Method InvalidateImpl

examples/CustomWidget.cpp:59–146

InvalidateImpl is called by SFGUI whenever something happens that might make the widget look different. It returns an sfg::RenderQueue containing the graphical elements that will be rendered to display the widget on the screen.

		// sfg::RenderQueue containing the graphical elements that will
		// be rendered to display the widget on the screen.
		std::unique_ptr<sfg::RenderQueue> InvalidateImpl() const override {
			// In order to support engine themes, you should not hard-code
			// graphical parameters, but instead retrieve the properties you need
			// from the currently active engine. These properties determine
			// what your widget looks like and can be adjusted to affect a
			// large number of widgets at the same time.
			auto background_color = sfg::Context::Get().GetEngine().GetProperty<sf::Color>( "BackgroundColor", shared_from_this() );
			const auto& font_name = sfg::Context::Get().GetEngine().GetProperty<std::string>( "FontName", shared_from_this() );
			auto font_size = sfg::Context::Get().GetEngine().GetProperty<unsigned int>( "FontSize", shared_from_this() );

			// Fonts are stored in the engine resource manager. Once you have the name
			// of a font that has been loaded, you can get it from the resource manager.
			const auto& font = sfg::Context::Get().GetEngine().GetResourceManager().GetFont( font_name );

			std::unique_ptr<sfg::RenderQueue> queue( new sfg::RenderQueue );

			if( GetLabel().getSize() > 0 ) {
				auto metrics = sfg::Context::Get().GetEngine().GetTextStringMetrics( GetLabel(), *font, font_size );
				metrics.y = sfg::Context::Get().GetEngine().GetFontLineHeight( *font, font_size );

				// SFGUI widgets are made out of elementary pieces.
				// You have to request the renderer to give you each of
				// these pieces through one of the Create* methods.
				// You add these pieces to the RenderQueue that you return and it
				// will be rendered where the widget is displayed on the screen

				// Refer to the sfg::Renderer documentation for more information
				// on the Create* methods.

				auto inverted_color = sf::Color::White - background_color;
				inverted_color.a = 255;

				// Outer pane.
				queue->Add(
					sfg::Renderer::Get().CreatePane(
						sf::Vector2f( 0.f, 0.f ),
						GetAllocation().size,
						5.f,
						inverted_color,
						background_color,
						20.f
					)
				);

				auto inner_border_color = sf::Color::Green;

				// If the widget is active (currently pressed) change the inner border to red
				if( GetState() == State::ACTIVE ) {
					inner_border_color = sf::Color::Red;
				}

				// Inner pane.
				queue->Add(
					sfg::Renderer::Get().CreatePane(
						GetAllocation().size / 4.f,
						GetAllocation().size / 2.f,
						5.f,
						sf::Color(