Allow expanding environment variables in XRC file paths

Add a new flag wxXRC_USE_ENVVARS for wxXmlResourceFlags that triggers a
call to wxExpandEnvVars() for bitmap, icon and animation paths.

This flag is not set by default to avoid silently changing the behaviour
of existing applications.

Closes https://github.com/wxWidgets/wxWidgets/pull/1445

docs/doxygen/overviews/xrc_format.h

@@ -352,6 +352,9 @@ wxFileSystem URL) of the bitmap to use. For example:
 The value is interpreted as path relative to the location of XRC file where the
 reference occurs.
 
+Bitmap file paths can include environment variables that are expanded if
+wxXRC_USE_ENVVARS was passed to the wxXmlResource constructor.
+
 Alternatively, it is possible to specify the bitmap using wxArtProvider IDs.
 In this case, the property element has no textual value (filename) and instead
 has the @c stock_id XML attribute that contains stock art ID as accepted by

include/wx/xrc/xmlres.h

@@ -76,7 +76,8 @@ enum wxXmlResourceFlags
 {
     wxXRC_USE_LOCALE     = 1,
     wxXRC_NO_SUBCLASSING = 2,
-    wxXRC_NO_RELOADING   = 4
+    wxXRC_NO_RELOADING   = 4,
+    wxXRC_USE_ENVVARS    = 8
 };
 
 // This class holds XML resources from one or more .xml files
@@ -95,6 +96,9 @@ public:
     //        wxXRC_NO_RELOADING
     //              don't check the modification time of the XRC files and
     //              reload them if they have changed on disk
+    //        wxXRC_USE_ENVVARS
+    //              expand environment variables for paths
+    //              (such as bitmaps or icons).
     wxXmlResource(int flags = wxXRC_USE_LOCALE,
                   const wxString& domain = wxEmptyString);
 
@@ -105,6 +109,12 @@ public:
     //        wxXRC_NO_SUBCLASSING
     //              subclass property of object nodes will be ignored
     //              (useful for previews in XRC editors)
+    //        wxXRC_NO_RELOADING
+    //              don't check the modification time of the XRC files and
+    //              reload them if they have changed on disk
+    //        wxXRC_USE_ENVVARS
+    //              expand environment variables for paths
+    //              (such as bitmaps or icons).
     wxXmlResource(const wxString& filemask, int flags = wxXRC_USE_LOCALE,
                   const wxString& domain = wxEmptyString);
 
@@ -279,7 +289,7 @@ public:
     // Sets the global resources object and returns a pointer to the previous one (may be NULL).
     static wxXmlResource *Set(wxXmlResource *res);
 
-    // Returns flags, which may be a bitlist of wxXRC_USE_LOCALE and wxXRC_NO_SUBCLASSING.
+    // Returns flags, which is a bitlist of wxXmlResourceFlags.
     int GetFlags() const { return m_flags; }
     // Set flags after construction.
     void SetFlags(int flags) { m_flags = flags; }
@@ -591,6 +601,10 @@ public:
     // Gets the value of a boolean attribute (only "0" and "1" are valid values)
     bool GetBoolAttr(const wxString& attr, bool defaultv) wxOVERRIDE;
 
+    // Gets a file path from the given node, expanding environment variables in
+    // it if wxXRC_USE_ENVVARS is in use.
+    wxString GetFilePath(const wxXmlNode* node);
+
     // Returns the window associated with the handler (may be NULL).
     wxWindow* GetParentAsWindow() const { return m_handler->GetParentAsWindow(); }
 

interface/wx/xrc/xmlres.h

@@ -18,7 +18,14 @@ enum wxXmlResourceFlags
 
     /** Prevent the XRC files from being reloaded from disk in case they have been modified there
         since being last loaded (may slightly speed up loading them). */
-    wxXRC_NO_RELOADING   = 4
+    wxXRC_NO_RELOADING   = 4,
+
+    /**
+        Expand environment variables for paths in XRC (such as bitmaps or icons).
+
+        @since 3.1.3
+    */
+    wxXRC_USE_ENVVARS    = 8
 };
 
 
@@ -737,6 +744,16 @@ protected:
     */
     wxString GetText(const wxString& param, bool translate = true);
 
+    /**
+        Gets a file path from the given node.
+
+        This function expands environment variables in the path if
+        wxXRC_USE_ENVVARS is used.
+
+        @since 3.1.3
+    */
+    wxString GetFilePath(const wxXmlNode* node);
+
     /**
         Check to see if a parameter exists.
     */

samples/xrc/xrcdemo.cpp

@@ -90,6 +90,10 @@ bool MyApp::OnInit()
     // wxXRC docs for details.
     wxXmlResource::Get()->InitAllHandlers();
 
+    // Allow using environment variables in the file paths in the resources,
+    // while keeping the default wxXRC_USE_LOCALE flag.
+    wxXmlResource::Get()->SetFlags(wxXRC_USE_LOCALE | wxXRC_USE_ENVVARS);
+
 #if wxUSE_RIBBON
     wxXmlResource::Get()->AddHandler(new wxRibbonXmlHandler);
 #endif

src/xrc/xmladv.cpp

@@ -42,7 +42,7 @@
 #if wxUSE_ANIMATIONCTRL
 wxAnimation* wxXmlResourceHandlerImpl::GetAnimation(const wxString& param)
 {
-    const wxString name = GetParamValue(param);
+    wxString name = GetFilePath(GetParamNode(param));
     if ( name.empty() )
         return NULL;
 

src/xrc/xmlres.cpp

@@ -44,6 +44,7 @@
 #include "wx/xml/xml.h"
 #include "wx/hashset.h"
 #include "wx/scopedptr.h"
+#include "wx/config.h"
 
 #include <limits.h>
 #include <locale.h>
@@ -1825,7 +1826,7 @@ wxBitmap wxXmlResourceHandlerImpl::GetBitmap(const wxXmlNode* node,
     }
 
     /* ...or load the bitmap from file: */
-    wxString name = GetParamValue(node);
+    wxString name = GetFilePath(node);
     if (name.empty()) return wxNullBitmap;
 #if wxUSE_FILESYSTEM
     wxFSFile *fsfile = GetCurFileSystem().OpenFile(name, wxFS_READ | wxFS_SEEKABLE);
@@ -1898,7 +1899,7 @@ wxIconBundle wxXmlResourceHandlerImpl::GetIconBundle(const wxString& param,
             return stockArt;
     }
 
-    const wxString name = GetParamValue(param);
+    const wxString name = GetFilePath(GetParamNode(param));
     if ( name.empty() )
         return wxNullIconBundle;
 
@@ -1982,6 +1983,16 @@ wxImageList *wxXmlResourceHandlerImpl::GetImageList(const wxString& param)
     return imagelist;
 }
 
+wxString wxXmlResourceHandlerImpl::GetFilePath(const wxXmlNode* node)
+{
+    wxString path = GetParamValue(node);
+
+    if ( m_handler->m_resource->GetFlags() & wxXRC_USE_ENVVARS )
+        path = wxExpandEnvVars(path);
+
+    return path;
+}
+
 wxXmlNode *wxXmlResourceHandlerImpl::GetParamNode(const wxString& param)
 {
     wxCHECK_MSG(m_handler->m_node, NULL, wxT("You can't access handler data before it was initialized!"));