[FEM] fix solver console bugs

- for Elmer and Z88 on Windows several windows pop up (console windows). This is maybe annoying and the user is wondering what is going on, but the main problem is that when you close them, you break the solving process.
Therefore, on Windows only, hide the empty popup windows.

src/Mod/Fem/femsolver/elmer/tasks.py

@@ -121,10 +121,18 @@ class Solve(run.Solve):
                 if os.path.isdir(solvpath):
                     os.environ["ELMER_HOME"] = solvpath
                     os.environ["LD_LIBRARY_PATH"] = "$LD_LIBRARY_PATH:{}/modules".format(solvpath)
-            self._process = subprocess.Popen(
+            # hide the popups on Windows
+            if system() == "Windows":
+                self._process = subprocess.Popen(
                 [binary], cwd=self.directory,
                 stdout=subprocess.PIPE,
-                stderr=subprocess.PIPE)
+                stderr=subprocess.PIPE,
+                startupinfo=femutils.startProgramInfo("hide"))
+            else:
+                self._process = subprocess.Popen(
+                    [binary], cwd=self.directory,
+                    stdout=subprocess.PIPE,
+                    stderr=subprocess.PIPE)
             self.signalAbort.add(self._process.terminate)
             output = self._observeSolver(self._process)
             self._process.communicate()

src/Mod/Fem/femsolver/elmer/writer.py

@@ -33,6 +33,7 @@ import os
 import os.path
 import subprocess
 import tempfile
+from platform import system
 
 from FreeCAD import Console
 from FreeCAD import Units
@@ -223,7 +224,12 @@ class Writer(object):
                     unvPath,
                     "-scale", "0.001", "0.001", "0.001",
                     "-out", self.directory]
-            subprocess.call(args, stdout=subprocess.DEVNULL)
+            # hide the popups on Windows
+            if system() == "Windows":
+                subprocess.call(args, stdout=subprocess.DEVNULL,
+                    startupinfo=femutils.startProgramInfo("hide"))
+            else:
+                subprocess.call(args, stdout=subprocess.DEVNULL)
 
     def _writeStartinfo(self):
         path = os.path.join(self.directory, _STARTINFO_NAME)

src/Mod/Fem/femsolver/z88/tasks.py

@@ -31,6 +31,7 @@ __url__ = "https://www.freecadweb.org"
 import os
 import os.path
 import subprocess
+from platform import system
 
 import FreeCAD
 
@@ -118,23 +119,28 @@ class Solve(run.Solve):
         # TODO: search out for "Vector GS" and "Vector KOI" and print values
         # may be compare with the used ones
         self.pushStatus("Executing solver in test mode...\n")
-        self._process = subprocess.Popen(
-            [binary, "-t", "-" + solver],
-            cwd=self.directory,
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE)
-        self.signalAbort.add(self._process.terminate)
-        self._process.communicate()
-        self.signalAbort.remove(self._process.terminate)
+        Solve.runZ88(self, "-t", binary, solver, "hide")
 
         # run solver real mode
         self.pushStatus("Executing solver in real mode...\n")
-        binary = settings.get_binary("Z88")
-        self._process = subprocess.Popen(
-            [binary, "-c", "-" + solver],
-            cwd=self.directory,
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE)
+        # starting normal because the user must see the z88 window
+        Solve.runZ88(self, "-c", binary, solver, "normal")
+
+    def runZ88(self, command, binary, solver, state):
+        # minimize or hide the popups on Windows
+        if system() == "Windows":
+            self._process = subprocess.Popen(
+                [binary, command, "-" + solver],
+                cwd=self.directory,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                startupinfo=femutils.startProgramInfo(state))
+        else:
+            self._process = subprocess.Popen(
+                [binary, command, "-" + solver],
+                 cwd=self.directory,
+                 stdout=subprocess.PIPE,
+                 stderr=subprocess.PIPE)
         self.signalAbort.add(self._process.terminate)
         self._process.communicate()
         self.signalAbort.remove(self._process.terminate)