I tried your snippet and after commenting out the scene, #include scene, stadt_setup(), stadt_symc(), the image load and sprite, and the textstrings, it worked fine for me. I created a sprite and added a text string. Worked full screen in AppGameKit classic and studio. Here is the code I used:
// Project: Test Full Screen
// Created: 2020-05-02
/// show all errors
SetErrorMode(2)
// set window properties
MaximizeWindow()
SetWindowTitle( "Test Full Screen" )
SetWindowSize(GetMaxDeviceWidth(),GetMaxDeviceHeight(), 1 )
SetwindowPosition(0,0)
SetWindowAllowResize( 1 ) // allow the user to resize the window
// set display properties
SetVirtualResolution( 1920, 1080 ) // doesn't have to match the window
// SetOrientationAllowed( 1, 1, 1, 1 ) // allow both portrait and landscape on mobile devices
SetSyncRate( 60, 0 ) // 30fps instead of 60 to save battery
SetScissor( 0,0,0,0 ) // use the maximum available screen space, no black borders
UseNewDefaultFonts( 1 )
#company_name "L_Lernen"
//#include "Stadt.scene"
//Stadt_setup()
// Verionsnummer (Versionnumber etc)
//SetTextString( Stadt_TitelText, GetTextString(Stadt_TitelText)+"0.5" )
//Learning sprite-stuff))
//Sprite-Testversuche
//LoadImage(1, "!Modell_Linkocarinaot.png")
//Sprite-Optionen
//CreateSprite(1,1) // 0: Sprite-Schlüssel(iSpriteIndex) / 1: LoadImage [Args]
//SetSpriteVisible(1, 1) // Sichtbarkeit bearbeiten [1/0]
//SetSpriteSize(1, 350.0, 670.0)
//SetSpritePosition(1, 350.0, 670.0)
//DeleteSprite(1)
newsprite = CreateSprite(0)
SetSpriteSize(newsprite, 100, 100)
SetSpriteColor(newsprite, 200, 100, 100, 255)
SetSpritePosition(newsprite, 400, 400)
CreateText(1, "hello test")
SetTextPosition(1, 100, 200)
SetTextSize(1, 30)
do
Print( ScreenFPS() )
//Stadt_Sync()
//dbg_zeigeCurPos( Stadt_zeigeCurPos ) // means showCursorPos (arg = Textlabel)
Sync()
loop
function dbg_zeigeCurPos(Ausgabeobjekt)
//while GetPointerPressed() = 1 (x#,y#)
x# = GetPointerX()
y# = GetPointerY()
//SetTextString(Ausgabeobjekt, "X: "+str(x#)+" | Y: "+str(y#))
//endwhile
endfunction