text: //
  // GUIslice Library Examples
  // - Calvin Hass
  // - https://www.impulseadventure.com/elec/guislice-gui.html
  // - https://github.com/ImpulseAdventure/GUIslice
  // - Example 05 (LINUX):
  //     Multiple page handling
  //     Background image
  //     Compound elements
  // - NOTE: The XSelNum compound element requires GSLC_FEATURE_COMPOUND enabled
  //
  
  #include "GUIslice.h"
  #include "GUIslice_ex.h"
  #include "GUIslice_drv.h"
  
  #include <libgen.h>       // For path parsing
  
  
  // Defines for resources
  #define MAX_PATH  255
  #define FONT_DROID_SANS "/usr/share/fonts/truetype/droid/DroidSans.ttf"
  #define IMG_BKGND       "/res/bkgnd1_320x240.bmp"
  char  m_strImgBkgnd[MAX_PATH];
  
  // Enumerations for pages, elements, fonts, images
  enum {E_PG_MAIN,E_PG_EXTRA};
  enum {E_ELEM_BTN_QUIT,E_ELEM_BTN_EXTRA,E_ELEM_BTN_BACK,
        E_ELEM_TXT_COUNT,E_ELEM_PROGRESS,
        E_ELEM_COMP1,E_ELEM_COMP2,E_ELEM_COMP3};
  enum {E_FONT_BTN,E_FONT_TXT,E_FONT_TITLE};
  
  bool      m_bQuit = false;
  
  // Free-running counter for display
  unsigned  m_nCount = 0;
  
  // Instantiate the GUI
  #define MAX_PAGE            2
  #define MAX_FONT            5
  #define MAX_ELEM_PG_MAIN    10  // Max # elements on main page
  #define MAX_ELEM_PG_EXTRA   10  // Max # elements on second page
  
  gslc_tsGui                  m_gui;
  gslc_tsDriver               m_drv;
  gslc_tsFont                 m_asFont[MAX_FONT];
  gslc_tsPage                 m_asPage[MAX_PAGE];
  gslc_tsElem                 m_asMainElem[MAX_ELEM_PG_MAIN];
  gslc_tsElemRef              m_asMainElemRef[MAX_ELEM_PG_MAIN];
  gslc_tsElem                 m_asExtraElem[MAX_ELEM_PG_EXTRA];
  gslc_tsElemRef              m_asExtraElemRef[MAX_ELEM_PG_EXTRA];
  
  gslc_tsXGauge               m_sXGauge;
  gslc_tsXSelNum              m_sXSelNum[3];
  
  
  #define MAX_STR             100
  
  // Configure environment variables suitable for display
  // - These may need modification to match your system
  //   environment and display type
  // - Defaults for GSLC_DEV_FB and GSLC_DEV_TOUCH are in GUIslice_config.h
  // - Note that the environment variable settings can
  //   also be set directly within the shell via export
  //   (or init script).
  //   - eg. export TSLIB_FBDEVICE=/dev/fb1
  void UserInitEnv()
  {
  #if defined(DRV_DISP_SDL1) || defined(DRV_DISP_SDL2)
    setenv((char*)"FRAMEBUFFER",GSLC_DEV_FB,1);
    setenv((char*)"SDL_FBDEV",GSLC_DEV_FB,1);
    setenv((char*)"SDL_VIDEODRIVER",GSLC_DEV_VID_DRV,1);
  #endif
  
  #if defined(DRV_TOUCH_TSLIB)
    setenv((char*)"TSLIB_FBDEVICE",GSLC_DEV_FB,1);
    setenv((char*)"TSLIB_TSDEVICE",GSLC_DEV_TOUCH,1);
    setenv((char*)"TSLIB_CALIBFILE",(char*)"/etc/pointercal",1);
    setenv((char*)"TSLIB_CONFFILE",(char*)"/etc/ts.conf",1);
    setenv((char*)"TSLIB_PLUGINDIR",(char*)"/usr/local/lib/ts",1);
  #endif
  }
  
  // Define debug message function
  static int16_t DebugOut(char ch) { fputc(ch,stderr); return 0; }
  
  // Button callbacks
  // - Show example of common callback function
  bool CbBtnCommon(void* pvGui,void *pvElemRef,gslc_teTouch eTouch,int16_t nX,int16_t nY)
  {
    gslc_tsGui*     pGui      = (gslc_tsGui*)(pvGui);
    gslc_tsElemRef* pElemRef  = (gslc_tsElemRef*)(pvElemRef);
    gslc_tsElem*    pElem     = gslc_GetElemFromRef(pGui,pElemRef);
    int16_t nElemId = pElem->nId;
    if (eTouch == GSLC_TOUCH_UP_IN) {
      if (nElemId == E_ELEM_BTN_QUIT) {
        m_bQuit = true;
      } else if (nElemId == E_ELEM_BTN_EXTRA) {
        gslc_SetPageCur(&m_gui,E_PG_EXTRA);
      } else if (nElemId == E_ELEM_BTN_BACK) {
        gslc_SetPageCur(&m_gui,E_PG_MAIN);
      }
    }
    return true;
  }
  
  
  // Create the default elements on each page
  // - strPath: Path to executable passed in to locate resource files
  bool InitOverlays(char *strPath)
  {
    gslc_tsElemRef*  pElemRef = NULL;
  
    gslc_PageAdd(&m_gui,E_PG_MAIN,m_asMainElem,MAX_ELEM_PG_MAIN,m_asMainElemRef,MAX_ELEM_PG_MAIN);
    gslc_PageAdd(&m_gui,E_PG_EXTRA,m_asExtraElem,MAX_ELEM_PG_EXTRA,m_asExtraElemRef,MAX_ELEM_PG_EXTRA);
  
    // -----------------------------------
    // Background
    strncpy(m_strImgBkgnd,strPath,MAX_PATH);
    strncat(m_strImgBkgnd,IMG_BKGND,MAX_PATH);
    gslc_SetBkgndImage(&m_gui,gslc_GetImageFromFile(m_strImgBkgnd,GSLC_IMGREF_FMT_BMP16));
  
    // -----------------------------------
    // PAGE: MAIN
  
    // Create background box
    pElemRef = gslc_ElemCreateBox(&m_gui,GSLC_ID_AUTO,E_PG_MAIN,(gslc_tsRect){20,50,280,150});
    gslc_ElemSetCol(&m_gui,pElemRef,GSLC_COL_WHITE,GSLC_COL_BLACK,GSLC_COL_BLACK);
  
    // Create title
    pElemRef = gslc_ElemCreateTxt(&m_gui,GSLC_ID_AUTO,E_PG_MAIN,(gslc_tsRect){10,10,310,40},
      "GUIslice Demo",0,E_FONT_TITLE);
    gslc_ElemSetTxtAlign(&m_gui,pElemRef,GSLC_ALIGN_MID_MID);
    gslc_ElemSetFillEn(&m_gui,pElemRef,false);
    gslc_ElemSetTxtCol(&m_gui,pElemRef,GSLC_COL_WHITE);
  
    // Create Quit button with text label
    pElemRef = gslc_ElemCreateBtnTxt(&m_gui,E_ELEM_BTN_QUIT,E_PG_MAIN,
      (gslc_tsRect){100,140,50,20},"Quit",0,E_FONT_BTN,&CbBtnCommon);
  
    // Create Extra button with text label
    pElemRef = gslc_ElemCreateBtnTxt(&m_gui,E_ELEM_BTN_EXTRA,E_PG_MAIN,
      (gslc_tsRect){170,140,50,20},"Extra",0,E_FONT_BTN,&CbBtnCommon);
  
    // Create counter
    pElemRef = gslc_ElemCreateTxt(&m_gui,GSLC_ID_AUTO,E_PG_MAIN,(gslc_tsRect){40,60,50,10},
      "Count:",0,E_FONT_TXT);
    pElemRef = gslc_ElemCreateTxt(&m_gui,E_ELEM_TXT_COUNT,E_PG_MAIN,(gslc_tsRect){100,60,50,10},
      "",0,E_FONT_TXT);
    gslc_ElemSetTxtCol(&m_gui,pElemRef,GSLC_COL_YELLOW);
  
    // Create progress bar
    pElemRef = gslc_ElemCreateTxt(&m_gui,GSLC_ID_AUTO,E_PG_MAIN,(gslc_tsRect){40,80,50,10},
      "Progress:",0,E_FONT_TXT);
    pElemRef = gslc_ElemXGaugeCreate(&m_gui,E_ELEM_PROGRESS,E_PG_MAIN,&m_sXGauge,(gslc_tsRect){100,80,50,10},
      0,100,0,GSLC_COL_GREEN,false);
  
    // Add compound element
    pElemRef = gslc_ElemXSelNumCreate(&m_gui,E_ELEM_COMP1,E_PG_MAIN,&m_sXSelNum[0],
      (gslc_tsRect){160,60,120,50},E_FONT_BTN);
  
    // -----------------------------------
    // PAGE: EXTRA
  
    // Create background box
    pElemRef = gslc_ElemCreateBox(&m_gui,GSLC_ID_AUTO,E_PG_EXTRA,(gslc_tsRect){40,40,240,160});
    gslc_ElemSetCol(&m_gui,pElemRef,GSLC_COL_WHITE,GSLC_COL_BLACK,GSLC_COL_BLACK);
  
    // Create Back button with text label
    pElemRef = gslc_ElemCreateBtnTxt(&m_gui,E_ELEM_BTN_BACK,E_PG_EXTRA,
      (gslc_tsRect){50,170,50,20},"Back",0,E_FONT_BTN,&CbBtnCommon);
  
    // Create a few labels
    int16_t    nPosY = 50;
    int16_t    nSpaceY = 20;
    pElemRef = gslc_ElemCreateTxt(&m_gui,GSLC_ID_AUTO,E_PG_EXTRA,(gslc_tsRect){60,nPosY,50,10},
      "Data 1",0,E_FONT_TXT); nPosY += nSpaceY;
    pElemRef = gslc_ElemCreateTxt(&m_gui,GSLC_ID_AUTO,E_PG_EXTRA,(gslc_tsRect){60,nPosY,50,10},
      "Data 2",0,E_FONT_TXT); nPosY += nSpaceY;
    pElemRef = gslc_ElemCreateTxt(&m_gui,GSLC_ID_AUTO,E_PG_EXTRA,(gslc_tsRect){60,nPosY,50,10},
      "Data 3",0,E_FONT_TXT); nPosY += nSpaceY;
  
    // Add compound element
    pElemRef = gslc_ElemXSelNumCreate(&m_gui,E_ELEM_COMP2,E_PG_EXTRA,&m_sXSelNum[1],
      (gslc_tsRect){130,60,120,50},E_FONT_BTN);
  
    pElemRef = gslc_ElemXSelNumCreate(&m_gui,E_ELEM_COMP3,E_PG_EXTRA,&m_sXSelNum[2],
      (gslc_tsRect){130,120,120,50},E_FONT_BTN);
  
    return true;
  }
  
  
  int main( int argc, char* args[] )
  {
    bool              bOk = true;
    char              acTxt[MAX_STR];
  
    // -----------------------------------
    // Initialize
    gslc_InitDebug(&DebugOut);
    UserInitEnv();
    if (!gslc_Init(&m_gui,&m_drv,m_asPage,MAX_PAGE,m_asFont,MAX_FONT)) { exit(1); }
  
    // Load Fonts
    // - In this example, we are loading the same font but at
    //   different point sizes. We could also refer to other
    //   font files as well.
    bOk = gslc_FontAdd(&m_gui,E_FONT_BTN,GSLC_FONTREF_FNAME,FONT_DROID_SANS,12);
    if (!bOk) { fprintf(stderr,"ERROR: FontAdd failed\n"); exit(1); }
    bOk = gslc_FontAdd(&m_gui,E_FONT_TXT,GSLC_FONTREF_FNAME,FONT_DROID_SANS,10);
    if (!bOk) { fprintf(stderr,"ERROR: FontAdd failed\n"); exit(1); }
    bOk = gslc_FontAdd(&m_gui,E_FONT_TITLE,GSLC_FONTREF_FNAME,FONT_DROID_SANS,32);
    if (!bOk) { fprintf(stderr,"ERROR: FontAdd failed\n"); exit(1); }
  
  
    // -----------------------------------
    // Create page elements
    // -----------------------------------
    InitOverlays(dirname(args[0])); // Pass executable path to find resource files
  
  
    // -----------------------------------
    // Start display
  
    // Start up display on main page
    gslc_SetPageCur(&m_gui,E_PG_MAIN);
  
    // Save some element references for quick access
    gslc_tsElemRef*  pElemCnt        = gslc_PageFindElemById(&m_gui,E_PG_MAIN,E_ELEM_TXT_COUNT);
    gslc_tsElemRef*  pElemProgress   = gslc_PageFindElemById(&m_gui,E_PG_MAIN,E_ELEM_PROGRESS);
  
    // -----------------------------------
    // Main event loop
  
    m_bQuit = false;
    while (!m_bQuit) {
  
      m_nCount++;
  
      // -----------------------------------
      // Perform drawing updates
      // - Note: we can make the updates conditional on the active
      //   page by checking gslc_GetPageCur() first.
  
      snprintf(acTxt,MAX_STR,"%u",m_nCount);
      gslc_ElemSetTxtStr(&m_gui,pElemCnt,acTxt);
  
      gslc_ElemXGaugeUpdate(&m_gui,pElemProgress,((m_nCount/200)%100));
  
  
      // Periodically call GUIslice update function
      gslc_Update(&m_gui);
  
    } // bQuit
  
  
    // -----------------------------------
    // Close down display
  
    gslc_Quit(&m_gui);
  
    return 0;
  }
  
  