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[apps/shared/interactive_curve_view_controller] Rewrite comment about addMargin

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This commit is contained in:
Ruben Dashyan
2019-05-10 14:22:12 +02:00
committed by Léa Saviot
parent 8cb2b99254
commit 2fb6824947
1 changed files with 17 additions and 26 deletions
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43
apps/shared/interactive_curve_view_controller.cpp
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@@ -35,38 +35,29 @@ InteractiveCurveViewController::InteractiveCurveViewController(Responder * paren
{
}
float InteractiveCurveViewController::addMargin(float x, float range, bool isVertical, bool isMin) {
/* We are adding margins. Let's name:
* - The current range: rangeBefore
* - The next range: rangeAfter
* - The bottom margin ratio with which we will evaluate if a point is too
* low on the screen: bottomRatioAfter
* - The bottom margin ratio with which we will evaluate if a point is too
* high on the screen: topRatioAfter
* - The ratios we need to use to create the margins: bottomRatioBefore and
* topRatioBefore
*
* We want to add margins so that:
* bottomRatioAfter*rangeAfter == bottomRatioBefore * rangeBefore
* topRatioAfter*rangeAfter == topRatioBefore * rangeBefore
* Knowing that:
* rangeAfter = (1+bottomRatioBefore+topRatioBefore)*rangeBefore
*
* We thus have:
* bottomRatioBefore = bottomRatioAfter / (1-bottomRatioAfter-topRatioAfter)
* topRatioBefore = topRatioAfter / (1-bottomRatioAfter-topRatioAfter)
*
* If we just used bottomRatioBefore = bottomRatioAfter and
* topRatioBefore = topRatioAfter, we would create too small margins and the
* controller might need to pan right after a Y auto calibration. */
float InteractiveCurveViewController::addMargin(float y, float range, bool isVertical, bool isMin) {
/* The provided min or max range limit y is altered by adding a margin.
* In pixels, the view's height occupied by the vertical range is equal to
* viewHeight - topMargin - bottomMargin.
* Hence one pixel must correspond to
* range / (viewHeight - topMargin - bottomMargin).
* Finally, adding topMargin pixels of margin, say at the top, comes down
* to adding
* range * topMargin / (viewHeight - topMargin - bottomMargin)
* which is equal to
* range * topMarginRatio / ( 1 - topMarginRatio - bottomMarginRatio)
* where
* topMarginRation = topMargin / viewHeight
* bottomMarginRatio = bottomMargin / viewHeight.
* The same goes horizontally.
*/
float topMarginRatio = isVertical ? cursorTopMarginRatio() : k_cursorRightMarginRatio;
float bottomMarginRatio = isVertical ? cursorBottomMarginRatio() : k_cursorLeftMarginRatio;
assert(topMarginRatio + bottomMarginRatio < 1); // Assertion so that the formula is correct
float ratioDenominator = 1 - bottomMarginRatio - topMarginRatio;
float ratio = isMin ? -bottomMarginRatio : topMarginRatio;
ratio = ratio / ratioDenominator;
return x+ratio*range;
return y + ratio * range;
}
const char * InteractiveCurveViewController::title() {