Using TWPPaintEngine to paint RTF text into a TVirtualStringTree cell

That is a very special question and you can ask me by e-mail, too.

Any feedback please?

Combined with what? It seems that the values in PaintEngine.Memo._PaintRectHeight respectively PaintEngine.Memo._PaintBottomPos are twips? Or what are they? What is the difference between _PaintRectHeight and _PaintBottomPos?

When you are dealing with normal (non-RTF) multiline text in a VST (TVirtualStringTree) you are supposed to use the Winapi.Windows.DrawText method with DT_CALCRECT or DT_WORDBREAK flags in the OnMeasureItem event. The resulting height of the text is passed to the lpRect parameter of the Winapi.Windows.DrawText method: NodeHeight := lpRect.Height.

This is how I attempt to measure the height of the text with the TWPPaintEngine class:

text := '...';
w := columnWidth; // 430 px
rtfData := TWPRTFDataCollection.Create( TWPRTFDataBlock );
pe := TWPPaintEngine.Create( Self );
bmp := TBitmap.Create;
try
	rtfData.MakeRTFProps;
	rtfData.Get( wpIsBody, wpraOnAllPages ).RtfText.AsString := text;

	pe.RTFData := rtfData;
	pe.RTFData.Header.LeftMargin := 0;
	pe.RTFData.Header.RightMargin := 0;
	pe.RTFData.Header.PageWidth := Round( w / Screen.PixelsPerInch * 1440 );
	pe.RTFData.Header.PageHeight := MaxInt;	// I don't know the required height yet - The text needs to fit in
	pe.ReformatAll( TRUE );
	
	bmp.PixelFormat := pf32Bit;
	bmp.SetSize( w, 1 ); // I don't know the height yet

	pe.Draw( bmp.Canvas,
		0, 0, MaxInt,
		Screen.PixelsPerInch, Screen.PixelsPerInch,
		0
	);
	
	// What is the correct value to use here to determine the NodeHeight in pixels?
	// ... pe.Memo._PaintBottomPos?
	// ... pe.Memo._PaintRectHeight?
	// ... Something else?
	
	// Using Round( pe.Memo._PaintBottomPos * 0.0666666667 ) at the moment, assuming _PaintBottomPos is in twips.	
	NodeHeight := ???;
finally
	bmp.Free;
	pe.RTFData := nil;
	pe.Free;
	rtfData.Free;
end;

This seems to work perfectly well for some text, while other text is cut off:

🖼 VXTNQbv.png (i.imgur.com)

You can use the resolution values from Memo
property CurrentXPixelsPerInch: Integer
property CurrentYPixelsPerInch: Integer

Thanks. This seems to work well. 👍🏻

In the TVirtualStringTree you need to calculate a node's height in the OnMeasureItem event. Do you have a suggestion on how to properly get the height of the rendered text?

I see there is PaintEngine.Memo._PaintRectHeight and PaintEngine.Memo._PaintBottomPos - Both seem to contain a value I can work with. For now I use height := PaintEngine.Memo._PaintBottomPos div 10 and it seems to get the job done in most cases.

Is there an other / better way?

I would solve this by buffered paint on a TBitmap.

Create a bitmap of the size of drawing area and paint on it. This can also be usewd for caching the drawing.

Any feedback on this?

I'm using TWPPaintEngine to paint RTF text into a TVirtualStringTree cell. This works in general but I have a problem.

Sometimes, when the cell (or the drawing area) is small, the drawing result seems to be messed up in terms of line breaks or spacing between the lines.

🖼 mlrIwMO.png (i.imgur.com)

When I expand the window just a few more pixels the text suddenly is drawn correctly:

🖼 2wncAu7.png (i.imgur.com)

Unfortunately this doesn't work for all texts:

🖼 9P0D8Qs.png (i.imgur.com)

In this case it doesn't seem to matter how wide the window is, the text is never drawn correctly:

🖼 umn9MlU.png (i.imgur.com)

What is the problem here and how can I fix that?

This is how I draw the text:

  paint3.RTFData := data^.RTFData;
  paint3.RTFData.Header.LeftMargin := 0;
  paint3.RTFData.Header.RightMargin := 0;
  paint3.RTFData.Header.PageWidth := Round( drawRect.Width / Screen.PixelsPerInch * 1440 );
  paint3.RTFData.Header.PageHeight := Round( drawRect.Height / Screen.PixelsPerInch * 1440 );
  paint3.Draw( TargetCanvas,
    drawRect.Left, drawRect.Top, drawRect.Height,
    Screen.PixelsPerInch, Screen.PixelsPerInch,
    0
  );

These are the RTF texts:

Example 1

{\rtf1\ansi\deff0\uc1\ansicpg1252\deftab720{\fonttbl{\f0\fnil\fcharset1 Arial;}{\f1\fnil\fcharset1 Tahoma;}{\f2\fnil\fcharset2 Wingdings;}{\f3\fnil\fcharset2 Symbol;}{\f4\fnil\fcharset4 Segoe UI Emoji;}}{\colortbl\red0\green0\blue0;\red255\green0\blue0;\red0\green128\blue0;\red0\green0\blue255;\red255\green255\blue0;\red255\green0\blue255;\red128\green0\blue128;\red128\green0\blue0;\red0\green255\blue0;\red0\green255\blue255;\red0\green128\blue128;\red0\green0\blue128;\red255\green255\blue255;\red192\green192\blue192;\red128\green128\blue128;\red0\green0\blue0;\red192\green255\blue192;}\wpprheadfoot1\paperw12240\paperh15840\margl1880\margr1880\margt1440\margb1440\headery720\footery720\ftnbj\sftnbj\sftnrstcont\nocolbal\sftnnar\saftnnar\fet0\endnhere\sectdefaultcl{\*\generator WPTools_9.4-PRM;}{\plain\f1\fs20 Innenputz 2lagig Leibung B 24 cm UP Kalkzement-Putzm. D 20mm OP Kalkzement-Putzm. gefilzt\line\line 2-lagiges Innenputzsystem DIN 18550-2 auf Leibung,\line\f1\cb16 Breite Leibung  '24'\f1\cb0   cm, Putzgrund Mauerwerk, Unterputz DIN EN 998-1 aus Kalkzement-Putzm\'F6rtel, Druckfestigkeitsklasse CS II (1,5 bis 5 N/mm2), Dicke Unterputz 20 mm, Oberputz aus Kalkzement-Putzm\'F6rtel, Putzoberfl\'E4che Qualit\'E4tsstufe 2 (Q2), gefilzt, \'FCbliche Beanspruchung, Arbeitsh\'F6he der zu bearbeitenden oder zu bekleidenden Fl\'E4che bis 3,5 m \'FCber der Standfl\'E4che des hierf\'FCr erforderlichen Ger\'FCstes, Ausf\'FChrung im Erdgeschoss.\par
}}

Example 2

{\rtf1\ansi\deff0\uc1\ansicpg1252\deftab720{\fonttbl{\f0\fnil\fcharset1 Arial;}{\f1\fnil\fcharset1 Tahoma;}{\f2\fnil\fcharset2 Wingdings;}{\f3\fnil\fcharset2 Symbol;}{\f4\fnil\fcharset4 Segoe UI Emoji;}}{\colortbl\red0\green0\blue0;\red255\green0\blue0;\red0\green128\blue0;\red0\green0\blue255;\red255\green255\blue0;\red255\green0\blue255;\red128\green0\blue128;\red128\green0\blue0;\red0\green255\blue0;\red0\green255\blue255;\red0\green128\blue128;\red0\green0\blue128;\red255\green255\blue255;\red192\green192\blue192;\red128\green128\blue128;\red0\green0\blue0;}\wpprheadfoot1\paperw12240\paperh15840\margl1880\margr1880\margt1440\margb1440\headery720\footery720\ftnbj\sftnbj\sftnrstcont\nocolbal\sftnnar\saftnnar\fet0\endnhere\sectdefaultcl{\*\generator WPTools_9.4-PRM;}{\plain\f1\fs20 Anputzleiste\line\line Anputzleiste als Anschluss bei Fenster-, T\'FCr- und \line sonstigen Bauteilen liefern und anbringen\line\line Ausbilden einer wind- und schlagregendichten, bewegungsf\'E4higen Systemanschlussfuge mit Anputzleiste, bestehend aus:\line - Kunststoffleiste, selbstklebend\line - integriertem, komprimiertem\line   Fugendichtband\line - Schutzfolienstreifen\line (Putzanschlag mit Kellenschnittvorgabe).\line Einbau nach Vorgaben des Herstellers.\line\line Aktivieren des integrierten Fugendichtbandes nach Fertigstellung der Putzarbeiten durch seitliches Herausziehen des Schutzfolienstreifens.\line\line\f1\cb8 Hersteller/Typ  Baukom Apu mini 6 mm\f1\cb0  \line vom Bieter einzutragen.\par
}}