GLUT doesn't detect properly more then 2 keys pressed?

I'm trying to make a small game using (free)GLUT. I know that it's old and there are better alternatives, but currently I prefer to stick with it and use it as much as possible. I program with C.

I'm currently trying to make GLUT detect properly all the keys I press. I use glutKeyboardFunc, glutKeyboardUpFunc, glutSpecialFunc and glutSpecialUpFunc to detect pressed keys and I store their state in a short array I created (I currently have only 5 usable keys, so I just created a specific array for them).

However, while everything works fine for 2 keys or less, the game doesn't detect properly 3 keys or more. While for some keys it detect the combination properly (that actually happens for only 1 specific combination), for others the function开发者_JAVA技巧s simply don't detect the third key that I press.

I checked my code a few times, and there is nothing special about the combination that does work. I also made glutKeyboardFunc and glutSpecialFunc directly print every key-press that they receive, and it seems they simply stop working after I press more then 2 keys.

Is it a known issue with GLUT or something? I googled a lot and didn't find anyone with a similar issue.

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I am not very into GLUT but as I know, but you should make sure, that your keyboard supports more than 2 input keys at once. This feature is called n-key rollover. This page says, that 2-key rollover may be a common value for some keyboards, but you dont need to trust this source.

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I'll clarify a point: The glutKeyBoardFunc is a callback i.e., it is invoked for every key pressed and re-executed over and over again and all the if-else (or switch-case) statements for various key combinations are executed. What it means is this - if you were to press 'A', '->' (right arrow) and 'D' all at once, depending on which key-press event was received first the callback will be executed accordingly. Sometimes with a delay and sometimes the on screen animation may stop momentarily.

GLUT is purely for educational/learning purposes but not good for full blown applications since that's not what it was designed for. You land up using OS specific libs or other languages (e.g., Qt) to embed OpenGL "window" within them and execute the keyboard events etc., The event handling in those (and/or OS specific frameworks) is radically different (and better) than GLUT.

You may want to keep your simultaneous key presses to a minimum. You may augment it with the mouse to get rid of the jerky response/processing...