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Only call lineTo if we are in a new pixel for linestring

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Rendering performance degrades as the context lineWidth increases when calling lineTo many times for the same pixel coordinate.  This appears to be a widespread performance issue and is very clearly improved by only calling lineTo when in a new pixel coordinate.
This commit is contained in:
Tim Schaub
2013-10-14 16:43:47 -06:00
parent 29221a9869
commit 71a6c4f270
1 changed files with 20 additions and 6 deletions
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26
src/ol/renderer/canvas/canvasvectorrenderer.js
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@@ -144,8 +144,12 @@ ol.renderer.canvas.Vector.prototype.renderLineStringFeatures_ =
function(features, symbolizer) {
var context = this.context_,
i, ii, feature, id, currentSize, geometry, components, j, jj, line,
k, kk, vec, strokeSize;
i, ii, feature, id, currentSize, geometry, components, j, jj,
coordinates, coordinate, k, kk, strokeSize;
var vec = [NaN, NaN, 0];
var pixel = [NaN, NaN];
var lastPixel = [NaN, NaN];
context.globalAlpha = symbolizer.opacity;
context.strokeStyle = symbolizer.color;
@@ -175,14 +179,24 @@ ol.renderer.canvas.Vector.prototype.renderLineStringFeatures_ =
components = geometry.getComponents();
}
for (j = 0, jj = components.length; j < jj; ++j) {
line = components[j];
for (k = 0, kk = line.getCount(); k < kk; ++k) {
vec = [line.get(k, 0), line.get(k, 1), 0];
coordinates = components[j].getCoordinates();
for (k = 0, kk = coordinates.length; k < kk; ++k) {
coordinate = coordinates[k];
vec[0] = coordinate[0];
vec[1] = coordinate[1];
goog.vec.Mat4.multVec3(this.transform_, vec, vec);
if (k === 0) {
lastPixel[0] = NaN;
lastPixel[1] = NaN;
context.moveTo(vec[0], vec[1]);
} else {
context.lineTo(vec[0], vec[1]);
pixel[0] = Math.round(vec[0]);
pixel[1] = Math.round(vec[1]);
if (pixel[0] !== lastPixel[0] || pixel[1] !== lastPixel[1]) {
context.lineTo(vec[0], vec[1]);
lastPixel[0] = pixel[0];
lastPixel[1] = pixel[1];
}
}
}
}