calling screen interactions via using function pointers

[MuratUnal]

Hello,

I am developing a software with STM32L4R9AI-Disco. I am trying to make

some menu screens. All screens have scroll wheels. the project has no touch. it

has physical buttons. I need screen transitions between all screen

combinations.

* I have interactions for screen transitions. When I call the interactions,

everything works well.

* I want to call the interactions via using function pointers. You can

see the source codes and explanations below.

* I need to know last selected items of scroll wheels for every closing

screen. Because when I return back the screen again, I need to setup scroll wheel

last position. I defined a struct type from my C code and a buffer to hold

variables from that struct types.

//my declarations from C code

typedef struct{
 
 void *intFuncPtr;               //function pointers for screen transition fuctions
 
 uint32_t parameter;          // scrollweels last positions
 
}screenTransitionType;
 
 
 
#define MAX_SCREEN_TRANSITION  20
 
screenTransitionType screenTransitionBuffer[MAX_SCREEN_TRANSITION];            //transition buffer
 
extern bool putScreenTransitionBuffer(screenTransitionType st);             //put new struct to      buffer
 
extern  bool pullScreenTransitionBuffer(screenTransitionType *st);          // pull last struct from buffer and destroy it //from buffer
 
extern bool checkLastScreenTransitionBuffer(screenTransitionType *st); // check and get last struct from buffer   //without destroy it from buffer

//one of my screen calls screen transition (it is inside the screen_modeMenuView.cpp)

void screen_modeMenuView::btn_enter_clicked()
 
{
 
 screenTransitionType st;                                                                                //define a screenTransitionType  variable 
 
 int itemIndex=scrollWheel_modeMenu.getSelectedItem();                      
 
 
 
 switch((modeMenuItem::modeMenuItemType)itemIndex){
 
   
 
   case modeMenuItem::MODE_MENU_ITEM_SETTINGS:
 
   void(FrontendApplicationBase::*ptr)()=         &FrontendApplicationBase::gotoscreen_modeMenuScreenCoverTransitionNorth;                //function pointer for 
 
	//return screen
 
     st.intFuncPtr = (void *&)(ptr);                                                                                  //save func pointer
 
     st.parameter=(uint32_t)modeMenuItem::MODE_MENU_ITEM_SETTINGS;        //save scrollwheel slected item
 
     if(putScreenTransitionBuffer(st)){                                                             //save them in buffer
 
       static_cast<FrontendApplication*>(Application::getInstance())
 
->gotoscreen_mainSettingsMenuScreenCoverTransitionSouth();             //change screen
 
     }
 
   break;
 
 }
 
 
 
}

//the other screen (screen_mainSettingsMenuView.cpp)

void screen_mainSettingsMenuView::btn_home_clicked()
 
{
 screenTransitionType st;
 
 void (FrontendApplicationBase::* ptr)(); //function pointer for screen transition function type
 if(checkLastScreenTransitionBuffer(&st)){       //get last screen parameters that already put on the buffer
 
ptr = (void (FrontendApplicationBase::* &)())(st.intFuncPtr); //get the transition function address from struct and store it to ptr
(static_cast<FrontendApplication*>(Application::getInstance())->*ptr)(); //call the transition function
 
 }

When i call the transition function via function pointer ptr and check it in debugger, my code goes to correct transition function:

void FrontendApplicationBase::gotoscreen_modeMenuScreenCoverTransitionNorth()
{
    transitionCallback = touchgfx::Callback<FrontendApplicationBase>(this, &FrontendApplication::gotoscreen_modeMenuScreenCoverTransitionNorthImpl);
    pendingScreenTransitionCallback = &transitionCallback;
}

but when my code run

transitionCallback = touchgfx::Callback<FrontendApplicationBase>(this, &FrontendApplication::gotoscreen_modeMenuScreenCoverTransitionNorthImpl);

this line in transition function, it goes to HardFauldHandler.

My question is how can i call transition function via function pointers? I guess my way is OK, and i can call transition function via pointer but i couldn’t understand why my code goes to HardFaultHandler.

if any idea, I will be happy.

Best Regards,

Murat

[Martin KJELDSEN]

Hi,

Check this example i prepared some time ago that pushes function pointers onto a stack, allowing a "go back to last view" functionality. Maybe this can give you some inspiration.

http://sw-center-st-com.s3-eu-west-1.amazonaws.com/touchgfx/TouchGFX/Community/gotoStack_example.zip

/Martin

[MuratUnal]

Hello Martin,

Thanks for your example. I regulated your code for my project and it is working very well.

I want to ask one more question.

I want to change screen transition speed but i couldn't find a way. Could you give me any advice, please?

[Martin KJELDSEN]

Great.

For transition speed check out touchgfx/transitions/SlideTransition.hpp, for instance (transitionSteps:(

   /**
     * @fn SlideTransition::SlideTransition(const uint8_t transitionSteps = 20) : Transition(), snapshot(), snapshotPtr(&snapshot), handleTickCallback(this, &SlideTransition::tickMoveDrawable), direction(templateDirection), animationSteps(transitionSteps), animationCounter(0), calculatedValue(0)
     *
     * @brief Constructor.
     *
     *        Constructor.
     *
     * @param transitionSteps Number of steps in the transition animation.
     */
    SlideTransition(const uint8_t transitionSteps = 20)
        : Transition(),
          snapshot(),
          snapshotPtr(&snapshot),
          handleTickCallback(this, &SlideTransition::tickMoveDrawable),
          direction(templateDirection),
          animationSteps(transitionSteps),
          animationCounter(0),
          calculatedValue(0)
    {
...

/Martin

[Martin KJELDSEN]

Additional info: What you can see from the code is that you're basically using "transitionSteps" to control how many steps you would like the animation to take - Based on that information, the transition class will calculate the "step" to take each tick in order to satisfy your requirement in terms of steps and easing equation.

    /**
     * @fn virtual void SlideTransition::handleTickEvent()
     *
     * @brief Handles the tick event when transitioning.
     *
     *        Handles the tick event when transitioning. It moves the contents of the Screen's
     *        container and a SnapshotWidget with a snapshot of the previous Screen. The
     *        direction of the transition determines the direction the contents of the
     *        container and the SnapshotWidget moves.
     */
    virtual void handleTickEvent()
    {
        ...
        Transition::handleTickEvent();
 
        // Calculate new position or stop animation
        animationCounter++;
        if (animationCounter <= animationSteps)
        {
            // Calculate value in [0;targetValue]
            calculatedValue = EasingEquations::cubicEaseOut(animationCounter, 0, targetValue, animationSteps);