[wpigui] Add hooks for custom load/save settings

Add GetPlatformSaveFileDir().

wpigui/src/main/native/cpp/wpigui.cpp

@@ -146,7 +146,12 @@ bool gui::Initialize(const char* title, int width, int height) {
   iniHandler.WriteAllFn = IniWriteAll;
   ImGui::GetCurrentContext()->SettingsHandlers.push_back(iniHandler);
 
-  io.IniFilename = gContext->iniPath.c_str();
+  if (gContext->loadSettings) {
+    gContext->loadSettings();
+    io.IniFilename = nullptr;
+  } else {
+    io.IniFilename = gContext->iniPath.c_str();
+  }
 
   for (auto&& initialize : gContext->initializers) {
     if (initialize) {
@@ -155,7 +160,11 @@ bool gui::Initialize(const char* title, int width, int height) {
   }
 
   // Load INI file
-  ImGui::LoadIniSettingsFromDisk(io.IniFilename);
+  if (gContext->loadIniSettings) {
+    gContext->loadIniSettings();
+  } else if (io.IniFilename) {
+    ImGui::LoadIniSettingsFromDisk(io.IniFilename);
+  }
 
   // Set initial window settings
   glfwWindowHint(GLFW_MAXIMIZED, gContext->maximized ? GLFW_TRUE : GLFW_FALSE);
@@ -283,6 +292,20 @@ void gui::Main() {
     // Poll and handle events (inputs, window resize, etc.)
     glfwPollEvents();
     PlatformRenderFrame();
+
+    // custom saving
+    if (gContext->saveSettings) {
+      auto& io = ImGui::GetIO();
+      if (io.WantSaveIniSettings) {
+        gContext->saveSettings(false);
+        io.WantSaveIniSettings = false;  // reset flag
+      }
+    }
+  }
+
+  // Save (if custom save)
+  if (gContext->saveSettings) {
+    gContext->saveSettings(true);
   }
 
   // Cleanup
@@ -292,7 +315,7 @@ void gui::Main() {
   ImGui::DestroyContext();
 
   // Delete the save file if requested.
-  if (gContext->resetOnExit) {
+  if (!gContext->saveSettings && gContext->resetOnExit) {
     fs::remove(fs::path{gContext->iniPath});
   }
 
@@ -367,6 +390,14 @@ void gui::AddLateExecute(std::function<void()> execute) {
   }
 }
 
+void gui::ConfigureCustomSaveSettings(std::function<void()> load,
+                                      std::function<void()> loadIni,
+                                      std::function<void(bool)> save) {
+  gContext->loadSettings = load;
+  gContext->loadIniSettings = loadIni;
+  gContext->saveSettings = save;
+}
+
 GLFWwindow* gui::GetSystemWindow() {
   return gContext->window;
 }
@@ -416,27 +447,31 @@ void gui::SetClearColor(ImVec4 color) {
   gContext->clearColor = color;
 }
 
-void gui::ConfigurePlatformSaveFile(const std::string& name) {
-  gContext->iniPath = name;
+std::string gui::GetPlatformSaveFileDir() {
 #if defined(_MSC_VER)
   const char* env = std::getenv("APPDATA");
   if (env) {
-    gContext->iniPath = env + std::string("/" + name);
+    return env + std::string("/");
   }
 #elif defined(__APPLE__)
   const char* env = std::getenv("HOME");
   if (env) {
-    gContext->iniPath = env + std::string("/Library/Preferences/" + name);
+    return env + std::string("/Library/Preferences/");
   }
 #else
   const char* xdg = std::getenv("XDG_CONFIG_HOME");
   const char* env = std::getenv("HOME");
   if (xdg) {
-    gContext->iniPath = xdg + std::string("/" + name);
+    return xdg + std::string("/");
   } else if (env) {
-    gContext->iniPath = env + std::string("/.config/" + name);
+    return env + std::string("/.config/");
   }
 #endif
+  return "";
+}
+
+void gui::ConfigurePlatformSaveFile(const std::string& name) {
+  gContext->iniPath = GetPlatformSaveFileDir() + name;
 }
 
 void gui::EmitViewMenu() {
@@ -473,7 +508,9 @@ void gui::EmitViewMenu() {
       ImGui::EndMenu();
     }
 
-    ImGui::MenuItem("Reset UI on Exit?", nullptr, &gContext->resetOnExit);
+    if (!gContext->saveSettings) {
+      ImGui::MenuItem("Reset UI on Exit?", nullptr, &gContext->resetOnExit);
+    }
     ImGui::EndMenu();
   }
 }

wpigui/src/main/native/include/wpigui.h

@@ -79,6 +79,36 @@ void AddEarlyExecute(std::function<void()> execute);
  */
 void AddLateExecute(std::function<void()> execute);
 
+/**
+ * Customizes save/load behavior.
+ *
+ * By default, the integrated ImGui functions are used for this;
+ * ImGui::LoadIniSettingsFromDisk(io.IniFilename) is called at startup, and
+ * ImGui default automatic save file handling is used via io.IniFilename.
+ *
+ * Calling this function results in the load function being called at startup,
+ * io.IniFilename set to null (which disables ImGui's integrated file saving),
+ * and the save function being called when io.WantSaveIniSettings is true.
+ * The loadIni function should call ImGui::LoadIniSettingsFromMemory() to load
+ * ImGui save data, and the save function should call
+ * ImGui::SaveIniSettingsToMemory() to get ImGui save data.
+ *
+ * The load function is called PRIOR to AddInit() functions, and the loadIni
+ * function is called AFTER to AddInit() functions.  This allows initialize
+ * functions that use custom storage to handle the loaded values, and initialize
+ * functions that use INI storage to add hooks prior to the load INI occurring.
+ *
+ * This must be called prior to Initialize().
+ *
+ * @param load load function
+ * @param loadIni load INI function
+ * @param save save function; false is passed periodically, true is passed once
+ *             when the main loop is exiting
+ */
+void ConfigureCustomSaveSettings(std::function<void()> load,
+                                 std::function<void()> loadIni,
+                                 std::function<void(bool exiting)> save);
+
 /**
  * Gets GLFW window handle.
  */
@@ -137,6 +167,14 @@ void SetStyle(Style style);
  */
 void SetClearColor(ImVec4 color);
 
+/**
+ * Gets the (platform-specific) absolute directory for save files.
+ *
+ * @return Absolute path, including trailing "/". Empty string if directory
+ *         could not be determined.
+ */
+std::string GetPlatformSaveFileDir();
+
 /**
  * Configures a save file (.ini) in a platform specific location. On Windows,
  * the .ini is saved in %APPDATA%; on macOS the .ini is saved in

wpigui/src/main/native/include/wpigui_internal.h

@@ -40,6 +40,9 @@ struct Context : public SavedSettings {
 
   GLFWwindow* window = nullptr;
 
+  std::function<void()> loadSettings;
+  std::function<void()> loadIniSettings;
+  std::function<void(bool exiting)> saveSettings;
   std::vector<std::function<void()>> initializers;
   std::vector<std::function<void(float scale)>> windowScalers;
   std::vector<std::pair<