added Timer feature

README.md

@@ -191,6 +191,16 @@ Useful text manipulation:
 
 Changing the font style assumes a tile width of 32 and the same symbol indexes! It also resets the font color and map so call this before doing anything else. 
 
+#### Utilities
+
+There's a game `Timer` class available using `engine->getTimer()`. It counts miliseconds, seconds, minutes and hours. 
+Do not forget this is an estimate as modulo and divide operations are expensive. 
+
+Each VBlank occurs every 280806 cycles (`CYCLES_PER_BLANK`), each cycle is 59.59ns
+So, each VBlank occurs every 16.73322954 miliseconds or 16733.22954 microseconds.
+The microseconds after the comma are rounded so irregularities are bound to occur after hours of timing..
+
+
 #### Error logging
 
 The text stream is also used if something goes wrong, there's a macro `failure_gba(WHOOPS)` that prints file, line, method and "exception" message to the text stream background. 

demos/demo1-basicfeatures/src/sample_start_scene.cpp

@@ -43,10 +43,19 @@ void SampleStartScene::load() {
             .buildPtr();
 
     TextStream::instance().setText("PRESS START", 3, 8);
+
+    engine->getTimer()->start();
     engine->enqueueMusic(zelda_music_16K_mono, zelda_music_16K_mono_bytes);
 }
 
 void SampleStartScene::tick(u16 keys) {
+    TextStream::instance().setText(engine->getTimer()->to_string(), 18, 1);
+
+    if(pressingAorB && !((keys & KEY_A) || (keys & KEY_B))) {
+        engine->getTimer()->toggle();
+        pressingAorB = false;
+    }
+
     if(keys & KEY_START) {
         if(!engine->isTransitioning()) {
             engine->enqueueSound(zelda_secret_16K_mono, zelda_secret_16K_mono_bytes);
@@ -63,5 +72,7 @@ void SampleStartScene::tick(u16 keys) {
         animation->flipVertically(true);
     } else if(keys & KEY_DOWN) {
         animation->flipVertically(false);
+    } else if((keys & KEY_A) || (keys & KEY_B)) {
+        pressingAorB = true;
     }
 }

demos/demo1-basicfeatures/src/sample_start_scene.h

@@ -12,6 +12,7 @@ private:
     std::unique_ptr<Sprite> animation;
     std::unique_ptr<Sprite> finalFantasyGuy;
     std::unique_ptr<Sprite> smiley;
+    bool pressingAorB = false;
 
 public:
     std::vector<Sprite *> sprites() override;

engine/CMakeLists.txt

@@ -18,7 +18,7 @@ add_library(${PROJECT_NAME}
         src/background/text_stream.cpp
         src/background/background.cpp
         src/effects/fade_out_scene.cpp
-        src/sound_control.cpp src/scene.cpp)
+        src/sound_control.cpp src/scene.cpp src/timer.cpp)
 
 target_include_directories(${PROJECT_NAME} PUBLIC
         $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>

engine/include/libgba-sprite-engine/gba_engine.h

@@ -12,6 +12,7 @@
 #include <libgba-sprite-engine/effects/scene_effect.h>
 #include "scene.h"
 #include "sound_control.h"
+#include "timer.h"
 
 #define GBA_SCREEN_WIDTH 240
 #define GBA_SCREEN_HEIGHT 160
@@ -26,6 +27,7 @@ private:
     bool disableTextBg;
     SpriteManager spriteManager;
 
+    static std::unique_ptr<Timer> timer;
     static std::unique_ptr<SoundControl> activeChannelA;
     static std::unique_ptr<SoundControl> activeChannelB;
 
@@ -40,6 +42,7 @@ private:
 public:
     GBAEngine();
 
+    Timer* getTimer();
     void setScene(Scene* scene);
     void dynamicallyAddSprite(Sprite* s) { spriteManager.add(s); }
     void transitionIntoScene(Scene* scene, SceneEffect* effect);

engine/include/libgba-sprite-engine/timer.h

@@ -0,0 +1,41 @@
+//
+// Created by Wouter Groeneveld on 06/12/18.
+//
+
+#ifndef GBA_SPRITE_ENGINE_PROJECT_TIMER_H
+#define GBA_SPRITE_ENGINE_PROJECT_TIMER_H
+
+#include <ostream>
+
+class Timer {
+private:
+    int microsecs, msecs, secs, minutes, hours;
+    bool active;
+
+public:
+
+    Timer() : active(false) {
+        reset();
+    }
+
+    void reset();
+    void start();
+    void toggle() {
+        if(isActive()) stop();
+        else start();
+    }
+    bool isActive() { return active; }
+    void stop();
+    void onvblank();
+
+    std::string to_string();
+
+    int getMsecs() { return msecs; }
+    int getSecs() { return secs; }
+    int getMinutes() { return minutes; }
+    int getHours() { return hours; }
+
+    friend std::ostream& operator<<(std::ostream& os, Timer& timer);
+};
+
+#endif //GBA_SPRITE_ENGINE_PROJECT_TIMER_H

engine/src/gba_engine.cpp

@@ -9,12 +9,17 @@
 
 std::unique_ptr<SoundControl> GBAEngine::activeChannelA;
 std::unique_ptr<SoundControl> GBAEngine::activeChannelB;
+std::unique_ptr<Timer> GBAEngine::timer;
 
 void GBAEngine::vsync() {
     while (REG_VCOUNT >= 160);
     while (REG_VCOUNT < 160);
 }
 
+Timer* GBAEngine::getTimer() {
+    return GBAEngine::timer.get();
+}
+
 void GBAEngine::onVBlank() {
     // WARNING this is a very dangerous piece of code.
     // GBA IRQs seem eager to crash or eat up CPU. Get in, disable stuff, work, enable, get out!
@@ -23,6 +28,8 @@ void GBAEngine::onVBlank() {
     unsigned short tempInterruptState = REG_IF;
 
     if((REG_IF & INTERRUPT_VBLANK) == INTERRUPT_VBLANK) {
+        GBAEngine::timer->onvblank();
+
         if(GBAEngine::activeChannelA) {
             if(GBAEngine::activeChannelA->done()) {
                 GBAEngine::activeChannelA->reset();
@@ -91,6 +98,7 @@ void GBAEngine::enqueueSound(const s8 *data, int totalSamples, int sampleRate, S
 }
 
 GBAEngine::GBAEngine() {
+    GBAEngine::timer = std::unique_ptr<Timer>(new Timer());
     // setup screen control flags
     REG_DISPCNT = DCNT_MODE0 | DCNT_OBJ | DCNT_OBJ_1D | DCNT_BG0 | DCNT_BG1 | DCNT_BG2 | DCNT_BG3;
 

engine/src/timer.cpp

@@ -0,0 +1,57 @@
+//
+// Created by Wouter Groeneveld on 06/12/18.
+//
+
+#include <libgba-sprite-engine/timer.h>
+#include <sstream>
+
+void Timer::onvblank() {
+    if(!active) return;
+
+    // each VBlank occurs every 280806 cycles (CYCLES_PER_BLANK), each cycle is 59.59ns
+    // So, each VBlank occurs every 16.73322954 miliseconds or 16733.22954 microseconds
+    // So, each second is 59,76132686219041 vblanks.
+    // to avoid any big rounding errors, divisions and modulos, estimate!
+    msecs += 16;
+    microsecs += 733;
+    if(microsecs >= 1000) {
+        msecs++;
+        microsecs -= 1000;
+    }
+
+    if(msecs >= 1000) {
+        secs++;
+        msecs -= 1000;
+    }
+    if(secs >= 60) {
+        minutes++;
+        secs -= 60;
+    }
+    if(minutes >= 60) {
+        hours++;
+        minutes -= 60;
+    }
+}
+
+std::string Timer::to_string() {
+    std::ostringstream stringStream;
+    stringStream << *this;
+    return stringStream.str();
+}
+
+std::ostream& operator<<(std::ostream &os, Timer &timer) {
+    os << timer.hours << "h:" << timer.minutes << "m:" << timer.secs << "s:" << timer.msecs;
+    return os;
+}
+
+void Timer::reset() {
+    microsecs = msecs = secs = minutes = hours = 0;
+}
+
+void Timer::start() {
+    active = true;
+}
+
+void Timer::stop() {
+    active = false;
+}

test/CMakeLists.txt

@@ -34,6 +34,7 @@ add_executable(unittest
         ../engine/src/sprites/sprite.cpp
         ../engine/src/allocator.cpp
         ../engine/src/palette/combined_palette.cpp
-        )
+        ../engine/src/timer.cpp
+        timertest.cpp)
 
 target_link_libraries(unittest ${GTEST_LIBRARY}/build/libgtest.a ${GTEST_LIBRARY}/build/libgtest_main.a)

test/timertest.cpp

@@ -0,0 +1,46 @@
+//
+// Created by Wouter Groeneveld on 06/12/18.
+//
+
+#include <gtest/gtest.h>
+#include <libgba-sprite-engine/timer.h>
+
+class TimerSuite : public ::testing::Test {
+protected:
+    Timer *t;
+
+    virtual void TearDown() {
+        delete t;
+    }
+
+    virtual void SetUp() {
+        t = new Timer();
+    }
+};
+
+
+TEST_F(TimerSuite, OnVBlankIncreasesMsecsAmountOfTimeIfStarted) {
+    t->start();
+    t->onvblank();
+    t->stop();
+    t->onvblank();
+
+    ASSERT_EQ(t->getMsecs(), 16);
+}
+
+TEST_F(TimerSuite, OnVBlankAfterEnoughTimesToGetToSec) {
+    t->start();
+
+    for(int i = 0; i < 100; i++) {
+        t->onvblank();
+    }
+
+    ASSERT_EQ(t->getSecs(), 1);
+    ASSERT_EQ(t->getMsecs(), 673);
+}
+
+TEST_F(TimerSuite, OnVBlankDoesNothingIfNotEnabled) {
+    t->onvblank();
+
+    ASSERT_EQ(t->getMsecs(), 0);
+}