Canvas not rendering on app start on Windows

BlitzMax Forums/MaxGUI Module/Canvas not rendering on app start on Windows

dooz	(Posted 2011) [#1]

I have built an app that contains two canvases, one for icons and one for a main area. When I start the app, I load icons into the first canvas, fire a redrawgadget event and it calls the draw code.

It works perfectly on Mac, but on Windows the icons don't show unless I move the screen around or cover the window with another window then bring it back into view.

I tried flipping several times and that works intermittently, however it's not a good fix.

I have also tried before and after showing the window.

Any help would be appreciated, thanks

skn3	(Posted 2011) [#2]

Can you post the bit of code where you are painting your gadget? Also are you using a hook or waitevent?

dooz	(Posted 2011) [#3]

This is a simplified version of what I am doing:

My main code is:

...

Global the_ui:UI = MainUI.Create()

AddHook EmitEventHook, event_hook

Repeat
WaitEvent()
Forever

End

Function event_hook:Object(id, data:Object, context:Object)

Local event:TEvent = TEvent(data)
If event = Null Then Return Null
the_ui.handle_event(event)
Return Null

End Function

...

The mainUI code:

Method handle_event(event:TEvent)

Select event.id

Case EVENT_GADGETPAINT

If TGadget(event.source) = _icon_canvas
draw_icons()
Endif

...

The simplified draw code:

Method draw_icons()

SetGraphics CanvasGraphics(_icon_canvas)
SetClsColor 0, 0, 0
Cls

For Local s:Shape = EachIn _shapes
DrawImage s._icon_img, 0, y
Next

...

Flip

' Note: If I put two additional Flips here, it works

End Method

skn3	(Posted 2011) [#4]

Ok a few things:

First of all you can put your code In a tag on this forum.

replace > With ] and < with [

Next in your eventhook make sure you are only returning null if you don't want anything else dealing with the event. By returning null always it can cause issues. Replace the two return nulls with

Function event_hook:Object(id, data:Object, context:Object)
    Local event:TEvent = TEvent(data)
    If event = Null Then Return data
    If the_ui.handle_event(event) = null Then Return null 'let the handle_event method decide

    'always rerun data if event is not handled
    Return data
End Function

Type the_ui_object
    Method handle_event:TEvent(event:TEvent)
        Select event.id
            Case EVENT_GADGETPAINT
                If TGadget(event.source) = _icon_canvas
                    draw_icons()

                    'return null as we have acted upon it and painted
                    Retun null
                End if
        End Select

        'return that the event wasn't dealt with
        Return event
    End Method
End Type

The last bit is that you need to make sure to set the viewport and virtual resolution like so:

SetGraphics CanvasGraphics(_icon_canvas)
SetVirtualResolution(_icon_canvas.clientwidth(),_icon_canvas.clientheight())
SetViewport(0,0,_icon_canvas.clientwidth(),_icon_canvas.clientheight())

Last edited 2011

Last edited 2011

Last edited 2011

xlsior

(Posted 2011) [#5]

Are you calling GLShareContexts() before creating your graphics canvas?

skidracer

(Posted 2011) [#6]

And make sure to set GLDriver.

John G

(Posted 2011) [#7]

Could you try both the DX7 or DX9 graphic drivers on the PC? I believe I've had a similar problem with an initial Splash screen using the DX9 driver -- but not DX7 or OpenGL.

dooz	(Posted 2011) [#8]

Thank you to everyone that helped.

I've fixed the event handling as suggested.

I am using GLShareContexts() already

And using the DX7 driver fixes appears to fix the problem.

So again all of you forum members makes working with BlitzMax a fantastic experience.

Paul