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Skip useless tasks in the worker to improve fast scrolling with scann…
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…ed books (bug 1866296)

When a page rendering is cancelled, a task is sent to the worker but before it's executed
the rendering task is: the cancel task is more or less useless in this case.
So in using the fact that draining the message queue has a higher priority
than draining the event one, it's possible to get all the current tasks, hence
it's possible to cancel some tasks which are before a cancel task.
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@calixteman
calixteman committed Dec 10, 2023
1 parent 5537298 commit db6d087
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Showing 2 changed files with 126 additions and 65 deletions.
29 changes: 21 additions & 8 deletions src/display/api.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1274,14 +1274,19 @@ class PDFDocumentProxy {
class PDFPageProxy {
#delayedCleanupTimeout = null;

#pageId;

#pendingCleanup = false;

static #_pageId = 1;

constructor(pageIndex, pageInfo, transport, pdfBug = false) {
this._pageIndex = pageIndex;
this._pageInfo = pageInfo;
this._transport = transport;
this._stats = pdfBug ? new StatTimer() : null;
this._pdfBug = pdfBug;
this.#pageId = PDFPageProxy.#_pageId++;
/** @type {PDFObjects} */
this.commonObjs = transport.commonObjs;
this.objs = new PDFObjects();
Expand Down Expand Up @@ -1358,6 +1363,7 @@ class PDFPageProxy {
const intentArgs = this._transport.getRenderingIntent(intent);

return this._transport.getAnnotations(
this.#pageId,
this._pageIndex,
intentArgs.renderingIntent
);
Expand All @@ -1368,7 +1374,7 @@ class PDFPageProxy {
* {Object} with JS actions.
*/
getJSActions() {
return this._transport.getPageJSActions(this._pageIndex);
return this._transport.getPageJSActions(this.#pageId, this._pageIndex);
}

/**
Expand Down Expand Up @@ -1428,7 +1434,9 @@ class PDFPageProxy {
this.#abortDelayedCleanup();

if (!optionalContentConfigPromise) {
optionalContentConfigPromise = this._transport.getOptionalContentConfig();
optionalContentConfigPromise = this._transport.getOptionalContentConfig(
this.#pageId
);
}

let intentState = this._intentStates.get(intentArgs.cacheKey);
Expand Down Expand Up @@ -1602,6 +1610,7 @@ class PDFPageProxy {
return this._transport.messageHandler.sendWithStream(
"GetTextContent",
{
pageId: this.#pageId,
pageIndex: this._pageIndex,
includeMarkedContent: includeMarkedContent === true,
disableNormalization: disableNormalization === true,
Expand Down Expand Up @@ -1661,7 +1670,7 @@ class PDFPageProxy {
* or `null` when no structure tree is present for the current page.
*/
getStructTree() {
return this._transport.getStructTree(this._pageIndex);
return this._transport.getStructTree(this.#pageId, this._pageIndex);
}

/**
Expand Down Expand Up @@ -1807,6 +1816,7 @@ class PDFPageProxy {
const readableStream = this._transport.messageHandler.sendWithStream(
"GetOperatorList",
{
pageId: this.#pageId,
pageIndex: this._pageIndex,
intent: renderingIntent,
cacheKey,
Expand Down Expand Up @@ -2923,8 +2933,9 @@ class WorkerTransport {
});
}

getAnnotations(pageIndex, intent) {
getAnnotations(pageId, pageIndex, intent) {
return this.messageHandler.sendWithPromise("GetAnnotations", {
pageId,
pageIndex,
intent,
});
Expand Down Expand Up @@ -2983,14 +2994,16 @@ class WorkerTransport {
return this.#cacheSimpleMethod("GetDocJSActions");
}

getPageJSActions(pageIndex) {
getPageJSActions(pageId, pageIndex) {
return this.messageHandler.sendWithPromise("GetPageJSActions", {
pageId,
pageIndex,
});
}

getStructTree(pageIndex) {
getStructTree(pageId, pageIndex) {
return this.messageHandler.sendWithPromise("GetStructTree", {
pageId,
pageIndex,
});
}
Expand All @@ -2999,9 +3012,9 @@ class WorkerTransport {
return this.messageHandler.sendWithPromise("GetOutline", null);
}

getOptionalContentConfig() {
getOptionalContentConfig(pageId) {
return this.messageHandler
.sendWithPromise("GetOptionalContentConfig", null)
.sendWithPromise("GetOptionalContentConfig", { pageId })
.then(results => {
return new OptionalContentConfig(results);
});
Expand Down
162 changes: 105 additions & 57 deletions src/shared/message_handler.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,12 @@ function wrapReason(reason) {
}

class MessageHandler {
#cancelledPageIds = new Set();

#executorRunning = false;

#queue = [];

constructor(sourceName, targetName, comObj) {
this.sourceName = sourceName;
this.targetName = targetName;
Expand All @@ -81,71 +87,111 @@ class MessageHandler {
this.callbackCapabilities = Object.create(null);
this.actionHandler = Object.create(null);

this._onComObjOnMessage = event => {
const data = event.data;
if (data.targetName !== this.sourceName) {
return;
}
if (data.stream) {
this.#processStreamMessage(data);
return;
}
if (data.callback) {
const callbackId = data.callbackId;
const capability = this.callbackCapabilities[callbackId];
if (!capability) {
throw new Error(`Cannot resolve callback ${callbackId}`);
this._onComObjOnMessage = ({ data }) => {
if (data.targetName === this.sourceName) {
// The meesages in the worker queue are processed with a
// higher priority than the tasks in the event queue.
// So, postponing the task execution, will ensure that the message
// queue is drained.
// If at some point we've a cancelled task (e.g. GetOperatorList),
// we're able to skip the task execution with the same pageId.
this.#queue.push(data);
if (data.pageId && data.stream === StreamKind.CANCEL) {
this.#cancelledPageIds.add(data.pageId);
}
delete this.callbackCapabilities[callbackId];

if (data.callback === CallbackKind.DATA) {
capability.resolve(data.data);
} else if (data.callback === CallbackKind.ERROR) {
capability.reject(wrapReason(data.reason));
} else {
throw new Error("Unexpected callback case");
if (!this.#executorRunning) {
this.#executorRunning = true;
this.#postponeExecution();
}
return;
}
const action = this.actionHandler[data.action];
if (!action) {
throw new Error(`Unknown action from worker: ${data.action}`);
};
comObj.addEventListener("message", this._onComObjOnMessage);
}

#postponeExecution() {
setTimeout(this.#executor.bind(this), 0);
}

#executor() {
if (this.#queue.length === 0) {
this.#cancelledPageIds.clear();
this.#executorRunning = false;
return;
}

const data = this.#queue.shift();

if (data.stream) {
if (
data.stream === StreamKind.CANCEL ||
!this.#cancelledPageIds.has(data.pageId)
) {
this.#processStreamMessage(data);
}
if (data.callbackId) {
const cbSourceName = this.sourceName;
const cbTargetName = data.sourceName;
this.#postponeExecution();
return;
}

new Promise(function (resolve) {
resolve(action(data.data));
}).then(
function (result) {
comObj.postMessage({
sourceName: cbSourceName,
targetName: cbTargetName,
callback: CallbackKind.DATA,
callbackId: data.callbackId,
data: result,
});
},
function (reason) {
comObj.postMessage({
sourceName: cbSourceName,
targetName: cbTargetName,
callback: CallbackKind.ERROR,
callbackId: data.callbackId,
reason: wrapReason(reason),
});
}
);
return;
const pageId = data.data?.pageId;
if (pageId && this.#cancelledPageIds.has(pageId)) {
this.#postponeExecution();
return;
}

if (data.callback) {
const callbackId = data.callbackId;
const capability = this.callbackCapabilities[callbackId];
if (!capability) {
throw new Error(`Cannot resolve callback ${callbackId}`);
}
if (data.streamId) {
this.#createStreamSink(data);
return;
delete this.callbackCapabilities[callbackId];

if (data.callback === CallbackKind.DATA) {
capability.resolve(data.data);
} else if (data.callback === CallbackKind.ERROR) {
capability.reject(wrapReason(data.reason));
} else {
throw new Error("Unexpected callback case");
}
this.#postponeExecution();
return;
}
const action = this.actionHandler[data.action];
if (!action) {
throw new Error(`Unknown action from worker: ${data.action}`);
}
if (data.callbackId) {
const cbSourceName = this.sourceName;
const cbTargetName = data.sourceName;

new Promise(function (resolve) {
resolve(action(data.data));
}).then(
result => {
this.comObj.postMessage({
sourceName: cbSourceName,
targetName: cbTargetName,
callback: CallbackKind.DATA,
callbackId: data.callbackId,
data: result,
});
},
reason => {
this.comObj.postMessage({
sourceName: cbSourceName,
targetName: cbTargetName,
callback: CallbackKind.ERROR,
callbackId: data.callbackId,
reason: wrapReason(reason),
});
}
);
} else if (data.streamId) {
this.#createStreamSink(data);
} else {
action(data.data);
};
comObj.addEventListener("message", this._onComObjOnMessage);
}
this.#postponeExecution();
}

on(actionName, handler) {
Expand Down Expand Up @@ -224,6 +270,7 @@ class MessageHandler {
sourceName = this.sourceName,
targetName = this.targetName,
comObj = this.comObj;
const pageId = data?.pageId;

return new ReadableStream(
{
Expand Down Expand Up @@ -276,6 +323,7 @@ class MessageHandler {
targetName,
stream: StreamKind.CANCEL,
streamId,
pageId,
reason: wrapReason(reason),
});
// Return Promise to signal success or failure.
Expand Down

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