Add software focus capability to Ruida driver

This feature is not configurable at the moment; we could make it configurable if needed.

Tested on an OMTech Polar with a Ruida 6442s controller.

Author: TheAssassin

src/main/java/de/thomas_oster/liblasercut/drivers/Ruida.java

@@ -591,7 +591,6 @@ public void writeJobCode(LaserJob job, ProgressListener pl) throws IOException {
 
     for (JobPart p : job.getParts())
     {
-      float focus;
       boolean engrave = false;
 
       if ((p instanceof RasterPart) || (p instanceof Raster3dPart))
@@ -651,13 +650,27 @@ public void writeJobCode(LaserJob job, ProgressListener pl) throws IOException {
             {
               LaserProperty pr = cmd.getProperty();
               FloatMinMaxPowerSpeedFocusFrequencyProperty prop = (FloatMinMaxPowerSpeedFocusFrequencyProperty) pr;
+              float focus = prop.getFocus();
               if (first_prop) {
                 first_prop = false;
                 currentMinPower = cmd_layer_percent("c631", part_number, currentMinPower, prop.getMinPower());
                 currentMaxPower = cmd_layer_percent("c632", part_number, currentMaxPower, prop.getPower());
                   // prop speed is in %, ruida speed is in mm/s (0..1000)
                 currentSpeed = cmd_layer_absoluteMM("c904", part_number, currentSpeed, prop.getSpeed() * getMaxVectorCutSpeed() / 100);
-                // focus - n/a
+
+                // negative focus is not applicable on the test device (uses 6442s)
+                if (focus <= 0) {
+                  focus = 0;
+                }
+
+                // configure axis velocity, affects move speed of Z axis
+                stream.hex("c903").absoluteMM(5);
+                // move Z axis to desired focus valueu
+                // the value depends on the device
+                // on an OMTech Polar, for instance, focus needs to be set to 17 - <thickness>
+                // for instance, for a 3mm thick material, one needs to configure a focus of 14.0
+                stream.hex("800B").absoluteMM(focus);
+
                 // frequency
                 stream.hex("c660").byteint(part_number).hex("00").longint(prop.getFrequency());
                 // color - red for now
@@ -690,6 +703,9 @@ public void writeJobCode(LaserJob job, ProgressListener pl) throws IOException {
       currentSpeed = -1;
     }
 
+    // move Z axis back to 0
+    stream.hex("800B").absoluteMM(0);
+
     /* work interval */
     stream.hex("DA010620").longint(travel_distance).longint(travel_distance);
     /* stop */