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--- new:input [2018/02/15 15:01] – created korshun
+++ new:input [2018/02/17 12:10] (current) – korshun
@@ Line 1: / Line 1: @@
-====== GetPlayerInput wrappers ======
+====== Input library ======
-Key states:
+ACSUtils provides a set of wrappers for [[zdoom>GetPlayerInput]] to make writing correct input code easier.
-  * Up
+===== Basic concepts =====
-  * Down
-  * Pressed
-  * Released
+  * Every key is either **up** or **down** at any time.
+  * If the key was up the previous tic, but is now down, it is said to have been **pressed**.
+  * If the key was down the previous tic, but is now up, it is said to have been **released**.
+  * If the key has been pressed or released, it is said to have been **toggled**.
+ACSUtils provide a way to easily check these all these states for every key without writing compliated ''GetPlayerInput'' expressions.
+===== What's the point of "pressed" and "released"? =====
+Say, you have an on-screen button to sell items that can be [[mouse|clicked with mouse]]:
+<code>
+if (/* check that mouse cursor is inside the button */)
+    if (GetPlayerInput(-1, INPUT_BUTTONS) & BT_ATTACK)) // check left mouse button click
+        SellItem();
+</code>
+**This code is wrong.** If the player clicks the button once, it will likely cause him to sell multiple items. That's because this code checks if the mouse button is **down**. But the mouse button may be down for multiple tics after a click, as it may not be immediately released.
+To avoid this bug, you need to check if the button was up the previous tic, but is now down. And that's exactly what the **pressed** state means. The ''KeyPressed'' function contains all the repetitive code to perform this check:
+<code>
+if (/* check that mouse cursor is inside the button */)
+    if (KeyPressed(BT_ATTACK)) // check left mouse button click
+        SellItem();
+</code>
+Now the button works correctly. Performing an action on releasing the button can be done the same way using ''KeyReleased''.
+===== Functions =====
+To check one key or a key combination:
+  * ''bool KeyUp(int key)''
+  * ''bool KeyDown(int key)''
+  * ''bool KeyPressed(int key)''
+  * ''bool KeyReleased(int key)''
+  * ''bool KeyToggled(int key)''
+Examples:
+Checking one key:
+<code>
+if (KeyPressed(BT_ATTACK))
+    print(s:"You clicked left mouse button");
+</code>
+Checking a key combination:
+<code>
+if (KeyDown(BT_FORWARD | BT_BACK))
+    print(s:"You are trying to move forward and back at the same time."
+          s:"You are not going anywhere this way.");
+</code>
+<note important>If you try to use ''KeyPressed'' with a key combination, you are requiring that the whole combination is pressed within the same tic. It is extremely hard to do so.</note>
+To check if at least one of the keys is in a given state:
+  * ''bool KeyUpAny(int keys)''
+  * ''bool KeyDownAny(int keys)''
+  * ''bool KeyPressedAny(int keys)''
+  * ''bool KeyReleasedAny(int keys)''
+  * ''bool KeyToggledAny(int keys)''
+For example:
+<code>
+if (KeyPressedAny(BT_ATTACK | BT_ALTATTACK))
+    print(s:"You just tried to shoot.");
+</code>
+<code>
+if (KeyDownAny(BT_FORWARD | BT_BACK | BT_MOVELEFT | BT_MOVERIGHT))
+    print(s:"You are trying to move.");
+</code>
+To use these wrappers on players other than the activator, prefix any of the above functions with ''Player'' and add player number as the first argument:
+  * ''bool PlayerKeyUp(int player, int key)''
+  * ''bool PlayerKeyDown(int player, int key)''
+  * ''bool PlayerKeyPressed(int player, int key)''
+  * ''bool PlayerKeyReleased(int player, int key)''
+  * ''bool PlayerKeyToggled(int player, int key)''
+  * ''bool PlayerKeyUpAny(int player, int keys)''
+  * ''bool PlayerKeyDownAny(int player, int keys)''
+  * ''bool PlayerKeyPressedAny(int player, int keys)''
+  * ''bool PlayerKeyReleasedAny(int player, int keys)''
+  * ''bool PlayerKeyToggledAny(int player, int keys)''

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