Error if a window isn't open when love.system.set/getClipboardText are called (resolves issue #1290).

--HG--
branch : minor

src/modules/system/sdl/System.cpp

@@ -20,6 +20,7 @@
 
 // LOVE
 #include "System.h"
+#include "window/Window.h"
 
 // SDL
 #include <SDL_clipboard.h>
@@ -46,13 +47,27 @@ int System::getProcessorCount() const
 	return SDL_GetCPUCount();
 }
 
+bool System::isWindowOpen() const
+{
+	auto window = Module::getInstance<window::Window>(M_WINDOW);
+	return window != nullptr && window->isOpen();
+}
+
 void System::setClipboardText(const std::string &text) const
 {
+	// SDL requires the video subsystem to be initialized and a window to be
+	// opened in order for clipboard text to work, on at least some platforms.
+	if (!isWindowOpen())
+		throw love::Exception("A window must be created in order for setClipboardText to function properly.");
+
 	SDL_SetClipboardText(text.c_str());
 }
 
 std::string System::getClipboardText() const
 {
+	if (!isWindowOpen())
+		throw love::Exception("A window must be created in order for getClipboardText to function properly.");
+
 	std::string text("");
 
 	char *ctext = SDL_GetClipboardText();

src/modules/system/sdl/System.h

@@ -54,6 +54,8 @@ public:
 
 private:
 
+	bool isWindowOpen() const;
+
 	static EnumMap<PowerState, SDL_PowerState, POWER_MAX_ENUM>::Entry powerEntries[];
 	static EnumMap<PowerState, SDL_PowerState, POWER_MAX_ENUM> powerStates;
 

src/modules/system/wrap_System.cpp

@@ -44,13 +44,15 @@ int w_getProcessorCount(lua_State *L)
 int w_setClipboardText(lua_State *L)
 {
 	const char *text = luaL_checkstring(L, 1);
-	instance()->setClipboardText(text);
+	luax_catchexcept(L, [&]() { instance()->setClipboardText(text); });
 	return 0;
 }
 
 int w_getClipboardText(lua_State *L)
 {
-	luax_pushstring(L, instance()->getClipboardText());
+	std::string text;
+	luax_catchexcept(L, [&]() { text = instance()->getClipboardText(); });
+	luax_pushstring(L, text);
 	return 1;
 }