1 files changed, 55 insertions, 9 deletions
diff --git a/installer_scripts/template.iss b/installer_scripts/template.iss
index aab1e912..a2654c36 100755
--- a/installer_scripts/template.iss
+++ b/installer_scripts/template.iss
@@ -32,6 +32,7 @@ VersionInfoCompany={#URL}
 VersionInfoCopyright=Copyright (C) {#COPYRIGHT}
 VersionInfoDescription=An open-source machine embroidery design platform based on Inkscape.
 VersionInfoTextVersion={#VERSION}
+VersionInfoVersion=1.0
 WizardStyle=modern
 ShowLanguageDialog=no
 
@@ -68,17 +69,62 @@ Name: "English"; Description: "English";
 Source: "{#PATHTODIST}\inkstitch\*"; DestDir: "{app}\inkstitch\inkstitch"; Flags: ignoreversion recursesubdirs createallsubdirs
 ; NOTE: Don't use "Flags: ignoreversion" on any shared system files 
 [Code]
+// SOURCE: https://stackoverflow.com/questions/2000296/inno-setup-how-to-automatically-uninstall-previous-installed-version 
+{ ///////////////////////////////////////////////////////////////////// }
+function GetUninstallString(): String;
+var
+  sUnInstPath: String;
+  sUnInstallString: String;
+begin
+  sUnInstPath := ExpandConstant('Software\Microsoft\Windows\CurrentVersion\Uninstall\{#emit SetupSetting("AppId")}_is1');
+  sUnInstallString := '';
+  if not RegQueryStringValue(HKLM, sUnInstPath, 'UninstallString', sUnInstallString) then
+    RegQueryStringValue(HKCU, sUnInstPath, 'UninstallString', sUnInstallString);
+  Result := sUnInstallString;
+end;
+
+
+{ ///////////////////////////////////////////////////////////////////// }
+function IsUpgrade(): Boolean;
+begin
+  Result := (GetUninstallString() <> '');
+end;
+
 
-function InitializeSetup(): Boolean;
+{ ///////////////////////////////////////////////////////////////////// }
+function UnInstallOldVersion(): Integer;
+var
+  sUnInstallString: String;
+  iResultCode: Integer;
 begin
-  Result := True;
-  if RegKeyExists(HKEY_LOCAL_MACHINE,
-       'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{#AppId}_is1') or
-     RegKeyExists(HKEY_CURRENT_USER,
-       'SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{#AppId}_is1') then
+{ Return Values: }
+{ 1 - uninstall string is empty }
+{ 2 - error executing the UnInstallString }
+{ 3 - successfully executed the UnInstallString }
+
+  { default return value }
+  Result := 0;
+
+  { get the uninstall string of the old app }
+  sUnInstallString := GetUninstallString();
+  if sUnInstallString <> '' then begin
+    sUnInstallString := RemoveQuotes(sUnInstallString);
+    if Exec(sUnInstallString, '/SILENT /NORESTART /SUPPRESSMSGBOXES','', SW_HIDE, ewWaitUntilTerminated, iResultCode) then
+      Result := 3
+    else
+      Result := 2;
+  end else
+    Result := 1;
+end;
+
+{ ///////////////////////////////////////////////////////////////////// }
+procedure CurStepChanged(CurStep: TSetupStep);
+begin
+  if (CurStep=ssInstall) then
   begin
-    MsgBox('The application is installed already.', mbInformation, MB_OK);
-    Result := False;
+    if (IsUpgrade()) then
+    begin
+      UnInstallOldVersion();
+    end;
   end;
 end;
-