Prevents Dear imgui reentry when a modal dialog is display on Windows

Author: andrewfb

include/cinder/app/msw/PlatformMsw.h

@@ -71,13 +71,19 @@ class CI_API PlatformMsw : public Platform {
 	//! Set the windows specific HWND, needed for some things like file dialogs.
 	void setHwnd( HWND hwnd )	{ mHwnd = hwnd; }
 
+	//! Returns whether the application is inside a modal dialog loop
+	bool		isInsideModalLoop() const { return mInsideModalLoop; }
+	//! Flags whether the application is currently inside the event loop of modal dialog
+	void		setInsideModalLoop( bool inside = true ) { mInsideModalLoop = inside; }
+
   private:
 	std::unique_ptr<std::ostream>	mOutputStream;
 	bool							mDirectConsoleToCout;
 
 	bool							mDisplaysInitialized;
 	std::vector<DisplayRef>			mDisplays;
 	HWND							mHwnd = nullptr;
+	bool							mInsideModalLoop = false;
 };
 
 //! MSW-specific Exception for failed resource loading, reports windows resource id and type

src/cinder/CinderImGui.cpp

@@ -10,6 +10,10 @@
 #include "cinder/gl/Context.h"
 #include "cinder/Clipboard.h"
 
+#if defined( CINDER_MSW )
+	#include "cinder/app/msw/PlatformMsw.h"
+#endif
+
 #include <unordered_map>
 
 static bool																   sInitialized = false;
@@ -653,6 +657,14 @@ static void ImGui_ImplCinder_NewFrameGuard( const ci::app::WindowRef& window )
 
 static void ImGui_ImplCinder_PostDraw()
 {
+#if defined( CINDER_MSW )
+	// Skip ImGui rendering when inside modal dialog loop, but reset trigger flag
+	if( static_cast<ci::app::PlatformMsw*>( ci::app::Platform::get() )->isInsideModalLoop() ) {
+		sTriggerNewFrame = true;
+		return;
+	}
+#endif
+
 	ImGui::Render();
 	ImDrawData* drawData = ImGui::GetDrawData();
 

src/cinder/app/msw/PlatformMsw.cpp

@@ -178,7 +178,11 @@ fs::path PlatformMsw::getOpenFilePath( const fs::path &initialPath, const std::v
 	ofn.Flags = OFN_PATHMUSTEXIST | OFN_FILEMUSTEXIST;
 
 	// Display the Open dialog box.
-	if( ::GetOpenFileNameW( &ofn ) == TRUE ) {
+	setInsideModalLoop( true );
+	BOOL result = ::GetOpenFileNameW( &ofn );
+	setInsideModalLoop( false );
+
+	if( result == TRUE ) {
 		return fs::path( ofn.lpstrFile );
 	}
 	else
@@ -214,7 +218,9 @@ fs::path PlatformMsw::getFolderPath( const fs::path &initialPath )
 	bi.lParam = reinterpret_cast<LPARAM>( initialPathWide.c_str() );
 	bi.lpfn = getFolderPathBrowseCallbackProc;
 	bi.lpszTitle = L"Pick a Directory";
+	setInsideModalLoop( true );
 	::LPITEMIDLIST pidl = ::SHBrowseForFolder( &bi );
+	setInsideModalLoop( false );
 	if( pidl ) {
 		// get the name of the folder
 		TCHAR path[MAX_PATH];
@@ -307,8 +313,12 @@ fs::path PlatformMsw::getSaveFilePath( const fs::path &initialPath, const std::v
 	}
 	ofn.Flags = OFN_SHOWHELP | OFN_OVERWRITEPROMPT;
 
-	// Display the Open dialog box.
-	if( ::GetSaveFileName( &ofn ) == TRUE )
+	// Display the Save dialog box.
+	setInsideModalLoop( true );
+	BOOL result = ::GetSaveFileName( &ofn );
+	setInsideModalLoop( false );
+
+	if( result == TRUE )
 		return fs::path( ofn.lpstrFile );
 	else
 		return fs::path();