' Screensaver sample with FreeBASIC. use FB_ScreenSaverKit.bas
'
' freeBASIC Screensaver Kit Updated - freebasic.net
' https://www.freebasic.net/forum/viewtopic.php?t=25235
'
' Windows10 x64 22H2 + FreeBASIC 1.10.1
' ssfbscrsample.bas ... License CC0 / Public Domain
' by mieki256
' Last updated: <2024/02/01 20:34:03 +0900>

#include "fb_screensaverkit.bas"

' use mmsystem
#include "windows.bi"
#include "win/mmsystem.bi"

timeBeginPeriod(1)

Randomize Timer

Const MAX_FPS = 60.0
Const PI = 3.141592653

Dim As Double start_time, prev_time, now_time, next_time, delta, one_frame
Dim As Integer frame_count
Dim As String fps_text = "FPS"

Dim As Integer sw, sh

'Start the Screen Saver
StartScreenSaver

#If 1
' get screen size. width and height
ScreenInfo sw, sh
#Else
'You can also find the width & height of the screen by using SaverInfo.ScrWidth & SaverInfo.ScrHeight
sw = SaverInfo.ScrWidth
sh = SaverInfo.ScrHeight
#Endif

' init work
Dim As Double x, y, dx, dy, r
x = sw / 2.0
y = sh / 2.0
dx = (CDbl(sw) / MAX_FPS) * 0.6
dy = (CDbl(sh) / MAX_FPS) * 0.4
r = sh / 16.0

start_time = Timer
prev_time = start_time
frame_count = 0

' main loop
Do Until SaverInfo.IsClosing = True

    ' get delta
    now_time = Timer
    delta = now_time - prev_time
    prev_time = now_time
    next_time = now_time + (1.0 / MAX_FPS)
    If delta < 0 Then delta = 1.0 / MAX_FPS

    ' count FPS
    If now_time >= start_time Then
        If (now_time - start_time) >= 1.0 Then
            fps_text = Str(frame_count) & " FPS"
            start_time += 1.0
            frame_count = 0
        End If
    Else
        start_time = now_time
    End If
    frame_count += 1

    ' move ball position
    x += (dx * MAX_FPS * delta)
    y += (dy * MAX_FPS * delta)

    If (x <= (r / 2) And dx < 0) Or (x >= (sw - (r / 2)) And dx > 0) Then dx *= -1.0
    If (y <= (r / 2) And dy < 0) Or (y >= (sh - (r / 2)) And dy > 0) Then dy *= -1.0

    If SaverInfo.IsClosing <> True Then
        ' draw start
        ' ScreenLock

        ' clear screen
        ' Line (0, 0)-(sw, sh), Rgb(0, 0, 0), BF
        color RGB(0, 0, 0), RGB(0, 0, 0)
        cls

        ' draw ball
        circle (x, y), r, RGB(255, 0, 0), , , , F

        ' darw FPS
        Draw String ((sw - Len(fps_text) * 8) / 2, 10), fps_text, RGB(255, 255, 255)

        ' draw end
        ' ScreenUnlock
    End If

    ' sleep
    If Timer < next_time Then
        Dim As Double wait_time = (next_time - Timer) * 1000.0
        If wait_time > 0 Then
            sleep wait_time
        End If
    End If
Loop

timeEndPeriod(1)