Configuring scales

Adding scales and changing main properties

You can specify any number of scales by setting the scale objects in the scales array. To configure scales, change the scales parameters values.

<script>
   import { getData } from "./common/data";
   import { Gantt } from "wx-svelte-gantt";

   const scales = [
      { unit: "month", step: 1, format: "MMMM yyy" },
      { unit: "day", step: 1, format: "d" },
   ];

</script>   

<Gantt tasks={data.tasks} {scales} />

Setting the start and end dates of the timescale

You can set the date range by using the start and end properties during initialization:

<script>
   import { getData } from "./data";
   import { Gantt } from "wx-svelte-gantt";
   
   const data = getData();
   let start = new Date(2022, 2, 5),
      end = new Date(2023, 3, 1);

</script>

<Gantt
   tasks={data.tasks}
   {start}
   {end} />

info

If the date range is not set, Gantt uses the dates of the loaded tasks and adds offsets before the first and after the last task in the scale. The offset is equal to one minimal unit of the current scale. The timescale changes dynamically when the tasks' dates are changed. But if the start and end values are set, the date range is fixed.

Styling cells

To style the cells of the time scale, use the css attribute in the corresponding scale object.

<script>
   import { getData } from "../data";
   import { Gantt } from "wx-svelte-gantt";

   const data = getData();

   const dayStyle = a => {
   const day = a.getDay() == 5 || a.getDay() == 6;
   return day ? "sday" : "";
};

  const complexScales = [
   { unit: "year", step: 1, format: "yyyy" },
   { unit: "month", step: 2, format: "MMMM yyy" },
   { unit: "week", step: 1, format: "w" },
   { unit: "day", step: 1, format: "d", css: dayStyle },
];
</script>

<Gantt
   {...skinSettings}
   tasks={data.tasks}
   links={data.links}
   scales={complexScales}
   start={new Date(2020, 2, 1)}
   end={new Date(2020, 3, 12)}
   cellWidth={60}
/>

Configuring the scale height

To configure the height of scales, apply the scaleHeight property and change its value in pixels:

<script>
   import { getData } from "./data";
   import { Gantt } from "wx-svelte-gantt";
 
   const data = getData();
 
   let scaleHeight = 50;

</script>   

<Gantt tasks={data.tasks} {scaleHeight} />

Setting autoScale

autoScale allows adjusting the timescale dynamically based on the provided start or/and end values.
If you provide the start and/or end values and set the autoScale to "true", the values will be used to define initial visible timescale range and the scale will change dynamically during interaction (for example, it will expand when tasks are added via drag and drop).
In case the start and/or end values are set and the autoScale is set to "false", the timescale is fixed and unchanged. If the start or/and end are not provided, the scale defaults to a range from the current date plus one month.

<script>
   import { getData } from "../data";
   import { Gantt } from "wx-svelte-gantt";

   const data = getData();

</script>

<Gantt
   {tasks}
   start={new Date(2023, 2, 1)}
   end={new Date(2024, 3, 12)}
   autoScale="true"
/>

Adding a custom scale unit

You can set your custom scale unit by applying the registerScaleUnit helper.

Example of custom halfYear unit:

<script>
  import { Gantt, registerScaleUnit } from "wx-svelte-gantt";
  import {
    getYear,
    addMonths,
    startOfMonth,
    endOfMonth,
  } from "date-fns";

  // Get the start date of the half-year
  function halfYearStart(date) {
    const d = new Date(date);
    const month = d.getMonth();  
    const startMonth = month < 6 ? 0 : 6; // January or July
    d.setMonth(startMonth);       
    return startOfMonth(d);
  }

  // Get the end date of the half-year
  function halfYearEnd(date) {
    const d = new Date(date);
    const month = d.getMonth();  
    const endMonth = month < 6 ? 5 : 11; // June or December
    d.setMonth(endMonth);         
    return endOfMonth(d);
  }

  // Add N half-years to a date
  function addHalfYears(date, amount) {
    const start = halfYearStart(date);
    return addMonths(start, amount * 6);
  }

  // Check if two dates are in the same half-year
  function isSameHalfYear(a, b) {
    const sa = halfYearStart(a);
    const sb = halfYearStart(b);
    return getYear(sa) === getYear(sb) && sa.getMonth() === sb.getMonth(); 
  }

  // Register the custom "halfYear" unit
  registerScaleUnit("halfYear", {
    start: halfYearStart,
    end: halfYearEnd,
    isSame: isSameHalfYear,
    add: addHalfYears,
  });

  // Define the scale using the new unit
  const scale = [
    { unit: "year", step: 1, format: "yyyy" },
    {
      unit: "halfYear",
      step: 1,
      format: (d) => (d.getMonth() < 6 ? "H1" : "H2"), 
    },
    { unit: "month", step: 1, format: "MMM" },
  ];
</script>

<Gantt scales={scale} />