JoystickThumbPad: Add center variable to control Y throttle behaviour

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

src/QmlControls/JoystickThumbPad.qml

@@ -11,15 +11,14 @@ Item {
     property real   xAxis:          0                   ///< Value range [-1,1], negative values left stick, positive values right stick
     property real   yAxis:          0                   ///< Value range [-1,1], negative values up stick, positive values down stick
     property bool   yAxisThrottle:  false               ///< true: yAxis used for throttle, range [1,0], positive value are stick up
+    property bool   yAxisThrottleCentered: false        ///< false: center yAxis in throttle for reverser and forward
     property real   xPositionDelta: 0                   ///< Amount to move the control on x axis
     property real   yPositionDelta: 0                   ///< Amount to move the control on y axis
-    property bool   throttle:       false
 
     property real   _centerXY:              width / 2
     property bool   _processTouchPoints:    false
-    property bool   _stickCenteredOnce:     false
     property real   stickPositionX:         _centerXY
-    property real   stickPositionY:         yAxisThrottle ? height : _centerXY
+    property real   stickPositionY:         yAxisThrottleCentered ? _centerXY : height
 
     QGCMapPalette { id: mapPal }
 
@@ -50,7 +49,7 @@ Item {
 
         // Center sticks
         stickPositionX = _centerXY
-        if (!yAxisThrottle) {
+        if (yAxisThrottleCentered) {
             stickPositionY = _centerXY
         }
     }
@@ -86,7 +85,7 @@ Item {
 
     QGCColoredImage {
         color:                      lightColors ? "white" : "black"
-        visible:                    throttle
+        visible:                    yAxisThrottle
         height:                     ScreenTools.defaultFontPixelHeight
         width:                      height
         sourceSize.height:          height
@@ -100,7 +99,7 @@ Item {
 
     QGCColoredImage {
         color:                      lightColors ? "white" : "black"
-        visible:                    throttle
+        visible:                    yAxisThrottle
         height:                     ScreenTools.defaultFontPixelHeight
         width:                      height
         sourceSize.height:          height
@@ -114,7 +113,7 @@ Item {
 
     QGCColoredImage {
         color:                      lightColors ? "white" : "black"
-        visible:                    throttle
+        visible:                    yAxisThrottle
         height:                     ScreenTools.defaultFontPixelHeight
         width:                      height
         sourceSize.height:          height
@@ -128,7 +127,7 @@ Item {
 
     QGCColoredImage {
         color:                      lightColors ? "white" : "black"
-        visible:                    throttle
+        visible:                    yAxisThrottle
         height:                     ScreenTools.defaultFontPixelHeight
         width:                      height
         sourceSize.height:          height