A Simple HTML Display Class

Listing 2: simphtml.cpp — Implementation of SimpleHTMLDisplay

#include <windows.h>
#include "simphtml.hpp"

#define PROP_SIMPLEHTML     TEXT("prop_simplehtml")

// Constructor - adds simple HTML capabilities to an edit control
SimpleHTMLDisplay::SimpleHTMLDisplay(HWND hWnd)
{
    TCHAR tchClass[40];

    // Initialise data and use SetProp to store data pointer
    shd_hwndEdit=hWnd;
    shd_lpFirstURL=0;
    shd_iRichEditVersion=0;
    SetProp(hWnd,PROP_SIMPLEHTML,(HANDLE)this);

    // Check the control class name to establish our abilities
    if (GetClassName(shd_hwndEdit,tchClass,40))
    {
        if (lstrcmpi(tchClass,TEXT("EDIT"))!=0)
        {
            if (lstrcmpi(tchClass,TEXT("RICHEDIT"))==0)
                shd_iRichEditVersion=1;
            else
            {
                shd_iRichEditVersion=2;
                SendMessage(shd_hwndEdit,EM_SETEVENTMASK,
                    0,ENM_LINK);
            }
        }
    }

    // Subclass the edit control
    shd_lpfnOrigProc=SetWindowLong(shd_hwndEdit,
        GWL_WNDPROC,(LONG)SubProc);
}


// Sub-class window procedure
LRESULT CALLBACK
SimpleHTMLDisplay::SubProc(HWND hWnd,UINT msg,WPARAM w,LPARAM l)
{
    SimpleHTMLDisplay *lpSHD;
    LONG lpfnOrigProc;

    // Get our data from window property
    lpSHD=(SimpleHTMLDisplay *)GetProp(hWnd,PROP_SIMPLEHTML);
    lpfnOrigProc=lpSHD->shd_lpfnOrigProc;

    switch (msg)
    {
        case WM_SETTEXT:
            lpSHD->PrintText((LPTSTR)l);
            return TRUE;

        case SHDMSG_GETURL:
            return (LRESULT)lpSHD->RetrieveURL((ENLINK *)l);

        case SHDMSG_HIGHLIGHTURL:
            lpSHD->HighlightURL((ENLINK *)l,w);
            return 0;

        case WM_DESTROY:
            delete lpSHD;
            break;
    }

    return CallWindowProc((WNDPROC)lpfnOrigProc,hWnd,msg,w,l);
}


// Set HTML text in the control
void SimpleHTMLDisplay::PrintText(LPTSTR lpszStr)
{
    int iPos,iStart,iInTag=0;
    CHARFORMAT2 cf;

    // Clear existing text
    CallWindowProc((WNDPROC)shd_lpfnOrigProc,
        shd_hwndEdit,WM_SETTEXT,0,0);

    // Check for null text
    if (!lpszStr || !*lpszStr)
        return;

    // Initialise edit control format structure
    cf.cbSize=(shd_iRichEditVersion>1)?sizeof(CHARFORMAT2):
                    sizeof(CHARFORMAT);

    // Parse the supplied data
    for (iPos=0,iStart=0;;iPos++)
    {
        // Check for end of string
        if (!lpszStr[iPos])
        {
            if (iStart<iPos && !iInTag)
                SendMessage(shd_hwndEdit,EM_REPLACESEL,
                    FALSE,(LPARAM)(lpszStr+iStart));
            break;
        }

        // HTML Tag?
        if (lpszStr[iPos]==TEXT('<'))
        {
            if (iStart<iPos && !iInTag)
            {
                LPTSTR lpszTemp;

                if (lpszTemp=(LPTSTR)malloc((iPos-iStart+1)*
                                                sizeof(TCHAR)))
                {
                    lstrcpyn(lpszTemp,lpszStr+iStart,
                        (iPos-iStart)+1);
                    SendMessage(shd_hwndEdit,EM_REPLACESEL,
                        FALSE,(LPARAM)lpszTemp);
                    free((LPVOID)lpszTemp);
                }
            }

            ++iInTag;

            // End of line?
            if (strnicmp(lpszStr+iPos,TEXT("<br>"),4)==0 ||
                strnicmp(lpszStr+iPos,TEXT("<p>"),3)==0)
            {
                SendMessage(shd_hwndEdit,EM_REPLACESEL,
                    FALSE,(LPARAM)TEXT("\r\n"));
            }

            // Tags are only interpreted with a richedit control
            if (shd_iRichEditVersion>0)
            {
                cf.dwMask=0;
                cf.dwEffects=0;

                // Bold?
                if (strnicmp(lpszStr+iPos,TEXT("<b>"),3)==0)
                {
                    cf.dwMask=CFM_BOLD;
                    cf.dwEffects=CFE_BOLD;
                }
                else
                if (strnicmp(lpszStr+iPos,TEXT("</b>"),4)==0)
                    cf.dwMask=CFM_BOLD;

                // Underline?
                else
                if (strnicmp(lpszStr+iPos,TEXT("<u>"),3)==0)
                {
                    cf.dwMask=CFM_UNDERLINE;
                    cf.dwEffects=CFE_UNDERLINE;
                }
                else
                if (strnicmp(lpszStr+iPos,TEXT("</u>"),4)==0)
                    cf.dwMask=CFM_UNDERLINE;

                // Italic?
                else
                if (strnicmp(lpszStr+iPos,TEXT("<i>"),3)==0)
                {
                    cf.dwMask=CFM_ITALIC;
                    cf.dwEffects=CFE_ITALIC;
                }
                else
                if (strnicmp(lpszStr+iPos,TEXT("</i>"),4)==0)
                    cf.dwMask=CFM_ITALIC;

                // Change font settings?
                else
                if (strnicmp(lpszStr+iPos,TEXT("<font"),5)==0)
                    HandleFont(lpszStr+iPos,&cf);
                else
                if (strnicmp(lpszStr+iPos,TEXT("</font>"),7)==0)
                {
                    cf.dwMask=CFM_COLOR;
                    cf.dwEffects=CFE_AUTOCOLOR;
                }

                // Links only supported with richedit 2.0 or better
                else
                if (shd_iRichEditVersion>1)
                {
                    if (strnicmp(lpszStr+iPos,
                            TEXT("<a href=\""),9)==0)
                    {
                        DWORD dwLink;

                        // Add link to list
                        dwLink=AddLink(lpszStr+iPos+8);

                        // Turn link state on, and store the URL
                        // node address in 'lcid'
                        cf.dwMask=CFM_LINK|CFM_COLOR|
                                    CFM_UNDERLINE|CFM_LCID;
                        cf.dwEffects=CFE_LINK|CFE_UNDERLINE;
                        cf.crTextColor=URL_NORMALCOLOR;
                        cf.lcid=(LCID)dwLink;
                    }
                    else
                    if (strnicmp(lpszStr+iPos,TEXT("</a>"),4)==0)
                    {
                        // Turn link state on, clear 'lcid' field
                        cf.dwMask=CFM_LINK|CFM_COLOR|
                                    CFM_UNDERLINE|CFM_LCID;
                        cf.dwEffects=CFE_AUTOCOLOR;
                        cf.lcid=0;
                    }
                }

                // Send formatting changes to control
                if (cf.dwMask)
                    SendMessage(shd_hwndEdit,EM_SETCHARFORMAT,
                        SCF_SELECTION,(LPARAM)&cf);
            }
        }

        // End of tag?
        else
        if (lpszStr[iPos]==TEXT('>') && iInTag)
        {
            if (--iInTag==0)
                iStart=iPos+1;
        }
    }
}


// Add a link to the list
DWORD SimpleHTMLDisplay::AddLink(LPTSTR lpszLink)
{
    TCHAR tchBuf[300];
    SimpleHTML_UrlNode *lpURL;
    int iLen;

    // Copy into buffer
    if (*lpszLink==TEXT('\"')) ++lpszLink;
    for (iLen=0;*lpszLink && *lpszLink!=TEXT('\"') && iLen<300;
        lpszLink++,iLen++)
        tchBuf[iLen]=*lpszLink;
    tchBuf[iLen]=0;

    // Allocate URL node and link into list
    if (lpURL=(SimpleHTML_UrlNode *)
            malloc(sizeof(SimpleHTML_UrlNode)+(iLen*sizeof(TCHAR))))
    {
        lstrcpy(lpURL->shu_tchURL,tchBuf);
        lpURL->shu_lpNext=shd_lpFirstURL;
        shd_lpFirstURL=lpURL;
    }
    return (DWORD)lpURL;
}


// Handle font changes in richedit control (only supports colors)
BOOL SimpleHTMLDisplay::HandleFont(LPTSTR lpszTag,CHARFORMAT2 *lpCF)
{
    while (*lpszTag && *lpszTag!=TEXT('>'))
    {
        if (strnicmp(lpszTag,TEXT("color="),6)==0)
        {
            // Get color string
            lpszTag+=6;
            if (*lpszTag==TEXT('\"')) ++lpszTag;

            // Only handle # which we assume means hex
            if (*lpszTag==TEXT('#'))
            {
                BYTE r,g,b;

                // Parse color value
                ++lpszTag;
                r=hexcharval(*(lpszTag++))<<4;
                r|=hexcharval(*(lpszTag++));
                g=hexcharval(*(lpszTag++))<<4;
                g|=hexcharval(*(lpszTag++));
                b=hexcharval(*(lpszTag++))<<4;
                b|=hexcharval(*(lpszTag++));

                // Turn color on in charformat
                lpCF->dwMask=CFM_COLOR;
                lpCF->dwEffects=0;
                lpCF->crTextColor=RGB(r,g,b);
                return 1;
            }
        }
        ++lpszTag;
    }
    return 0;
}


// Retrieve URL string from control
LPTSTR SimpleHTMLDisplay::RetrieveURL(ENLINK *lpLink)
{
    CHARFORMAT2 cf2;
    SimpleHTML_UrlNode *lpURL;

    // Set the selection to that of the link
    SendMessage(shd_hwndEdit,EM_HIDESELECTION,TRUE,0);
    SendMessage(shd_hwndEdit,EM_EXSETSEL,0,(LPARAM)&lpLink->chrg);

    // Get the URL information
    cf2.cbSize=sizeof(cf2);
    cf2.lcid=0;
    SendMessage(shd_hwndEdit,EM_GETCHARFORMAT,TRUE,(LPARAM)&cf2);
    lpURL=(SimpleHTML_UrlNode *)cf2.lcid;

    // Move cursor to position following the URL
    SendMessage(shd_hwndEdit,EM_SETSEL,
        lpLink->chrg.cpMax,lpLink->chrg.cpMax);
    SendMessage(shd_hwndEdit,EM_HIDESELECTION,FALSE,0);

    return (lpURL)?lpURL->shu_tchURL:0;
}


// Highlight URL text in control
void SimpleHTMLDisplay::HighlightURL(ENLINK *lpLink,BOOL fState)
{
    CHARFORMAT2 cf2;
    CHARRANGE cr;

    // Get current selection point
    SendMessage(shd_hwndEdit,EM_EXGETSEL,0,(LPARAM)&cr);

    // Set the selection to that of the link
    SendMessage(shd_hwndEdit,EM_HIDESELECTION,TRUE,0);
    SendMessage(shd_hwndEdit,EM_EXSETSEL,0,(LPARAM)&lpLink->chrg);

    // Change text format and redraw window immediately
    cf2.cbSize=sizeof(cf2);
    cf2.dwMask=CFM_COLOR|CFM_LINK;
    cf2.dwEffects=(fState)?0:CFE_LINK;
    cf2.crTextColor=(fState)?URL_CLICKCOLOR:URL_NORMALCOLOR;
    SendMessage(shd_hwndEdit,EM_SETCHARFORMAT,
        SCF_SELECTION,(LPARAM)&cf2);
    UpdateWindow(shd_hwndEdit);

    // Restore original cursor position
    cr.cpMin=cr.cpMin;
    SendMessage(shd_hwndEdit,EM_EXSETSEL,0,(LPARAM)&cr);
    SendMessage(shd_hwndEdit,EM_HIDESELECTION,FALSE,0);
}


// Destructor
SimpleHTMLDisplay::~SimpleHTMLDisplay()
{
    SimpleHTML_UrlNode *lpURL,*lpNext;

    // Free URL linked list
    for (lpURL=shd_lpFirstURL;lpURL;lpURL=lpNext)
    {
        lpNext=lpURL->shu_lpNext;
        free((LPVOID)lpURL);
    }

    SetWindowLong(shd_hwndEdit,GWL_WNDPROC,shd_lpfnOrigProc);
    RemoveProp(shd_hwndEdit,PROP_SIMPLEHTML);
}
//End of File