View source for Forms & Dialogs

{{PageHeader|Form Window & DialogBox}}


__TOC__


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{{TipHeader|How to drag a window without a caption}}
See:

{{WikiLink
|URL=https://wiki.tdcommunity.net/index.php?title=Win_messages#How_to_drag_a_window_without_a_caption
|TEXT=How to drag a window without a caption
}}


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{{TipHeader|How to force a window on the taskbar}}
When a top-level window is created without a specific parent (hWndNULL) the window will be visible on the Windows taskbar.<br>
Windows created using a parent, will not be shown.<br>
<br>
To be able to use a parent while creating a window AND having it placed on the taskbar, use the following:<br>
On creation of the window, set the GWL_EXSTYLE to WS_EX_APPWINDOW.<br>
<br>
Beware, a top level window with accessories enabled has a different internal window hierarchy compared to<br>
a window without accessories.<br>
For top level windows having accessories, hWndForm should be changed to the parent of hWndForm.<br>
You can not use SalParentWindow, that function will return the owner of the window.<br>
You need to call GetParent from WinApi as declared above.<br>
<br>
So, declare these external functions and system constants:<br>
<pre>
Library name: USER32.DLL
   Function: GetWindowLongA
      Export Ordinal: 0
      Returns
         Number: LONG
      Parameters
         Window Handle: HWND
         Number: INT

   Function: SetWindowLongA
      Export Ordinal: 0
      Returns
         Number: LONG
      Parameters
         Window Handle: HWND
         Number: INT
         Number: LONG

   Function: GetParent
      Export Ordinal: 0
      Returns
         Window Handle: HWND
      Parameters
         Window Handle: HWND


Constants
   System
      Number: GWL_EXSTYLE	= -20
      Number: WS_EX_APPWINDOW	= 0x00040000
</pre>

For top level windows without accessories enabled, do this:<br>
set the WS_EX_APPWINDOW style to the window (hWndForm) at creation:<br>

<pre>
On SAM_Create
   Call SetWindowLongA( hWndForm, GWL_EXSTYLE, GetWindowLongA( hWndForm, GWL_EXSTYLE ) | WS_EX_APPWINDOW )
</pre>

For top level windows WITH accessories enabled, do this:<br>
set the WS_EX_APPWINDOW style to the parent window of hWndForm at creation:<br>

<pre>
On SAM_Create
   Call SetWindowLongA( GetParent( hWndForm ), GWL_EXSTYLE, GetWindowLongA( GetParent( hWndForm ), GWL_EXSTYLE ) | WS_EX_APPWINDOW )
</pre>

The window will then be shown on the taskbar.


Here you can download a sample:

{{Download
|URL=https://samples.tdcommunity.net/index.php?dir=&file=WIKI_ShowWindowOnTaskbarWithAccessories.zip
|TEXT=WIKI_ShowWindowOnTaskbarWithAccessories.zip
}}


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{{TipHeader|Simulating a 'modal' form window}}
For dialogs we have flavors 'Modal' and 'Modeless'.<br>
A modal dialog is created using SalModalDialog. The execution will continue after the dialog has been closed.<br>
The modeless dialog is created using SalCreateWindow which will continue execution after the dialog is created.<br>


We do not have a 'modal' form window type, they are for default always modeless. So your application will not wait until the form is closed.<br>


But why not use a modal dialog when we need a window to "halt" your execution until it is closed?<br>
Well, there are some differences between dialogs and form windows. One of them is that a dialog does not have a menu strip and does not have<br>
a system menu (minimize, maximize).<br>
So when using a modal dialog, you will have to take those "limitations".<br>


Using this simple trick, we can "simulate" a modal form window:<br>


First create a modal dialog and hide it. On the SAM_CreateComplete of that modal dialog, you create the needed form window.<br>
Because the modal dialog is still open, the execution will wait until the hidden modal dialog is closed.<br>
Now, when closing the form window, notify the hidden dialog that the form has been closed. Then the dialog will end itself.<br>
After the hidden dialog has closed, the execution will continue.<br>


This may come in handy when you have a form window which is used in different workflows. For instance, a form window is used to display images.<br>
In one workflow you need to create a floating window in your application, while the user is executing other tasks. In this case you need a "normal" form window.<br>
In the other workflow, you want to display the image using the same form, but now the application should wait until the form is closed.<br>
By using this trick you can achieve this, so reusing the same form as "modeless" and "modal" flavors.<br>


Here you can download a sample:

{{Download
|URL=https://samples.tdcommunity.net/index.php?dir=&file=WIKI_ModalForm.zip
|TEXT=WIKI_ModalForm.zip
}}


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{{TipHeader|Prevent window disable when modal dialog is created}}
When a modal dialog is created, all top level windows currently open (forms/dialogs) are disabled until the modal dialog is closed.<br>
You might want specific windows to remain accessible, even when a modal dialog is created.<br>
For instance, if you have a floating window having functions which should always be accessible by the user, independent of modal dialogs.<br>
Or you have a log/trace window which should never be disabled by the application workflow.


With a fairly simple trick you are able to prevent windows being disabled on creation of modal dialogs.


On creation of a modal dialog, every top level window which is currently open will be disabled and will receive the Windows API message : WM_ENABLE.
This message is to inform the window that it has been disabled or enabled.


The trick is just to enable the window when it receives WM_ENABLE on indication that the window was disabled.<br>
First define the Windows message constant:

<pre>
Constants
   System
      Number: WM_ENABLE = 0x000A
</pre>

Then code under message actions for the window which should never be disabled:

<pre>
On WM_ENABLE
   If wParam = FALSE
      Call SalEnableWindow( hWndForm )
</pre>

(The wParam contains TRUE when the window was enabled and FALSE when it was disabled).


This is enough to prevent the top level window ever being disabled.<br>
But we have to take messageboxes into account.<br>
When a SalMessageBox is created, it normally disables all open windows until the messagebox is closed.<br>
When it is needed to retain this feature, so a window will be disabled when a messagebox is displayed, we need to code something extra.


We create a wrapper function for SalMessageBox, called PALMessageBox. This custom function will set a global variable to TRUE just before it calls SalMessageBox.<br>
So when the messagebox is opened and WM_ENABLE will be processed by all other open windows, we can query the global boolean to see if a messagebox was the reason for the disable.<br>
When this is the case, we do not enable the window to keep it disabled as expected:

<pre>
On WM_ENABLE
   If wParam = FALSE AND NOT gbMessageBoxOpen
      Call SalEnableWindow( hWndForm )
</pre>


Unfortunately we have another issue to consider: when a window has a frame (hWndFrame).<br>
On TD 5.1 and up, forms and dialogs having accessories enabled (toolbar, statusbar) will have a frame window around the normal window.<br>
And in this case, the WM_ENABLE is send to the frame window instead of the window itself.<br>
That means, we are unable to code the WM_ENABLE message under message actions, as this will only process messages on hWndForm and not hWndFrame.


To solve this, we need to subclass WM_ENABLE on hWndFrame and send it to hWndForm using subclasser.<br>
When a window is created and it has a frame, do this to subclass the message:

<pre>
On SAM_Create
   Call RegSubclass( hWndFrame, WM_ENABLE, hWndForm, PAM_WMENABLE_SubClassed, SUBCLASS_FLAG_AFTER )
</pre>

This will relay the WM_ENABLE message to hWndForm and will be relayed as the custom user message PAM_WMENABLE_SubClassed.<br>
We code this message then under message actions, just as WM_ENABLE.<br>
Then a framed window will react like expected.


Here you can download a sample (ANSI and UNICODE):

{{Download
|URL=https://samples.tdcommunity.net/index.php?dir=&file=WIKI_ModalDialogNoDisable.zip
|TEXT=WIKI_ModalDialogNoDisable.zip
}}



[[Category:Top Level Windows]]