SecondBASIC Studio HBLANK Example

[+Gemintronic]

dra600n of Second Dimension posted a small HBLANK example I'd like to share here.  Basically, if you want to mess with the display on a certain scanline this is how you do it.  In this example we're changing out a whole palette on a certain line.  This is good if you want a status bar with a different set of palettes or a water effect like in Sonic 3.

 

Note that you will most likely get artifacts like "CRAM dots" if you mess with hblank even a little.

 

    hBlank 111
    
    On hInt GoSub hbl
    On vInt GoSub vbl
    
    Enable hInt
    Enable vInt
    
    hint_counter = 111
    
    End
    
    
vbl:
    Palettes pal1,0,0,16
    
    j = JoyPad(0)

    If j.0 = 1 Or j.1 = 1 Then
        hint_counter+=j.1-j.0
        hBlank hint_counter
    End If
    
    Return
    
    
hbl:
    Palettes pal2,0,0,16
    Return
    
    
    
pal1:
    DataInt $0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000
    DataInt $0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000
    
pal2:
    DataInt $0EEE,$0000,$0000,$0000,$0000,$0000,$0000,$0000
    DataInt $0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000