MFC: How do you Paint a CTabView Background When no tabs exist? - winapi

I what to display some text, probably using DrawText() on to the CTabView client area when no tabs exist to explain why they don't exist. However, CTabView::OnPaint() is not called except once at the app startup. Also when all tabs hidden the CTabView::OnDraw() is not called. I suppose the CMFCTabCtrl may be the one getting the OnPaint() callbacks? But nonetheless, how do you output something to that row/col of a CSplitterWnd occupied by a CTabView when all tabs are not shown (hidden via CMFCTabCtrl::ShowTab()). ??
TIA!!

The tab control works that way that all tab views are hidden - except the one which is open.
Where no tab view is open, none will receive a paint message (nor WM_ERASEBACKGROUND).
You could try implementing your paint stuff in the tab control's OnPaint handler.

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Removing/hiding the toolbar tracking separator

I'm working on adding support in my app for full-height sidebars, as introduced in macOS 11.
The trick is, when the window tab bar is visible, I want to turn the full-height sidebar off. The two don't mix well when the sidebar content is different in each window, as it is in my app. See Xcode for an example of what I want to do (View > Show Window Tab Bar). See Preview for an example of what I want to avoid (open two multi-page PDFs and put them in a single tabbed window).
What's working:
I observe the window's tabbedWindows property, and toggle the fullSizeContentView flag in its styleMask accordingly. Thus the window's style updates as needed when I hide and show the tab bar.
What's not working: I need to have a sidebarTrackingSeparator item in my toolbar in order to have some items above the sidebar. But when fullSizeContentView is off, that item appears as a plain separator. I don't want it to be visible at all in that state.
There isn't a straightforward way to hide a toolbar item, especially if it doesn't have a view, which it turns out this one doesn't.
I tried removing the separator item and re-adding it when the window state toggles, but that leads to Cocoa throwing exceptions, complaining that only one tracking item can be registered at a time. This would seem to be a bug, but Xcode manages it somehow.
So how can I properly toggle my window and toolbar state without having that visible separator?
It looks like I've solved the problem by saving the separator item when I see it in toolbarWillAddItem, and then returning it from toolbar(_:itemForItemIdentifier:willBeInsertedIntoToolbar:) to avoid having a new instance created. That way, removing and re-adding the item works without having exceptions thrown.
The last little snag was to not remove and re-add the separator blindly. The window state may have been preserved across app launches, so I needed to not make assumptions about how the window would initially appear.

How to stop event propagation despite WS_EX_NOACTIVATE?

I have a semi-transparent form (using AlphaBlend) that acts as an overlay. For the user to still be able to interact with the window below I have set WS_EX_NOACTIVATE on my form so all right and left clicks go through to the other window.
However I have a few clickable labels on my form. Clicking those and performing the appropriate action works fine since despite the WS_EX_NOACTIVATE flag the OnClick methods are called, but the click will (obviousely) also propagate to the other window, which I do not want in this case.
So, does anyone know how to "stop" the click being sent through to the window below in case I already handled it in my form ? Basically I would like being able to chose whether the click "belongs to me" and does not get propagated or whether the window below mine receives it.
As Rob explained, WS_EX_NOACTIVATE is not relevant here. Most likely you used WS_EX_TRANSPARENT and that made your window transparent to mouse clicks.
To get finer grained control of mouse click transparency, handle the WM_NCHITTEST message in your top level window. Return HTTRANSPARENT for regions that you want to be "click through". Otherwise return, for example, HTCLIENT.
Wm_ex_NoActivate should be irrelevant here. That just controls whether your window receives the input focus. Indeed, if you start with a scratch program and do nothing but change the extended window style, you'll see that when you click within the bounds of that program's window, the clicks are handled in the usual way, except that the window is never activated; programs behind that window do not receive any click events.
Therefore, to make your label controls eat click events instead of forwarding them to the windows behind them, you need to find out what you did to make them start forwarding those messages and simply stop doing that, whatever that is.

Auto resize a dialog control when parent window is resized WinApi

I am trying to show a web page in a dialog control. All is working fine till I maximize the parent window, the inner control with webpage retains its size and so a blank area is left at the side of window. I want to know is there any WS_* message or something I can use to auto resize control when we resize the main window. I am using resource hacker so may be there can be some trick I should know.
Any help is appreciated.
Thanks.
The application must perform the resize. And it does so when it receives a WM_SIZE message for the parent control.
You are not going to be able change this by modifying the resources in a pre-existing binary. You are going to need to write some code to respond to that message.
The way I'd try seeing as I've never tried to hack something like this in.
Would be to see if the web control had an anchors property.
Its should be being passed a wm-size message, it's just not doing anything with it.
If you anchor all four corners of the webcontrol it should resize relative to it's parent.
The other way this is done is through explicit code that handles a resize event, don't think you could hack that in very easily though.

what happen at background when you click inside a textbox?

Inside a MFC dialog, I have 2 overlapping rows of text boxes (what user can see is only one row). when I clicked a button, i shifted down the row at bottom, so now user can see both rows.
The problem is if I have some data loaded in DoDataExchange() for the text boxes, I wouldn't be able to see them showing when the dialog boots up. But when I click inside the text box, the data shows.
I want to know what exactly happen when I clicked a UI? What drawing functions are invoked at backgrounds? So I can fix my problem.
Thank you.
ZQ
Nothing is drawn when you click, maybe you are seeing an Invalidate() being triggered for some reason that redraws the text boxes. Or maybe the parent control (dialog, I assume) doesn't have WS_CLIPCHILDREN set, or some other funny things are happening with the WS_CLIPXXX flags (they're somewhat of a black art).
More to the point, use Spy++ to check what 'happens' when you click - i.e. the messages that are posted at each point in time.

Why are some items greyed out in Spy++'s Windows view?

To modify a window of another program, I need to find a specific SysTreeView32 in it using EnumChildWindows API call.
When I inspect the window using Spy++, there are a number of SysTreeView32's in it but all are greyed out except one, which is the one I'm looking for.
The following picture is an example of grey items:
Why are the shown items gray and what API call does Spy++ use to know whether it should grey out an item or not?
Those are just non-visible windows - ie HWNDs that don't have the WS_VISIBLE style bit set. They are often worker windows - windows that just exist to process various messages in the background - or in some cases are UI that's yet to become visible. For example, a window that lets you hide or show a toolbar may just hide it by making it invisible rather than destroying it and recreating it later.
In your specific case, the WorkerW could be a placeholder for some other piece of UI that's not needed right now, while the msctl_statusbar32 looks like it's a hidden status bar.

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