BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  OwnerDraw LisBbox & Scrolling          BorlandTalk.com Forum Index -> C++ Builder (VCL Components Usage) View previous topic :: View next topic   Author Message Ralph Gamble Guest Posted: Wed May 16, 2007 6:30 pm    Post subject: OwnerDraw LisBbox & Scrolling I have an OwnerDraw ListBox On the left side of the ListBbox I have a series of bitmaps. Depending a condition I want to output a Text On top of the Bit map. I have inserted The code to output the Text in the bit map in OnDrawItem. It seems to work correctly except when I scroll. When I scroll and a bit map that needs Text is at the bottom it draws correctly, but as soon as I move down one more position it disappears. What am I missing and how do I fix this. Thanks in advance Ralph Back to top Remy Lebeau (TeamB) Guest Posted: Wed May 16, 2007 9:32 pm    Post subject: Re: OwnerDraw LisBbox & Scrolling "Ralph Gamble" <ralphgamble (AT) rogers (DOT) com> wrote in message news:464b0785$1 (AT) newsgroups (DOT) borland.com... Quote: When I scroll and a bit map that needs Text is at the bottom it draws correctly, but as soon as I move down one more position it disappears. What am I missing and how do I fix this. Please show your actual code. Gambit Back to top Ralph Gamble Guest Posted: Wed May 16, 2007 10:26 pm    Post subject: Re: OwnerDraw LisBbox & Scrolling Here is code //--------------------------------------------------------------------------- void __fastcall TMainForm::ListBoxDrawItem(TWinControl *Control, int Index, TRect &Rect, TOwnerDrawState State) { TBitBtn *Btn = ((TBitBtn*)(ListBox->Items->Objects[Index])); Btn->Left = Rect.Left; Btn->Top = Rect.Top; Btn->Visible = true; TBitBtn *BtnAhead = BAH[Index]; BtnAhead->Top = Rect.Top; if( !Btn->Visible ) Btn->Visible = true; else Btn->Repaint(); // to remove some color shift when button looses focus TRect rect = Rect; rect.Left += Btn->Width; TCanvas *Cvs = ((TListBox*)Control)->Canvas; Cvs->FillRect(rect); if( State.Contains(odFocused) ) Cvs->DrawFocusRect(rect); if( State.Contains(odSelected) ) { Cvs->Brush->Color = clHighlight; Cvs->Pen->Color = clHighlightText; } else { Cvs->Brush->Color = clWindow; Cvs->Pen->Color = clWindowText; } if (ListBox->Items->Strings[Index]!=""){ OutPutTextString(Cvs,ListBox->Items->Strings[Index],rect.Left+5, rect.Top+6); } Cvs->Brush->Color = clWindow; TCData* APtr=GetDataPtr(Btn->Tag); if (APtr!=NULL){ if ((Index==0)&&(AuctionOver())) BtnAhead->Visible = false; else BtnAhead->Visible = true; // This is the text that dissapears if (APtr->TotalMeaning>1) Astrix(Cvs,rect.left,rect.top); } } //--------------------------------------------------------------------------- void __fastcall TMainForm::Astrix(TCanvas* Cvs, int x1, int y1) { // save old //TColor old=Cvs->Font->Color; //TColor oldBrush=Cvs->Brush->Color; //int oldSize=Cvs->Font->Size; // draw Blue astrix Cvs->Brush->Color=clBtnFace; Cvs->Font->Color=clBlue; Cvs->Font->Size=14; Cvs->TextOut(x1-10,y1,"*"); // restore old //Cvs->Brush->Color=oldBrush; //Cvs->Font->Color=old; //Cvs->Font->Size=oldSize; } The Second line from bottom od drawitem is the line of code that draws the disaperaring test Ralph Back to top Remy Lebeau (TeamB) Guest Posted: Thu May 17, 2007 12:01 am    Post subject: Re: OwnerDraw LisBbox & Scrolling "Ralph Gamble" <ralphgamble (AT) rogers (DOT) com> wrote in message news:464b3ee5$1 (AT) newsgroups (DOT) borland.com... Quote: Btn->Left = Rect.Left; Btn->Top = Rect.Top; Btn->Visible = true; TBitBtn *BtnAhead = BAH[Index]; BtnAhead->Top = Rect.Top; if( !Btn->Visible ) Btn->Visible = true; else Btn->Repaint(); You should not be manipulating buttons (or any control, for that matter) from inside a drawing event. Intercept the WM_HSCROLL and WM_VSCROLL messages instead. Alternatively, instead of trying to synchronize a real button to the ListBox, you could simply use the DrawFrameControl() function to draw an image of a button directly onto the Canvas each time the OnDrawItem event is triggered. Then you don't need a real button at all, and the scrolling will always work without extra processing on your part. As for button clicks, you can use the ListBox's ItemAtPos() and ItemRect() methods inside the OnMouse... events, check if the clicking is occuring in the button area, and then react accordingly. Quote: TRect rect = Rect; rect.Left += Btn->Width; TCanvas *Cvs = ((TListBox*)Control)->Canvas; Cvs->FillRect(rect); You are not clearing out the area of the the Canvas that cooresponds to the button. The previous drawing will be preserved in the new drawing. You should always clear the entire TRect area. The button will redraw itself over the new drawing later, so you should always be sure to start with a blank slate each time. Quote: if( State.Contains(odFocused) ) Cvs->DrawFocusRect(rect); That should be your last drawing operation, not your first. Quote: // This is the text that dissapears You are clearing the area of the Canvas that contains the text (as you should be) but you are then drawing the text conditionally. So chances are, your conditions are not being met every time you expect them to be, so the text is not being redrawn when you want it to be. Gambit Back to top Ralph Gamble Guest Posted: Thu May 17, 2007 7:19 pm    Post subject: Re: OwnerDraw LisBbox & Scrolling Thanks Remy I can see what I was doing cannot work. During scrolling the button is redrawn on top of the text (astrix) that I just output. I guess my brain was out of gear when I wrote this. I wanted the appearance of a real button with a glyph in it so the reason for TBitBtn. When I Looked at DrawFrameControl() I cannot see how to Draw a bit Button with a glyph. I can also see how I could change the Glyph to get the desired effect but am now concerned with your comment Quote: You should not be manipulating buttons (or any control, for that matter) from inside a drawing event. I cant see what is wrong with changing position & visibility. (The buttons are activated through the ListBox OnClick event) Could you please briefly explain why the above general rule applies. Quote: Intercept the WM_HSCROLL and WM_VSCROLL messages instead. I'm going to try the above approach, I've never done it before, but from some of your previous posts I should be able to work through it. (good for my education). Once again thanks for your detailed analysis and comments. Ralph Back to top Remy Lebeau (TeamB) Guest Posted: Thu May 17, 2007 10:03 pm    Post subject: Re: OwnerDraw LisBbox & Scrolling "Ralph Gamble" <ralphgamble (AT) rogers (DOT) com> wrote in message news:464c6473$1 (AT) newsgroups (DOT) borland.com... Quote: I wanted the appearance of a real button with a glyph in it so the reason for TBitBtn. When I Looked at DrawFrameControl() I cannot see how to Draw a bit Button with a glyph. Just draw a normal button (DFC_BUTTON, DFCS_BUTTONPUSH), and then draw your glyph on top of that. You can overlap drawing as much as you want within a single OnDrawItem event. Quote: You should not be manipulating buttons (or any control, for that matter) from inside a drawing event. I cant see what is wrong with changing position & visibility. Drawing events are called very often. Their sole purpose is to update the display, nothing else. That is very bad place to move things around, or do any kind of intense processing that is not related to drawing. Think about it - your list has a button on it. Something happens and the list needs to be repainted onscreen. But then you change the button mid-draw and now the list has to be repainted all over again to account for that change that was not necessary in the first place. Quote: (The buttons are activated through the ListBox OnClick event) That is where you should be updating the visibility and poistioning. Not in the OnDrawItem event. Gambit Back to top Ralph Gamble Guest Posted: Mon May 21, 2007 11:21 pm    Post subject: Re: OwnerDraw LisBbox & Scrolling Thank you for all your help. I tried the DrawFrameControl() route and intercepting the vertical scroll message. The DrawframeControl() did not perform exacly what I wanted for appearance. So I rewrote the button synchronization method moving all the code outside the OnDrawItem event and everything works perfectly now. I had the wrong idea on draw item events. thanks for point me in right direction. 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