BeginPopupModal() can have an optional close-window button (#249)

imgui.cpp

@@ -3234,7 +3234,7 @@ bool ImGui::BeginPopup(const char* str_id)
     return BeginPopupEx(str_id, ImGuiWindowFlags_ShowBorders);
 }
 
-bool ImGui::BeginPopupModal(const char* name, ImGuiWindowFlags extra_flags)
+bool ImGui::BeginPopupModal(const char* name, bool* p_opened, ImGuiWindowFlags extra_flags)
 {
     ImGuiState& g = *GImGui;
     ImGuiWindow* window = g.CurrentWindow;
@@ -3246,9 +3246,14 @@ bool ImGui::BeginPopupModal(const char* name, ImGuiWindowFlags extra_flags)
     }
 
     ImGuiWindowFlags flags = extra_flags|ImGuiWindowFlags_Popup|ImGuiWindowFlags_Modal|ImGuiWindowFlags_NoSavedSettings;
-    bool opened = ImGui::Begin(name, NULL, ImVec2(0.0f, 0.0f), -1.0f, flags);
-    if (!opened) // Opened can be 'false' when the popup is completely clipped (e.g. zero size display)
+    bool opened = ImGui::Begin(name, p_opened, ImVec2(0.0f, 0.0f), -1.0f, flags);
+    if (!opened || (p_opened && !*p_opened)) // Opened can be 'false' when the popup is completely clipped (e.g. zero size display)
+    {
         ImGui::EndPopup();
+        if (opened)
+            ClosePopup(id);
+        return false;
+    }
 
     return opened;
 }

imgui.h

@@ -171,8 +171,8 @@ namespace ImGui
     // Popup
     IMGUI_API void          OpenPopup(const char* str_id);                                      // mark popup as open. popup identifiers are relative to the current ID-stack (so OpenPopup and BeginPopup needs to be at the same level). close childs popups if any. will close popup when user click outside, or activate a pressable item, or CloseCurrentPopup() is called within a BeginPopup()/EndPopup() block.
     IMGUI_API bool          BeginPopup(const char* str_id);                                     // return true if popup if opened and start outputting to it. only call EndPopup() if BeginPopup() returned true!
-    IMGUI_API bool          BeginPopupModal(const char* name, ImGuiWindowFlags extra_flags = 0); 
-    IMGUI_API bool          BeginPopupContextItem(const char* str_id, int mouse_button = 1);    // helper to open and begin popup when clicked on last item
+    IMGUI_API bool          BeginPopupModal(const char* name, bool* p_opened = NULL, ImGuiWindowFlags extra_flags = 0);             // modal dialog (can't close them by clicking outside)
+    IMGUI_API bool          BeginPopupContextItem(const char* str_id, int mouse_button = 1);                                        // helper to open and begin popup when clicked on last item
     IMGUI_API bool          BeginPopupContextWindow(bool also_over_items = true, const char* str_id = NULL, int mouse_button = 1);  // helper to open and begin popup when clicked on current window
     IMGUI_API bool          BeginPopupContextVoid(const char* str_id = NULL, int mouse_button = 1);                                 // helper to open and begin popup when clicked in void (no window)
     IMGUI_API void          EndPopup();