add pause and play buttons to gooey

src/gooey.cpp

@@ -45,14 +45,14 @@ void drawEllipseParameters(ellipse_parameters& ep);
 void drawGravitaationalBody(grav_body& body);
 void drawOrbitalElements(orbital_elements& el);
 void drawSatelliteWindow(satellite& sat);
-void drawSystemWindow(system_2body& sys);
+void drawSystemWindow(system_2body& sys, bool& running);
 
 const static int G_WIDTH = 300;
 const static ImVec2 V_SPACER(0, 10);
 const int H_FLAGS = ImGuiTreeNodeFlags_DefaultOpen;
 
 void
-gooDraw(SDL_Window* window, system_2body& sys)
+gooDraw(SDL_Window* window, system_2body& sys, bool& running)
 {
 	ImGui_ImplOpenGL3_NewFrame();
 	ImGui_ImplSDL2_NewFrame(window);
@@ -64,7 +64,7 @@ gooDraw(SDL_Window* window, system_2body& sys)
 	ImGui::SetNextWindowSize(ImVec2(G_WIDTH, y));
 	ImGui::Begin("Gooey");
 
-	drawSystemWindow(sys);
+	drawSystemWindow(sys, running);
 	drawSatelliteWindow(sys.sat);
 	drawGravitaationalBody(sys.body);
 	drawOrbitalElements(sys.elements);
@@ -124,19 +124,20 @@ drawSatelliteWindow(satellite& sat)
 		ImGui::Text("flight path angle:   %f", sat.gamma);
 		ImGui::Dummy(V_SPACER);
 	}
-
 }
 
-void drawSystemWindow(system_2body& sys)
+void drawSystemWindow(system_2body& sys, bool& running)
 {
 	if (ImGui::CollapsingHeader("2 Body System:", H_FLAGS)) {
+		if (ImGui::Button("||")) running = false;
+		ImGui::SameLine();
+		if (ImGui::Button("|>")) running = true;
+		ImGui::SameLine();
+		ImGui::Text("running: %s", (running > 0) ? "true" : "false");
+
 		ImGui::Text("time_step:");
 		ImGui::SameLine();
-		uint step = 1;
+		ImGui::InputDouble("##", &sys.time_step, 1);
-		ImGui::InputScalar("##other.time_step",
-			ImGuiDataType_U32,
-			&sys.time_step, &step
-		);
 		ImGui::Text("epsilon, spec. orb. energy: %f", sys.epsilon);
 		ImGui::Text("h, angular momentum:        %f", sys.h);
 		ImGui::Text("r_apoapsis:                 %f", sys.r_apoapsis);

src/gooey.h

@@ -16,5 +16,5 @@ bool
 gooProcessEvent(SDL_Event &e);
 
 void
-gooDraw(SDL_Window* window, system_2body& sys);
+gooDraw(SDL_Window* window, system_2body& sys, bool& running);
 

src/main.cpp

@@ -14,6 +14,7 @@
 
 
 const double SCALING = 0.001;
+static bool g_running = false;
 static system_2body g_sys = {0};
 static MemoryArena* g_arena = nullptr;
 
@@ -128,6 +129,7 @@ loadScene(RenderState* rs)
 	double mu = 398601.68;	// NOTE: gravitational parameter
 	double r = 6378;		// NOTE: body radius in km
 	g_sys = systemInit(gravBodyInit(mu, r), orbitInit(a, e));
+	g_running = true;
 
 	// TODO: streamline the boilerplate in init_X_Entity functions
 	g_arena = arenaInit(16);
@@ -201,11 +203,12 @@ preFrameCallback(RenderState* rs)
 void
 postFrameCallback(RenderState* rs)
 {
-	gooDraw(rs->handles.window, g_sys);
-	g_sys.ep = ellipseInitAE(g_sys.ep.a, g_sys.ep.e);
-	updateSatelliteModel(g_sys, g_sys.sat);
-
 	static Entity* satellite = nullptr;
+	gooDraw(rs->handles.window, g_sys, g_running);
+
+	if (g_running) {
+		updateSatelliteModel(g_sys, g_sys.sat);
+		g_sys.ep = ellipseInitAE(g_sys.ep.a, g_sys.ep.e);
 
 		if (satellite == nullptr) {
 			RenderGroup* rg = getRenderGroupByName(rs, "manual mesh group");
@@ -215,6 +218,7 @@ postFrameCallback(RenderState* rs)
 		assert(satellite);
 		updateSatelliteEntity(satellite, g_sys.sat);
 		//updateOrbit(g_sys, ellipse_entity);
+	}
 }
 
 int