Board index » cppbuilder » Two images on a TBitBtn.....how?

2005-09-07 04:34:01 AM
cppbuilder96
Hello, I'm trying to display an additional bitmap image on a TBitBtn besides the one already there. I don't need additional up/down/disabled images on this thing, I just need another image on the opposite side of the text from the bitmap that normally shows up there. I would like to do this by creating a new component and inheriting from TBitBtn (or TButton) and not have to create a completely new component from scratch. I know how to create new TBitmaps and I also know how to draw one on a TCanvas object. The problem is getting a TCanvas object onto a TButton or TBitBtn so I can pop the bitmap in there (I know Borland had to, somehow, to make the TBitBtn in the first place). Thanks.
 

"Andy Piskur" < XXXX@XXXXX.COM >wrote in message
The VCL does not draw anything for it.
TBitBtn creates an instance of TCanvas in its constructor. Whenever the
TBitBtn redraws itself, it assigns the TCanvas::Handle property to whatever
HDC the OS provides to TBitBtn for drawing onto. However, you do not have
access to the TCanvas that TBitBtn uses. It is declared as private.
In order to change TBitBtn's drawing behavior, you will have to intercept
the CN_DRAWITEM message and then use your own TCanvas object.
Gambit
 

"Remy Lebeau \(TeamB\)" < XXXX@XXXXX.COM >wrote:
 

{smallsort}

"Andy Piskur" < XXXX@XXXXX.COM >wrote in message
TSpeedButton also has a TControlCanvas that is created in he TGraphicControl
constructor, and then the TControlCanvas::Handle is assigned to an HDC that
is provided by the WM_PAINT message.
Canvas property that is accessible to descendant classes. Simple override
the virtual Paint() method to do your own drawing.
Gambit
 

"Remy Lebeau \(TeamB\)" < XXXX@XXXXX.COM >wrote:
 

Nevermind about the TImageList and trying to get that to work. I am just drawing the bitmap directly on the canvas as I should have done all along using the Draw or StretchDraw methods. I am still having trouble with the new secondary image not getting redrawn after a resize though. Whatever the trigger is to make the original glyph and the text re-adjust and then redraw itself, I would like to know so that I can call my adjust function and then redraw the second bitmap. This problem occurs whenever I change the properties as well. If there was an OnChange event that I could manipulate I would do so but there doesn't appear to be an OnChange anywhere in the hierarchy. As before, when I try to override the Resize() method and then place the new component on a form, I get an error message and it never gets placed. Any help is appreciated. Thanks.
 

"Andy Piskur" < XXXX@XXXXX.COM >wrote in message
automatically redraws the component, causing Paint() to be called again.
Simply take the current dimensions into account whenever Paint() is called.
to issue a new WM_PAINT message when appropriate. Paint() is called in
response to WM_PAINT.
responsible for specifying the X and Y coordinates where the image is to be
drawn. Inside of Paint(), simply take the current dimensions of the
component, calculate a suitable X and Y for the drawing, and then Draw() the
image.
Gambit
 

"Andy Piskur" < XXXX@XXXXX.COM >wrote in message
recalculate and redraw your image every time Paint() is called.
image to Invalidate() itself so that the OS sends a new WM_PAINT message to
the component, thus triggering the Paint() method.
correctly. The native components don't override it for drawing anyway.
Gambit
 

"Remy Lebeau \(TeamB\)" < XXXX@XXXXX.COM >wrote: