@woosh/meep-engine/src/engine/animation/curve/editor/updateAxisRange.js

Pure JavaScript game engine. Fully featured and production ready.

/**
 *  Modify the axis start and end value based on given scaling
 * @param {number} axisLength
 * @param {number} cursorToGraphPos
 * @param {number} axisStart
 * @param {number} axisEnd
 * @param {number} scaling
 * @returns {(number|*)[]}
 */
export function updateAxisRange(axisLength,cursorToGraphPos, axisStart, axisEnd, scaling){

    let axisRange = axisEnd - axisStart;
    const ratioCursorToGraphX = cursorToGraphPos / axisLength;
    const axisCentre = axisStart + (ratioCursorToGraphX * axisRange);

    axisRange = (axisEnd - axisStart) / scaling;
    axisStart = axisCentre - (ratioCursorToGraphX * axisRange);
    axisEnd = axisCentre + (1 - ratioCursorToGraphX) * axisRange;

    return [axisStart, axisEnd];
}