Installation routine checks now if there exists a previous installation and asks whether it should uninstall it or not.

git-svn-id: svn://svn.code.sf.net/p/actiongame/code/trunk/ac@6693 e016b1c5-ed68-44aa-a2f7-31cac88cffde

source/vcpp/buildEnv/ac.nsi

@@ -358,6 +358,8 @@ FunctionEnd
 
 Function WelcomePage
 
+    Call CheckPrevInstallation
+
     nsDialogs::Create /NOUNLOAD 1044
     Pop $DIALOG
 
@@ -468,7 +470,7 @@ Function InstallationTypePage
     Pop $R1 ; minor version
  
     StrCmp $R0 "6" 0 winvercheckdone ; vista
-   
+    
         ; suggest multiuser option on vista and later
         !insertmacro MUI_INSTALLOPTIONS_WRITE "InstallTypes.ini" "Field 2" "State" "1"
         !insertmacro MUI_INSTALLOPTIONS_WRITE "InstallTypes.ini" "Field 1" "State" "0"
@@ -502,6 +504,18 @@ Function ConfigureWithoutAppdata
 
 FunctionEnd
 
+Function CheckPrevInstallation
+    
+    ReadRegStr $0 HKLM "Software\Microsoft\Windows\CurrentVersion\Uninstall\${AC_SHORTNAME}" "UninstallString"
+    StrCmp $0 "" isnotinstalled isinstalled
+    isinstalled:
+    MessageBox MB_YESNO "A previous installation was detected. Would you like to uninstall before installation?" IDNO uninstallno
+    ExecWait "$0"
+    uninstallno:
+    isnotinstalled:
+    
+FunctionEnd
+
 ; Installer Sections
 
 Section "AssaultCube ${AC_FULLVERSION}" AC