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175 lines
8.6 KiB
Markdown
175 lines
8.6 KiB
Markdown
The **_KEYDOWN** function returns whether modifying keys like CTRL, ALT, SHIFT, and any other keys are pressed.
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## Syntax
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> return% = **_KEYDOWN(***code&***)**
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* 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.
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* The POSITIVE [LONG](LONG) *code* value can be from any function key that needs to be monitored in a key press combination.
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* Unicode references:
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* 1) What is the glyph represented by that UNICODE value: [Unicode Format Info](http://www.fileformat.info/info/unicode/char/search.htm)
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* 2) Which fonts support the characters I want to use: [Unicode Fonts](http://en.wikipedia.org/wiki/Unicode_typefaces#Comparison_of_fonts)
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* 3) What was the format again?: [Unicode Formats](http://www.birds-eye.net/definition/u/unicode.shtml)
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* 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.
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* An important difference between [INKEY$](INKEY$) and [_KEYHIT](_KEYHIT) is how they work when **CTRL, ALT** or **SHIFT** are used. [INKEY$](INKEY$) returns a different code if you hold down CTRL, ALT or SHIFT before pressing F1 (for example). [_KEYHIT](_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.
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* **Keyboards with Alt Gr key:** [_KEYHIT](_KEYHIT) may return both Alt(100307) and Ctrl(100306) codes when key is pressed or released.
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* **Linux with foreign keyboards:** [SHELL](SHELL) [_HIDE](_HIDE) "setxkbmap us" will setup a keyboard to read US [Scancodes](Scancodes).
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```text
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**The QB64 Virtual Key constant values used: **
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**0-255**: [ASCII](ASCII) values (Refer to [http://en.wikipedia.org/wiki/Code_page_437 CP437])
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**256-65535**: [ASCII](ASCII) character codes (unaffected by SHIFT/ALT/CTRL modifiers)
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Use [CVI](CVI) to convert ASCII 2-byte codes to _KEYDOWN values.
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' **_KEYDOWN Keyboard Values**
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'
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**'Esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 Sys ScL Pause**
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' 27 15104 15360 15616 15872 16128 16384 16640 16896 17152 17408 34048 34304 +316 +302 +019
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**'`~ 1! 2@ 3# 4$ 5% 6^ 7& 8* 9( 0) -_ =+ BkSp Ins Hme PUp NumL / * -**
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'126 33 64 35 36 37 94 38 42 40 41 95 43 8 20992 18176 18688 +300 47 42 45
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** 96 49 50 51 52 53 54 55 56 57 48 45 61*
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**'Tab Q W E R T Y U I O P [{ ]} \| Del End PDn 7Hme 8/▲ 9PU + **
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' 9 81 87 69 82 84 89 85 73 79 80 123 125 124 21248 20224 20736 18176 18432 18688 43
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** 113 119 101 114 116 121 117 105 111 112 91 93 92 55 56 57 *
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**'CapL A S D F G H J K L ;: '" Enter 4/◄- 5 6/-►
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'+301 65 83 68 70 71 72 74 75 76 58 34 13 19200 19456 19712 **E**
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** 97 115 100 102 103 104 106 107 108 59 39 52 53 54 * **n**
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**'Shift Z X C V B N M ,< .> /? Shift ▲ 1End 2/▼ 3PD t**
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'+304 90 88 67 86 66 78 77 60 62 63 +303 18432 20224 20480 20736 **e**
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** 122 120 99 118 98 110 109 44 46 47 49 50 51 * **r**
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**'Ctrl Win Alt Spacebar Alt Win Menu Ctrl ◄- ▼ -► 0Ins .Del **
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'+306 +311 +308 32 +307 +312 +319 +305 19200 20480 19712 20992 21248 13
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' * 48 46*
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'
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' ** Lower value = LCase/NumLock On __________________ + = add 100000 **
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```
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```text
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**65536-&H40000000: QB64-specific Virtual Key codes:**
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CONST KEY_PAUSE& = 100019
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CONST KEY_NUMLOCK& = 100300
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CONST KEY_CAPSLOCK& = 100301
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CONST KEY_SCROLLOCK& = 100302
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CONST KEY_RSHIFT& = 100303
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CONST KEY_LSHIFT& = 100304
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CONST KEY_RCTRL& = 100305
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CONST KEY_LCTRL& = 100306
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CONST KEY_RALT& = 100307
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CONST KEY_LALT& = 100308
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CONST KEY_RMETA& = 100309 'Left 'Apple' key (MacOSX)
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CONST KEY_LMETA& = 100310 'Right 'Apple' key (MacOSX)
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CONST KEY_LSUPER& = 100311 'Left "Windows" key
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CONST KEY_RSUPER& = 100312 'Right "Windows"key
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CONST KEY_MODE& = 100313 '"AltGr" key
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CONST KEY_COMPOSE& = 100314
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CONST KEY_HELP& = 100315
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CONST KEY_PRINT& = 100316
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CONST KEY_SYSREQ& = 100317
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CONST KEY_BREAK& = 100318
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CONST KEY_MENU& = 100319
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CONST KEY_POWER& = 100320
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CONST KEY_EURO& = 100321
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CONST KEY_UNDO& = 100322
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CONST KEY_KP0& = 100256
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CONST KEY_KP1& = 100257
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CONST KEY_KP2& = 100258
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CONST KEY_KP3& = 100259
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CONST KEY_KP4& = 100260
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CONST KEY_KP5& = 100261
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CONST KEY_KP6& = 100262
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CONST KEY_KP7& = 100263
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CONST KEY_KP8& = 100264
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CONST KEY_KP9& = 100265
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CONST KEY_KP_PERIOD& = 100266
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CONST KEY_KP_DIVIDE& = 100267
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CONST KEY_KP_MULTIPLY& = 100268
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CONST KEY_KP_MINUS& = 100269
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CONST KEY_KP_PLUS& = 100270
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CONST KEY_KP_ENTER& = 100271
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CONST KEY_KP_INSERT& = 200000
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CONST KEY_KP_END& = 200001
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CONST KEY_KP_DOWN& = 200002
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CONST KEY_KP_PAGE_DOWN& = 200003
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CONST KEY_KP_LEFT& = 200004
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CONST KEY_KP_MIDDLE& = 200005
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CONST KEY_KP_RIGHT& = 200006
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CONST KEY_KP_HOME& = 200007
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CONST KEY_KP_UP& = 200008
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CONST KEY_KP_PAGE_UP& = 200009
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CONST KEY_KP_DELETE& = 200010
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CONST KEY_SCROLL_LOCK_MODE& = 200011
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CONST KEY_INSERT_MODE& = 200012
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**&H40000000 up**: [Unicode](Unicode) using the **cyberbit.ttf** font when available.
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**Use [_KEYHIT](_KEYHIT) to find the key codes to be monitored by _KEYDOWN! **
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```
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Comparing the _KEYDOWN returns using [CONST](CONST) values with 2 byte [INKEY$](INKEY$) returns.
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```vb
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CONST RSHIFT& = 100303
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CONST LSHIFT& = 100304
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DO
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x = _KEYHIT
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IF x = CVI(CHR$(0) + CHR$(59)) THEN
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IF _KEYDOWN(LSHIFT&) OR _KEYDOWN(RSHIFT&) THEN
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PRINT "KEYHIT: SHIFT + F1"
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ELSE
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PRINT "KEYHIT: F1"
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END IF
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END IF
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k$ = INKEY$ 'compare key press return values
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IF k$ = CHR$(0) + CHR$(59) THEN PRINT "INKEY$: F1"
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IF k$ = CHR$(0) + CHR$(84) THEN PRINT "INKEY$: SHIFT+F1"
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LOOP UNTIL k$ = CHR$(27) 'escape key exit
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```
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How to calculate the _KEYDOWN codes of the 2 byte INKEY$ arrow key codes using [CVI](CVI).
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```vb
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SCREEN 12
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x = 320: y = 240
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col = _RGB(255, 0, 0)
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radius = 20
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DO
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CLS
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LOCATE 1, 1: PRINT "Use the arrow keys to move the circle."
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CIRCLE (x, y), radius, col
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PAINT (x, y), col
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IF _KEYDOWN(CVI(CHR$(0) + "P")) THEN y = y + 1 '_KEYDOWN(20480)
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IF _KEYDOWN(CVI(CHR$(0) + "H")) THEN y = y - 1 '_KEYDOWN(18432)
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IF _KEYDOWN(CVI(CHR$(0) + "K")) THEN x = x - 1 '_KEYDOWN(19200)
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IF _KEYDOWN(CVI(CHR$(0) + "M")) THEN x = x + 1 '_KEYDOWN(19712)
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_DISPLAY
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_LIMIT 100 'limit to 100 frames per second
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LOOP
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```
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> *Explanation:* When [CVI](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](ASCII) code of "P" which is 80. CVI multiplies 80 * 256 = 20480.
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## See Also
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* [_KEYHIT](_KEYHIT), [Unicode](Unicode), [Code Pages](Code-Pages) (by region)
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* [_MAPUNICODE](_MAPUNICODE), [_MAPUNICODE (function)](_MAPUNICODE-(function))
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* [INKEY$](INKEY$), [ASCII](ASCII), [CVI](CVI)
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* [INP](INP)(&H60), [Scancodes](Scancodes)
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* [ON KEY(n)](ON-KEY(n)), [KEY(n)](KEY(n)), [KEY n](KEY-n)
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* [Windows Libraries](Windows-Libraries)
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