add wesnoth.show_lua_console, as a debugging aide

This allows some sort of "drop into debug" mode for lua if your
script detects an error.

We could consider to actually add an "option to attach debugger"
as an error handling mechanism, but it might be complicated
because of wesnoth exceptions which must go through lua and be
treated as lua errors, and we cannot handle two exceptions at once
obviously, so the lua interpreter is probably not safe to run that
way in general. Anyways this commit does not do that.

src/scripting/lua_gui2.cpp

@@ -16,6 +16,7 @@
 
 #include "gui/auxiliary/canvas.hpp"     // for tcanvas
 #include "gui/auxiliary/window_builder.hpp"  // for twindow_builder, etc
+#include "gui/dialogs/lua_interpreter.hpp"
 #include "gui/widgets/clickable.hpp"    // for tclickable_
 #include "gui/widgets/control.hpp"      // for tcontrol
 #include "gui/widgets/multi_page.hpp"   // for tmulti_page
@@ -438,4 +439,10 @@ int intf_set_dialog_active(lua_State *L)
 	return 0;
 }
 
+int show_lua_console(lua_State * /*L*/, CVideo & video, lua_kernel_base * lk)
+{
+	gui2::tlua_interpreter::display(video, lk);
+	return 0;
+}
+
 } // end namespace lua_gui2

src/scripting/lua_gui2.hpp

@@ -17,6 +17,7 @@
 
 struct lua_State;
 class CVideo;
+class lua_kernel_base;
 
 namespace lua_gui2 {
 
@@ -27,6 +28,7 @@ int intf_set_dialog_markup(lua_State *L);
 int intf_set_dialog_canvas(lua_State *L);
 int intf_set_dialog_active(lua_State *L);
 int show_dialog(lua_State *L, CVideo & video);
+int show_lua_console(lua_State*L, CVideo & video, lua_kernel_base * lk);
 
 } // end namespace lua_gui2
 

src/scripting/lua_kernel_base.cpp

@@ -110,6 +110,24 @@ int lua_kernel_base::intf_show_dialog(lua_State *L)
 	return lua_gui2::show_dialog(L, *video_);
 }
 
+// The show lua console callback is similarly a method of lua kernel
+int lua_kernel_base::intf_show_lua_console(lua_State *L)
+{
+	if (!video_) {
+		ERR_LUA << "Cannot show dialog, no video object is available to this lua kernel.";
+		lua_error(L);
+		return 0;
+	}
+
+	if (cmd_log_.external_log_ != NULL) {
+		std::string message = "There is already an external logger attached to this lua kernel, you cannot open the lua console right now.";
+		log_error(message.c_str());
+		cmd_log_ << message << "\n";
+		return 0;
+	}
+
+	return lua_gui2::show_lua_console(L, *video_, this);
+}
 
 // End Callback implementations
 
@@ -238,6 +256,7 @@ lua_kernel_base::lua_kernel_base(CVideo * video)
 		{ "dofile", 		boost::bind(&lua_kernel_base::intf_dofile, this, _1)},
 		{ "require", 		boost::bind(&lua_kernel_base::intf_require, this, _1)},
 		{ "show_dialog",	boost::bind(&lua_kernel_base::intf_show_dialog, this, _1)},
+		{ "show_lua_console",	boost::bind(&lua_kernel_base::intf_show_lua_console, this, _1)},
 		{ NULL, NULL }
 	};
 

src/scripting/lua_kernel_base.hpp

@@ -89,6 +89,9 @@ protected:
 	// Show a dialog to the currently connected video object (if available)
 	int intf_show_dialog(lua_State * L);
 
+	// Show the interactive lua console (for debugging purposes)
+	int intf_show_lua_console(lua_State * L);
+
 	// Execute a protected call. Error handler is called in case of an error, using syntax for log_error and throw_exception above. Returns true if successful.
 	bool protected_call(int nArgs, int nRets, error_handler);
 	// Load a string onto the stack as a function. Returns true if successful, error handler is called if not.