From 0e630bc4f16bc6019cdb0135cd82c8832502d8ef Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Sat, 18 Dec 2021 11:43:57 +0000
Subject: [PATCH] Fix pre-GTK3 build failures in puttyapp / ptermapp.

These alternate frontends using the GtkApplication class don't work
before GTK3, because the GtkApplication class didn't exist. In the old
mkfiles.pl system, the simplest way to prevent a build failure was to
just compile them anyway but make them reduce to a stub main(). But
now, with the new library-based code organisation, library search
order issues mean that these applications won't build at all.

Happily, with cmake, it's also easy to simply omit these binaries from
the build completely depending on our GTK version.
---
 cmake/gtk.cmake             |  3 +++
 unix/CMakeLists.txt         | 44 ++++++++++++++++++++-----------------
 unix/main-gtk-application.c | 19 ++--------------
 3 files changed, 29 insertions(+), 37 deletions(-)

diff --git a/cmake/gtk.cmake b/cmake/gtk.cmake
index 145f214b..85ecb7de 100644
--- a/cmake/gtk.cmake
+++ b/cmake/gtk.cmake
@@ -12,6 +12,9 @@ macro(try_pkg_config_gtk VER PACKAGENAME)
       (PUTTY_GTK_VERSION STREQUAL ANY OR PUTTY_GTK_VERSION STREQUAL ${VER}))
     find_package(PkgConfig)
     pkg_check_modules(GTK ${PACKAGENAME})
+    if(GTK_FOUND)
+      set(GTK_VERSION ${VER})
+    endif()
   endif()
 endmacro()
 try_pkg_config_gtk(3 gtk+-3.0)
diff --git a/unix/CMakeLists.txt b/unix/CMakeLists.txt
index 0490cf5c..9bdd2522 100644
--- a/unix/CMakeLists.txt
+++ b/unix/CMakeLists.txt
@@ -155,17 +155,19 @@ if(GTK_FOUND)
     ${GTK_LIBRARIES} ${X11_LIBRARIES})
   installed_program(pterm)
 
-  add_executable(ptermapp
-    pterm.c
-    main-gtk-application.c
-    ${CMAKE_SOURCE_DIR}/stubs/nocmdline.c
-    ${CMAKE_SOURCE_DIR}/stubs/nogss.c
-    ${CMAKE_SOURCE_DIR}/proxy/nosshproxy.c
-    pty.c)
-  be_list(ptermapp pterm)
-  target_link_libraries(ptermapp
-    guiterminal eventloop settings charset utils
-    ${GTK_LIBRARIES} ${X11_LIBRARIES})
+  if(GTK_VERSION GREATER_EQUAL 3)
+    add_executable(ptermapp
+      pterm.c
+      main-gtk-application.c
+      ${CMAKE_SOURCE_DIR}/stubs/nocmdline.c
+      ${CMAKE_SOURCE_DIR}/stubs/nogss.c
+      ${CMAKE_SOURCE_DIR}/proxy/nosshproxy.c
+      pty.c)
+    be_list(ptermapp pterm)
+    target_link_libraries(ptermapp
+      guiterminal eventloop settings charset utils
+      ${GTK_LIBRARIES} ${X11_LIBRARIES})
+  endif()
 
   add_executable(putty
     putty.c
@@ -179,15 +181,17 @@ if(GTK_FOUND)
     PROPERTIES LINK_INTERFACE_MULTIPLICITY 2)
   installed_program(putty)
 
-  add_executable(puttyapp
-    putty.c
-    main-gtk-application.c
-    ${CMAKE_SOURCE_DIR}/stubs/nocmdline.c)
-  be_list(puttyapp PuTTY SSH SERIAL OTHERBACKENDS)
-  target_link_libraries(puttyapp
-    guiterminal eventloop sshclient otherbackends settings
-    network crypto charset utils
-    ${GTK_LIBRARIES} ${X11_LIBRARIES})
+  if(GTK_VERSION GREATER_EQUAL 3)
+    add_executable(puttyapp
+      putty.c
+      main-gtk-application.c
+      ${CMAKE_SOURCE_DIR}/stubs/nocmdline.c)
+    be_list(puttyapp PuTTY SSH SERIAL OTHERBACKENDS)
+    target_link_libraries(puttyapp
+      guiterminal eventloop sshclient otherbackends settings
+      network crypto charset utils
+      ${GTK_LIBRARIES} ${X11_LIBRARIES})
+  endif()
 
   add_executable(puttytel
     putty.c
diff --git a/unix/main-gtk-application.c b/unix/main-gtk-application.c
index fb924009..b6c2807b 100644
--- a/unix/main-gtk-application.c
+++ b/unix/main-gtk-application.c
@@ -84,21 +84,8 @@ char *x_get_default(const char *key) { return NULL; }
 const bool buildinfo_gtk_relevant = true;
 
 #if !GTK_CHECK_VERSION(3,0,0)
-/* This front end only works in GTK 3. If that's not what we've got,
- * it's easier to just turn this program into a trivial stub by ifdef
- * in the source than it is to remove it in the makefile edifice. */
-int main(int argc, char **argv)
-{
-    fprintf(stderr, "GtkApplication frontend doesn't work pre-GTK3\n");
-    return 1;
-}
-GtkWidget *make_gtk_toplevel_window(GtkFrontend *frontend) { return NULL; }
-void launch_duplicate_session(Conf *conf) {}
-void launch_new_session(void) {}
-void launch_saved_session(const char *str) {}
-void session_window_closed(void) {}
-void window_setup_error(const char *errmsg) {}
-#else /* GTK_CHECK_VERSION(3,0,0) */
+#error This front end only works in GTK 3
+#endif
 
 static void startup(GApplication *app, gpointer user_data)
 {
@@ -336,5 +323,3 @@ int main(int argc, char **argv)
 
     return status;
 }
-
-#endif /* GTK_CHECK_VERSION(3,0,0) */