Canvas:onMouseWheel()

Canvas:onMouseWheel(delta, buttons)event

This event is fired when the user rotates the mouse wheel while beeing over the Canvas.

Parameters

delta

A numberthat indicates the distance the wheel is rotated, expressed in multiples or divisions of 120.
A positive value indicates that the wheel was rotated forward, away from the user, a negative value indicates that the wheel was rotated backward, toward the user.

buttons

A table which fields indicates if mouse buttons or special keys have been pressed during the mouse up event :

"left": true if left mouse button is pressed, false otherwise
"right": true if right mouse button is pressed, false otherwise
"middle": true if middle mouse button is pressed, false otherwise
"control": true if the CONTROL key is pressed, false otherwise
"shift": true if the SHIFT mouse button is pressed, false otherwise

Return value

The event returns no value.

Example


--! luart-extensions
import ui
require "canvas"

local win = ui.Window("Canvas - onMouseWheel event example", "fixed", 320, 240)

local c = ui.Canvas(win)
c.align = "all"

local width = c.width/2
local height = c.height/2
local scale = 1

function c:onMouseWheel(delta)
    scale = scale + 0.05*delta/120 
end

function c:onPaint()
  self:begin()
  self:clear()
  c:identity()
  c:scale(scale, scale)
  c:fillrect(width-35, height-35, width+35, height+35, 0xA569BDFF)
  self:flip()
end

await win:showasync()