[fpc-pascal] pas2js Webgl unit committed

[Michael Van Canneyt]

On Tue, 1 May 2018, Ryan Joseph wrote:

>
>
>> On May 1, 2018, at 8:28 PM, Michael Van Canneyt <michael at freepascal.org> wrote:
>> 
>> Check the canvas demo (demo/rtl/democanvas2d.pas)
>
> something like this?
>
> var
>  canvas: TJSElement; // What type should this be?
>  gl: TJSWebGLRenderingContext;
> begin
>  canvas := document.createElement('canvas');
>  document.body.appendChild(canvas);
>  gl := canvas.getContext('webgl');

You must do
   gl := TJSWebGLRenderingContext(canvas.getContext('webgl'));

because getContext can return various classes depending on the argument.

>  canvas.width := newWidth;
>  canvas.height := newHeight;
>  gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
>
> Not sure about the type which createElement returns that has the getContext method.

createElement returns guaranteed TJSElement, but normally it will be TJSHTMLCanvasElement
for your call.

So
   canvas: TJSHTMLCanvasElement;

begin
   canvas:=TJSHTMLCanvasElement(document.createElement('canvas'));


> Do you need document.body.appendChild also? Sorry it’s been a long time since I used JS to do even simple things. Never knew it well.

Yes, you need that too to insert the new element in the DOM tree.

Michael.