Graphics in WebCanvas

Targets Web
1

Can I create graphics in a webcanvas in other than in the paint event?

2

Sure, you can always put your drawing code into methods. However, you’ll need to call them from within the Paint event.

3

Hallo Alex,
how can I do this ‘you’ll need to call them from within the Paint event’ ?
With Realbasic Pro I did it this way: me.graphics.drawline… . But this seems not to work with a WebCanvas.
So, ist there another way to do this?
Knut

4

Paint event:

RunMyMethod(g as Graphics)

RunMyMethod:

g.Drawline…

5

… but I just want to do this for example from the the MouseDown-Event to make changes on the graphic if the mousebutton is clicked over the canvas. IMHO: Your example is execute from start from the paint-event.

6

You might instead try drawing directly to your own Picture (that is a property of the web page). And then in the Canvas.Paint event handler, draw the picture.

7

Hi Paul, how can I do this?

8

Create a property of the page MyPic As Picture

Instantiate it in the shown event with the webCanvas dimensions

In your mouseDown event you draw to it. i.e.: MyPic.Graphics.Drawline(…)

In the WebCanvas Paint event you draw your picture in the graphics(g) property g.DrawPicture(MyPic, …)

9

The same as usual. Anywhere you want, just draw directly to an instantiated Picture property. It essentially acts as an off-screen buffer:

mPictureBuffer.ForeColor = &cff0000 mPictureBuffer.FillRect(0, 0, 50, 50)

Then in the Paint event handler, draw the buffer picture in the WebCanvas:

g.DrawPicture(mPictureBuffer, 0, 0)