BGRACanvas2D Save and Restore Problem

[Coxy]

When I use BGRACanvas2D Save and Restore with baseline set to 'top' I get different output from when no Save and Restore called.

Lazarus: 2.0.10
FPC Version: 3.2.0
bgrabitmappack: 11.2.1.0

Example Code:

Code: Pascal  [Select][+][-]

1. unit Unit1;
2.  
3. {$mode objfpc}{$H+}
4.  
5. interface
6.  
7. uses
8.   Classes, SysUtils, Forms, Controls, Graphics, Dialogs, StdCtrls, BGRABitmap,
9.   BGRACanvas2D, BGRABitmapTypes;
10.  
11. type
12.  
13.   { TForm1 }
14.  
15.   TForm1 = class(TForm)
16.     Label1: TLabel;
17.     Label2: TLabel;
18.     procedure FormCreate(Sender: TObject);
19.     procedure FormDestroy(Sender: TObject);
20.     procedure FormPaint(Sender: TObject);
21.   private
22.     FImg : TBGRABitmap;
23.   public
24.  
25.     procedure PrepImg;
26.   end;
27.  
28. var
29.   Form1: TForm1;
30.  
31. implementation
32.  
33. {$R *.lfm}
34.  
35. { TForm1 }
36.  
37. procedure TForm1.FormCreate(Sender: TObject);
38. begin
39.   PrepImg;
40. end;
41.  
42. procedure TForm1.FormDestroy(Sender: TObject);
43. begin
44.   FImg.Free;
45. end;
46.  
47. procedure TForm1.FormPaint(Sender: TObject);
48. begin
49.   FImg.Draw(Canvas,100,100);
50. end;
51.  
52. procedure TForm1.PrepImg;
53. const
54.   TextLine = 'Test Text';
55. var
56.   ts : TCanvas2dTextSize;
57.   ctx : TBGRACanvas2D;
58. begin
59.   FImg.Free;
60.   FImg := TBGRABitmap.Create(1,1);
61.  
62.   ctx := FImg.Canvas2D;
63.  
64.   ctx.textBaseline:='top';
65.   ctx.fontName:='Tohoma';
66.   ctx.fontStyle:=[];
67.   ctx.fontEmHeight:=100;
68.   ctx.fillStyle(BGRA(240,0,0));
69.  
70.   ts := ctx.measureText(TextLine);
71.  
72.   FImg.SetSize(trunc(ts.width),trunc(ts.height));
73.   FImg.FillTransparent;
74.  
75.   //ctx.save;
76.   //ctx.restore;
77.  
78.   //ctx.textBaseline:='top';
79.  
80.   ctx.fillText(TextLine,0,0);
81. end;
82.  
83. end.
84.  

Run three times

i) Save, Restore and baseline commented out.
ii) Save and Restore uncommented, baseline commented out.
iii) Save, Restore and baseline uncommented.

Looks like an 'alphabetic' baseline is used after restore. You shouldn't need to set this after a Restore.

Output from these runs below.

[Coxy]

A little more info for this issue.

Modified unit BGRACanvas2D and added property to TBGRACanvas2D

Code: Pascal  [Select][+][-]

1.     property currState:TBGRACanvasState2D read currentState;
2.  

Original example code modified to,

Code: Pascal  [Select][+][-]

1.   a := ctx.currState;
2.   ctx.save;
3.   ctx.restore;
4.   b := ctx.currState;
5.  

Inspecting 'a' and 'b' shows 'TEXTBASELINE' changed to 'alphabetic' from 'top', see images below.

TBGRACanvas2D.Save calls TBGRACanvasState2D.Duplicate to create copy of current state, it does not copy 'textBaseline'. I've added code to copy this value which resolves this issue.

Code: Pascal  [Select][+][-]

1.   result.fontStyle := fontStyle;
2.   result.textDirection:= textDirection;
3.   result.textBaseline:=textBaseline;      // Mod by Coxy
4.  
5.   result.lineWidth := lineWidth;
6.   result.penStroker.LineCap := penStroker.LineCap;
7.  

Is this a valid fix or was the value not copied for some obscure reason?

Other members that have changed are 'FCLIPMASKOWNED' and 'PENSTROKER'.

[circular]

Thanks for reporting the problem.

I have applied your change in the Duplicate function of the state.

Regarding ClipMaskOwned and PenStroker, it is normal that the value would change. The mask is not actually duplicated when the state is duplicated and the pen stroker is a helper class and what matters here is that its properties would be the same.