Cwnd getdc null

Download Microsoft Edge More info. Contents Exit focus mode. GetDC function winuser. Please rate your experience Yes No. Any additional feedback? In this article. Most Points The Distinguished Expert awards are presented to the top veteran and rookie experts to earn the most points in the top 50 topics.

Join our community to see this answer! Unlock 1 Answer and 8 Comments. Andrew Hancock - VMware vExpert. See if this solution works for you by signing up for a 7 day free trial. What do I get with a subscription? With your subscription - you'll gain access to our exclusive IT community of thousands of IT pros. Each call to the BeginPaint member function must have a matching call to the EndPaint member function. If the caret is in the area to be painted, the BeginPaint member function automatically hides the caret to prevent it from being erased.

Binds the calling object's default simple bound property such as an edit control , as marked in the type library, to the underlying cursor that is defined by the DataSource , UserName , Password , and SQL properties of the data-source control. Binds a cursor-bound property on a data-bound control such as a grid control to a data-source control and registers that relationship with the MFC binding manager.

The BringWindowToTop member function should be used to uncover any window that is partially or completely obscured by any overlapping windows.

Call the SetWindowPos function to change a window's position in the Z-order. The BringWindowToTop function does not change the window style to make it a top-level window. On input, this structure contains the client rectangle. After the method is finished, this structure contains the window rectangle that can contain the specified client rectangle. For more usage restrictions, see AdjustWindowRectEx.

Call this member function to remove a tool tip from the screen if a tool tip is currently displayed. Using this member function has no effect on tool tips managed by your code. Usually called from CDialog::OnInitDialog to center dialog boxes relative to the main window of the application. By default, the function centers child windows relative to their parent window, and pop-up windows relative to their owner.

If the pop-up window isn't owned, it is centered relative to the screen. To center a window relative to a specific window that isn't the owner or parent, the pAlternateOwner parameter may be set to a valid window. Removes CWnd from the chain of Clipboard viewers and makes the window specified by hWndNext the descendant of the CWnd ancestor in the chain.

Selects places a check mark next to or clears removes a check mark from a button, or it changes the state of a three-state button. If nCheck is nonzero, the CheckDlgButton member function places a check mark next to the button; if 0, the check mark is removed.

For three-state buttons, if nCheck is 2, the button state is indeterminate. Selects adds a check mark to a given radio button in a group and clears removes a check mark from all other radio buttons in the group. Determines which, if any, of the child windows belonging to CWnd contains the specified point. This parameter can be a combination of the following values:.

Identifies the child window that contains the point. It is NULL if the given point lies outside of the client area. If the point is within the client area but isn't contained within any child window, CWnd is returned. This member function will return a hidden or disabled child window that contains the specified point. More than one window may contain the given point. Converts the client coordinates of a given point or rectangle on the display to screen coordinates.

The new screen coordinates are relative to the upper-left corner of the system display. The ClientToScreen member function assumes that the given point or rectangle is in client coordinates. This member function is called by RunModalLoop to determine when the modal state should be exited. Nonzero if modal loop is to be continued; 0 when EndModalLoop is called. Creates the specified child window and attaches it to the CWnd object. Use the AfxRegisterWndClass function to register window classes.

User-defined window classes are available in the module where they are registered. The CWnd::OnCreate method is called before the Create method returns, and before the window becomes visible. Can be one of the following values. CreateCaret automatically destroys the previous caret shape, if any, regardless of which window owns the caret.

Once created, the caret is initially hidden. To show the caret, the ShowCaret member function must be called. The system caret is a shared resource. CWnd should create a caret only when it has the input focus or is active. It should destroy the caret before it loses the input focus or becomes inactive. For example, "CIRC3. The name needs to match the same name registered by the control.

In either case, CreateControl converts the string to the corresponding class ID. Sets the value of the control's Caption or Text property if any. It must not be NULL. The default value is NULL , indicating that the control initializes itself without restoring its state from any persistent storage. If not NULL , it should be a pointer to a CFile -derived object which contains the control's persistent data, in the form of either a stream or a storage.

This data could have been saved in a previous activation of the client. The CFile can contain other data, but must have its read-write pointer set to the first byte of persistent data at the time of the call to CreateControl. This data is needed only for creating controls that require a run-time license key.

If the control supports licensing, you must provide a license key for the creation of the control to succeed. The default value is NULL. CreateControl creates an ActiveX control instead of an ordinary window. Only a subset of the Windows dwStyle flags are supported for CreateControl :.

Required if you want the control to be visible immediately, like ordinary windows. A disabled window cannot receive input from the user. Can be set if the control has an Enabled property. Can be set if control has a BorderStyle property. The user can change the keyboard focus from one control in the group to the next by using the direction keys. Dimensions for child windows are relative to the top-left corner of the client area of the parent window.

Dimensions for top-level windows are relative to the top-left corner of the screen. If this parameter is 0, the width is set to the system-defined window-border width.

If this parameter is 0, the height is set to the system-defined window-border height. The parameters nWidth and nHeight specify the caret's width and height in logical units ; the exact width and height in pixels depend on the mapping mode. Using the window-border width or height ensures that the caret will be visible on a high-resolution display.

The CreateGrayCaret member function automatically destroys the previous caret shape, if any, regardless of which window owns the caret. The CreateSolidCaret member function automatically destroys the previous caret shape, if any, regardless of which window owns the caret.

The Windows window isn't created and attached until the CreateEx or Create member function is called. The default window procedure provides default processing for any window message that an application does not process. This member function ensures that every message is processed. Calls the default window procedure, which provides default processing for any window message that an application does not process. It should be called with the same parameters as those received by the window procedure.

Deletes any temporary CWnd objects created by the FromHandle member function. The DestroyWindow member function sends appropriate messages to the window to deactivate it and remove the input focus.

It also destroys the window's menu, flushes the application queue, destroys outstanding timers, removes Clipboard ownership, and breaks the Clipboard-viewer chain if CWnd is at the top of the viewer chain. It does not destroy the CWnd object. DestroyWindow is a place holder for performing cleanup. But even if you override this function in your CWnd -derived class, DestroyWindow isn't necessarily called. If DestroyWindow isn't called in the MFC code, then you have to explicitly call it in your own code if you want it to be called.

Assume, for example, you have overridden DestroyWindow in a CView -derived class. If the window is the parent of any windows, these child windows are automatically destroyed when the parent window is destroyed.

The DestroyWindow member function destroys child windows first and then the window itself. See the example for CWnd::Attach. DlgDirList modifies this string, which should be long enough to contain the modifications. For more information, see the following "Remarks" section. It can be any combination of the following values:. If the exclusive bit is set, only files of the specified type are listed; otherwise normal files and files of the specified type are listed.

In this example, drive is a drive letter, directory is a valid directory name, and filename is a valid filename that must contain at least one wildcard. The wildcards are a question mark?

DlgDirListComboBox modifies this string, so this data shouldn't be in the form of a string literal. See the following "Remarks" section. Specifies the outcome of the function. It is nonzero if a listing was made, even an empty listing. A 0 return value implies that the input string did not contain a valid search path. It fills the list box of the combo box specified by nIDComboBox with the names of all files that match the path given by lpPathSpec. If you specify a zero-length string for lpPathSpec , the current directory will be used and lpPathSpec will not be modified.

It assumes that the list box has been filled by the DlgDirList member function and that the selection is a drive letter, a file, or a directory name. The DlgDirSelect member function copies the selection to the buffer given by lpString. If there is no selection, lpString does not change.

It does not allow more than one filename to be returned from a list box. The list box must not be a multiple-selection list box.

It assumes that the list box has been filled by the DlgDirListComboBox member function and that the selection is a drive letter, a file, or a directory name. If there is no selection, the contents of the buffer are not changed.

Never call this function directly. It is called by the UpdateData member function. Call UpdateData to initialize a dialog box's controls or retrieve data from a dialog box. When you derive an application-specific dialog class from CDialog , you need to override this member function if you wish to utilize the framework's automatic data exchange and validation. The Add Variable wizard will write an overridden version of this member function for you containing the desired "data map" of dialog data exchange DDX and validation DDV global function calls.

To automatically generate an overridden version of this member function, first create a dialog resource with the dialog editor, then derive an application-specific dialog class. Then use the Add Variable wizard to associate variables, data, and validation ranges with various controls in the new dialog box. The wizard then writes the overridden DoDataExchange , which contains a data map. The DoDataExchange overridden member function must precede the macro statements in your source file.

Call this member function from within a window, using a CWnd pointer, in your application's CWinApp::InitInstance function to indicate that the window accepts dropped files from the Windows File Manager or File Explorer. Captures the mouse and tracks its movement until the user releases the left button, presses the ESC key, or moves the mouse outside the drag rectangle around the specified point.

The function determines the coordinates of the drag rectangle by using this point. If the user moved the mouse outside of the drag rectangle while holding down the left button, the return value is nonzero. If the user did not move the mouse outside of the drag rectangle while holding down the left button, the return value is zero. Draws a wire-frame rectangle and animates it to indicate the opening of an icon or the minimizing or maximizing of a window.

The effect is similar to minimizing or maximizing a window. The function draws the window caption into this device context. For a complete list of values, see DrawCaption. If a menu bar is changed after Windows has created the window, call this function to draw the changed menu bar.

See the example for CWnd::GetMenu. MFC's default Active Accessibility support is sufficient for standard windows and controls, including ActiveX controls; however, if your CWnd -derived class contains nonwindowed user interface elements, MFC has no way of knowing about them.

In that case, you must override the appropriate Active Accessibility member functions in your class, and you must call EnableActiveAccessibility in the class's constructor. Enables or disables the dynamic layout manager.

When dynamic layout is enabled, the position and size of child windows can adjust dynamically when the user resizes the window. If you want to enable dynamic layout, you have to do more than just call this method. You also have to provide dynamic layout information which species how the controls in the window respond to size changes. You can specify this information in the resource editor, or programmatically, for each control.

See Dynamic Layout. Can have one of the following values:. Nonzero if the arrows are enabled or disabled as specified. Otherwise it is 0, which indicates that the arrows are already in the requested state or that an error occurred.

If the window has a sibling scroll-bar control, that scroll bar is used; otherwise the window's own scroll bar is used. Simply calling EnableToolTips isn't enough to display tool tips for your child controls unless the parent window is derived from CFrameWnd. See Tool Tips. The default tool tips provided for your windows by EnableToolTips do not have text associated with them. If this parameter is TRUE , the tracking tool tips will be enabled.

Indicates the state before the EnableWindow member function was called. The return value is nonzero if the window was previously disabled. The return value is 0 if the window was previously enabled or an error occurred. Tracking tool tips are tool tip windows that you can dynamically position on the screen. By rapidly updating the position, the tool tip window appears to move smoothly, or "track. If this parameter is TRUE , the window will be enabled. When input is disabled, input such as mouse clicks and keystrokes is ignored.

When input is enabled, the window processes all input. A window must be enabled before it can be activated. For example, if an application is displaying a modeless dialog box and has disabled its main window, the main window must be enabled before the dialog box is destroyed. Otherwise, another window will get the input focus and be activated. If a child window is disabled, it is ignored when Windows tries to determine which window should get mouse messages. By default, a window is enabled when it is created.

After a window has been created, an application can also use the EnableWindow member function to enable or disable the window. An application can use this function to enable or disable a control in a dialog box.

A disabled control cannot receive the input focus, nor can a user access it. The nResult parameter is propagated to the return value from RunModalLoop. The EndPaint member function is required for each call to the BeginPaint member function, but only after painting is complete. If the caret was hidden by the BeginPaint member function, EndPaint restores the caret to the screen. See the example for CWnd::BeginPaint. ExecuteDlgInit will use resources bound to the executing module, or resources from other sources.

However, in certain applications, for example some ActiveX controls, these methods might not be invoked by the framework, and you will need to call FilterToolTipMessage yourself.

For more information, see Methods of Creating Tool Tips. Returns the top-level CWnd whose window class is given by lpszClassName and whose window name, or title, is given by lpszWindowName.

Identifies the window that has the specified class name and window name. It is NULL if no such window is found. The search begins with the next child window in the Z order.

The child window must be a direct child window of hwndParent , not just a descendant window. If this parameter is NULL , all window names match. If the function succeeds, the return value is a pointer to the window object having the specified class and window names. If the function fails, the return value is NULL. Nonzero if the window was active before the call to the FlashWindow member function; otherwise 0. For successive flashing, create a system timer and repeatedly call FlashWindow.

Flashing the CWnd means changing the appearance of its title bar as if the CWnd were changing from inactive to active status, or vice versa. An inactive title bar changes to an active title bar; an active title bar changes to an inactive title bar. Typically, a window is flashed to inform the user that it requires attention but that it does not currently have the input focus. The bInvert parameter should be FALSE only when the window is getting the input focus and will no longer be flashing; it should be TRUE on successive calls while waiting to get the input focus.

This function always returns nonzero for minimized windows. If the window is minimized, FlashWindow will flash the window's icon; bInvert is ignored for minimized windows. If dwTimeout is zero, the function uses the default cursor blink rate. The return value specifies the window's state before the call to the FlashWindowEx function. If the window caption was drawn as active before the call, the return value is nonzero.

Otherwise, the return value is zero. Returns a pointer to a CWnd object when given a handle to a window. If a CWnd object isn't attached to the handle, a temporary CWnd object is created and attached. This function, unlike FromHandle , does not create temporary objects. Called by the framework to retrieve the address of an IDispatch interface for the specified child. Call the base class version and then add the nonwindowed child elements. Override this function in your CWnd -derived class to describe your object's default action.

Called by framework to retrieve a string that describes the visual appearance of the specified object. Override this function in your CWnd -derived class to describe your object. Call the base class version and add your description. Override this function in your CWnd -derived class to provide help text for your object.

Called by the framework to retrieve the full path of the WinHelp file associated with the specified object and the identifier of the appropriate topic within that file. Override this function in your CWnd -derived class to provide help information about your object. Override this function in your CWnd -derived class to identify the keyboard shortcut for your object. Override this function in your CWnd -derived class to return the name of your object.

The variable is set to NULL if no parent exists, or if the child cannot access its parent. The active window or NULL if no window was active at the time of the call.

The pointer may be temporary and shouldn't be stored for later use. The active window is either the window that has the current input focus or the window explicitly made active by the SetActiveWindow member function. For a complete list of possible values, see GetAncestor. If the function succeeds, the return value is a pointer to the ancestor window object. Identifies the window that has the mouse capture. It is NULL if no window has the mouse capture. Only one window has the mouse capture at any given time.

A window receives the mouse capture when the SetCapture member function is called. This window receives mouse input whether or not the cursor is within its borders.

Retrieves the client coordinates of the caret's current position and returns them as a CPoint. CPoint object containing the coordinates of the caret's position. Copies the client coordinates of the CWnd client area into the structure pointed to by lpRect. The left and top members will be 0. The right and bottom members will contain the width and height of the window. The client coordinates specify the upper-left and lower-right corners of the client area. Since client coordinates are relative to the upper-left corners of the CWnd client area, the coordinates of the upper-left corner are 0,0.

See the example for CWnd::IsIconic. Identifies the window that owns the Clipboard if the function is successful. Otherwise, it is NULL. Identifies the window currently responsible for displaying the Clipboard if successful; otherwise NULL for example, if there is no viewer. You shouldn't release this IUnknown pointer. Typically, you would use to obtain a specific interface of the control.

The interface pointer returned by GetControlUnknown isn't reference-counted. Returns a pointer to the message this window is currently processing. Should only be called when in an On Message message-handler member function.

Returns a pointer to the MSG structure that contains the message the window is currently processing. Should only be called when in an On Message handler. Retrieves a pointer to a common, class, or private device context for the client area depending on the class style specified for the CWnd. For common device contexts, GetDC assigns default attributes to the context each time it is retrieved.

For class and private contexts, GetDC leaves the previously assigned attributes unchanged. The device context can be used in subsequent graphics device interface GDI functions to draw in the client area. Unless the device context belongs to a window class, the ReleaseDC member function must be called to release the context after painting. This value is used for drawing during tracking.

This value sets the device context's origin to the upper-left corner of the CWnd window. The device context for the specified window if the function is successful; otherwise NULL.

This function, which is an extension to the GetDC function, gives an application more control over how and whether a device context for a window is clipped. Unless the device context belongs to a window class, the ReleaseDC function must be called to release the context after drawing.

Since only five common device contexts are available at any given time, failure to release a device context can prevent other applications from gaining access to a device context. The device context render target for the specified window if the function is successful; otherwise NULL.

For more information on temporary windows see Technical Note 3. This member function searches the entire tree of child windows, not only the windows that are immediate children. Identifies the Windows desktop window. This pointer may be temporary and shouldn't be stored for later use. The desktop window covers the entire screen and is the area on top of which all icons and other windows are painted. Returns the window or control ID value for any child window, not only that of a control in a dialog box.

The numeric identifier of the CWnd child window if the function is successful; otherwise 0. Since top-level windows do not have an ID value, the return value of this function is invalid if the CWnd is a top-level window.

A pointer to the given control or child window. Find centralized, trusted content and collaborate around the technologies you use most.

Connect and share knowledge within a single location that is structured and easy to search. But in this case you may not need a temporary dc. You can simply use the desktop dc, as long as you are not writing on the desktop dc, or not selecting anything in to desktop dc. As for temporary windows, dummyWnd. It will however end in resource leak because ReleaseDC is never called. Since the font will be drawn on specific windows, the device context of the windows will be required for correct drawing.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Create CWnd in library Ask Question.