Window - Modal dialogs

main.cc

@@ -261,6 +261,7 @@ void T_Main::render( )
 		glClear( GL_COLOR_BUFFER_BIT );
 	}
 
+	Globals::Window( ).handleDialogs( );
 	glUseProgram( 0 );
 	glBindProgramPipeline( 0 );
 	Globals::Textures( ).reset( );

window.cc

@@ -3,6 +3,84 @@
 #include "imgui_impl_sdl.h"
 #include <imgui_internal.h>
 
+
+/*= A_ModalDialog ============================================================*/
+
+A_ModalDialog::A_ModalDialog(
+		char const* const id ) noexcept
+	: id_{ id , uint32_t( strlen( id ) + 1 ) }
+{}
+
+A_ModalDialog::~A_ModalDialog( )
+{ }
+
+void A_ModalDialog::initDialog( ) noexcept
+{}
+
+void A_ModalDialog::onCancel( ) noexcept
+{ }
+
+bool A_ModalDialog::draw( ) noexcept
+{
+	using namespace ImGui;
+	if ( !open_ ) {
+		OpenPopup( id_.data( ) );
+		open_ = true;
+	}
+
+	initDialog( );
+	if ( initialSize_ ) {
+		SetNextWindowSize( *initialSize_ , ImGuiCond_Appearing );
+	}
+
+	bool ok{ false };
+	bool keep{ BeginPopupModal( id_.data( ) , nullptr , ImGuiWindowFlags_NoResize ) };
+	if ( keep ) {
+		const bool canUseOK{ drawDialog( ) };
+
+		const ImVec2 ws( GetWindowContentRegionMax( ) );
+		auto const& style( GetStyle( ) );
+		const float innerWidth{ ws.x - 2 * style.FramePadding.x };
+		constexpr float nButtons{ 2.f };
+		const ImVec2 buttonSize{ std::max( 40.f ,
+				( innerWidth - nButtons * style.FramePadding.x ) / nButtons ) ,
+		      0.f
+		};
+
+		if ( !canUseOK ) {
+			PushItemFlag( ImGuiItemFlags_Disabled , true );
+			PushStyleVar( ImGuiStyleVar_Alpha ,
+					GetStyle( ).Alpha * .5f );
+		}
+		if ( Button( "OK" , buttonSize ) ) {
+			ok = true;
+			keep = false;
+		}
+		if ( !canUseOK ) {
+			PopItemFlag( );
+			PopStyleVar( );
+		}
+		SameLine( 0 );
+		keep = !Button( "Cancel" , buttonSize ) && keep;
+
+		if ( !keep ) {
+			CloseCurrentPopup( );
+		}
+		EndPopup( );
+	}
+	if ( !keep ) {
+		if ( ok ) {
+			onOK( );
+		} else {
+			onCancel( );
+		}
+	}
+	return keep;
+}
+
+
+/*= T_Window =================================================================*/
+
 namespace {
 #include "font-awesome.inl"
 
@@ -11,8 +89,7 @@ static const ImWchar IconsRanges_[] = {
 	ICON_MAX_FA ,
 	0
 };
-}
-
+} // namespace <anon>
 
 T_Window::T_Window( )
 {
@@ -95,3 +172,15 @@ void T_Window::swap( ) const
 {
 	SDL_GL_SwapWindow( window );
 }
+
+void T_Window::handleDialogs( ) noexcept
+{
+	const auto nDialogs{ modals_.size( ) };
+	for ( auto i = 0u ; i < nDialogs ; i ++ ) {
+		const bool keep{ modals_[ i ]->draw( ) };
+		assert( keep || i + 1 == nDialogs );
+		if ( !keep ) {
+			modals_.removeLast( );
+		}
+	}
+}

window.hh

@@ -4,6 +4,47 @@
 #endif
 
 
+// Base class for a modal dialog that can be pushed to the window's modal
+// stack.
+class A_ModalDialog
+{
+    private:
+	const T_String id_;
+	bool open_{ false };
+	T_Optional< ImVec2 > initialSize_;
+
+    protected:
+	A_ModalDialog( char const* id ) noexcept;
+
+	void setInitialSize( const float width ,
+			const float height ) noexcept
+		{ initialSize_.setNew( width , height ); }
+
+	// Initialisation, called right before the window is opened.
+	// Does nothing by default.
+	virtual void initDialog( ) noexcept;
+
+	// Draw the dialog box's contents, returns true if the OK button
+	// should be enabled.
+	virtual bool drawDialog( ) noexcept = 0;
+
+	// Handlers for both OK and Cancel. The former must be overridden,
+	// the latter defaults to "do nothing".
+	virtual void onOK( ) noexcept = 0;
+	virtual void onCancel( ) noexcept;
+
+    public:
+	NO_COPY( A_ModalDialog );
+	NO_MOVE( A_ModalDialog );
+	virtual ~A_ModalDialog( );
+
+	// Draw and handle the dialog box. Returns true if it must be kept,
+	// or false if it must be removed from the stack.
+	bool draw( ) noexcept;
+};
+using P_ModalDialog = T_OwnPtr< A_ModalDialog >;
+
+
 struct T_Window
 {
 	T_Window( );
@@ -15,6 +56,10 @@ struct T_Window
 
 	void swap( ) const;
 
+	void pushDialog( P_ModalDialog dialog ) noexcept
+		{ modals_.add( std::move( dialog ) ); }
+	void handleDialogs( ) noexcept;
+
 	ImFont* defaultFont( ) const noexcept
 		{ return defaultFont_; }
 	ImFont* smallFont( ) const noexcept
@@ -25,5 +70,6 @@ struct T_Window
 	SDL_GLContext gl;
 	ImFont* defaultFont_;
 	ImFont* smallFont_;
+	T_AutoArray< P_ModalDialog , 8 > modals_;
 };