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refactor(datepicker): avoid frequent template expressions re-evaluati… #1806

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10 changes: 1 addition & 9 deletions projects/element-ng/datepicker/components/si-calendar-body.component.html
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Original file line number Diff line number Diff line change
Expand Up @@ -12,15 +12,7 @@
class="si-calendar-cell"
[attr.data-row]="rowIndex"
[attr.data-col]="colIndex"
[class.range-hover]="
previewRange() && selection().previewRangeHover(col, activeHover(), startDate())
"
[class.range-hover-end]="
previewRange() && selection().previewRangeHoverEnd(col, activeHover(), startDate())
"
[class.range]="selection().inRange(col, startDate(), endDate())"
[class.range-start]="selection().isRangeSelected(col, startDate())"
[class.range-end]="selection().isRangeSelected(col, endDate())"
[class]="cellRangeClasses()[rowIndex][colIndex]"
>
<button
siCalendarDateCell
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31 changes: 31 additions & 0 deletions projects/element-ng/datepicker/components/si-calendar-body.component.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -201,6 +201,37 @@ export class SiCalendarBodyComponent {
: new SingleSelectionStrategy(this.compareAdapter())
);

protected readonly cellRangeClasses = computed(() => {
const rows = this.rows();
const previewRange = this.previewRange();
const sel = this.selection();
const hover = this.activeHover();
const start = this.startDate();
const end = this.endDate();

return rows.map(row =>
row.map(col => {
const classes: string[] = [];
if (previewRange && sel.previewRangeHover(col, hover, start)) {
classes.push('range-hover');
}
if (previewRange && sel.previewRangeHoverEnd(col, hover, start)) {
classes.push('range-hover-end');
}
if (sel.inRange(col, start, end)) {
classes.push('range');
}
if (sel.isRangeSelected(col, start)) {
classes.push('range-start');
}
if (sel.isRangeSelected(col, end)) {
classes.push('range-end');
}
return classes.join(' ');
})
);
});
Comment on lines +204 to +233
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@gemini-code-assist gemini-code-assist bot Apr 2, 2026

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medium

The cellRangeClasses computed signal currently depends on activeHover() unconditionally. This means the entire grid's classes will be re-calculated on every mouse move, even when range selection is disabled or the preview is turned off.

To optimize performance, especially in single selection mode, you should only read the activeHover() signal when it's actually needed for the range preview logic. This prevents the computed signal from registering a dependency on activeHover when it wouldn't affect the output.

  protected readonly cellRangeClasses = computed(() => {
    const rows = this.rows();
    const sel = this.selection();
    const previewRange = this.previewRange();
    const start = this.startDate();
    const end = this.endDate();

    // Only track hover if it's actually needed for the preview logic.
    // This prevents unnecessary re-computations during mouse movement 
    // when range selection or preview is disabled.
    const hover = (previewRange && sel instanceof RangeSelectionStrategy) 
      ? this.activeHover() 
      : undefined;

    return rows.map(row =>
      row.map(col => {
        const classes: string[] = [];
        if (hover) {
          if (sel.previewRangeHover(col, hover, start)) {
            classes.push('range-hover');
          }
          if (sel.previewRangeHoverEnd(col, hover, start)) {
            classes.push('range-hover-end');
          }
        }
        if (sel.inRange(col, start, end)) {
          classes.push('range');
        }
        if (sel.isRangeSelected(col, start)) {
          classes.push('range-start');
        }
        if (sel.isRangeSelected(col, end)) {
          classes.push('range-end');
        }
        return classes.join(' ');
      })
    );
  });


/**
* Focus calendar cell which is marked as active cell.
*/
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