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Small fix for hit detection on a canvas layer as an illegal feature id might result at a location where the edge of one feature intersects the interior of another. This is due to antialiasing on the hit context canvas which can't be turned off, unfortunately.

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This commit is contained in:
Arjen Kopinga
2012-02-22 15:39:31 +01:00
parent d6e28e5ab9
commit 1119146486
3 changed files with 13 additions and 4 deletions
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11
lib/OpenLayers/Renderer/Canvas.js
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@@ -786,7 +786,7 @@ OpenLayers.Renderer.Canvas = OpenLayers.Class(OpenLayers.Renderer, {
* layer.
*/
getFeatureIdFromEvent: function(evt) {
var feature;
var featureId, feature;
if (this.hitDetection) {
// this dragging check should go in the feature handler
if (!this.map.dragging) {
@@ -797,7 +797,14 @@ OpenLayers.Renderer.Canvas = OpenLayers.Class(OpenLayers.Renderer, {
if (data[3] === 255) { // antialiased
var id = data[2] + (256 * (data[1] + (256 * data[0])));
if (id) {
feature = this.features["OpenLayers.Feature.Vector_" + (id - 1 + this.hitOverflow)][0];
featureId = "OpenLayers.Feature.Vector_" + (id - 1 + this.hitOverflow);
try {
feature = this.features["OpenLayers.Feature.Vector_" + (id - 1 + this.hitOverflow)][0];
} catch(err) {
// Because of antialiasing on the canvas, when the hit location is at a point where the edge of
// one symbol intersects the interior of another symbol, a wrong hit color (and therefore id) results.
// todo: set Antialiasing = 'off' on the hitContext as soon as browsers allow it.
}
}
}
}