HSPTV!掲示板

GetOpenFileNameA 関数を OFN_NODEREFERENCELINKS フラグを付与して起動すれば、
URLファイルのパスはとれそうでした。
https://learn.microsoft.com/ja-jp/windows/win32/api/commdlg/ns-commdlg-openfilenamea

// 参考元：
// https://wiki.hsp.moe/%E5%B0%8F%E3%83%AF%E3%82%B6%EF%BC%8F%E3%83%95%E3%82%A1%E3%82%A4%E3%83%AB%E9%81%B8%E6%8A%9E%E3%83%80%E3%82%A4%E3%82%A2%E3%83%AD%E3%82%B0.html

#uselib "Comdlg32.DLL"
#func GetOpenFileName "GetOpenFileNameA" int
 
#define BUFSIZE     260
#define FILTERSIZE  512
#define ALLTYPE                "ALL files (*.*)@*.*@"
#define OFN_FILEMUSTEXIST    $00001000
#define OFN_NODEREFERENCELINKS 0x00100000

    mref bmscr , 67
    
    dim  ofn  , 22
    sdim aplFilter , FILTERSIZE+1
    sdim usrFilter , FILTERSIZE+1
    sdim filename  , BUFSIZE+1
 
    aplFilter  = ALLTYPE + "@"
    usrFilter  = "ユーザ選択フィルタ (*.*)@*.*@" + "@"
 
    repeat
        await 0
        mutch=instr(aplFilter,start,"@")
        if mutch = -1 : break
        poke aplFilter , start + mutch , $00
        start += mutch + 1
    loop
    start = 0
    repeat
        await 0
        mutch=instr(usrFilter,start,"@")
        if mutch = -1 : break
        poke usrFilter , start + mutch , $00
        start += mutch + 1
    loop
    
        ofn.0    = 88                ; lStructSize
        ofn.1    = bmscr.13          ; hwndOwner
        ofn.2    = bmscr.14          ; hInstance
        ofn.3=varptr(aplFilter)         ; lpstrFilter
        ofn.4=varptr(usrFilter)         ; lpstrCustomFilter
        ofn.5    = FILTERSIZE        ; nMaxCustFilter
        ofn.6    = 1                  ; nFilterIndex
        ofn.7=varptr(filename)          ; lpstrFile
        ofn.8    = BUFSIZE           ; nMaxFile
        ofn.9    = 0                  ; lpstrFileTitle
        ofn.10  = 0                  ; nMaxFileTitle
        ofn.11  = 0                  ; lpstrInitialDir
        ofn.12  = 0                  ; lpstrTitle
        ofn.13  = OFN_FILEMUSTEXIST | OFN_NODEREFERENCELINKS  ; Flags
        
        prm=varptr(ofn)
 
        GetOpenFileName prm
        if stat = 0{
            dialog "失敗" , 0 , "終了確認" : end
        }
    mes filename
    stop