C / C++ / MFC

Help de-activating system menu in window

28-Mar-01 15:11

In OnSetCursor, set the cursor if the mousepos is within the desired rect.

Christian

The content of this post is not necessarily the opinion of my yadda yadda yadda.

To understand recursion, we must first understand recursion.

Peter Sjöström28-Mar-01 6:49

Peter Sjöström

28-Mar-01 6:49

I've got a problem. Our software processes some messages in a CPropertySheet derived main window class. When a user presses "ALT" key, the system menu is activated, same thing when user click on the top left window icon, the system menu drops down.

At this stage, when menu is active/down, the window doesn't process any incoming messages. I have written a separate thread that sends heartbeats to check if this state happens and now want to do somthing to de-activate the menu automatically wthout user intervention.

How?

I know that if I click somewhere in the window with the mouse, it de-activates the menu and messages gets processed again.

(Assume this software is run 24 hours a day and operator forgets to check it. By accident an operator press ALT and leaves. Now I want to detect this and fix the state to normal)

Re: Help de-activating system menu in window

Sir Gras of Berger28-Mar-01 9:30

Sir Gras of Berger

28-Mar-01 9:30

IMHO, stuff that needs to be running 24h a day shouldn't be in a UI thread at all. (It probably shouldn't even be in a process that has a UI thread, but in a service.) So put that stuff in a background thread and leave the UI thread to do UI processing only.

If you can't because the messages you need to process are real windows messages (and you can't change that), process them with a different, hidden window -- which you could put in a different UI thread, though I'm not sure that's necessary.

If you take the approach that you want to detect a stalled situation and terminate it, you have to make sure you identify all possible stall situations ahead of time. You've identified one already, and even if there aren't any others now, you or someone else might add one in the future.

By using a different thread and/or window, you're more likely to be able to handle all possible stall situations without failing to process the incoming messages. The UI will get out of sync with data perhaps, but the messages will still be processed.

Re: Help de-activating system menu in window

Peter Sjöström28-Mar-01 21:32

Peter Sjöström

28-Mar-01 21:32

You are right and I agree. However, the code is 6 years old and very complex (read bad). I was just hoping someone had a solution so I won't have to re-write all this code, also risking introducing bugs.

Oh, well, off we go...

Help de-activating system menu in window

Peter Sjöström28-Mar-01 6:48

Peter Sjöström

28-Mar-01 6:48

Flickering...?

Manfred Ramosch28-Mar-01 3:45

28-Mar-01 3:45

// // This is, what I have actually written into my dialog's OnPaint()-function:
//

CClientDC dc(this);

CPen WhitePen;
CPen BlackPen;
CBrush BlackBrush;

WhitePen.CreatePen(PS_SOLID, 1, RGB(255,255,255));
BlackPen.CreatePen(PS_SOLID, 1, RGB(0,0,0));
BlackBrush.CreateSolidBrush(RGB(0,0,0));

CPen* pOriginalPen = dc.SelectObject(&BlackPen);
dc.Rectangle(24, 10, 80, 30);

dc.SelectObject(&BlackBrush);
dc.Rectangle(24, 10, 80, 30);

//
// Instead of the last two lines I've also tried it with:
//

dc.FillSolidRectangle(24, 10, 80, 30 RGB(0,0,0));

//
// How can I get rid of this flickering of the black rectangle in my dialog??? Confused | :confused:

//
//
// Thanks in adv.
//
//
// Manfred
//

---

Programming is knowing...

C^hris L^osinger28-Mar-01 8:17

C^hris L^osinger

28-Mar-01 8:17

override the dialog's OnEraseBackground (use classWizard). just return TRUE.

this will prevent the dialog's background color from being drawn

-c

------------------------------
Smaller Animals Software, Inc.
http://www.smalleranimals.com

Erik Funkenbusch28-Mar-01 12:42

Erik Funkenbusch

28-Mar-01 12:42

A few problems with your code:

First, you should be using CPaintDC in an OnPaint message. This is done automatically by the framework.

Second, You are creating pens and brushes, then selecting them into the DC, but not deselecting them which means that when the CPen is destroyed, it will not delete the pen you created (because it's selected in the DC) and will cause a resource leak.

Manfred Ramosch29-Mar-01 2:31

29-Mar-01 2:31

To your first:

Why should I use CPaintDC instead of CClientCD ?
I'm having a dialog-based application and only want to paint a Piano-keyboard onto
the screen. This I will do once when entering the Dialog. At runtime I will change the
colors of single keys so no need for redrawing the whole keyboard - only single keys...

To your second:

I guess with 'deselecting' you mean 'deleting' my pens and brushes. Because deselecting
happens everytime I select a new Object with the SelectObject() function.

So do I get it right now ???

1 - Every DC has at least one original PEN, BRUSH, FONT, BITMAP and RGN.
2 - When creating a new e.g. PEN/BRUSH I have to store the original PEN/BRUSH with

CPen* pOriginalPen = dc.SelectObject(&NewPen);
CBrush* pOriginalBrush = dc.SelectObject(&NewBrush);

3 - and give it back to the DC at the end of the function.

dc.SelectObject(pOriginalPen);
dc.SelectObject(pOriginalBrush);

4 - Every pen, region, font, bitmap or brush created with e.g.

BlackPen.CreatePen(PS_SOLID, 1, RGB(0, 0, 0));
WhitePen.CreatePen(PS_SOLID, 1, RGB(255, 255, 255));
BlackBrush.CreateSolidBrush(RGB(0, 0, 0);
WhiteBrush.CreateSolidBrush(RGB(255, 255, 255);

5 - must explicitely be deleted with
(respectively AFTER having given my OriginalObjects back to the DC)

BlackPen.DeleteObject();
WhitePen.DeleteObject();
BlackBrush.DeleteObject();
WhiteBrush.DeleteObject();

6 - This means the objects are not deleted automatically at the end of the function.

I wonder why this DC related things are relatively difficult in comparison with other
parts of the MFC. I went through all the DC-related SDK and MSDN stuff and through
several books but this is realy not explained rather clearly in any place.

Hope that someone can get me out of this only-one part I do not realy get in my brain.

Thanks

Manfred

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Programming is knowing... (should be Wink | ;-)

)

Christian Graus29-Mar-01 3:01

29-Mar-01 3:01

1/ You should use CPaintDC because CCLientDC is for getting a DC outside CPaintDC. I know you should never call CPaintDC outside OnPaint, but I admit you'll have to look elsewhere for a definitive answer as to why the reverse is true.

2/ Correct. Also true for bitmaps, but if you only select one bitmap into a DC, you'll never notice.

3/ Also correct.

4&5/ No. They are classes and have destructors. The CDC destructor cannot destory a pen it does not have, but if the DC is deleted in it's originla state, the destructors will do the rest.

6/ The GDI stuff is a thin wrapper on Win32 functions, and so it has not changed much. Although try writing this stuff in Win32 where you DO have to delete everything and it gets a bit harder.

Christian

The content of this post is not necessarily the opinion of my yadda yadda yadda.

To understand recursion, we must first understand recursion.

Erik Funkenbusch29-Mar-01 13:23

Erik Funkenbusch

29-Mar-01 13:23

You must use CPaintDC in OnPaint because CPaintDC calls BeginPaint() and EndPaint() to validate the window regions when a WM_PAINT message is sent.

Look up CPaintDC and read the documentation.

When you select a pen or brush into the DC but do not unselect it (by selecting the original resource), then when the CPen or CBrush goes out of scope, the destructor attempts to delete the brush or pen, but cannot because it's selected in the DC. That means the delete fails and the resource is never deleted.

You don't have to explicitly delete the brushes or pens, since this is done automatically by the destructor of the CPen or CBrush object, so long as the brush or pen is not currently selected in a DC.

Christian Graus28-Mar-01 12:53

28-Mar-01 12:53

The advice you were given re: leaks is spot on, but to stop flickering, you need to double buffer. This means create a new bitmap and DC, draw into it and then copy the whole lot onto your dialog in one Blt at the end. Also, don't call CPaintDC until you're about to do the Blt and you won't need to undermine OnEraseBackground, which can have some nasty side effects. What will happen is this:

CDC myDC;
// Create DC, select bitmap and draw what you want on your dialog

CPaintDC dc(this);
// Background has been erased if necessary
// Now BitBlt from your other DC, so that the effect is immediate and you get no flicker

Christian

The content of this post is not necessarily the opinion of my yadda yadda yadda.

To understand recursion, we must first understand recursion.

Manfred Ramosch29-Mar-01 2:54

29-Mar-01 2:54

OKI

For now I selected the CRgn as my object of desire because

1 - I want to paint a Piano-Keyboard onto the screen in my Dialog
2 - When comparing OnLButtonDown(nFlags, point) with PtInRegion(point)
I can easily find and repaint single keys.
3 - Regions don't flicker - not in BLUE, not in BLACK not in any color

Is there any disadvantage of using Regions ?

Thanks for your help

Manfred

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Programming is knowing...

Christian Graus29-Mar-01 3:06

29-Mar-01 3:06

I've never used regions, but in reading about them, I'm not sure that this is what they are for. However, as I say, I am hardly qualified to comment as I have not used them.

IF they work, then great, unless someone else can shed more light on any disadvantages, but certainly I'd suggest the double buffering method is the way one usually eliminates flicker, and a method you will end up with as the only viable alternative at some stage if your drawing to the screen becomes progressively more complex. I am assuming you're not building a region off screen and then drawing it in one go - if you are, then you've done what I suggested in any case.

Good luck with it.

Christian

The content of this post is not necessarily the opinion of my yadda yadda yadda.

To understand recursion, we must first understand recursion.

Manfred Ramosch29-Mar-01 3:54

29-Mar-01 3:54

Quick answer...

I've defined every key of my piano-keyboard as a region. That means 88 keys(regions).
52 white keys and 36 black keys.

- CRgn-Array as a Member of my Dialog

CRgn KeyRegion[88];

- In the constructor of my dialog I create them all

KeyRegion[KeyNumber].CreateRectRgn();

- so I guess the array gets automatically deleted when destroying the dialog
- should not be leaking...

- In my function OnPaintKeyboard() I paint all my 88 keys

CClientDC dc(this);

CBrush BlackBrush;
BlackBrush.CreateSolidBrush(RGB(0,0,0));
CBrush WhiteBrush;
WhiteBrush.CreateSolidBrush(RGB(255,255,255));

- With...

dc.PaintRgn(&KeyRegion[KeyNumber]);

- I can paint my region in the color of the previous selected Brush-Object e.g.

dc.SelectObject(&BlackBrush);

That looks good to me... - And to you ???

I have a second function OnPaintKey() that paints a single key only - not the whole keyboard.

1 - One Question is wherefrom should I call my OnPaintKeyboard() function so that the whole
keyboard gets painted when the dialog gets visible on screen?

2 - Second Question is wherefrom should I call my OnPaintKeyboard() function so that the whole
keyboard gets correctly redrawn when necessary?(Overlaping windows or Moving and removing out
of the visible screen...)

3 - Third Question: Where can I use my OnPaintKey() function (for a single key!!!) so that not
every key has to be redrawn when only the color of one key changes ?

Manfred

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Programming is knowing...

Christian Graus29-Mar-01 10:26

How do I completely evict help from my project ?

29-Mar-01 10:26

IN terms of initial drawing, you can use ONInitDialog, but the whole system revolves around OnPaint, so that's really where you should do all your drawing. Invalidate() will cause OnPaint to be called, and it is called when the window is shown. INvalidateRect() allows you to get only a portion of the screen redrawn - it also calls OnPaint. If the bool passed to either is true then OnEraseBackground is called first.

So you should call from OnPaint and force single key redraw by invalidating a region instead of the dialog.

Christian

The content of this post is not necessarily the opinion of my yadda yadda yadda.

To understand recursion, we must first understand recursion.

Christian Graus27-Mar-01 15:34