Added an example that demonstrates commands related to silent installers

git-svn-id: https://svn.code.sf.net/p/nsis/code/NSIS/trunk@3289 212acab6-be3b-0410-9dea-997c60f758d6

Examples/silent.nsi

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+# This example shows how to handle silent installers.
+# In short, you need IfSilent and the /SD switch for MessageBox to make your installer
+# really silent when the /S switch is used.
+
+Name "Silent"
+OutFile "silent.exe"
+
+# uncomment the following line to make the installer silent by default.
+; SilentInstall silent
+
+Function .onInit
+  # `/SD IDYES' tells MessageBox to automatically choose IDYES if the installer is silent
+  # in this case, the installer can only be silent if the user used the /S switch or if
+  # you've uncommented line number 5
+  MessageBox MB_YESNO|MB_ICONQUESTION "Would you like the installer to be silent from now on?" \
+    /SD IDYES IDNO no IDYES yes
+
+  # SetSilent can only be used in .onInit and doesn't work well along with `SetSilent silent'
+
+  yes:
+    SetSilent silent
+    Goto done
+  no:
+    SetSilent normal
+  done:
+FunctionEnd
+
+Section
+  IfSilent 0 +2
+    MessageBox MB_OK|MB_ICONINFORMATION 'This is a "silent" installer'
+
+  # there is no need to use IfSilent for this one because the /SD switch takes care of that
+  MessageBox MB_OK|MB_ICONINFORMATION "This is not a silent installer" /SD IDOK
+
+  # when `SetOverwrite on' (which is the default) is used, the installer will show a message
+  # if it can't open a file for writing. On silent installers, the ignore option will be
+  # automatically selected. if `AllowSkipFiles off' (default is on) was used, there is no
+  # ignore option and the cancel option will be automatically selected.
+
+  # on is default
+  ; AllowSkipFiles on
+
+  # lock file
+  FileOpen $0 $TEMP\silentOverwrite w
+  # try to extract - will fail
+  File /oname=$TEMP\silentOverwrite silent.nsi
+  # unlcok
+  FileClose $0
+
+  # this will always show on silent installers because ignore is the option automatically
+  # selected when a file can't be opened for writing on a silent installer
+  MessageBox MB_OK|MB_ICONINFORMATION "This message box always if the installer is silent"
+
+  AllowSkipFiles off
+
+  # lock file
+  FileOpen $0 $TEMP\silentOverwrite w
+  # try to extract - will fail
+  File /oname=$TEMP\silentOverwrite silent.nsi
+  # unlcok
+  FileClose $0
+SectionEnd