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Added a shared cached dummy canvas context that may be used by Kinetic.Text methods.

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This greatly improves performances when creating lots of Kinetic.Text nodes, especially on mobile devices.
This commit is contained in:
Louis Jolibois
2013-03-14 19:34:35 +01:00
parent 5c590bb88f
commit 5ca21992de
1 changed files with 12 additions and 9 deletions
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21
src/shapes/Text.js
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@@ -21,7 +21,10 @@
ATTR_CHANGE_LIST = ['fontFamily', 'fontSize', 'fontStyle', 'padding', 'align', 'lineHeight', 'text', 'width', 'height'],
// cached variables
attrChangeListLen = ATTR_CHANGE_LIST.length;
attrChangeListLen = ATTR_CHANGE_LIST.length,
// shared dummy canvas context
dummyContext = null;
/**
* Text constructor
@@ -66,7 +69,9 @@
lineHeight: 1
});
this.dummyCanvas = document.createElement(CANVAS);
if (!dummyContext) {
dummyContext = document.createElement(CANVAS).getContext(CONTEXT_2D);
}
// call super constructor
Kinetic.Shape.call(this, config);
@@ -177,16 +182,14 @@
return this.textHeight;
},
_getTextSize: function(text) {
var dummyCanvas = this.dummyCanvas,
context = dummyCanvas.getContext(CONTEXT_2D),
fontSize = this.getFontSize(),
var fontSize = this.getFontSize(),
metrics;
context.save();
context.font = this.getFontStyle() + SPACE + fontSize + PX_SPACE + this.getFontFamily();
dummyContext.save();
dummyContext.font = this.getFontStyle() + SPACE + fontSize + PX_SPACE + this.getFontFamily();
metrics = context.measureText(text);
context.restore();
metrics = dummyContext.measureText(text);
dummyContext.restore();
return {
width: metrics.width,
height: parseInt(fontSize, 10)