CODEWITHSUNDEEP
delphitwebbrowser
MattLaza
MattLaza

Reputation: 199

Set Font Size in TWebBrowser Selection

I have a email client which allows the user to change font, font size, bold, italics etc.

The issue l am having is when l try to change the font size of the selection either up or down i get a "EVariantTypeCastError" with a message of "Could not convert variant of type Null into type OleStr". This exception gets thrown on TextRange.queryCommandValue('FONTSIZE').

procedure TForm1.act_FontIncreaseExecute(Sender: TObject);
var
    Selection: IHTMLSelectionObject;
    HtmlPage: IHTMLDocument2;
    TextRange: IHTMLTxtRange;
    Parent: IHTMLElement2;
    s: string;
    i, mode: Integer;
begin

    HtmlPage := self.HtmlEditor.Document as IHTMLDocument2;
    Selection := HtmlPage.Selection;

    TextRange := Selection.createRange as IHTMLTxtRange;
    if (TextRange <> nil) then
    begin
        s := TextRange.queryCommandValue('FONTSIZE');
        val(s, i, mode);
        if mode = 0 then
            HtmlPage.execCommand('FONTSIZE', False, inttostr(i + 1))
    end;
end;

Is this the correct approach to increase the size of the font for the selection?

Edit 1:

Sample HTML:

<HTML><HEAD></HEAD>
<BODY>
<P>
    <SPAN style='FONT-SIZE: 7pt;'>
        Test Text
    </SPAN>
</P>
</BODY></HTML>

It looks like the issue lies with the FONT-SIZE Style. When this is taken out then no exception is thrown. My end goal is to be able to copy and paste from outlook and this is a stripped down example of that. When l use other styles such as color:red then no exceptions are thrown. So it looks like its just FONT-SIZE that is has the issue with.

Edit 2

Exception Stack Trace

Exception Stack Trace

Upvotes: 1

Views: 970

Answers (2)

kobik
kobik

Reputation: 21242

Is this the correct approach to increase the size of the font for the selection?

.queryCommandValue('FONTSIZE') refers to the FONT tag surrounding the text range (font sizes 1-7): e.g. 

<FONT size=1>Test Text</FONT>

In your HTML example there is no FONT tag. You need to handle the FONT-SIZE Style attribute (CSS) of the surrounding SPAN.

e.g. (no error checking to simplify the example):

if (TextRange <> nil) then
begin
  ...
  ShowMessage(TextRange.parentElement.style.fontSize);
end;

This will show 7pt. Your specific exception cause is explained by @whosrdaddy answer (queryCommandValue returns null for the reason I explained)

Upvotes: 3

whosrdaddy
whosrdaddy

Reputation: 11860

As you found out, in some cases the query will return NULL and then the Val() command will fail.

The solution is simple, assume standard font size when you get null:

procedure TForm1.FontIncreaseExecute;

var
    Selection: IHTMLSelectionObject;
    HtmlPage: IHTMLDocument2;
    TextRange: IHTMLTxtRange;
    s: OleVariant;
    i, mode: Integer;

 begin  
  HtmlPage := WebBrowser1.Document as IHTMLDocument2;
  Selection := HtmlPage.Selection;
  TextRange := Selection.createRange as IHTMLTxtRange;
  if (TextRange <> nil) then
   begin
    s := TextRange.queryCommandValue('FONTSIZE');
    if VarisNull(s) then
     s := 0; // fall back to standard font size
    Val(s, i, mode);
    if mode = 0 then
    HtmlPage.execCommand('FONTSIZE', False, inttostr(i + 1))
   end;
end;

Upvotes: 1

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