Text scaling within a TppDrawCommand

rbuser

I have created my own component to draw a scale on a report (similar to a
ruler).
The number of steps shown on the scale is selectable as is the font used to
display
the numbers on the scale. All is displayed correctly in the designer.

Unfortunately, when I switch to the viewer display the font is not scaled as
you zoom in and out.

My TppScaleDrawCommand is based on a TppDrawShape and in the Draw function
I draw the scale, assign the required font to the TppDevice canvas and use
the
Canvas.TextOut command to draw the text on the canvas.

Being new to the problems of drawing on device canvases I am obviously
missing a step.

Any comments would be helpful

ATM
--

digitalmetaphors

The scaling should be handled by the screendevice. See the ScaleVertices and
DrawText routines in ppViewr.pas. It should scale the size and then scale
the font height for you automatically for TppDrawTexts. You don't have a
TppDrawText descendent, but rather you have a TppDrawShape descendent, so it
won't be scaled automatically by the screen device. You need to read the
ScaleY and ScaleX properties of the screen device at runtime to get the
scale to apply it to your draw command. Access the screen device by
referencing TppViewer(Report.PreviewForm.Viewer).ScreenDevice.


Cheers,

Jim Bennett
Digital Metaphors

rbuser

If you are generating an image you shouldn't have to bother about
handling the scaling. Normally ReportBuilder handles it by using the
drawcommands.

I would suggest you to take a look at the Paintbox component source
code. It is small and shows how to let the drawcommand handle the zoom.

The component can be found at:

http://perso.b2b2c.ca/dlemire/comps/twpaintbox.zip

Daniel

rbuser

As I read your post, I've noticed that you draw on the device canvas and
I wouldn't suggest that because I'm not sure that the text will be
exported if you use export devices to save the report as pdf or other
formats.

I would suggest you to write to a canvas. You're already using a
TppDrawCommand so why not use it to draw the text.

Here's two functions that might help you:

procedure TRBPaintboxCDW.PropertiesToDrawCommand(aDrawCommand:
TppDrawCommand);
var
lDC : HDC;
lMetafile : TMetafile;
lMetaFileCanvas : TMetaFileCanvas;
lDrawCommand : TppDrawImage;
lRect : TRect;
begin

inherited PropertiesToDrawCommand(aDrawCommand);
if (aDrawCommand is TppDrawImage) then
begin
// Copy the component properties to the draw command
lDrawCommand := TppDrawImage(aDrawCommand);
lDrawCommand.Left := PrintPosRect.Left;
lDrawCommand.Top := PrintPosRect.Top;
lDrawCommand.Width := PrintPosRect.Right - PrintPosRect.Left;
lDrawCommand.Height := PrintPosRect.Bottom - PrintPosRect.Top;
lDrawCommand.DirectDraw := True;

lRect.Left := 0;
lRect.Top := 0;
lRect.Right := spWidth;
lRect.Bottom := spHeight;

// Create the metafile for the output
lMetafile := TMetafile.Create();
lMetaFile.Width := spWidth;
lMetaFile.Height := spHeight;

// Get the device context of the printing device
if (ppPrinter <> nil) and (ppPrinter.DC <> 0) then
lDC := ppPrinter.DC
else
lDC := GetDC(0);

// Create the canvas to draw on
lMetaFileCanvas := TMetaFileCanvas.Create(lMetaFile, ldc);
if not Transparent then
begin
lMetaFileCanvas.Brush.Color := Color;
lMetaFileCanvas.Fillrect(lRect);
end;

Draw you text here without the need to care about scalling

lMetaFileCanvas.Free;

// Assign the metafile to the picture property
lDrawCommand.Picture.Graphic := lMetafile;
lMetaFile.Free;

// Release the device context
if (ppPrinter = nil) or (ppPrinter.DC = 0) then
ReleaseDC(0,lDC);
end;
end;


procedure TRBPaintboxCDW.PaintDesignControl(aCanvas: TCanvas);
begin
if FPainting then Exit;

FPainting := True;
try
if FDrawCommand = nil then
FDrawCommand := TppDrawImage.Create(nil);
PrintPosRect := ppRect(0, 0, mmWidth, mmHeight);

// In design time just draw a simple border with name
if (pppcDesigning in DesignState) then
begin
with aCanvas do
begin
brush.style := bsClear;
pen.color := clBlack;
polyline([point(0,0),
point(spwidth-1,0),
point(spWidth-1, spHeight-1),
point(0,spHeight-1),
point(0,0)]);
TextOut(1,1,Name);
end;
end
else
begin
PropertiesToDrawCommand(FDrawCommand);
aCanvas.StretchDraw(spClientRect,
FDrawCommand.Picture.Graphic);
end;
finally
FPainting := False;
end;
end;



There functions come from the paintbox that I talked about in my
previous post.

Hope this helps

Daniel