Add support for combining 2 axes into one virtual axis. (#11)

Reviewed-on: #11

internal/mappingrules/mapping_rule_axis_combined.go

@@ -0,0 +1,51 @@
+package mappingrules
+
+import (
+	"git.annabunches.net/annabunches/joyful/internal/logger"
+	"github.com/holoplot/go-evdev"
+)
+
+type MappingRuleAxisCombined struct {
+	MappingRuleBase
+	InputLower *RuleTargetAxis
+	InputUpper *RuleTargetAxis
+	Output     *RuleTargetAxis
+}
+
+func NewMappingRuleAxisCombined(base MappingRuleBase, inputLower *RuleTargetAxis, inputUpper *RuleTargetAxis, output *RuleTargetAxis) *MappingRuleAxisCombined {
+	inputLower.OutputMax = 0
+	inputUpper.OutputMin = 0
+	return &MappingRuleAxisCombined{
+		MappingRuleBase: base,
+		InputLower:      inputLower,
+		InputUpper:      inputUpper,
+		Output:          output,
+	}
+}
+
+func (rule *MappingRuleAxisCombined) MatchEvent(device Device, event *evdev.InputEvent, mode *string) (*evdev.InputDevice, *evdev.InputEvent) {
+	if !rule.MappingRuleBase.modeCheck(mode) ||
+		!(rule.InputLower.MatchEvent(device, event) ||
+			rule.InputUpper.MatchEvent(device, event)) {
+
+		return nil, nil
+	}
+
+	// Since lower and upper are guaranteed to have opposite signs,
+	// we can just sum them.
+	var value int32
+	value += getValueFromAbs(rule.InputLower)
+	value += getValueFromAbs(rule.InputUpper)
+
+	return rule.Output.Device.(*evdev.InputDevice), rule.Output.CreateEvent(value, mode)
+}
+
+func getValueFromAbs(ruleTarget *RuleTargetAxis) int32 {
+	absInfo, err := ruleTarget.Device.AbsInfos()
+	if err != nil {
+		logger.LogErrorf(err, "WARNING: Couldn't get axis data for device '%s'", ruleTarget.DeviceName)
+		return 0
+	}
+
+	return ruleTarget.NormalizeValue(absInfo[ruleTarget.Axis].Value)
+}