Workshop › Klondike Solitaire › Step 28 of 40

Where did you grab it?

What we are doing

Sometimes you want a different place than the one a tap picks, so cards can also be dragged. First, drag remembers where the card was grabbed: dx, dy, the pointer's offset from the card's corner, and the pointer itself, x, y.

```js
const cx = pileX(h.key)
const cy = cardY(h.key, h.index)
drag = { from: h.key, index: h.index, dx: p.x - cx, dy: p.y - cy, x: p.x, y: p.y, moved: false }
```

What it means

• cx, cy is the held card's top-left corner.
• dx, dy is how far the pointer is from that corner; it stays the same while dragging.
• x, y is where the pointer is now; moved will tell a drag from a tap.

Your turn

In the pointerdown listener, replace the last line (drag = { from: h.key, index: h.index }) with the three lines.

Skills: Keyboard and mouse input

← Count the moves Follow the pointer →

All steps

1. The green table
2. Draw one card
3. The face of a card
4. Red and black
5. A deck of 52
6. Shuffle
7. Piles in one object
8. Deal the seven columns
9. A place for every pile
10. Put the piles on the table
11. Fan out the columns
12. Outlines for empty places
13. Turn over a card
14. Space turns a card
15. Go through the stock again
16. What is under the pointer?
17. Hitting a card in a column
18. Tap the stock
19. Rule 1: building a column
20. Rule 2: building a foundation
21. Move cards by the rules
22. Turn over the uncovered card
23. Find where a card goes
24. Pick up a card
25. Tap to move
26. A move counter
27. Count the moves
28. Where did you grab it?
29. Follow the pointer
30. Draw the held cards at the pointer
31. Drop it where you want
32. Drop a king into an empty column
33. A clock
34. Winning
35. You won!
36. A new game
37. The best time
38. Snapshots of the table
39. Undo
40. Build it yourself: finish by itself