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bmx-ng / bmx-ng

The Open Source BlitzMax Compiler Project
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[BUG] Unhandled Exception: Attempt to access field or method of Null #138

Open alexefu73 opened 2 years ago

alexefu73 commented 2 years ago

I had downloaded and installed BlitzMax (BlitzMax_linux_x64_0.129.3.45.tar.xz) on my platform (GNU/Linux Deepin 20.2.1.x64bit). And tested compiling some basic BlitzMax code. It's work as expected correctly. But when I started to test MaxGUI I had a trouble in running the tested app when creating the Canvas, with resulting in popup window contains the following message:

Unhandled Exception: Attempt to access field or method of Null object

And when I opened the debug panel, it's show me that the 'canvas' variable is (NULL) that supposed to get TGadget object from CreateCanvas function.. look at the picture down.

So, what is the problem? How could I fix the problem? Thanks for care,

blitzmax_maxgui_bug

maxgui_bug_createCanvas

braxtonrivers commented 2 years ago

even though it may appear to be a bug the canvas actually requires a graphics context to render to, so this can be solved by simply adding in the following import

Import brl.glmax2d

this should solve your issue

alexefu73 commented 2 years ago

even though it may appear to be a bug the canvas actually requires a graphics context to render to, so this can be solved by simply adding in the following import

Import brl.glmax2d

this should solve your issue

Thanks sir, I added this import line 'import brl.glmax2d', but it's still the error continually appearing when running the result app.

braxtonrivers commented 2 years ago

Does this sample work for you?

SuperStrict 

Framework MaxGui.Drivers
Import brl.timerdefault
Import brl.eventqueue
Import brl.glmax2d

Global GAME_WIDTH:Int=320
Global GAME_HEIGHT:Int=240

' create a centered window with client size GAME_WIDTH,GAME_HEIGHT

Local wx:Int=(ClientWidth(Desktop())-GAME_WIDTH)/2
Local wy:Int=(ClientHeight(Desktop())-GAME_HEIGHT)/2

Local window:TGadget=CreateWindow("My Canvas",wx,wy,GAME_WIDTH,GAME_HEIGHT,Null,WINDOW_TITLEBAR)'|WINDOW_CLIENTCOORDS)

' create a canvas for our game
Local canvas:TGadget=CreateCanvas(0,0,320,240,window)

' create an update timer

CreateTimer 60

While WaitEvent()
    Select EventID()
        Case EVENT_TIMERTICK
            RedrawGadget canvas

        Case EVENT_GADGETPAINT
            SetGraphics CanvasGraphics(canvas)
            SetOrigin 160,120
            SetLineWidth 5
            Cls
            Local t:Int=MilliSecs()
            DrawLine 0,0,120*Cos(t),120*Sin(t)
            DrawLine 0,0,80*Cos(t/60),80*Sin(t/60)
            Flip

        Case EVENT_MOUSEMOVE
            Print "MOVE!"

        Case EVENT_WINDOWCLOSE
            FreeGadget canvas
            End

        Case EVENT_APPTERMINATE
            End
    End Select
Wend

I should mention that I am on Win 11, and do not have any linux boxes.

alexefu73 commented 2 years ago

I entered this example and the same error is still appear.

braxtonrivers commented 2 years ago

It could be an issue on linux then, hopefully one of the linux guru's can confirm and then assist further with bug reporting, apologies.

alexefu73 commented 2 years ago

Ok!

GWRon commented 2 years ago

Maybe a GTK3 issue? GTK3 raised some issues here and there ... and with more recent Linux Distros MaxGUI shows aging symptoms (also on MacOS).

The samples work here but I am on Mint 18 and 19. Could check in a VM - just pass me the download page of your distro (and the flavour you used).

alexefu73 commented 2 years ago

I'm using Deepin 20.2.1, downloaded it from here: https://www.deepin.org/en/download/

GWRon commented 2 years ago

I built it here - with newest BMX NG (updated bcc, modules, ...)

Testcodes.zip

Does it work for you?

GWRon commented 2 years ago

Ok, installed in a VM ... can replicate your issue and my testcode runs ... need to check if updating BMX will do.

GWRon commented 2 years ago

OK ... if you updated complete Blitzmax, it will work ... but as there is a hen-egg issue (newer compiler needs newer brl.mod - and brl.mod needs newer compiler) I will do a "manual" update instruction here:

remove blitzmax/mod/maxgui.mod and replace it with the downloaded one (do not forget to remove the "-master" from the folder name!)

remove blitzmax/mod/brl.mod:

and replace them with the according folders from the downloaded brl.mod-master.zip (only the above ".mod" folders ... other folders might require new BCC/compiler stuff ... so do not touch them for now :D)

When then compiling ... it should work (did so in my VM) Why? We fixed some stuff meanwhile ... so next stable release would work out of the box but for now you need to make your hands a bit dirty.

markcwm commented 2 years ago

This should only require you to use the latest maxgui.mod, specifically the GTK3 modules, with Blitzmax NG 0.129 release.

At least that's all I had to do to fix the same issue CreateCanvas returns Null in Linux fixed here (GTK3) Enable TGTKCanvas.

GWRon commented 2 years ago

only updating maxgui wasn't enough because newer maxgui relies on changes in brl.mod ... (in graphics.mod ... and max2d.mod ) and once you update them - you also need to update the systemdefault stuff.

alexefu73 commented 2 years ago

OK ... if you updated complete Blitzmax, it will work ... but as there is a hen-egg issue (newer compiler needs newer brl.mod - and brl.mod needs newer compiler) I will do a "manual" update instruction here:

remove blitzmax/mod/maxgui.mod and replace it with the downloaded one (do not forget to remove the "-master" from the folder name!)

remove blitzmax/mod/brl.mod:

  • glgraphics.mod
  • glmax2d.mod
  • graphics.mod
  • max2d.mod
  • system.mod
  • systemdefault.mod

and replace them with the according folders from the downloaded brl.mod-master.zip (only the above ".mod" folders ... other folders might require new BCC/compiler stuff ... so do not touch them for now :D)

When then compiling ... it should work (did so in my VM) Why? We fixed some stuff meanwhile ... so next stable release would work out of the box but for now you need to make your hands a bit dirty.

Thank you so much, it's now working as expected.

Thanks,