Code to refresh desktop programmatically

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Introduction

Refresh desktop programmatically

Following code that uses only Win32 API and written in C++ will mimic F5 key action on desktop. This code already tested with BCC55, worked as intended. Please do some error checking yourself in 'F5Desk()' function.

#include <windows.h>

typedef char str64[64];
typedef char str256[256];
typedef char str1024[1024];

#define HKCU   HKEY_CURRENT_USER

BOOL SetString(HKEY hkeymom, str256 pkeyname, 
      str64 pvalname, str1024 pvaldata)
{  HKEY hkey = 0;
   if(RegCreateKeyEx(hkeymom, pkeyname, 0, 
      NULL, REG_OPTION_NON_VOLATILE, KEY_WRITE, NULL, 
      &hkey, NULL) != ERROR_SUCCESS)
      return FALSE;
   LONG rtn = RegSetValueEx(hkey, pvalname, 0, 
      REG_SZ, (BYTE*)pvaldata, lstrlen(pvaldata));
   RegCloseKey(hkey);
   if(rtn == ERROR_SUCCESS)    
      return TRUE;
   return FALSE;
}

BOOL ReadString(HKEY hkeymom, str256 pkeyname, 
      str64 pvalname, str1024 pvaldata)
{  HKEY hkey = 0;
   DWORD dw;
   if(RegOpenKeyEx(hkeymom, pkeyname, 0, KEY_READ, &hkey) != ERROR_SUCCESS)
   {  strcpy(pvaldata, "");
      return FALSE;
   }
   LONG rtn = RegQueryValueEx(hkey, pvalname, NULL, &dw, NULL, NULL);
   if((rtn != ERROR_SUCCESS) || (dw != REG_SZ))
   {  RegCloseKey(hkey);        
      strcpy(pvaldata, "");
      return FALSE;    
   }
   dw = 1024;
   RegQueryValueEx(hkey, pvalname, NULL, NULL, (BYTE*)pvaldata, &dw);
   RegCloseKey(hkey);
   return TRUE;
}

int myexp (int y)
{  int ii = 1;
   for (int cnt = 0; cnt < y; cnt++)
      ii *= 10;
   return ii;     
}

BOOL StringToInt(str1024 sz, int* ires)
{  //temp string
   str1024 szi = "";
   //copy character that represent number or negative sign only to temp string
   for(unsigned int cnt = 0; cnt < strlen(sz); cnt++)
   {  //if not 0 to 9 or negative sign then break
      if((sz[cnt] != 45) && (sz[cnt] != 48) && 
         (sz[cnt] != 49) & (sz[cnt] != 50) && 
         (sz[cnt] != 51) && (sz[cnt] != 52) && 
         (sz[cnt] != 53) && (sz[cnt] != 54) && 
         (sz[cnt] != 55) && (sz[cnt] != 56) && (sz[cnt] != 57))
         break;          
      //if negative sign but not in first letter then break
      if((sz[cnt] == 45) && (cnt != 0))
         break;
      //add to temp string
      switch(sz[cnt])
      {  case 45:    strcat(szi, "-");    break;
         case 48:    strcat(szi, "0");    break;
         case 49:    strcat(szi, "1");    break;
         case 50:    strcat(szi, "2");    break;
         case 51:    strcat(szi, "3");    break;
         case 52:    strcat(szi, "4");    break;
         case 53:    strcat(szi, "5");    break;
         case 54:    strcat(szi, "6");    break;
         case 55:    strcat(szi, "7");    break;
         case 56:    strcat(szi, "8");    break;
         case 57:    strcat(szi, "9");    break;
      }
   }
   //if length of temp string = 0 then return FALSE     
   if(!strlen(szi))    
   {  *ires = 0;    
      return FALSE;
   }
   //if length of temp string = 1 but only negative sign in it, return FALSE
   else if((strlen(szi) == 1) && !strcmp(szi, "-"))    
   {  *ires = 0;    
      return FALSE;
   }
   //flag for negative or positive number
   BOOL flag = FALSE;
   //if there is negative sign in temp string then flag = TRUE
   if(strchr(szi, '-'))    flag = TRUE;    
   int ii = 0;
   strrev(szi);
   //convert temp string to number 
   for(unsigned int cnt = 0; cnt < strlen(szi); cnt++)
   {   switch(szi[cnt])
       {   case 48:    ii += 0 * myexp(cnt);        break;    
           case 49:    ii += 1 * myexp(cnt);        break;    
           case 50:    ii += 2 * myexp(cnt);        break;    
           case 51:    ii += 3 * myexp(cnt);        break;    
           case 52:    ii += 4 * myexp(cnt);        break;    
           case 53:    ii += 5 * myexp(cnt);        break;    
           case 54:    ii += 6 * myexp(cnt);        break;    
           case 55:    ii += 7 * myexp(cnt);        break;    
           case 56:    ii += 8 * myexp(cnt);        break;    
           case 57:    ii += 9 * myexp(cnt);        break;    
       }
   }
   //if flag and number > 0 then negative the number
   if((ii > 0) && flag)    ii /= -1; 
   *ires = ii;
   return TRUE;
}

void F5Desk()
{  str1024 szres = "";
   //read current icon size, usually 32 (in Windows® XP)
   ReadString(HKCU, "Control Panel\\Desktop\\WindowMetrics", 
         "Shell Icon Size", szres);
   int ii = 0;
   //translate to number 
   StringToInt(szres, &ii);
   //increase it by 1
   ii++;
   //convert back to string
   wsprintf(szres, "%i", ii);
   //now, change the icon size 
   SetString(HKCU, "Control Panel\\Desktop\\WindowMetrics", 
      "Shell Icon Size", szres);
   //find taskbar and make it can't redraw
   HWND hwndtask = FindWindow("Shell_traywnd", "");
   SendMessage(hwndtask, WM_SETREDRAW, FALSE, 0);
   //broadcast the icon size change, so the desktop will be refreshed
   SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 
      SPI_SETNONCLIENTMETRICS, 0, 
      SMTO_ABORTIFHUNG, 100000, NULL);
   //make the icon size go back to original number
   ii--;
   wsprintf(szres, "%i", ii);
   SetString(HKCU, "Control Panel\\Desktop\\WindowMetrics", 
         "Shell Icon Size", szres);
   SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 
      SPI_SETNONCLIENTMETRICS, 0, 
      SMTO_ABORTIFHUNG, 100000, NULL);
   //make taskbar can redraw again
   SendMessage(hwndtask, WM_SETREDRAW, TRUE, 0);
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, 
   LPSTR lpCmdLine, int nCmdShow)
{  F5Desk();
   return 0;    
}

Copyright notice

• This code is based on work by Rocky Mountain Computer Consulting, Inc.
• This code is provided free. Use it as you wish, but all responsibilities are yours.
• You should include this Copyright notice in your Copyright notice, or, Readme, or similar thing if you use this code or get know-how from this code and you use it in your program.
• This code is supplied from an anonymous man in Semarang, Indonesia.