firemonkey - Fmx TMemo 无法正确显示 base64 字符串

Question

我需要在 TMemo 中显示 base64 键。不幸的是，不可能适当地显示这个 base64 字符串：它在每个“/”处被回车符截断，或者在系统地开始新行的任何“+”处被截断！我尝试了我所知道的一切，用一个长短语（没有回车）来制作这个字符串，但没有成功。如果可能在调整表单和 TMemo 的大小时自动调整大小，如何获得 base64 中的扁平字符串（没有回车）？非常感谢。

Answer 1

对于那些感兴趣的人，下面的代码：一个带有 TMemo（备忘录）的 TForm。该解决方案适用于扁平 Base64 字符串。最后不再在每个 / 或 + 处截断字符串。也许下面的解决方案需要调整，但它对我来说已经足够了。当然，在处理应用程序中的 b64 字符串之前，需要对其进行过滤以消除 CR-LF，但这没关系。我使用事件：TMemo 的 OnKeyDown、OnResize、OnPainting。我编写了一个特定的函数 formatMemo(..) 来适当地对齐行。该代码仅接受真正的 B64 字符，并过滤错误字符（如果有）。

#define IS_B64(c) (isalnum(c) || (c == '/') || (c == '+') || (c == '='))

//Adjustments work for Courier New, standard size:
const float FW=7.2;//Font width
const diff=25;//Room for vert. scroll bar

//Gives the number of characters in one line of the TMemo:
//  width : width in pixels where to put the line of chars
//  font_sz : the average width of a character
//  returns the number of characters by line of the TMemo
inline int nchars(int width, float font_sz)
{
    return int(float(width-diff)/font_sz);
}//nchars
//---------------------------------------------------------------------------

//Formats the memo to a certain length of characters:
//  *p : the memo to format
//  nc : the number of characters for each line.
void formatMemo(TMemo *p, int nc)
{
    if(p==0) return;
    AnsiString src, dest;//UnicodeString is less fast...
    //Filter everything as B64 only:
    for(int i=1; i<=p->Text.Length(); ++i) {//Indexing is "1-based" like on Delphi (except on mobiles)
        if(IS_B64(p->Text[i])) dest += p->Text[i];
    }
    p->Lines->Clear();//Erases everyting
    int length=dest.Length(), units=length/nc, remain=length%nc;
    for( int k=0 ; k<units ; ++k) {
        p->Lines->Append( dest.SubString(1+k*nc, nc) );
    }
    if(remain) {
        p->Lines->Append( dest.SubString(1+units*nc, remain) );
    }
}//formatMemo
//---------------------------------------------------------------------------

void __fastcall TForm1::memoKeyDown(TObject *Sender, WORD &Key, System::WideChar  &KeyChar,
          TShiftState Shift)
{
    //This event is triggered before the character is sent in Text.
    //Saves caret position:
    TCaretPosition p={memo->CaretPosition.Line, memo->CaretPosition.Pos};
    memo->Tag=0;//Don't do a format.

    if(Key==0 && !IS_B64(KeyChar))//Printable KeyChar
    {
        //Changes the entry into '0':
        KeyChar='0';
        KeyDown(Key,KeyChar,Shift);

        //Put a backspace to erase:
        Key=vkBack; KeyChar=0;
        KeyDown(Key,KeyChar,Shift);
    }
    else memo->Tag=1;//Programs a format in the OnPainting
    memo->SetFocus();
    memo->CaretPosition=p;//Repositions the caret
}
//---------------------------------------------------------------------------

//In case of resize, reformat the TMemo
void __fastcall TForm1::memoResize(TObject *Sender)
{
    formatMemo(memo, nchars(memo->Width,FW));
}
//---------------------------------------------------------------------------

void __fastcall TForm1::memoPainting(TObject *Sender, TCanvas *Canvas, const TRectF &ARect)
{
    //We will use the Tag of the memo as a parameter, to plan a reformat.
    if(memo->Tag){//A format is asked by OnKeyDown.
        TCaretPosition p={memo->CaretPosition.Line, memo->CaretPosition.Pos};
        formatMemo(memo, nchars(memo->Width,FW));
        memo->SetFocus();
        memo->CaretPosition=p;
        memo->Tag=0;//Done
    }
}
//---------------------------------------------------------------------------