Harden plugins against failure on XP, and...

... improve messaging for XP users on why some image formats aren't supported.

This commit also softens messaging in the Tools > 3rd-party libraries menu when users manually update local library copies.  This relates to #435 - thank you to @user-by for the suggestion!

Author: tannerhelland

Forms/Tools_PluginManager.frm

@@ -278,7 +278,7 @@ Attribute VB_Exposed = False
 'Last update: allow libraries to be missing but OK, like libavif (which is downloaded on-demand)
 '
 'I've considered merging this form with the main Tools > Options dialog, but that dialog
-' is already cluttered, and I really prefer that users don't mess around with 3rd-party libraries.
+' is already cluttered and I'd prefer that average users don't interact with this dialog at all.
 ' So this dialog exists as a standalone UI, and it should really be used only if there are problems.
 '
 'As of April '16, this dialog should never need to be updated against new libraries.  All library
@@ -578,15 +578,25 @@ Private Function CheckLibraryStateUI(ByVal pluginID As CORE_PLUGINS, Optional By
             'Version mismatch
             Else
                 dstStateString = g_Language.TranslateMessage("installed, but version is unexpected")
-                dstStateUIColor = m_Colors.RetrieveColor(PDPM_BadText)
-                CheckLibraryStateUI = False
+                dstStateUIColor = m_Colors.RetrieveColor(PDPM_GoodText)
+                CheckLibraryStateUI = True
             End If
 
         'Plugin is disabled
         Else
-            dstStateString = g_Language.TranslateMessage("installed, but disabled by user")
+            
+            'If this is as simple as an XP compatibility issue (more prevalent now that PD supports
+            ' a variety of modern image formats that can't be built in XP-compatible ways),
+            ' let the user know
+            If (Not OS.IsVistaOrLater) And PluginManager.IsPluginUnavailableOnXP(pluginID) Then
+                dstStateString = g_Language.TranslateMessage("incompatible with Windows XP")
+            Else
+                dstStateString = g_Language.TranslateMessage("installed, but disabled by user")
+            End If
+            
             dstStateUIColor = m_Colors.RetrieveColor(PDPM_BadText)
             CheckLibraryStateUI = False
+            
         End If
 
     'Plugin is not present on the machine.  For some libraries, this is problematic (e.g. critical libraries like lcms).
@@ -597,7 +607,7 @@ Private Function CheckLibraryStateUI(ByVal pluginID As CORE_PLUGINS, Optional By
         dstStateString = g_Language.TranslateMessage("not installed")
 
         'If this plugin doesn't ship with PD, leave it marked as OK
-        If IsPluginAvailableOnDemand(pluginID) Then
+        If PluginManager.IsPluginAvailableOnDemand(pluginID) Then
             dstStateUIColor = m_Colors.RetrieveColor(PDPM_GoodText)
             CheckLibraryStateUI = True
         Else
@@ -686,7 +696,7 @@ Private Sub LibraryChanged()
         Else
 
             'On-demand libraries are not a problem if they simply haven't been installed yet
-            If IsPluginAvailableOnDemand(pluginIndex) Then
+            If PluginManager.IsPluginAvailableOnDemand(pluginIndex) Then
                 lblPluginVersion.Caption = g_Language.TranslateMessage("not installed, but available on-demand")
                 lblPluginVersion.ForeColor = m_Colors.RetrieveColor(PDPM_GoodText)
             Else
@@ -702,7 +712,7 @@ Private Sub LibraryChanged()
         hypLicense.URL = PluginManager.GetPluginLicenseURL(pluginIndex)
 
         'Some plugins support optional explanation text.
-        If IsPluginAvailableOnDemand(pluginIndex) And (Not PluginManager.IsPluginCurrentlyInstalled(pluginIndex)) Then
+        If PluginManager.IsPluginAvailableOnDemand(pluginIndex) And (Not PluginManager.IsPluginCurrentlyInstalled(pluginIndex)) Then
 
             Dim actionTarget As String
             If (pluginIndex = CCP_AvifExport) Or (pluginIndex = CCP_AvifImport) Then
@@ -730,20 +740,3 @@ Private Sub LibraryChanged()
     End If
 
 End Sub
-
-'Some libraries are available on-demand (like libavif, which is enormous and most users won't need it).
-' It's OK if these libraries are missing on a default install - it just means the user hasn't triggered
-' any actions that prompt their download.
-Private Function IsPluginAvailableOnDemand(ByVal pluginID As CORE_PLUGINS) As Boolean
-
-    Select Case pluginID
-    
-        Case CCP_AvifExport, CCP_AvifImport
-            IsPluginAvailableOnDemand = True
-            
-        Case Else
-            IsPluginAvailableOnDemand = False
-    
-    End Select
-
-End Function

Modules/Plugin_8bf.bas

@@ -304,9 +304,11 @@ Public Function GetInitialEffectTimestamp() As Currency
 End Function
 
 Public Function GetPspiVersion() As String
-    Dim ptrVersion As Long
-    ptrVersion = pspiGetVersion()
-    If (ptrVersion <> 0) Then GetPspiVersion = Strings.StringFromCharPtr(ptrVersion, False, 3, True) & ".0"
+    If (m_LibHandle <> 0) And m_LibAvailable Then
+        Dim ptrVersion As Long
+        ptrVersion = pspiGetVersion()
+        If (ptrVersion <> 0) Then GetPspiVersion = Strings.StringFromCharPtr(ptrVersion, False, 3, True) & ".0"
+    End If
 End Function
 
 Public Function InitializeEngine(ByRef pathToDLLFolder As String) As Boolean

Modules/Plugin_AVIF.bas

@@ -251,6 +251,7 @@ End Function
 Public Function GetVersion(ByVal testExportLibrary As Boolean) As String
 
     GetVersion = vbNullString
+    If (Not OS.IsVistaOrLater) Then Exit Function
 
     Dim okToCheck As Boolean
     If testExportLibrary Then

Modules/Plugin_CharLS.bas

@@ -234,9 +234,11 @@ Public Sub ForciblySetAvailability(ByVal newState As Boolean)
 End Sub
 
 Public Function GetVersion() As String
-    Dim vMajor As Long, vMinor As Long, vPatch As Long
-    charls_get_version_number vMajor, vMinor, vPatch
-    GetVersion = vMajor & "." & vMinor & "." & vPatch
+    If (m_LibHandle <> 0) And m_LibAvailable Then
+        Dim vMajor As Long, vMinor As Long, vPatch As Long
+        charls_get_version_number vMajor, vMinor, vPatch
+        GetVersion = vMajor & "." & vMinor & "." & vPatch
+    End If
 End Function
 
 Public Function InitializeEngine(ByRef pathToDLLFolder As String) As Boolean

Modules/Plugin_ExifTool.bas

@@ -645,6 +645,8 @@ Public Function GetExifToolVersion() As String
             If (InStr(1, outputString, "[", vbBinaryCompare) <> 0) Then outputString = Left$(outputString, InStr(1, outputString, "[", vbBinaryCompare) - 1)
             GetExifToolVersion = Trim$(outputString)
 
+        Else
+            GetExifToolVersion = vbNullString
         End If
 
     End If
@@ -1429,18 +1431,20 @@ End Sub
 ' ALSO NOTE: This function is a heavily modified version of code originally written by Joacim Andersson. A download link to his
 ' original version is available at the top of this module.
 Public Function ShellExecuteCapture(ByVal sApplicationPath As String, sCommandLineParams As String, ByRef dstString As String, Optional bShowWindow As Boolean = False) As Boolean
-
+    
+    dstString = vbNullString
+    
     Dim hPipeRead As Long, hPipeWrite As Long
     Dim hCurProcess As Long
     Dim sa As SECURITY_ATTRIBUTES
-    Dim baOutput() As Byte
+    
     Dim sNewOutput As String
     Dim lBytesRead As Long
 
     'This pipe buffer size is effectively arbitrary, but I haven't had any problems with 1024
     Const BUFFER_SIZE As Long = 1024
-
-    dstString = vbNullString
+    
+    Dim baOutput() As Byte
     ReDim baOutput(0 To BUFFER_SIZE - 1) As Byte
 
     With sa
@@ -1453,7 +1457,7 @@ Public Function ShellExecuteCapture(ByVal sApplicationPath As String, sCommandLi
         PDDebug.LogAction "Failed to start plugin service (couldn't create pipe)."
         Exit Function
     End If
-
+    
     hCurProcess = GetCurrentProcess()
 
     'Replace the inheritable read handle with a non-inheritable one. (MSDN suggestion)
@@ -1495,7 +1499,7 @@ Public Function ShellExecuteCapture(ByVal sApplicationPath As String, sCommandLi
         Exit Function
     End If
 
-    CloseHandle hPipeRead
+    If (hPipeRead <> 0) Then CloseHandle hPipeRead
     If (hPipeWrite <> 0) Then CloseHandle hPipeWrite
     If (hCurProcess <> 0) Then CloseHandle hCurProcess
 

Modules/Plugin_Management.bas

@@ -3,17 +3,21 @@ Attribute VB_Name = "PluginManager"
 '3rd-Party Library Manager
 'Copyright 2014-2022 by Tanner Helland
 'Created: 30/August/15
-'Last updated: 28/February/22
-'Last update: add resvg
+'Last updated: 13/October/22
+'Last update: add a function for querying XP-compatibility; this will make it easier for the plugin manager UI
+'             to notify a user that non-functional plugins are simple XP-compatibility issues, not technical problems
 '
 'As with any project of reasonable size, PhotoDemon can't supply all of its needs through WAPI alone.
-' A number of third-party libraries are required for correct program operation.
+' Current builds require a number of third-party libraries for full feature availability.  (Some of these
+' libraries are mandatory, some are not; PD will attempt to gracefully degrade feature availability if it
+' can, but if you're acquiring PD from photodemon.org or it's official GitHub page you never need to
+' worry about this.)
 '
-'To simplify the management of these libraries, I've created this "plugin manager".  Its purpose is
+'To simplify the management of external libraries, I've created this small "plugin manager".  It exists
 ' to make third-party library deployment and maintainence easier in a "portable" application context.
 '
 'When adding a new required library, please make sure to read the module-level declarations,
-' particularly the CORE_PLUGINS enum and the CORE_PLUGIN_COUNT constant at the top of this page.
+' particularly the CORE_PLUGINS enum and the CORE_PLUGIN_COUNT constant at the top of this file.
 '
 'Unless otherwise noted, all source code in this file is shared under a simplified BSD license.
 ' Full license details are available in the LICENSE.md file, or at https://photodemon.org/license/
@@ -23,13 +27,13 @@ Attribute VB_Name = "PluginManager"
 Option Explicit
 
 'This constant is used to iterate all core plugins (as listed under the CORE_PLUGINS enum),
-' so if you add or remove a plugin, YOU MUST update this.  PD iterates plugins in order, so if
-' you do not update this, the plugin at the end of the chain (probably zstd) won't get
+' so if you add or remove a plugin, YOU MUST UPDATE THIS.  PhotoDemon iterates plugins in order,
+' so if you do not update this count, the plugin at the end of the chain (probably zstd) won't be
 ' initialized and PD will crash.
 Private Const CORE_PLUGIN_COUNT As Long = 14
 
 'Currently supported core plugins.  These values are arbitrary and can be changed without consequence, but THEY MUST
-' ALWAYS BE SEQUENTIAL, STARTING WITH ZERO, because the enum is iterated using For loops (e.g. during initialization).
+' ALWAYS BE SEQUENTIAL, STARTING WITH ZERO, because the enum is iterated using for..next loops (during initialization).
 Public Enum CORE_PLUGINS
     CCP_CharLS
     CCP_ExifTool
@@ -468,40 +472,63 @@ Public Function IsPluginCurrentlyInstalled(ByVal pluginEnumID As CORE_PLUGINS) A
     IsPluginCurrentlyInstalled = Files.FileExists(PluginManager.GetPluginPath & GetPluginFilename(pluginEnumID))
 End Function
 
-'PD loads plugins in two waves.  Before the splash screen appears, "high-priority" plugins are loaded.  These include the
-' decompression plugins required to decompress things like the splash screen image.  Much later in the load process,
-' we load the rest of the program's core plugins.  This function determines which wave a plugin is loaded during.
+'Some libraries are available on-demand (like libavif, which is enormous and most users won't need it).
+' It's OK if these libraries are missing on a default install - it just means the user hasn't triggered
+' any actions that prompt their download.
+Public Function IsPluginAvailableOnDemand(ByVal pluginID As CORE_PLUGINS) As Boolean
+    
+    IsPluginAvailableOnDemand = False
+    
+    Select Case pluginID
+        Case CCP_AvifExport, CCP_AvifImport
+            IsPluginAvailableOnDemand = True
+    End Select
+    
+End Function
+
+'PD loads plugins in two waves.  Before the splash screen appears, "high-priority" plugins are loaded.
+' These include compression plugins required to decompress things like the splash screen image.
+'
+'Much later in the load process, we load other third-party libraries (if necessary - some may yet be loaded
+' on-demand, as user operations require.
+'
+'This function determines if a plugin is forcibly loaded during that initial "high-priority" wave, or later.
 Public Function IsPluginHighPriority(ByVal pluginEnumID As CORE_PLUGINS) As Boolean
+    
+    IsPluginHighPriority = False
+    
     Select Case pluginEnumID
-        Case CCP_AvifExport
-            IsPluginHighPriority = False
-        Case CCP_AvifImport
-            IsPluginHighPriority = False
-        Case CCP_CharLS
-            IsPluginHighPriority = False
-        Case CCP_ExifTool
-            IsPluginHighPriority = False
-        Case CCP_EZTwain
-            IsPluginHighPriority = False
-        Case CCP_FreeImage
-            IsPluginHighPriority = False
         Case CCP_libdeflate
             IsPluginHighPriority = True
-        Case CCP_libjxl
-            IsPluginHighPriority = False
         Case CCP_LittleCMS
             IsPluginHighPriority = True
         Case CCP_lz4
             IsPluginHighPriority = True
-        Case CCP_pspiHost
-            IsPluginHighPriority = False
-        Case CCP_libwebp
-            IsPluginHighPriority = False
-        Case CCP_resvg
-            IsPluginHighPriority = False
         Case CCP_zstd
             IsPluginHighPriority = True
     End Select
+    
+End Function
+
+'As I've attempted to support more modern image formats (e.g. AVIF, HEIF, JPEG XL), I've also had to accept
+' that it's just not feasible to build some of the required 3rd-party libraries in XP-compatible ways.
+' This function can be used to query whether a plugin was disabled simply because it's not XP-compatible.
+' (Ignore the return of this function when running on Vista+, obviously.)
+Public Function IsPluginUnavailableOnXP(ByVal pluginEnumID As CORE_PLUGINS) As Boolean
+    
+    IsPluginUnavailableOnXP = False
+    
+    Select Case pluginEnumID
+        Case CCP_AvifExport
+            IsPluginUnavailableOnXP = True
+        Case CCP_AvifImport
+            IsPluginUnavailableOnXP = True
+        Case CCP_libjxl
+            IsPluginUnavailableOnXP = True
+        Case CCP_resvg
+            IsPluginUnavailableOnXP = True
+    End Select
+    
 End Function
 
 'Simplified function to return the expected version number of a plugin.  These numbers change with each PD release, and they can

Modules/Plugin_WebP.bas

@@ -57,7 +57,9 @@ Public Function GetHandle_LibWebPMux() As Long
 End Function
 
 Public Function GetVersion() As String
-    
+        
+    If (m_hLibWebP = 0) Or (Not m_LibAvailable) Then Exit Function
+        
     'Byte version numbers get packed into a long
     Dim versionAsInt(0 To 3) As Byte
 

Modules/Plugin_lz4.bas

@@ -125,9 +125,11 @@ Public Sub ReleaseLz4()
 End Sub
 
 Public Function GetLz4Version() As String
-    Dim ptrVersion As Long
-    ptrVersion = CallCDeclW(LZ4_versionNumber, vbLong)
-    GetLz4Version = ptrVersion
+    If (m_Lz4Handle <> 0) Then
+        Dim ptrVersion As Long
+        ptrVersion = CallCDeclW(LZ4_versionNumber, vbLong)
+        GetLz4Version = ptrVersion
+    End If
 End Function
 
 Public Function IsLz4Available() As Boolean

Modules/Plugin_zstd.bas

@@ -196,7 +196,7 @@ Public Sub ReleaseZstd()
 End Sub
 
 Public Function GetZstdVersion() As Long
-    GetZstdVersion = CallCDeclW(ZSTD_versionNumber, vbLong)
+    If (m_ZstdHandle <> 0) Then GetZstdVersion = CallCDeclW(ZSTD_versionNumber, vbLong)
 End Function
 
 Public Function IsZstdAvailable() As Boolean