uinput-controller: Initial support for keymaps

Keymap can be set with environment variable REMOTE_TOUCHPAD_UINPUT_KEYMAP

inputcontrol/keymap.go

@@ -0,0 +1,130 @@
+//go:build uinput
+
+/*
+ *    Copyright (c) 2023 Unrud <unrud@outlook.com>
+ *
+ *    This file is part of Remote-Touchpad.
+ *
+ *    Remote-Touchpad is free software: you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation, either version 3 of the License, or
+ *    (at your option) any later version.
+ *
+ *    Remote-Touchpad is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with Remote-Touchpad.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package inputcontrol
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+	"unsafe"
+)
+
+const bkeymapFileSignature = "bkeymap"
+
+// uapi/linux/keyboard.h
+const (
+	nrKeys       = 128
+	maxNrKeymaps = 256
+	nrShift      = 9
+
+	ktLatin  = 0
+	ktShift  = 7
+	ktLetter = 11
+)
+
+type KeyCombo struct {
+	Key       int
+	ShiftKeys [nrShift]int
+}
+
+type Keymap struct {
+	keyComboMap map[rune]KeyCombo
+}
+
+func (keymap Keymap) Get(character rune) (keyCombo KeyCombo, found bool) {
+	keyCombo, found = keymap.keyComboMap[character]
+	return
+}
+
+func LoadKeymap(name string) (*Keymap, error) {
+	if len(name) == 0 || strings.HasPrefix(name, "-") {
+		return nil, fmt.Errorf("invalid keymap name: %#v", name)
+	}
+	bkeymap, err := exec.Command("loadkeys", "--bkeymap", name).Output()
+	if err != nil {
+		return nil, err
+	}
+	if !strings.HasPrefix(string(bkeymap), bkeymapFileSignature) {
+		return nil, fmt.Errorf("invalid bkeymap: signature not found")
+	}
+	bkeymapHeader := bkeymap[len(bkeymapFileSignature):]
+	var keymaps [][nrKeys]int
+	if len(bkeymapHeader) < maxNrKeymaps {
+		return nil, fmt.Errorf("invalid bkeymap: EOF")
+	}
+	currentBkeymap := bkeymapHeader[maxNrKeymaps:]
+	for keymapIndex := 0; keymapIndex < maxNrKeymaps; keymapIndex += 1 {
+		if bkeymapHeader[keymapIndex] == 0 {
+			continue
+		}
+		if len(currentBkeymap) < nrKeys*2 {
+			return nil, fmt.Errorf("invalid bkeymap: EOF")
+		}
+		for len(keymaps) <= keymapIndex {
+			keymaps = append(keymaps, [nrKeys]int{})
+		}
+		for key := 0; key < nrKeys; key += 1 {
+			var keysym uint16
+			copy(unsafe.Slice((*byte)(unsafe.Pointer(&keysym)), 2),
+				currentBkeymap[key*2:])
+			keymaps[keymapIndex][key] = int(keysym)
+		}
+		currentBkeymap = currentBkeymap[nrKeys*2:]
+	}
+	keymap := Keymap{keyComboMap: make(map[rune]KeyCombo)}
+	if len(keymaps) == 0 {
+		return &keymap, nil
+	}
+	var shiftKeys [nrShift]int
+	for key, keysym := range keymaps[0] {
+		keyType := keysym >> 8
+		keyValue := keysym & 0xff
+		if keyType == ktShift && keyValue < nrShift && shiftKeys[keyValue] == 0 {
+			shiftKeys[keyValue] = key
+		}
+	}
+keymapLoop:
+	for keymapIndex := range keymaps {
+		var activeShiftKeys [nrShift]int
+		for i, shiftKey := range shiftKeys {
+			if keymapIndex&(1<<i) != 0 {
+				if shiftKey == 0 {
+					continue keymapLoop
+				}
+				activeShiftKeys[i] = shiftKey
+			}
+		}
+		for key, keysym := range keymaps[keymapIndex] {
+			keyType := keysym >> 8
+			keyValue := keysym & 0xff
+			if (keyType != ktLatin && keyType != ktLetter) || keyValue == 0 {
+				continue
+			}
+			character := rune(keyValue)
+			if _, ok := keymap.keyComboMap[character]; ok {
+				continue
+			}
+			keymap.keyComboMap[character] = KeyCombo{key, activeShiftKeys}
+		}
+	}
+	return &keymap, nil
+}