Wire App into Main.cpp

App.c

@@ -15,6 +15,8 @@ App *app_NewApp() {
 	app->player  = player_NewSystem(app);
 	app->entity  = entity_NewSystem(app);
 
+	app->wantQuit = false;
+
 	return app;
 }
 

App.h

@@ -6,12 +6,18 @@
 #include "Input.h"
 #include "Types.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 
 typedef struct _App {
 	System_Physics *physics;
 	System_Player  *player;
 	System_Input   *input;
 	System_Entity  *entity;
+
+	bool wantQuit;
 } App;
 
 App *app_NewApp();
@@ -19,3 +25,8 @@ void app_DeleteApp(App *app);
 
 void app_Advance(App *app, Duration deltaTime);
 void app_Render();
+
+
+#ifdef __cplusplus
+}
+#endif

App_Render.cpp

@@ -3,5 +3,9 @@
 #include <graphics.h>
 
 
+extern "C" {
+
+
 void app_Render() {
 }
+}

Input.c

@@ -3,9 +3,21 @@
 #include "App.h"
 
 #include <stdlib.h>
+#include <stdio.h>
 #include <windows.h>
 
 
+const char *input_KeyNames[input_Key_Count] = {
+	"Left",
+	"Right",
+	"Up",
+	"Down",
+	"Jump",
+	"Attack",
+	"Spell",
+	"Use",
+	"Escape"};
+
 void input_SetDefaultKeymap(System_Input *sys) {
 	sys->systemKeymap[input_Key_Up]     = 'W';
 	sys->systemKeymap[input_Key_Left]   = 'A';
@@ -15,6 +27,7 @@ void input_SetDefaultKeymap(System_Input *sys) {
 	sys->systemKeymap[input_Key_Attack] = 'J';
 	sys->systemKeymap[input_Key_Spell]  = 'K';
 	sys->systemKeymap[input_Key_Use]    = 'L';
+	sys->systemKeymap[input_Key_Escape] = VK_ESCAPE;
 }
 
 System_Input *input_NewSystem(App *super) {
@@ -36,9 +49,10 @@ void input_Advance(System_Input *sys) {
 		// Checks the most significiant bit (of the SHORT returned)
 		if ((GetAsyncKeyState(sys->systemKeymap[i]) & 0x8000) != 0) {
 			// Pressed
-			if (sys->keys[i] == JustReleased || sys->keys[i] == Released)
+			if (sys->keys[i] == JustReleased || sys->keys[i] == Released) {
+				fprintf(stderr, "[input_Advance] Key %s pressed\n", input_KeyNames[i]);
 				sys->keys[i] = JustPressed;
-			else
+			} else
 				sys->keys[i] = Pressed;
 		} else {
 			// Released
@@ -48,4 +62,9 @@ void input_Advance(System_Input *sys) {
 				sys->keys[i] = Released;
 		}
 	}
+
+	if (sys->keys[input_Key_Escape] == JustPressed) {
+		fprintf(stderr, "[input_Advance] Let's quit now!\n");
+		sys->super->wantQuit = true;
+	}
 }

Input.h

@@ -19,19 +19,12 @@ typedef enum {
 	input_Key_Attack,
 	input_Key_Spell,
 	input_Key_Use,
+	input_Key_Escape,
 	input_Key_Count
 } input_Key;
 
 // Names for input_Key
-const char *input_KeyNames[input_Key_Count] = {
+extern const char *input_KeyNames[input_Key_Count];
-	"Left",
-	"Right",
-	"Up",
-	"Down",
-	"Jump",
-	"Attack",
-	"Spell",
-	"Use"};
 
 
 // States a key might in

Main.cpp

@@ -1,17 +1,37 @@
+#include <cwchar>
 #include <graphics.h>
 #include <stdio.h>
 
+#include "App.h"
 #include "Types.h"
 
 
 int main() {
 	TimePoint startup = time_Now();
+	TimePoint lastFrame, lastUpdate, frameCounter;
+	lastFrame = lastUpdate = frameCounter = time_Now();
+	int frameCount                        = 0;
+
+	initgraph(1280, 720);
+
+	App *app = app_NewApp();
+	while (!app->wantQuit) {
+		if (time_Since(frameCounter).microseconds >= 1000000) { // 1 sec
+			Duration d = time_Reset(&frameCounter);
+			fprintf(stderr, "[Main] %d frames in the last %.4lf seconds\n", frameCount, duration_Seconds(d));
+			frameCount = 0;
+		}
+		frameCount++;
+
+		app_Advance(app, time_Reset(&lastUpdate));
+
+		app_Render();
+
+		Duration toSleep = {.microseconds = 1000000 / 30 - time_Reset(&lastFrame).microseconds};
+		duration_Sleep(toSleep);
+	}
 
-	initgraph(640, 480);
-	circle(200, 200, 100);
-	Sleep(5000);
 	closegraph();
-
 	printf("%.6lf seconds has elapsed\n", duration_Seconds(time_Since(startup)));
 	return 0;
 }

Types.c

@@ -1,6 +1,8 @@
 
 #include "Types.h"
+#include <math.h>
 #include <windows.h>
+#include <timeapi.h>
 
 static inline double dmin(double x, double y) {
 	return x < y ? x : y;
@@ -75,6 +77,19 @@ Box2 box2_OffsetY(Box2 box, double offsetY) {
 
 static double freqInverse = 0.0;
 
+
+void duration_Sleep(const Duration t) {
+	if (t.microseconds <= 0)
+		return;
+	// https://learn.microsoft.com/zh-cn/windows/win32/api/timeapi/nf-timeapi-timebeginperiod
+	// timeBeginPeriod() and friends
+	TIMECAPS tc;
+	timeGetDevCaps(&tc, sizeof(TIMECAPS));
+	timeBeginPeriod(tc.wPeriodMin);
+	Sleep((DWORD)(round(duration_Milliseconds(t)))); // Only millisecond precision. Sad
+	timeEndPeriod(tc.wPeriodMin);
+}
+
 TimePoint time_Now() {
 	// Reference: https://github.com/SFML/SFML/blob/2.6.x/src/SFML/System/Win32/ClockImpl.cpp
 
@@ -98,3 +113,9 @@ Duration time_Difference(TimePoint now, TimePoint prev) {
 	Duration d = {.microseconds = now.microseconds - prev.microseconds};
 	return d;
 }
+Duration time_Reset(TimePoint *prev) {
+	TimePoint now = time_Now();
+	Duration  d   = time_Difference(now, *prev);
+	*prev         = now;
+	return d;
+}

Types.h

@@ -43,10 +43,12 @@ typedef struct {
 	int64_t microseconds;
 } Duration;
 
-static inline double duration_Seconds(const Duration t) { return ((double)t.microseconds) / 1000.0 / 1000.0; }
+static inline double duration_Seconds(const Duration t) { return ((double)t.microseconds) / 1000000.0; }
 static inline double duration_Milliseconds(const Duration t) { return ((double)t.microseconds) / 1000.0; }
+// This function has a precision of at most 1ms under Windows. Sad
+void duration_Sleep(const Duration t);
 
-// A Time point since the start of the program.
+// A Time point, counted since a fixed point in the past.
 typedef struct {
 	int64_t microseconds;
 } TimePoint;
@@ -54,6 +56,7 @@ typedef struct {
 TimePoint time_Now();
 Duration  time_Since(TimePoint prev);
 Duration  time_Difference(TimePoint now, TimePoint prev);
+Duration  time_Reset(TimePoint *prev);
 
 // 1e-6
 extern const double EPS;