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Rearrange code in ScrollbarPair set so that all the getAttribute

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calls come before all of the setAttribute calls.  This gets rid
of an unnecessary layout pass on mouseMove events.
This commit is contained in:
picklesrus 2016-02-29 10:22:51 -08:00
parent 217c7d7c8a
commit 39653b697d
1 changed files with 28 additions and 18 deletions
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46
core/scrollbar.js
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@ -139,30 +139,40 @@ Blockly.ScrollbarPair.prototype.set = function(x, y) {
// This function is equivalent to:
// this.hScroll.set(x);
// this.vScroll.set(y);
// However, that calls setMetrics twice. Combining them speeds up rendering.
// However, that calls setMetrics twice which causes a chain of
// getAttribute->setAttribute->getAttribute resulting in an extra layout pass.
// Combining them speeds up rendering.
var xyRatio = {};
var knobValue = x * this.hScroll.ratio_;
this.hScroll.svgKnob_.setAttribute('x', knobValue);
var barLength = parseFloat(this.hScroll.svgBackground_.getAttribute('width'));
var ratio = knobValue / barLength;
if (isNaN(ratio)) {
ratio = 0;
}
xyRatio.x = ratio;
var hKnobValue = x * this.hScroll.ratio_;
var vKnobValue = y * this.vScroll.ratio_;
var knobValue = y * this.vScroll.ratio_;
this.vScroll.svgKnob_.setAttribute('y', knobValue);
var barLength =
var hBarLength =
parseFloat(this.hScroll.svgBackground_.getAttribute('width'));
var vBarLength =
parseFloat(this.vScroll.svgBackground_.getAttribute('height'));
var ratio = knobValue / barLength;
if (isNaN(ratio)) {
ratio = 0;
}
xyRatio.y = ratio;
xyRatio.x = this.getRatio_(hKnobValue, hBarLength);
xyRatio.y = this.getRatio_(vKnobValue, vBarLength);
this.workspace_.setMetrics(xyRatio);
};
this.hScroll.svgKnob_.setAttribute('x', hKnobValue);
this.vScroll.svgKnob_.setAttribute('y', vKnobValue);
}
/**
* Helper to calculate the ratio of knob value to bar length.
* @param {number} barLength The length of the scroll bar.
* @param {number} knobValue The value of the knob.
* @private
*/
Blockly.ScrollbarPair.prototype.getRatio_ = function(knobValue, barLength) {
var ratio = knobValue / barLength;
if (isNaN(ratio)) {
return 0;
}
return ratio;
}
// --------------------------------------------------------------------