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[Plot] Add comments

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Add comments to plot code introduced to handle
subscribed telemetry only, to work around removal
of the cache to reduce memory usage, WTD-751.
This commit is contained in:
Victor Woeltjen 2015-01-29 12:10:00 -08:00
parent 5e2e0b4116
commit 230ba3eb5c
2 changed files with 28 additions and 4 deletions
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3
platform/features/plot/src/PlotController.js
View File

@ -69,6 +69,8 @@ define(
.forEach(updateSubplot);
}
// Reinstantiate the plot updater (e.g. because we have a
// new subscription.) This will clear the plot.
function recreateUpdater() {
updater = new PlotUpdater(
subscription,
@ -77,6 +79,7 @@ define(
);
}
// Handle new telemetry data in this plot
function updateValues() {
if (updater) {
updater.update();

29
platform/features/plot/src/elements/PlotUpdater.js
View File

@ -11,8 +11,6 @@ define(
var MAX_POINTS = 86400,
INITIAL_SIZE = 675; // 1/128 of MAX_POINTS
function identity(x) { return x; }
/**
* The PlotPreparer is responsible for handling data sets and
* preparing them to be rendered. It creates a WebGL-plottable
@ -34,14 +32,20 @@ define(
lengthArray = [],
bufferArray = [];
// Make sure there is enough space in a buffer to accomodate a
// new point at the specified index. This will updates buffers[id]
// if necessary.
function ensureBufferSize(buffer, id, index) {
// Check if we don't have enough room
if (index > buffer.length / 2) {
// If we don't, can we expand?
if (index < MAX_POINTS) {
// Double the buffer size
buffer = buffers[id] =
new Float32Array(buffer, 0, buffer.length * 2);
buffer = buffers[id] = new Float32Array(
buffer,
0,
buffer.length * 2
);
} else {
// Just shift the existing buffer
buffer.copyWithin(0, 2);
@ -51,6 +55,7 @@ define(
return buffer;
}
// Add data to the plot.
function addData(obj) {
var id = obj.getId(),
index = lengths[id] || 0,
@ -58,11 +63,14 @@ define(
domainValue = subscription.getDomainValue(obj),
rangeValue = subscription.getRangeValue(obj);
// If we don't already have a data buffer for that ID,
// make one.
if (!buffer) {
buffer = new Float32Array(INITIAL_SIZE);
buffers[id] = buffer;
}
// Make sure there's data to add, and then add it
if (domainValue !== undefined && rangeValue !== undefined &&
(index < 1 || domainValue !== buffer[index * 2 - 2])) {
// Use the first observed domain value as a domainOffset
@ -85,6 +93,7 @@ define(
return buffer;
}
// Update min/max domain values for these objects
function updateDomainExtrema(objects) {
max[0] = Number.NEGATIVE_INFINITY;
min[0] = Number.POSITIVE_INFINITY;
@ -99,6 +108,7 @@ define(
});
}
// Handle new telemetry data
function update() {
var objects = subscription.getTelemetryObjects();
bufferArray = objects.map(addData);
@ -108,6 +118,7 @@ define(
updateDomainExtrema(objects);
}
// Prepare buffers and related state for this object
function prepare(telemetryObject) {
var id = telemetryObject.getId();
lengths[id] = 0;
@ -116,6 +127,9 @@ define(
bufferArray.push(buffers[id]);
}
// Initially prepare state for these objects.
// Note that this may be an empty array at this time,
// so we also need to check during update cycles.
subscription.getTelemetryObjects().forEach(prepare);
return {
@ -172,6 +186,13 @@ define(
getBuffers: function () {
return bufferArray;
},
/**
* Get the number of points in the buffer with the specified
* index. Buffers are padded to minimize memory allocations,
* so user code will need this information to know how much
* data to plot.
* @returns {number} the number of points in this buffer
*/
getLength: function (index) {
return lengthArray;
},