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Transparent CSliderCtrl Class

Nic Wilson

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14 Nov 2002CPOL

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A MFC Transparent CSliderCtrl class

Introduction

This is a MFC transparent slider class. As it uses CSliderCtrl as its base class it can be used as a replacement class for any CSliderCtrl object. Tic marks are fully supported as can be seen in the screen shot above. To use, add this class to your project. Add your sliders to your project normally, then change the CSliderCtrl type in your .h file to CMySliderControl and #include the MySliderControl.h file. Once compiled your sliders will be transparent and if you have auto tics set then these too will show.

Update

V2.0 Re-wrote parts of the class. Added the ability to redraw the controls when the backgrounds had changed. Added custom transparent channel and custom thumb with optional colours. The demo source has been updated to show the background changing.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By

Nic Wilson

Web Developer

Australia

This member has not yet provided a Biography. Assume it's interesting and varied, and probably something to do with programming.

Comments and Discussions

Re: DrawTransparent() question

David Cole30-Jul-04 7:00

30-Jul-04 7:00

Why don't you try Invalidate() followed by UpdateWindow()? UpdateWindow() forces a paint to happen right now synchronously which is probably a side effect of the SetRange TRUE param...

David Cole

Re: DrawTransparent() question

dhclark3-Nov-10 8:11

3-Nov-10 8:11

I've tried just about everyone's suggestions regarding this, and this is the only one I have found to work. I have one more suggestion, however. If the CMySliderControl object happens to be disabled, the background color is not updated. Try this:

if (bRepaint == TRUE) 
{
   Invalidate();
   BOOL bEnabled = IsWindowEnabled();
   if ( !bEnabled )
      EnableWindow();
   int min, max;
   CSliderCtrl::GetRange(min, max);
   CSliderCtrl::SetRange(min, max);
   if ( !bEnabled )
      EnableWindow(FALSE);
}

This works every time under all conditions (so far). Thanks to everyone who has contributed to this!

Better way to know vertical from horizontal?

Harold Bamford20-Nov-02 17:27

20-Nov-02 17:27

In your code for DrawChannel(), you ask if there is a better way to determine if the control is vertical or horizontal. Try:

// get channel orientation
BOOL IsVertical = (TBS_VERT & GetStyle()) ? TRUE : FALSE;

Having said that, I have GOT to ask what this is all about:

crect = lpcd->rc;
if (IsVertical)
    crect.InflateRect(1, 0, 1, 0);
else
    crect.InflateRect(0, 2, 0, 2);
DrawEdge(pDC->m_hDC, &crect, EDGE_SUNKEN, BF_RECT | BF_ADJUST);

It looks like the goal of DrawChannel() is merely to capture the background bitmap and then finish the channel. Wouldn't it be easier to just capture the background in OnCustomDraw() and set

*pResult = CDRF_DODEFAULT;

What have I missed here?

And while I'm asking dumb questions, why do you use the DC for the parent window rather than the current window?

Thanks for your help on this. Obviously, I'm a GDI beginner... Confused | :confused:

Confused | :confused:

Re: Better way to know vertical from horizontal?

Nic Wilson21-Nov-02 11:18

21-Nov-02 11:18

Harold Bamford wrote:
In your code for DrawChannel(), you ask if there is a better way to determine if the control is vertical or horizontal. Try:

Great! I could not find that anywhere I will give it a try!

Harold Bamford wrote:
It looks like the goal of DrawChannel() is merely to capture the background bitmap and then finish the channel. Wouldn't it be easier to just capture the background in OnCustomDraw() and set *pResult = CDRF_DODEFAULT;

The class is unfinished and this is skeleton code for those who wish to alter the channel, some users do not know how to do this. I also like the type of channel this draws, I have expanded it further to fill the channel with various colours to the left, right or both sides of the slider sort of like a progress bar built in.
I will upload changes soon.

Harold Bamford wrote:
And while I'm asking dumb questions, why do you use the DC for the parent window rather than the current window?

The parent DC holds the background image we use to make the control transparent.

Nic

Changing the background image

Atlantys22-Sep-02 7:51

22-Sep-02 7:51

I got the first post! Big Grin | :-D

Big Grin | :-D

This is a very cool class, (almost) exactly what I need.
It's "almost" because I've found one thing I wish it could do for me.

The background bitmap of my dialog changes while the program is running (so it's not just set once and that's it). So obviously, I would like the background image the slider saves to be changed. Unfortunetaly, the old background image, behind the sliderctrl, is still shown when I change to the new background.

GDI is NOT something I know well, but I tried to do this myself, but I couldn't. I tried deleting/clearing m_dcBk and m_bmpBk, but that didn't work, as well as some other funky things that created all kinds of ASSERT failures.

Any help would be greatly appreciated!
Thanks. Big Grin | :-D

Big Grin | :-D

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