3 ms·

Another way to avoid the flickering was to wait for the screen refresh interrupt before writing to the video buffer, but it did slow things down if you weren't

• ygra 13y ago
  The flickering most likely was the result of the most naïve way of redrawing the screen: clrscr(); draw(); This redraws twice, by first clearing and then overwriting again. The flickering should go away completely if you actually redraw the screen, e.g. gotoxy(1, 1); draw(); At least in the things I wrote in Turbo Pascal back in the day this was enough to fix performance problems from drawing too. gotoxy() calls cost time too and simply writing a large bunch of characters in one go is often fast enough. Of course, writing directly to video memory is by far the fastest approach. The last time I had fun with this was with FreePascal in my first semester with a friend. We wrote a text-mode UI library for one assignment (it wasn't strictly necessary, but it was a fun learning experience); it had a message loop that handled focus and dispatched input to controls, full-screen "windows", sub-screen dialogs, and buttons, text input boxes, combo boxes, and tabular view. We used gotoxy() and write() calls throughout, which had the benefit that we could test it on my friend's old VT-100 terminal as well (it was slow as hell, though, but you could literally see where to optimize draw calls, similar to using X remotely over a slow network where you can watch it draw each menu half a dozen times), but planned on moving to a more optimized strategy. Alas, we never really had the time for a v2 rewrite so the project just went to die. And by now it's probably of no use to anyone anyway (but it taught me a lot about how windowing systems work or at least can work).