window zoom and minimizing oddities

[RobertoBozzolo]

I just came across this message which addresses a problem that has been bothering me for a long time

Specifically: some applications of mine need to run maximized so I use SetPanelAttribute (hparent, ATTR_WINDOW_ZOOM, VAL_MAXIMIZE); to directly show the main panel to full screen. According to the function help, Setting the ATTR_WINDOW_ZOOM attribute always makes the panel visible so I do not need (and actually do not call) DisplayPanel to show the window. So far, so good.

A problem arises when the user tries to minimize the main window, as in some conditions he's not able to restore the window any more, leaving killing the program as the only solution to gain control again. The program however is still running in the background even if minimized.

This happens only if the window is minimized using "Show desktop" button in the taskbar: using window minimize button permits to restore it all the times.

Just to add a bit of salt  if the window is minimized at least once using the minimize button, subsequent uses of Show desktop button do not prevent from restoring it normally! 

Now according to Yves post, if I first call DisplayPanel and then SetPanelAttribute to maximize it this problem do not appear any more. The first tests I made seem to abide by this statement.

Is this the expected behaviour? Can anybody explain why it is happening?

If this is the expected behaviour, in my opinion at least a note should be added to the help stating this risk.

[LuisG]

Hi Roberto,

Yes, this is a known bug (search the page for "37666"). According to the workaround blurb for this bug, it is true that you can avoid this problem by calling DisplayPanel first.

Calling DisplayPanel and then zooming the window could conceivably cause some flashiness, although when I tried it it was barely noticeable. If it is a problem for you, there is some Windows SDK trickery you could do to programmatically shrink down the "normal" size of the window to a minuscule amount and then restore it after maximizing it, so that it will be the desired size when the user restores it. Let me know if you need to do this, and I can try to come up with a working example.

Luis

[Wolfgang]

Ah Luis,

couldn't you have written that this and other bugs will be fixed in the next SP...

[RobertoBozzolo]

Hello Luis,

I would be pleased if you can show me some code about that, since maximizing the window after DisplayPanel has some problems especially with very large screens and complex UIs. If I understand your message correctly you are suggesting to call SetPanelAttribute to display the panel maximized and then reshape it by a few pixels and restore it so that it does not suffer from following iconizations?

[LuisG · Accepted solution]

Yes, that's what I had in mind. The idea was to try to avoid, as much as possible, showing the panel between the DisplayPanel call and the call that then maximizes it (in order to avoid flashiness), and to do this without permanently modifying the original, non-maximized bounds of the panel, so that if and when the user restores it later, it restores to the correct position.

Something like this:

WINDOWPLACEMENT placement;
intptr_t        windowHandle;
Rect            oldPos;

errChk (panelHandle = LoadPanel (0, "User Interface Application.uir", PANEL));

// save non-maximized panel bounds
GetPanelAttribute (panelHandle, ATTR_TOP, &oldPos.top);
GetPanelAttribute (panelHandle, ATTR_LEFT, &oldPos.left);
GetPanelAttribute (panelHandle, ATTR_WIDTH, &oldPos.width);
GetPanelAttribute (panelHandle, ATTR_HEIGHT, &oldPos.height);

// override non-maximized bounds in order to try to avoid showing the panel before it's been maximized.
// If, as a result of this, it ends up being maximized to a monitor other than the desired one,
// you might have to experiment with a different top/left position (or, alternatively, not even try to change the

// top/left and hope that changing the height/width will suffice)
SetPanelPos (panelHandle, -10000, -10000);
SetPanelSize (panelHandle, 1, 1);

// display panel prior to maximizing in order to work around CVI bug
errChk (DisplayPanel (panelHandle));
SetPanelAttribute (panelHandle, ATTR_WINDOW_ZOOM, VAL_MAXIMIZE);

// we can't use CVI function to restore the non-maximized bounds, since it would have the side effect of
// de-maximizing the panel. Therefore, we will use SetWindowPlacement to accomplish the same thing.
// Obtain the current window placement and update only its rcNormalPosition.
GetPanelAttribute (panelHandle, ATTR_SYSTEM_WINDOW_HANDLE, (intptr_t *)&windowHandle);
placement.length = sizeof (WINDOWPLACEMENT);

GetWindowPlacement ((HWND)windowHandle, &placement);
placement.rcNormalPosition.top = oldPos.top;
placement.rcNormalPosition.left = oldPos.left;
placement.rcNormalPosition.right = placement.rcNormalPosition.left + oldPos.width;
placement.rcNormalPosition.bottom = placement.rcNormalPosition.top + oldPos.height;

SetWindowPlacement ((HWND)windowHandle, &placement);

[RobertoBozzolo]

Ok thanks for sharing this code: the first attempts I made confirm that this is what I expect for my application.