text: //*****************************************************************************
  //
  // hello_widget.c - Simple hello world example using Widgets
  //
  // Copyright (c) 2013-2015 Texas Instruments Incorporated.  All rights reserved.
  // Software License Agreement
  //
  // Texas Instruments (TI) is supplying this software for use solely and
  // exclusively on TI's microcontroller products. The software is owned by
  // TI and/or its suppliers, and is protected under applicable copyright
  // laws. You may not combine this software with "viral" open-source
  // software in order to form a larger program.
  //
  // THIS SOFTWARE IS PROVIDED "AS IS" AND WITH ALL FAULTS.
  // NO WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT
  // NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. TI SHALL NOT, UNDER ANY
  // CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL, OR CONSEQUENTIAL
  // DAMAGES, FOR ANY REASON WHATSOEVER.
  //
  // This is part of revision 2.1.2.111 of the DK-TM4C129X Firmware Package.
  //
  //*****************************************************************************
  
  #include <stdbool.h>
  #include <stdint.h>
  #include "driverlib/rom.h"
  #include "driverlib/rom_map.h"
  #include "driverlib/sysctl.h"
  #include "grlib/grlib.h"
  #include "grlib/widget.h"
  #include "grlib/canvas.h"
  #include "grlib/pushbutton.h"
  #include "drivers/frame.h"
  #include "drivers/kentec320x240x16_ssd2119.h"
  #include "drivers/pinout.h"
  #include "drivers/touch.h"
  
  //*****************************************************************************
  //
  //! \addtogroup example_list
  //! <h1>Hello using Widgets (hello_widget)</h1>
  //!
  //! A very simple ``hello world'' example written using the TivaWare Graphics
  //! Library widgets.  It displays a button which, when pressed, toggles
  //! display of the words ``Hello World!'' on the screen.  This may be used as
  //! a starting point for more complex widget-based applications.
  //
  //*****************************************************************************
  
  //*****************************************************************************
  //
  // Forward reference to various widget structures.
  //
  //*****************************************************************************
  extern tCanvasWidget g_sBackground;
  extern tPushButtonWidget g_sPushBtn;
  
  //*****************************************************************************
  //
  // Forward reference to the button press handler.
  //
  //*****************************************************************************
  void OnButtonPress(tWidget *psWidget);
  
  //*****************************************************************************
  //
  // The canvas widget acting as the background to the display.
  //
  //*****************************************************************************
  Canvas(g_sBackground, WIDGET_ROOT, 0, &g_sPushBtn,
         &g_sKentec320x240x16_SSD2119, 10, 25, 300, (240 - 25 -10),
         CANVAS_STYLE_FILL, ClrBlack, 0, 0, 0, 0, 0, 0);
  
  //*****************************************************************************
  //
  // The button used to hide or display the "Hello World" message.
  //
  //*****************************************************************************
  RectangularButton(g_sPushBtn, &g_sBackground, 0, 0,
                    &g_sKentec320x240x16_SSD2119, 60, 60, 200, 40,
                    (PB_STYLE_OUTLINE | PB_STYLE_TEXT_OPAQUE | PB_STYLE_TEXT |
                     PB_STYLE_FILL | PB_STYLE_RELEASE_NOTIFY),
                    ClrDarkBlue, ClrBlue, ClrWhite, ClrWhite,
                    g_psFontCmss22b, "Show Welcome", 0, 0, 0, 0, OnButtonPress);
  
  //*****************************************************************************
  //
  // The canvas widget used to display the "Hello!" string.  Note that this
  // is NOT hooked into the active widget tree (by making it a child of the
  // g_sPushBtn widget above) yet since we do not want the widget to be displayed
  // until the button is pressed.
  //
  //*****************************************************************************
  Canvas(g_sHello, &g_sPushBtn, 0, 0,
         &g_sKentec320x240x16_SSD2119, 10, 150, 300, 40,
         (CANVAS_STYLE_FILL | CANVAS_STYLE_TEXT),
         ClrBlack, 0, ClrWhite, g_psFontCm40, "Hello World!", 0, 0);
  
  //*****************************************************************************
  //
  // A global we use to keep track of whether or not the "Hello" widget is
  // currently visible.
  //
  //*****************************************************************************
  bool g_bHelloVisible = false;
  
  //*****************************************************************************
  //
  // The error routine that is called if the driver library encounters an error.
  //
  //*****************************************************************************
  #ifdef DEBUG
  void
  __error__(char *pcFilename, uint32_t ui32Line)
  {
  }
  #endif
  
  //*****************************************************************************
  //
  // This function is called by the graphics library widget manager in the
  // context of WidgetMessageQueueProcess whenever the user releases the
  // "Press Me!" button.  We use this notification to display or hide the
  // "Hello!" widget.
  //
  // This is actually a rather inefficient way to accomplish this but it's
  // a good example of how to add and remove widgets dynamically.  In
  // normal circumstances, you would likely leave the g_sHello widget
  // linked into the tree and merely add or remove the text by changing
  // its style then repainting.
  //
  // If using this dynamic add/remove strategy, another useful optimization
  // is to use a black canvas widget that covers the same area of the screen
  // as the widgets that you will be adding and removing.  If this is the used
  // as the point in the tree where the subtree is added or removed, you can
  // repaint just the desired area by repainting the black canvas rather than
  // repainting the whole tree.
  //
  //*****************************************************************************
  void
  OnButtonPress(tWidget *psWidget)
  {
      g_bHelloVisible = !g_bHelloVisible;
  
      if(g_bHelloVisible) {
          //
          // Add the Hello widget to the tree as a child of the push
          // button.  We could add it elsewhere but this seems as good a
          // place as any.  It also means we can repaint from g_sPushBtn and
          // this will paint both the button and the welcome message.
          //
          WidgetAdd((tWidget *)&g_sPushBtn, (tWidget *)&g_sHello);
  
          //
          // Change the button text to indicate the new function.
          //
          PushButtonTextSet(&g_sPushBtn, "Hide Welcome");
  
          //
          // Repaint the pushbutton and all widgets beneath it (in this case,
          // the welcome message).
          //
          WidgetPaint((tWidget *)&g_sPushBtn);
      } else {
          //
          // Remove the Hello widget from the tree.
          //
          WidgetRemove((tWidget *)&g_sHello);
  
          //
          // Change the button text to indicate the new function.
          //
          PushButtonTextSet(&g_sPushBtn, "Show Welcome");
  
          //
          // Repaint the widget tree to remove the Hello widget from the
          // display.  This is rather inefficient but saves having to use
          // additional widgets to overpaint the area of the Hello text (since
          // disabling a widget does not automatically erase whatever it
          // previously displayed on the screen).
          //
          WidgetPaint(WIDGET_ROOT);
      }
  }
  
  //*****************************************************************************
  //
  // Print "Hello World!" to the display on the Intelligent Display Module.
  //
  //*****************************************************************************
  int
  main(void)
  {
      tContext sContext;
      uint32_t ui32SysClock;
  
      //
      // Run from the PLL at 120 MHz.
      //
      ui32SysClock = MAP_SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
                                             SYSCTL_OSC_MAIN | SYSCTL_USE_PLL |
                                             SYSCTL_CFG_VCO_480), 120000000);
  
      //
      // Configure the device pins.
      //
      PinoutSet();
  
      //
      // Initialize the display driver.
      //
      Kentec320x240x16_SSD2119Init(ui32SysClock);
  
      //
      // Initialize the graphics context.
      //
      GrContextInit(&sContext, &g_sKentec320x240x16_SSD2119);
  
      //
      // Draw the application frame.
      //
      FrameDraw(&sContext, "hello-widget");
  
      //
      // Initialize the touch screen driver.
      //
      TouchScreenInit(ui32SysClock);
  
      //
      // Set the touch screen event handler.
      //
      TouchScreenCallbackSet(WidgetPointerMessage);
  
      //
      // Add the compile-time defined widgets to the widget tree.
      //
      WidgetAdd(WIDGET_ROOT, (tWidget *)&g_sBackground);
  
      //
      // Paint the widget tree to make sure they all appear on the display.
      //
      WidgetPaint(WIDGET_ROOT);
  
      //
      // Loop forever, processing widget messages.
      //
      while(1) {
          //
          // Process any messages from or for the widgets.
          //
          WidgetMessageQueueProcess();
      }
  }
  