Creates a new BufferMap with a given buffer limit.
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pub fn new(max_mem: usize) -> BufferMap {
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BufferMap {
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map: HashMap::new(),
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mem: 0,
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max_mem: max_mem,
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counter: 0,
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}
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}
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pub fn insert_buffers(&mut self, display: &NativeDisplay, buffers: Vec<Box<LayerBuffer>>) {
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for mut buffer in buffers.into_iter() {
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buffer.mark_wont_leak();
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self.insert(display, buffer)
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}
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}
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/// Insert a new buffer into the map.
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pub fn insert(&mut self, display: &NativeDisplay, new_buffer: Box<LayerBuffer>) {
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let new_key = BufferKey::get(new_buffer.get_size_2d());
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// If all our buffers are the same size and we're already at our
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// memory limit, no need to store this new buffer; just let it drop.
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if self.mem + new_buffer.get_mem() > self.max_mem && self.map.len() == 1 &&
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self.map.contains_key(&new_key) {
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new_buffer.destroy(display);
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return;
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}
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self.mem += new_buffer.get_mem();
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// use lazy insertion function to prevent unnecessary allocation
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let counter = &self.counter;
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match self.map.entry(new_key) {
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Occupied(entry) => {
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entry.into_mut().buffers.push(new_buffer);
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}
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Vacant(entry) => {
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entry.insert(BufferValue {
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buffers: vec!(new_buffer),
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last_action: *counter,
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});
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}
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}
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let mut opt_key: Option<BufferKey> = None;
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while self.mem > self.max_mem {
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let old_key = match opt_key {
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Some(key) => key,
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None => {
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match self.map.iter().min_by(|&(_, x)| x.last_action) {
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Some((k, _)) => *k,
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None => panic!("BufferMap: tried to delete with no elements in map"),
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}
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}
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};
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if {
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let list = &mut self.map.get_mut(&old_key).unwrap().buffers;
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let condemned_buffer = list.pop().take().unwrap();
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self.mem -= condemned_buffer.get_mem();
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condemned_buffer.destroy(display);
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list.is_empty()
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}
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{ // then
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self.map.remove(&old_key); // Don't store empty vectors!
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opt_key = None;
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} else {
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opt_key = Some(old_key);
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}
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}
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}
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// Try to find a buffer for the given size.
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pub fn find(&mut self, size: Size2D<usize>) -> Option<Box<LayerBuffer>> {
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let mut flag = false; // True if key needs to be popped after retrieval.
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let key = BufferKey::get(size);
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let ret = match self.map.get_mut(&key) {
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Some(ref mut buffer_val) => {
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buffer_val.last_action = self.counter;
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self.counter += 1;
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let buffer = buffer_val.buffers.pop().take().unwrap();
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self.mem -= buffer.get_mem();
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if buffer_val.buffers.is_empty() {
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flag = true;
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}
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Some(buffer)
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}
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None => None,
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};
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if flag {
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self.map.remove(&key); // Don't store empty vectors!
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}
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ret
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}
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pub fn mem(&self) -> usize {
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self.mem
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}
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}
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