From dceb24ad7c319ca5200dab92083f91b30af88a65 Mon Sep 17 00:00:00 2001
From: Vadim Zeitlin <vadim@wxwidgets.org>
Date: Tue, 12 Jan 2021 02:17:39 +0100
Subject: [PATCH] Add support for WXWEBREQUEST_BACKEND environment variable

Defining this variable overrides the default backend choice.

Document the variable itself and also extend wxWebSession::New()
documentation.
---
 docs/doxygen/overviews/envvars.h |  6 ++++++
 interface/wx/webrequest.h        | 17 +++++++++++++++--
 src/common/webrequest.cpp        | 15 +++++++++------
 3 files changed, 30 insertions(+), 8 deletions(-)

diff --git a/docs/doxygen/overviews/envvars.h b/docs/doxygen/overviews/envvars.h
index b3604df420..7a3426e5fc 100644
--- a/docs/doxygen/overviews/envvars.h
+++ b/docs/doxygen/overviews/envvars.h
@@ -26,5 +26,11 @@ wxWidgets programs.
         @c /usr/local or @c /usr). You can set WXPREFIX if you are for example
         distributing a binary version of an application and you don't know in advance
         where it will be installed.}
+@itemdef{WXWEBREQUEST_BACKEND,
+         This variable can be set to override the choice of the default backend
+         used by wxWebRequest, see wxWebSession::New(). Most common use is to
+         set it to @c "CURL" to force using libcurl-based implementation under
+         MSW or macOS platforms where the native implementation would be chosed
+         by default.}
 */
 
diff --git a/interface/wx/webrequest.h b/interface/wx/webrequest.h
index 25e1a3f0fa..7973e1f197 100644
--- a/interface/wx/webrequest.h
+++ b/interface/wx/webrequest.h
@@ -610,15 +610,28 @@ public:
     /**
         Creates a new wxWebSession object.
 
+        @a backend may be specified explicitly by using of the predefined @c
+        wxWebSessionBackendWinHTTP, @c wxWebSessionBackendURLSession or @c
+        wxWebSessionBackendCURL constants to select the corresponding backend
+        or left empty to select the default backend. The default depends on the
+        the current platform: WinHTTP-based implementation is used under MSW,
+        NSURLSession-based one under macOS and libcurl-based otherwise.
+
+        Further, if @c WXWEBREQUEST_BACKEND environment variable is defined, it
+        overrides the default backend selection, allowing to force the use of
+        libcurl-based implementation by default under MSW or macOS platforms,
+        for example.
+
         Use IsOpened() to check if the session creation succeeded.
 
         @param backend
-            The backend web session implementation to use.
+            The backend web session implementation to use or empty to use the
+            default implementation as described above.
 
         @return
             The created wxWebSession
     */
-    static wxWebSession New(const wxString& backend = wxWebSessionBackendDefault);
+    static wxWebSession New(const wxString& backend = wxString());
 
     /**
         Allows to check if the specified backend is available at runtime.
diff --git a/src/common/webrequest.cpp b/src/common/webrequest.cpp
index d5380b48be..5de8f13949 100644
--- a/src/common/webrequest.cpp
+++ b/src/common/webrequest.cpp
@@ -39,9 +39,9 @@
 #include "wx/private/webrequest_curl.h"
 #endif
 
-extern WXDLLIMPEXP_DATA_NET(const char) wxWebSessionBackendWinHTTP[] = "wxWebSessionBackendWinHTTP";
-extern WXDLLIMPEXP_DATA_NET(const char) wxWebSessionBackendURLSession[] = "wxWebSessionBackendURLSession";
-extern WXDLLIMPEXP_DATA_NET(const char) wxWebSessionBackendCURL[] = "wxWebSessionBackendCURL";
+extern WXDLLIMPEXP_DATA_NET(const char) wxWebSessionBackendWinHTTP[] = "WinHTTP";
+extern WXDLLIMPEXP_DATA_NET(const char) wxWebSessionBackendURLSession[] = "URLSession";
+extern WXDLLIMPEXP_DATA_NET(const char) wxWebSessionBackendCURL[] = "CURL";
 
 wxDEFINE_EVENT(wxEVT_WEBREQUEST_STATE, wxWebRequestEvent);
 wxDEFINE_EVENT(wxEVT_WEBREQUEST_DATA, wxWebRequestEvent);
@@ -824,13 +824,16 @@ wxWebSession wxWebSession::New(const wxString& backendOrig)
     wxString backend = backendOrig;
     if ( backend.empty() )
     {
+        if ( !wxGetEnv("WXWEBREQUEST_BACKEND", &backend) )
+        {
 #if wxUSE_WEBREQUEST_WINHTTP
-        backend = wxWebSessionBackendWinHTTP;
+            backend = wxWebSessionBackendWinHTTP;
 #elif wxUSE_WEBREQUEST_URLSESSION
-        backend = wxWebSessionBackendURLSession;
+            backend = wxWebSessionBackendURLSession;
 #elif wxUSE_WEBREQUEST_CURL
-        backend = wxWebSessionBackendCURL;
+            backend = wxWebSessionBackendCURL;
 #endif
+        }
     }
 
     wxStringWebSessionFactoryMap::iterator factory = gs_factoryMap.find(backend);