132 lines
3.9 KiB
C++
132 lines
3.9 KiB
C++
#include "keydecoder.h"
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#include "ps2controller.h"
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// Constants used for key decoding
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constexpr unsigned char BREAK_BIT = 0x80;
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constexpr unsigned char PREFIX_1 = 0xe0;
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constexpr unsigned char PREFIX_2 = 0xe1;
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Key KeyDecoder::decode(unsigned char code) {
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Key key = modifier;
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// All keys that are introduced by the MF II keyboard (compared to the older
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// AT keyboard) always send a prefix value as first byte.
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if (code == PREFIX_1 || code == PREFIX_2) {
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prefix = code;
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} else {
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// Releasing a key is, for us, only important for the modifier keys such
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// as SHIFT, CTRL and ALT, For other, non-modifier keys, we ignore the
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// break code.
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bool pressed = (code & BREAK_BIT) == 0;
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// A key's break code is identical to its make code with an additionally
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// set BREAK_BIT
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Key::Scancode scancode =
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static_cast<Key::Scancode>(code & (~BREAK_BIT));
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// We ignore "new" special keys, such as the Windows key
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if (scancode < Key::Scancode::KEYS) {
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// save state
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status[static_cast<size_t>(scancode)] = pressed;
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// Take a closer look at modifier make and break events
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bool isModifier = true;
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switch (scancode) {
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// both shifts are handled equally
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case Key::Scancode::KEY_LEFT_SHIFT:
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case Key::Scancode::KEY_RIGHT_SHIFT:
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modifier.shift = pressed;
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break;
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case Key::Scancode::KEY_LEFT_ALT:
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if (prefix == PREFIX_1) {
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modifier.alt_right = pressed;
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} else {
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modifier.alt_left = pressed;
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}
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break;
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case Key::Scancode::KEY_LEFT_CTRL:
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if (prefix == PREFIX_1) {
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modifier.ctrl_right = pressed;
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} else {
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modifier.ctrl_left = pressed;
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}
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break;
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default:
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isModifier = false;
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}
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// For keys other than modifiers, we only care about the make code
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if (pressed && !isModifier) {
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switch (scancode) {
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case Key::Scancode::KEY_CAPS_LOCK:
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modifier.caps_lock ^= 1;
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setLed(PS2Controller::LED_CAPS_LOCK,
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modifier.caps_lock);
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break;
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case Key::Scancode::KEY_SCROLL_LOCK:
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modifier.scroll_lock ^= 1;
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setLed(PS2Controller::LED_SCROLL_LOCK,
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modifier.scroll_lock);
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break;
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case Key::Scancode::KEY_NUM_LOCK: // Can be both NumLock
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// and pause
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// On old keyboards, the pause functionality was only
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// accessible by pressing Ctrl+NumLock. Modern MF-II
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// keyboards therefore send exactly this code
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// combination when the pause key was pressed. Normally,
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// the pause key does not provide an ASCII code, but we
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// check that anyway. In either case, we're now done
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// decoding.
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if (modifier.ctrl_left) { // pause key
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key.scancode = scancode;
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} else { // NumLock
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modifier.num_lock ^= 1;
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setLed(PS2Controller::LED_NUM_LOCK,
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modifier.num_lock);
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}
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break;
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// Special case scan code 53: This code is used by both the
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// minus key on the main keyboard and the division key on
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// the number block. When the division key was pressed, we
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// adjust the scancode accordingly.
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case Key::Scancode::KEY_SLASH:
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if (prefix == PREFIX_1) {
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key.scancode = Key::Scancode::KEY_DIV;
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key.shift = true;
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} else {
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key.scancode = scancode;
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}
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break;
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default:
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key.scancode = scancode;
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// When NumLock is enabled and a key on the keypad was
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// pressed, we want return the ASCII and scan codes of
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// the corresponding numerical key instead of the arrow
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// keys. The keys on the cursor block (prefix ==
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// PREFIX_1), however, should remain usable. Therefore,
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// as a little hack, we deactivate the NumLock for these
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// keys.
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if (modifier.num_lock && prefix == PREFIX_1) {
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key.num_lock = false;
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}
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}
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}
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}
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// The prefix is only valid for the immediately following code, which
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// was just handled.
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prefix = 0;
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}
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return key;
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}
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