[Wiki] Double Gradient article

[lainz]

Or you OO-ify it a bit so it's easier to re-use, something like:

Code: Pascal  [Select][+][-]

1.   // Gradientfiller for the form background
2.   // It's a 50/50 scale so both gradients meet in the middle.
3.   gfPaint := TGradientFiller.Create(gdHorizontal);
4.   gfPaint.AddGradient(clYellow, clBlue, gdHorizontal, 50);
5.   gfPaint.AddGradient(clBlue, clGreen, gdHorizontal, 50);
6.   //...
7.   // Form paint:
8.   gfPaint.Draw(self.Canvas, self.ClientRect);
9.  

Couldn't resist  

here is a new article about this 'Gradient Filler':

http://wiki.lazarus.freepascal.org/Gradient_Filler

The article is a draft.

[eny]

Errors, I would not say something, if it worked fine.
Whats on you not on me?  I think where both using Lazarus latest stable version.

Couldn't say. My version is in my sig; do you have the same (or newer) version?

[mac.1]

If there were errors, pls say the error message and the line.

I'm working on a Transparent Version - So you can overlay 2 Gradients. But it is very slow ( 100ms for 400x300 on intel 2500k)
It's also working, but it seems only to work with TImage.

Maybe a multithreading version will follow - but at the moment i haven't enought time for that...

[lainz]

nGradient with alpha is very slow, try to use TBGRABitmap instead TBitmap.

I think 'Gradient Filler' is better than 'Double Gradient' & 'nGradient' because is object oriented and have more features.

EDIT: but Gradient Filler has a flickering bug, when you change a property, like 'globaldirection' and repaint a paintbox the first thing you can see is a red background, also if you are using 'self.doublebuffered:=true', to avoid this first you need to store the gradient in a bitmap and then draw the bitmap instead drawing directly the Tgradientfiller.

[qdos]

I get a an error message.
It reacts to "  for p in FGradients do  " ??

[eny]

I get a an error message.
It reacts to "  for p in FGradients do  " ??

I use the new 'for x in y' syntax that was introduced in a recent version of FPC (see my sig).
If you use an older version you'll have to iterate through the list via an integer:

Code: Pascal  [Select][+][-]

1. var i: integer;
2.     gi: TGradientInfo;
3. //...
4.   for i := 0 to FGradients.Count-1 do        
5.   begin
6.     gi := FGradients(i) as TGradientInfo;
7.     // do processing...

Note the brackets in 'FGradients(i)' are square brackets, but I don't know how to post them.

EDIT: but Gradient Filler has a flickering bug

Not really: the idea is that GradientFiller paints a gradient on a canvas be it a Form.Canvas or a Bitmap.Canvas.
If used directly on a visible canvas it might flicker, as does all painting on a visible Canvas.
FWIW: if I set DoubleBuffered to true on my own forms, the flicker is gone.

Having said that: it's very easy to exend the functionality of TGradientFiller to store a local copy of the gradient and use that in the Draw method.
And only regenerate when any of the properties change...

[lainz]

Code: [Select]

Not really: the idea is that GradientFiller paints a gradient on a canvas be it a Form.Canvas or a Bitmap.Canvas.
If used directly on a visible canvas it might flicker, as does all painting on a visible Canvas.
FWIW: if I set DoubleBuffered to true on my own forms, the flicker is gone.
Yes i forget it, thanks I will try Bitmap.Canvas.

[eny]

An update on the gradient subject.
There is a Delphi component TGradient that generates some more fancy gradients (http://www.delphiarea.com/downloads). It's incompatible with Lazarus because of the use of TBitmap.ScanLine.
The attachment contains a lazarus class (TGradientsFiller) that solves that and a demo app to show it's use.
Have fun.

[xenblaise]

Nice Form;
I'm only using

lazarus-0.9.28.2-fpc-2.2.4-win32 <stable>

Probably it won't work out, just as I tried the first sample code.

The error line;

// Populate the listbox with all style descriptions
  for s in C_STYLE_DESCRIPTION do

The error message;

ufrmmain1.pas(87,7) Error: Ordinal expression expected
ufrmmain1.pas(87,9) Fatal: Syntax error, ":=" expected but "in" found

Can you attach an exe zip file, just exited to view it personally.


thanks

[eny]

The 'downgrade' is fairly easy to do. Change the loop to:

Code: Pascal  [Select][+][-]

1. var i: TGradientstyle;
2. //...
3.   for i := low(C_STYLE_DESCRIPTION) to high(C_STYLE_DESCRIPTION) do
4.     cbStyles.Items.Append(C_STYLE_DESCRIPTION[ i ]);

Can you attach an exe zip file, just exited to view it personally.

Sure: Win$ only...

[xenblaise]

I got the binary, but I didn't fix the code with the one you gave
 

  var i: TGradientstyle; 

 for i := low(C_STYLE_DESCRIPTION) to high(C_STYLE_DESCRIPTION) do 
cbStyles.Items.Append(C_STYLE_DESCRIPTION[ i ]); 

Probably because I'm using;
lazarus-0.9.28.2-fpc-2.2.4-win32 <stable>
and NOT like your signature version


but, thanks a lot, really.

[lainz]

I got the binary, but I didn't fix the code with the one you gave
 

  var i: TGradientstyle; 

 for i := low(C_STYLE_DESCRIPTION) to high(C_STYLE_DESCRIPTION) do 
cbStyles.Items.Append(C_STYLE_DESCRIPTION[ i ]); 

Probably because I'm using;
lazarus-0.9.28.2-fpc-2.2.4-win32 <stable>
and NOT like your signature version


but, thanks a lot, really.

is very old 'stable' 0.9.28.

The new gradients filler is cool

[xenblaise]

The new gradients filler is cool

Very Cool

The usage?
is the problem, because you have to use semi transparent buttons, listboxex, labels, and others.

If you don't?, your form will look very fancy and lazy


It's much better if you guys include transparent tabsets, boxes, buttons, labels.  From that, lets see what the form looks like.

[lainz]

The new gradients filler is cool

Very Cool

The usage?
is the problem, because you have to use semi transparent buttons, listboxex, labels, and others.

If you don't?, your form will look very fancy and lazy


It's much better if you guys include transparent tabsets, boxes, buttons, labels.  From that, lets see what the form looks like.

I don't know how.

This isn't only for Forms backround, you can use with paintbox or with custom controls.