CreateParams issue

[Mecena]

hi all!

I have an aggrieviating problem concerning using CreateParams on my forms. I'm using compositing style (cp.ExStyle|=0x02000000) to eliminate flicker and it works wonderfully in most cases. However, i've noticed that on controls such as ListBox and TabControl it cancels the effect of drawing in OnDrawItem handler. I've read that compositing style can do that with 3rd party controls. Is there a way to get both the OnDrawItem stuff and compositing to work?
(In OnDrawItem i'm doing some user drawing, such as mnemonics and coloring stuff)

thanx,
M.

[mldisibio]

If someone else has a direct answer, please jump in.

This is not a direct answer, but perhaps a workaround.
If you've read through the entire post on MSDN : Flicker-Free Painting you probably already know that the composite painting flag is not compatible with Vista, and presents several other quirks, such as what you have pointed out.

The workaround I have gone with is this:
- Override the Form.OnResizeBegin method:
- Loop through each visible control on the form and stop its drawing with the WM_SETREDRAW(0) message.
- Override the From.OnResizeEnd method:
- Redraw the controls by sending the WM_SETREDRAW(1) message.

I do not propose this is the only way to stop flicker or the best, but it avoids the issues with the CompositePaint flag.

The one drawback to this solution is that when you drag/resize your form, you do not see the effect on the controls until you let go of the Resize drag cursor. So it is not as "seamless" as the composite flag. Nonetheless, I think it will solve your problem, because the WM_SETREDRAW message should (but I haven't proven) fire the OnDrawItem event you need.

[Mecena]

thanx, i'll give it a try!

M.

If someone else has a direct answer, please jump in.

This is not a direct answer, but perhaps a workaround.
If you've read through the entire post on MSDN : Flicker-Free Painting you probably already know that the composite painting flag is not compatible with Vista, and presents several other quirks, such as what you have pointed out.

The workaround I have gone with is this:
- Override the Form.OnResizeBegin method:
- Loop through each visible control on the form and stop its drawing with the WM_SETREDRAW(0) message.
- Override the From.OnResizeEnd method:
- Redraw the controls by sending the WM_SETREDRAW(1) message.

I do not propose this is the only way to stop flicker or the best, but it avoids the issues with the CompositePaint flag.

The one drawback to this solution is that when you drag/resize your form, you do not see the effect on the controls until you let go of the Resize drag cursor. So it is not as "seamless" as the composite flag. Nonetheless, I think it will solve your problem, because the WM_SETREDRAW message should (but I haven't proven) fire the OnDrawItem event you need.

[Mecena]

i tried your solution, but unfortunately it doesn't improve quality in the way compositing style does, and there are unwelcome side effects; it does howerver resolve the OnDrawItem issue, all goes well there..
thanx anyway!

If someone else has a direct answer, please jump in.

This is not a direct answer, but perhaps a workaround.
If you've read through the entire post on MSDN : Flicker-Free Painting you probably already know that the composite painting flag is not compatible with Vista, and presents several other quirks, such as what you have pointed out.

The workaround I have gone with is this:
- Override the Form.OnResizeBegin method:
- Loop through each visible control on the form and stop its drawing with the WM_SETREDRAW(0) message.
- Override the From.OnResizeEnd method:
- Redraw the controls by sending the WM_SETREDRAW(1) message.

I do not propose this is the only way to stop flicker or the best, but it avoids the issues with the CompositePaint flag.

The one drawback to this solution is that when you drag/resize your form, you do not see the effect on the controls until you let go of the Resize drag cursor. So it is not as "seamless" as the composite flag. Nonetheless, I think it will solve your problem, because the WM_SETREDRAW message should (but I haven't proven) fire the OnDrawItem event you need.

[mldisibio]

Bummer. Let me just ask a few more things before I abandon you to the flicker netherworld.

- Did you remove the Composite flag before you tried my solution?
- Did you set the DrawMode property correctly (OwnerDrawFixed)?
- Is your flicker problem on the intial drawing or during resizing?
- If the problem is during the initial drawing of the control, and since you are doing your own painting, have you tried the double-buffering technique without the composite flag?

I realize that the OnDrawItem is somewhat of an "iteration" method...one for each tab or list item...so double buffering may not even be possible because it assumes you are drawing everything at once...I'm just throwing out ideas here that maybe get you thinking of a different workaround.

[Mecena]

to answer yr questions:
- yes i did, in fact i tried both combos
- DrawMode is set to OwnerDrawFixed
- flickering is related to initial drawing, resizing is disabled
- double buffering using SetStyles doesn't help, tried that too.. only i switch it on every control type i'm using (since i have my own wrappers).. maybe if i tried that..

i do have an alternative solution which i've implemented to resolve flicker during initialization and that is fading, but it is cca 250 ms slower than normal loading, and i want my forms to be super-responsive; but fading doesn't solve flicker during i.e. tabpage switching etc.

i'll try double buffering all my wrappers and reapply yr solution.

Bummer. Let me just ask a few more things before I abandon you to the flicker netherworld.

- Did you remove the Composite flag before you tried my solution?
- Did you set the DrawMode property correctly (OwnerDrawFixed)?
- Is your flicker problem on the intial drawing or during resizing?
- If the problem is during the initial drawing of the control, and since you are doing your own painting, have you tried the double-buffering technique without the composite flag?

I realize that the OnDrawItem is somewhat of an "iteration" method...one for each tab or list item...so double buffering may not even be possible because it assumes you are drawing everything at once...I'm just throwing out ideas here that maybe get you thinking of a different workaround.