_KEYDOWN

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The _KEYDOWN function returns whether modifying keys like CTRL, ALT, SHIFT, and any other keys are pressed.


Contents

Syntax

return% = _KEYDOWN(code&)


  • The return value is -1 if a specified key is pressed or 0 if it was not pressed. It can be used to monitor key combinations.
  • The POSITIVE LONG code value can be from any function key that needs to be monitored in a key press combination.
  • Unicode references:
  • 1) What is the glyph represented by that UNICODE value: Unicode Format Info
  • 2) Which fonts support the characters I want to use: Unicode Fonts
  • 3) What was the format again?: Unicode Formats
  • A UTF32 value is usually(but by no means always!) the same as a UTF16 value just with the top 2 bytes set to 0.
  • An important difference between INKEY$ and _KEYHIT is how they work when CTRL, ALT or SHIFT are used. INKEY$ returns a different code if you hold down CTRL, ALT or SHIFT before pressing F1 (for example). _KEYHIT will return the same code regardless of which modifiers were used but you can check _KEYDOWN to see which modifying keys are being used.
  • Keyboards with Alt Gr key: _KEYHIT may return both Alt(100307) and Ctrl(100306) codes when key is pressed or released.
  • Linux with foreign keyboards: SHELL _HIDE "setxkbmap us" will setup a keyboard to read US Scancodes.


The QB64 Virtual Key constant values used: 0-255: ASCII and Extended code values (Refer to CP437) 256-65535: ASCII 2-byte character codes (unaffected by SHIFT/ALT/CTRL modifiers) Use CVI to convert ASCII 2-byte codes to _KEYDOWN values. ' _KEYDOWN Keyboard Values ' 'Esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 Sys ScL Pause ' 27 15104 15360 15616 15872 16128 16384 16640 16896 17152 17408 34048 34304 +316 +302 +019 '`~ 1! 2@ 3# 4$ 5% 6^ 7& 8* 9( 0) -_ =+ BkSp Ins Hme PUp NumL / * - '126 33 64 35 36 37 94 38 42 40 41 95 43 8 20992 18176 18688 +300 47 42 45 ' 96 49 50 51 52 53 54 55 56 57 48 45 61 'Tab Q W E R T Y U I O P [{ ]} \| Del End PDn 7Hme 8/▲ 9PU + ' 9 81 87 69 82 84 89 85 73 79 80 123 125 124 21248 20224 20736 18176 18432 18688 43 ' 113 119 101 114 116 121 117 105 111 112 91 93 92 55 56 57 'CapL A S D F G H J K L  ;: '" Enter 4/◄- 5 6/-► '+301 65 83 68 70 71 72 74 75 76 58 34 13 19200 19456 19712 E ' 97 115 100 102 103 104 106 107 108 59 39 52 53 54 n 'Shift Z X C V B N M ,< .> /? Shift ▲ 1End 2/▼ 3PD t '+304 90 88 67 86 66 78 77 60 62 63 +303 18432 20224 20480 20736 e ' 122 120 99 118 98 110 109 44 46 47 49 50 51 r 'Ctrl Win Alt Spacebar Alt Win Menu Ctrl ◄- ▼ -► 0Ins .Del '+306 +311 +308 32 +307 +312 +319 +305 19200 20480 19712 20992 21248 13 ' 48 46 ' ' Lower value = LCase/NumLock On __________________ + = add 100000

NOTE: The above commented table can be copied and pasted directly into the QB64 IDE


65536-&H40000000: QB64-specific Virtual Key codes: CONST KEY_PAUSE& = 100019 CONST KEY_NUMLOCK& = 100300 CONST KEY_CAPSLOCK& = 100301 CONST KEY_SCROLLOCK& = 100302 CONST KEY_RSHIFT& = 100303 CONST KEY_LSHIFT& = 100304 CONST KEY_RCTRL& = 100305 CONST KEY_LCTRL& = 100306 CONST KEY_RALT& = 100307 CONST KEY_LALT& = 100308 CONST KEY_RMETA& = 100309 'Left 'Apple' key (MacOSX) CONST KEY_LMETA& = 100310 'Right 'Apple' key (MacOSX) CONST KEY_LSUPER& = 100311 'Left "Windows" key CONST KEY_RSUPER& = 100312 'Right "Windows"key CONST KEY_MODE& = 100313 '"AltGr" key CONST KEY_COMPOSE& = 100314 CONST KEY_HELP& = 100315 CONST KEY_PRINT& = 100316 CONST KEY_SYSREQ& = 100317 CONST KEY_BREAK& = 100318 CONST KEY_MENU& = 100319 CONST KEY_POWER& = 100320 CONST KEY_EURO& = 100321 CONST KEY_UNDO& = 100322 CONST KEY_KP0& = 100256 CONST KEY_KP1& = 100257 CONST KEY_KP2& = 100258 CONST KEY_KP3& = 100259 CONST KEY_KP4& = 100260 CONST KEY_KP5& = 100261 CONST KEY_KP6& = 100262 CONST KEY_KP7& = 100263 CONST KEY_KP8& = 100264 CONST KEY_KP9& = 100265 CONST KEY_KP_PERIOD& = 100266 CONST KEY_KP_DIVIDE& = 100267 CONST KEY_KP_MULTIPLY& = 100268 CONST KEY_KP_MINUS& = 100269 CONST KEY_KP_PLUS& = 100270 CONST KEY_KP_ENTER& = 100271 CONST KEY_KP_INSERT& = 200000 CONST KEY_KP_END& = 200001 CONST KEY_KP_DOWN& = 200002 CONST KEY_KP_PAGE_DOWN& = 200003 CONST KEY_KP_LEFT& = 200004 CONST KEY_KP_MIDDLE& = 200005 CONST KEY_KP_RIGHT& = 200006 CONST KEY_KP_HOME& = 200007 CONST KEY_KP_UP& = 200008 CONST KEY_KP_PAGE_UP& = 200009 CONST KEY_KP_DELETE& = 200010 CONST KEY_SCROLL_LOCK_MODE& = 200011 CONST KEY_INSERT_MODE& = 200012 &H40000000 up: Unicode using the cyberbit.ttf font when available. Use _KEYHIT to find the key codes to be monitored by _KEYDOWN!

Example 1: Comparing the _KEYDOWN returns using constant values with 2 byte INKEY$ returns.

CONST RSHIFT& = 100303 CONST LSHIFT& = 100304 DO x = _KEYHIT IF x = CVI(CHR$(0) + CHR$(59)) THEN IF _KEYDOWN(LSHIFT&) OR _KEYDOWN(RSHIFT&) THEN PRINT "KEYHIT: SHIFT + F1" ELSE PRINT "KEYHIT: F1" END IF END IF k$ = INKEY$ 'compare key press return values IF k$ = CHR$(0) + CHR$(59) THEN PRINT "INKEY$: F1" IF k$ = CHR$(0) + CHR$(84) THEN PRINT "INKEY$: SHIFT+F1" LOOP UNTIL k$ = CHR$(27) 'escape key exit

Code by Galleon


Example 2: How to calculate the _KEYDOWN codes of the 2 byte INKEY$ arrow key codes using CVI.

SCREEN 12 x = 320: y = 240 col = _RGB(255, 0, 0) radius = 20 DO CLS LOCATE 1, 1: PRINT "Use the arrow keys to move the circle." CIRCLE (x, y), radius, col PAINT (x, y), col IF _KEYDOWN(CVI(CHR$(0) + "P")) THEN y = y + 1 '_KEYDOWN(20480) IF _KEYDOWN(CVI(CHR$(0) + "H")) THEN y = y - 1 '_KEYDOWN(18432) IF _KEYDOWN(CVI(CHR$(0) + "K")) THEN x = x - 1 '_KEYDOWN(19200) IF _KEYDOWN(CVI(CHR$(0) + "M")) THEN x = x + 1 '_KEYDOWN(19712) _DISPLAY _LIMIT 100 'limit to 100 frames per second LOOP

Code by Galleon
Explanation: When CVI is used with a 2 byte code, the code of the first character(0) is added to the second character code which is multiplied by 256. In the example, code zero is added to the ASCII code of "P" which is 80. CVI multiplies 80 * 256 = 20480.


See also:



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