Change the expression heatmap to canvas.

[yubowenok]

Performance:

• Resizing the view shall not trigger re-render. Otherwise it is impossible to resize when the matrix shows all cells.

Bugs:

• Dragging the zoom box sometimes does not work. Only after moving the mouse for some distance does the drag box appear. The drag box is then positioned incorrectly with shifts.
• Mousedown -> move left+up -> move right+down: The box then does not reflect the current range. That is, the mouse is inside the drag box. However, it should be the range defined by MouseDownPosition -> CurrentMousePosition.
• After zooming out and then resizing, the canvas size does not get resized correctly.

[liana-yang]

@yubowenok You can review this pr now.

[yubowenok]

Can we prevent the canvas from being larger than the view when resizing to a smaller size? One possible solution would be to scale the canvas during the view resize, but without a redraw (Or even simpler, you can just truncate the canvas during resizing).

[yubowenok]

This css might work for the purpose.

.view {
  overflow: hidden;
}

However, I'm not sure if there will be any side effects somewhere else.

[liana-yang]

@yubowenok It works well.

[yubowenok]

LGTM