ImGui widgets record their dimensions, invalidate lower uis

The invalidation logic is already there, we just have to set the
`dimensions` so that it knows what we drew over.

src/cata_imgui.cpp

@@ -198,6 +198,22 @@ void cataimgui::client::process_input( void *input )
 
 #endif
 
+void cataimgui::point_to_imvec2( point *src, ImVec2 *dest )
+{
+    if( src != nullptr && dest != nullptr ) {
+        dest->x = src->x;
+        dest->y = src->y;
+    }
+}
+
+void cataimgui::imvec2_to_point( ImVec2 *src, point *dest )
+{
+    if( src != nullptr && dest != nullptr ) {
+        dest->x = src->x;
+        dest->y = src->y;
+    }
+}
+
 void cataimgui::window::draw_colored_text( std::string const &text, const nc_color &color,
         float wrap_width, bool *is_selected, bool *is_focused, bool *is_hovered )
 {
@@ -303,6 +319,13 @@ class cataimgui::window_impl
             window_adaptor->is_imgui = true;
             window_adaptor->on_redraw( [this]( ui_adaptor & ) {
                 win_base->draw();
+                point catapos;
+                point catasize;
+                ImVec2 impos = ImGui::GetWindowPos();
+                ImVec2 imsize = ImGui::GetWindowSize();
+                imvec2_to_point( &impos, &catapos );
+                imvec2_to_point( &imsize, &catasize );
+                window_adaptor->position( catapos, catasize );
             } );
             window_adaptor->on_screen_resize( [this]( ui_adaptor & ) {
                 is_resized = true;

src/cata_imgui.h

@@ -13,6 +13,9 @@ struct SDL_Renderer;
 struct SDL_Window;
 #endif
 
+struct point;
+class ImVec2;
+
 namespace cataimgui
 {
 struct bounds {
@@ -55,6 +58,9 @@ class client
 #endif
 };
 
+void point_to_imvec2( point *src, ImVec2 *dest );
+void imvec2_to_point( ImVec2 *src, point *dest );
+
 class window
 {
         std::unique_ptr<class window_impl> p_impl;

src/third-party/imgui/imconfig.h

@@ -90,6 +90,7 @@
         constexpr ImVec4(const MyVec4& f) : x(f.x), y(f.y), z(f.z), w(f.w) {}   \
         operator MyVec4() const { return MyVec4(x,y,z,w); }
 */
+
 //---- ...Or use Dear ImGui's own very basic math operators.
 //#define IMGUI_DEFINE_MATH_OPERATORS