set sentinel value used by TWBT

library/include/modules/Renderer.h

@@ -5,6 +5,13 @@
 #pragma once
 
 namespace DFHack { namespace Renderer {
+    // If the the 'x' parameter points to this value, then the 'y' parameter will
+    // be interpreted as a boolean flag for whether to return map coordinates (false)
+    // or text tile coordinates (true). Only TWBT implements this logic, and this
+    // sentinel value can be removed once DF provides an API for retrieving the
+    // two sets of coordinates.
+    DFHACK_EXPORT extern const int32_t GET_MOUSE_COORDS_SENTINEL;
+
     struct DFHACK_EXPORT renderer_wrap : public df::renderer {
         void set_to_null();
         void copy_from_parent();

library/modules/Renderer.cpp

@@ -9,6 +9,8 @@ using DFHack::Renderer::renderer_wrap;
 
 static renderer_wrap *original_renderer = NULL;
 
+const int32_t Renderer::GET_MOUSE_COORDS_SENTINEL = 0xcd1aa471;
+
 bool init()
 {
     if (!original_renderer)

plugins/overlay.cpp

@@ -1,5 +1,3 @@
-#include "df/renderer.h"
-
 #include "df/viewscreen_adopt_regionst.h"
 #include "df/viewscreen_adventure_logst.h"
 #include "df/viewscreen_announcelistst.h"
@@ -90,6 +88,8 @@
 #include "VTableInterpose.h"
 #include "uicommon.h"
 
+#include "modules/Renderer.h"
+
 using namespace DFHack;
 
 DFHACK_PLUGIN("overlay");
@@ -105,7 +105,7 @@ static const std::string button_text = "[ DFHack Launcher ]";
 static bool clicked = false;
 
 static bool handle_click() {
-    int32_t x = 0, y = 0;
+    int32_t x = Renderer::GET_MOUSE_COORDS_SENTINEL, y = (int32_t)true;
     if (!enabler->mouse_lbut_down || clicked ||
             !enabler->renderer->get_mouse_coords(&x, &y)) {
         DEBUG(log).print(