delphi - How to access TFrame's canvas? -


using: delphi xe2, vcl 32-bit application, windows 8

i'm trying paint background of frame onto panel (i'm using tjvpanel, because exposes onpaint event) child control of frame.

after reading this post , adding canvas field, still not successful.

after calling showaddreceiptpanel, should draw frame's (tfrmmyframe) window contents controls on (which include grid , pagecontrol) on foreground panel, grayscaled, after being processed proeffectimage method, instead shows opaque white background. missing something?

here's code:

type   tfrmmyframe = class(tframe)     pnlhdr: tpanel;     pnladdnewbg: tjvpanel;     procedure pnladdnewbgpaint(sender: tobject);   private     { private declarations }     fbgimg: tproeffectimage;     fcnvs: tcanvas;      procedure paintwindow(dc: hdc); override;     procedure showaddreceiptpanel;     procedure hideaddreceiptpanel;     procedure resizepanel_pnladdnewbg;    public     { public declarations }     constructor create(aowner: tcomponent); override;     destructor destroy; override;   end;  constructor tfrmmyframe.create(aowner: tcomponent); begin   inherited;    fbgimg := tproeffectimage.create(nil);   fcnvs := tcanvas.create;  end;  destructor tfrmmyframe.destroy; begin   if assigned(fbgimg)     fbgimg.free;    if assigned(fcnvs)     fcnvs.free;    inherited; end;  procedure tfrmmyframe.showaddreceiptpanel; begin   resizepanel_pnladdnewbg;   pnladdnewbg.visible := true; end;  procedure tfrmmyframe.paintwindow(dc: hdc); begin   inherited;    fcnvs.handle := dc; end;  procedure tfrmmyframe.pnladdnewbgpaint(sender: tobject); var   l, t, w, h: integer;   srct, drct: trect; begin    // copy frame canvas bgimg bitmap   l := 0;   t := pnlhdr.height;   w := clientwidth;   h := clientheight - t;    srct := trect.create(l, t, w, h);   fbgimg.width := w;   fbgimg.height := h;   drct := trect.create(l, t, w, h);   fbgimg.canvas.copymode := cmsrccopy;   fbgimg.canvas.copyrect(drct, fcnvs, srct); //  fbgimg.picture.savetofile('c:\tmp\a.bmp');    fbgimg.effect_antialias;   fbgimg.effect_grayscale;    // draw bgimg onto option panel   tjvpanel(sender).canvas.copymode := cmsrccopy;   tjvpanel(sender).canvas.draw(0, 0, fbgimg.picture.graphic); end;  procedure tfrmmyframe.resizepanel_pnladdnewbg; var   x1, y1, x2, y2: integer;   bmp: tbitmap; begin   x1 := 0;   y1 := pnlhdr.height;   x2 := clientwidth;   y2 := clientheight - y1;    pnladdnewbg.setbounds(x1, y1, x2, y2); end;

the dc assign canvas handle valid during paintwindow call. use outside function when not valid , hence behaviour observe.

i think should able solve problem calling paintto method. create bitmap of right size , pass canvas paintto.


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