How to get the progress of a TRichEdit? - c++

Question

I have a simple 'brut' big text file (20MB). I would like to show it in a TRichEdit. The problem is that it takes 6 seconds for the showing. I would like to put a progess bar in the bottom of the application to avoid this bad UX design.
My question is how to get the progress of the TRichEdit showing ? With the TRichEdit::LoadFromStream method, it goes from 0 to 100% fast (less than 1 second) but after the application wait 6 secondes during the first show.
I created this class FileStreamProgress with TFileStream inherit. I overide the TFileStream::Read()
int __fastcall FileStreamProgress::Read(void *Buffer, int Count)
{
__int64 previousPosition = this->Position;
int ret = TFileStream::Read(Buffer, Count);
if (this->Position == 0 || this->Position == this->Size || (previousPosition/128000) != (this->Position/128000)) {
ProgressCallBack(ProgressCallBackParam1, this->Position, this->Size);
}
return ret;
}
static void FileStreamProgress::ProgressCallBack(void*thiz, int i, int max)
{
TProgressBar* ProgressBar = (TProgressBar*)thiz;
if (ProgressBar)
{
if (max > 0)
{
ProgressBar->Position = int(i * 100 / max);
}
if (Application)
{
Sleep(1);
Application->ProcessMessages();
}
}
}
This is how I test it :
void MyApp::CreatePage(AnsiString filename)
{
ProgressBar->Visible = true;
FileStreamProgress::ProgressCallBackParam1 = (void*)this->ProgressBar;
TFileStream * stream = new FileStreamProgress(filename.c_str(), fmOpenRead);
TPageMemo* Page = new TPageMemo(this);
Page->Parent = PControl;
Page->PageControl = PControl;
MessageDlg("111",mtError,TMsgDlgButtons()<<mbOK,0);
Page->Texte->Lines->LoadFromStream(stream);
MessageDlg("222",mtError,TMsgDlgButtons()<<mbOK,0);
PControl->ActivePage = Page;
}
There are 7 secondes between the 2 message dialogs "111" and "222". And my progress bar wait 6 secondes at 100% (during the showing)

Answer 1

I tried to go deeper with the win32 API's SendMessage and Handle without the expected result.
At the end, I used a TMemo yesterday cuz it's a brut text. It's very fast (instant open) but some functions are missing like FindTextW(). I rewrote it. Thanks
http://docwiki.embarcadero.com/RADStudio/Rio/en/Memo_and_Rich_Edit_Controls

Answer 2

was curious so I tested the TRichEdit and came up with this:
//---------------------------------------------------------------------------
void load_text(TRichEdit *re,AnsiString filename,TProgressBar *pb)
{
// variables
int hnd,adr,siz,len,i;
const int _buf=128*1024; // buffer size
AnsiString s,s0;
char buf[_buf+1];
// open file and detect size
hnd=FileOpen(filename,fmOpenRead); if (hnd<0) return;
siz=FileSeek(hnd,0,2);
FileSeek(hnd,0,0);
// prepare progress bar
pb->Position=0;
pb->Max=siz;
pb->Visible=true;
// process txt file by chunks
for (s0="",adr=0;adr<siz;)
{
// update progress bar and GUI
pb->Position=adr;
Application->ProcessMessages();
// load chunk
len=FileRead(hnd,buf,_buf);
adr+=len; buf[len]=0;
// handle cutted lines by chunk size
s=s0; s0="";
// ignore last 2 lines for chunks (except last chunk)
if (len==_buf)
{
// skip last line
for (i=len-1;i>=0;i--)
if ((buf[i]==13)||(buf[i]==10))
{
i--;
if (i>=0)
if (buf[i]!=buf[i+1]) // different eol code to ignore empty line
if ((buf[i]==13)||(buf[i]==10)) // eol code
i--;
break;
}
// skip another line to avoid inserting empty line if eol is cutted
for (;i>=0;i--)
if ((buf[i]==13)||(buf[i]==10))
{
s0+=buf+i+1; // copy last 2 lines into s0
i--;
if (i>=0)
if (buf[i]!=buf[i+1]) // different eol code to ignore empty line
if ((buf[i]==13)||(buf[i]==10)) // eol code
i--;
i++; if (i<0) i=0; buf[i]=0; // end of string
break;
}
}
// last chunk ignore last eol
else{
// skip last line
i=len-1;
if ((buf[i]==13)||(buf[i]==10)) // eol code
{
i--;
if (buf[i]!=buf[i+1]) // different eol code to ignore empty line
if ((buf[i]==13)||(buf[i]==10)) // eol code
i--;
i++; if (i<0) i=0; buf[i]=0; // end of string
}
}
// add actual chunk
s+=buf;
re->Lines->Add(s);
}
// tidy up
pb->Visible=false;
FileClose(hnd); hnd=-1;
}
//---------------------------------------------------------------------------
Looks like it works without the ending pause you describe however that might be related to version of IDE/VCL/compiler I am using BDS2006 Turbo C++. When Tested on ~23 MByte STL file the load time is ~10sec (TMemo takes twice of that god know why)...
The saved file (while PlainText=true) is identical to the loaded one so the code should be correct.
Here animated GIF of preview:
while used like this:
void __fastcall TForm1::FormActivate(TObject *Sender)
{
//tbeg();
load_text(re_txt,"in.txt",pb_progress);
//tend();
//Caption=tstr();
re_txt->Lines->SaveToFile("out.txt");
}
where pb_progress is the TProgressBar and and re_txt is the TRichEdit.
As you can see no callback is needed ...
PS. If you want to measure the time like I did (the commented lines) the implementations of tbeg/tend/tstr functions are here:
performance.h