C / C++ / MFC

How to handle drawing into bitmaps and PAINT issues

14-Jul-09 9:08

tuan1111 wrote:
Vietnam

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dhomas13-Jul-09 16:05

Re: How to handle drawing into bitmaps and PAINT issues

13-Jul-09 16:05

I've created an application that loads a bitmap, and draws on it using various graphics functions (text, bitmap, etc) depending on various things that the user does (pressing keys, clicking buttons, etc). I was able to implement most everything I wanted to do, but there are problems related to not having used OnPaint, so when other windows cover my window, as expected the graphics I drew disappear. I understand the reason this happens, but I'm not quite sure what the simple work around is.

I can't do all my drawing in OnPaint, because well that would be weird. Smile | :)

I've started with a standard MFC Dialog App with a CStatic control. Here's fake code basics of what I have in OnInit():

CBitmap bmpIntro;
bmpIntro.LoadBitmap(IDB_Intro);

CStatic c_Image;
c_Image.SetBitmap(bmpIntro);

Now, problem #1 is that I want to put some intro text on this bitmap to appear when the window first opens. Putting it in OnInit() or OnPaint() doesn't seem to work.

The other problem is that as things progress, I'm using c_Image.GetDC() to draw all kinds of stuff into the CStatic control, and at any given moment, anything could be displayed depending on what the user initiated. Too much for OnPaint() to know what to recreate.

Since the CStatic already knows how to OnPaint() the original bitmap back into the dialog, is there a way I can draw into the original bitmap, so I don't have to worry about OnPaint() myself? And then somehow tell the CStatic to update itself? Or possibly I draw everything twice, once into the CStatic, and once into the original bitmap it is using.

Again, this seems kludgy, surely there's a more sensible way? And then how also to resolve problem #1?

modified on Monday, July 13, 2009 10:43 PM

«_Superman_»13-Jul-09 16:57

Re: How to handle drawing into bitmaps and PAINT issues

13-Jul-09 16:57

dhomas wrote:
I can't do all my drawing in OnPaint, because well that would be weird.

It is not weird for Windows.

If all your drawing is in the CStatic control, derive your own class class from CStatic, override its OnPaint method and do your drawing there.

«_Superman_»
I love work. It gives me something to do between weekends.

dhomas13-Jul-09 17:03

Re: How to handle drawing into bitmaps and PAINT issues

13-Jul-09 17:03

That would be very complex, since OnPaint() wil have no idea what it has to draw as I explained already.

«_Superman_»13-Jul-09 17:07

Re: How to handle drawing into bitmaps and PAINT issues

13-Jul-09 17:07

In this scenario what would be appropriate is to set a variable to different values depending on user actions.
And in the OnPaint you could have a switch statement.

switch (action)
{
   case 1:
      // Draw some text
      break;

   case 2:
      // Draw another bitmap
      break;
   .
   .
   .
}

Whenever the user initiates an action -

action = 1;
static.Invalidate();

«_Superman_»
I love work. It gives me something to do between weekends.

dhomas13-Jul-09 17:14

Re: How to handle drawing into bitmaps and PAINT issues

13-Jul-09 17:14

And how does that resolve repainting when another window overlaps this application. It still has no idea what to draw. Keeping a list of all the actions is simply not sensible. The simple approach seems to somehow be in drawing into the original bitmap, and copying from that back into the control when repainting is needed. But, I can't figure out how to do that. And can't find any other approach.

«_Superman_»13-Jul-09 17:27

Re: How to handle drawing into bitmaps and PAINT issues

13-Jul-09 17:27

I don't understand your exact requirement, but how would you do a reverse of a particular user action if you draw into the original bitmap.

Let us say the user clicked a check box and you want to display the text "Image checked" on the bitmap.
Now you want to remove the text if the user unchecks the checkbox.

If you do not have such a situation where an action will be undone, you could draw onto the original bitmap.

To modify the bitmap, I guess you just need to create a CDC object and use CDC::SelectObject to select the CBitmap object into it. Now you could use the drawing function of the CDC class to draw on the bitmap.

«_Superman_»
I love work. It gives me something to do between weekends.

dhomas13-Jul-09 17:52

Re: How to handle drawing into bitmaps and PAINT issues

13-Jul-09 17:52

I don't need to reverse any actions. Okay here's an analogy...

You have a black chalkboard. It's got nothing on it. A bunch of people go up to the chalkboard and write all over it. At some point, someone pulls down a screen in front of part of the chalkboard. The problem is... when the screen is put back up, the part of the chalkboard that was covered is now erased.

How do I code to resolve that issue.

«_Superman_»13-Jul-09 18:03

Re: How to handle drawing into bitmaps and PAINT issues

13-Jul-09 18:03

dhomas wrote:
when the screen is put back up

This is what I meant by reverse an action.

«_Superman_»
I love work. It gives me something to do between weekends.

dhomas13-Jul-09 18:07

Pausing the Application until a OK Button is pressed?

13-Jul-09 18:07

This seems to suggest an approach that may work...

http://www.codeguru.com/forum/showthread.php?t=305095[^]

dipuks13-Jul-09 13:02

dipuks

13-Jul-09 13:02

Hello

I am working on a Win32 Application in Visual Studio 2003 environment.

I want the whole app to wait until USER click an OK button on the screen.

This app has multiple threads running simultaneously. So is it possible to stop the whole app until an OK button is pressed?

Re: Pausing the Application until a OK Button is pressed?

Stuart Dootson13-Jul-09 13:23

Stuart Dootson

13-Jul-09 13:23

you could suspend[^] all your threads (EXCEPT the UI thread, of course!) when you start the wait and resume[^] them if OK is pressed?

Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p

why we can't overload .,->, :: operators?

sam_psycho13-Jul-09 9:51

sam_psycho

13-Jul-09 9:51

why we can't overload .,->, :: operators?

Re: why we can't overload .,->, :: operators?

David Crow13-Jul-09 9:54

Re: why we can't overload .,->, :: operators?

13-Jul-09 9:54

The -> operator can be overloaded. The others cannot. See here for why.

sam_psycho13-Jul-09 10:09

sam_psycho

13-Jul-09 10:09

Thnx very good link....i got many things cleared Smile | :)

VC++ -- Minimize all windows within MDI

blueflame21313-Jul-09 8:38

13-Jul-09 8:38

Hello,
I'm having problems with minimizing all windows within an MDI at the same time. I can loop through all open windows and minimize them one at a time (but that causes lots of delay with more than 5 windows, as they all go one after the other).

I can minimize the whole application with:
::SendMessage(pMainFrame->m_hWnd, WM_SYSCOMMAND, SC_MINIMIZE, 0);

or I can minimize individual active frames with:
::SendMessage(pMainFrame->GetActiveFrame()->m_hWnd, WM_SYSCOMMAND, SC_MINIMIZE, 0);

But how do I minimize them all at once?

Thanks for your help,
Dave

David Crow13-Jul-09 9:08

13-Jul-09 9:08

That's not a standard message but an application-specific thing. As far as I know, closing them one at a time is your only option.

Just for grins, what would happen if you posted the message instead:

::PostMessage(pMainFrame->GetActiveFrame()->m_hWnd, WM_SYSCOMMAND, SC_MINIMIZE, 0);

pMainFrame->GetActiveFrame()->PostMessage(WM_SYSCOMMAND, SC_MINIMIZE, 0);

blueflame21313-Jul-09 9:30

13-Jul-09 9:30

Both just minimize the active frame (window), and not all frames.

I thought there would be something more standard(MFC) I could just send to the mainFrame which handles it all, similar to the way MFC handles tiling or cascading windows.

David Crow13-Jul-09 9:33

13-Jul-09 9:33

blueflame213 wrote:
Both just minimize the active frame (window), and not all frames.

Didn't you put it in a loop?

blueflame21313-Jul-09 9:42

13-Jul-09 9:42

Sorry, I may not have been clear enough,

When minimizing a window, it shows the animation of the window title bar being minimized to the bottom.

When looping through all windows to minimize, the delay of having to watch each window individually be minimized becomes significant with many windows open.

I was wondering if there was something which would minimize all windows at once, without having to sit through each window displaying its "minimization animation".

I appreciate your help so far!

David Crow13-Jul-09 9:52

13-Jul-09 9:52

blueflame213 wrote:
Sorry, I may not have been clear enough,

No, you were perfectly clear. It's just that you said in the initial post, "I can loop through all open windows and minimize them one at a time" but in your last post you said, "Both just minimize the active frame (window), and not all frames." I assumed you removed the loop in the latter post, hence my confusion.

My suggestion to post the message instead of sending it was not meant to solve the problem but rather to minimize the perception of a delay.

If you had an example of an application that minimizes all open frames at once, you might could spy on it and see what messages, if any, are being used.

blueflame21313-Jul-09 10:36

13-Jul-09 10:36

Found a solution with using

ShowWindow(SW_HIDE) first and then ShowWindow(SW_MINIMIZE),
This way XP doesn't show it's "minimizing animation" while minimizing, and it speeds everything up significantly!

Thanks for all of your help!!

David Crow13-Jul-09 10:40