Custom Controls | Catch. A custom control is any child window which displays information or allows the user to interact with it in some way. This article describes the steps required to create a custom user control from scratch, using pure Win. This custom control will not be an Active. Creating A Windows ImageI want to program in Win32.How do I create a child window inside another program with an OpenGL canvas? . Is it possible to create child window in opengl.Validity of creating a Child window in a separate process to the parent (COM/win32) I have a COM based local-server (.exe) with say a method. X control, or possess any other magical properties. Rather, we will be creating a simple control, similar to the way edit controls, buttons or listboxes work. The example control we will build will be a simple text label, but will change colour whenever the user clicks on it. This simple example will be sufficient to help explain all the steps necessary to create any custom control. Getting Started. A custom control is nothing special. It is just a standard window, but created with the WS_CHILD style set. ![]() The custom part comes in because we write a new window procedure to provide the necessary control display and interaction. So, first things first. We're going to create a new source- file to put just the custom- control code in. ![]() Call this Cust. Ctrl. If you take this modular approach from the start you will find it so much easier to develop and maintain your code. This source file just needs to contain the following two lines for now. The < tchar. h> file enables us to write Unicode- compatible windows programs. In a few places in the code, you will see things like "TCHAR" and "_T". These are macros defined in < tchar. Unicode applications, if we want. Our custom control won't be Unicode, but it could be if we used the correct compiler settings. In order to create a new type of window, we need to register a new window class. This is achieved with the Register. Class. Ex API call, shown below. TCHAR sz. Class. Name[] = _T("Cust. Ctrl. 34. 5"). void Init. Creating A Window In Java![]() Custom. Control(). WNDCLASSEX wc. wc. Size = sizeof(wc). Class. Name = sz. I was trying without any success to create a child window with a menu bar in it. However, according to MSDN documentation windows with WS_CHILD styl. 2797567. · Hi, I'm wondering if the following idea would be possible: I have a win32 App(A) and from that I start another win32 App(B) using the CreateProcess call. Class. Name. wc. h. Instance = Get. Module. Handle(0). Wnd. Proc = Cust. Wnd. Proc. wc. h. Cursor = Load. Cursor (NULL, IDC_ARROW). Icon = 0. wc. Menu. Name = 0. wc. Background = (HBRUSH)Get. Sys. Color. Brush(COLOR_BTNFACE). Cls. Extra = 0. Wnd. Extra = 0. Icon. Sm = 0. Register. Class. Ex(& wc). So far so good. The next step is to write a window procedure (Cust. Wnd. Proc) which the custom control uses to process it's messages. This is just a standard window procedure, like the one shown below. LRESULT CALLBACK Cust. Wnd. Proc(HWND hwnd, UINT msg, WPARAM w. Param, LPARAM l. Param). Def. Window. Proc(hwnd, msg, w. Param, l. Param). Now, it may look as if this window procedure doesn't actually do anything, but this is not the case. The Def. Window. Proc API call performs alot of default processing (window focus, painting, activation etc) for a window. It is only when we need to provide additional functionality (like drawing the window focus) that we need to start filling in that switch statement to handle specific windows messages. Creating the control. Now we can create a custom control! There are two ways to do this.The first is to manually create the control at run- time (probably in the main window's WM_CREATE message, or something similar).This is achieved with the Create. here. Window. Ex API call, like this. HWND Create. Custom. Control(HWND hwnd. Parent). HWND hwnd. Ctrl. hwnd. Ctrl = Create. Window. Ex(. WS_EX_CLIENTEDGE, // give it a standard border. Class. Name. _T("A custom control"). WS_VISIBLE | WS_CHILD. Parent. NULL, Get. Module. Handle(0), NULL. Ctrl. }The second way, assuming you are using some kind of resource editor (like in Visual C++), is to create a custom control in a dialog template, in the exact same way you might place edit controls or list boxes on a dialog box. The only difference is, you create a "Custom Control", and manually define the name of the window class (in this case, "Cust. Ctrl. 34. 5"). When your dialog is created, Windows automatically creates the custom control for you, and gives it a control ID. Custom control state information. At some point in time, you will want to make the control do something. And, unless your control is going to be extremely simple, you will undoubtably want to define variables, text strings or arrays to represent the state of the control. For example, in a custom list control, you would at the very least need to keep track of the items in the list, using an array or linked list. You would also need a variable which keeps track of how many items there are in your list. In addition, if you want your control to be scrollable, you will need to keep track of the scrollbar position, and the minimum and maximum scroll ranges. You need to take my word that you will need to define a structure (or class, if you are using C++) which will encapsulate ALL of the control's state information. If you take this approach (and avoid using global variables), you will be able to create multiple custom controls at the same time, and each one will look after itself. We need to decide what attributes our custom control will have. The list below describes these attributes. Text colour (Foreground and Background). Display text (what the control actually displays). Font (what type- face the text will be drawn in)The following structure will hold some simple state information. COLORREF cr. Fore. Gnd; // Foreground text colour. COLORREF cr. Back. Gnd; // Background text colour. HFONT h. Font; // The font. HWND hwnd; // The control's window handle. Cust. Ctrl; The one element missing from this structure is the display text. For our simple example, this is not necessary, because every window has it's own window text. Therefore we will just use this standard window text when we draw the control. For more complicated controls (lists, edit controls), you would need to store the text yourself. Associating a structure with the custom control. At this point you will hit a stumbling block. The problem is, your custom window procedure is a simple callback function, which processes all messages for all custom controls you create. Depending on which window is currently having it's message processed, we will have to obtain the correct state structure for that window, and use that structure when processing the message. There are many ways to "attach" a structure to a window. Which one you use can depend on many things, but I will describe each method below. First though, we will define two simple functions, which will set and retrieve our custom structure for a window. Cust. Ctrl * Get. Cust. Ctrl(HWND hwnd). Cust. Ctrl *ccp = ??? Set. Cust. Ctrl(HWND hwnd, Cust. Ctrl *ccp). // attach pointer to window. The GWL_USERDATA area. Every window in the system has a 3. This 4 byte storage area is enough to store a pointer to a structure. We set this integer using Set. Window. Long, and retrieve the integer using Get. Window. Long. Using this technique, our function will look like this. Cust. Ctrl * Get. Cust. Ctrl(HWND hwnd). Cust. Ctrl *)Get. Window. Long(hwnd, GWL_USERDATA). Set. Cust. Ctrl(HWND hwnd, Cust. Ctrl *ccp). Set. Window. Long(hwnd, GWL_USERDATA, (LONG)ccp). This method is usually used when subclassing a control rather than writing one from scratch, because there are better alternatives. The problem with this method is that any application or window can set this user- data- area, so you need to be careful it is never used by two conflicting components. Window Properties. Window properties allow a program to attach multiple 3. In actual fact, a window property is really a HANDLE value (i. GDI resource). However, a HANDLE is still a 3. HANDLE. TCHAR sz. Prop. Name[] = _T("Cust. Ctrl. Ptr"). Cust. Ctrl * Get. Cust. Ctrl(HWND hwnd). return (Cust. Ctrl *)Get. Prop(hwnd, sz. Prop. Name). void Set. Cust. Ctrl(HWND hwnd, Cust. Ctrl *ccp). Set. Prop(hwnd, sz. Prop. Name, (HANDLE)ccp). This method will be a little slower than the rest, simply because of the string comparisons that windows will have to do when it retrieves a window property for us. It's not much slower though, and because we only need to do this once for every message we receive, it's not much of an overhead at all. Extra window bytes. This is the best way to go if you are writing a control from scratch. When you initially register a control's window class, you have the option of specifying how many extra bytes of user- storage each window of that class will contain. If we set this value to be the size of a pointer (to our state structure), then we can use this special- purpose space exclusively for our custom control. This then leaves the GWL_USERDATA area for other purposes. Register the window class. Wnd. Extra = sizeof( Cust. Create. Window function (Windows)Creates an overlapped, pop- up, or child window. It specifies the window class, window title, window style, and (optionally) the initial position and size of the window. The function also specifies the window's parent or owner, if any, and the window's menu. To use extended window styles in addition to the styles supported by Create. Window, use the Create. Window. Ex function. Syntax. HWND WINAPI Create. Window(. _In_opt_ LPCTSTR lp. Class. Name. _In_opt_ LPCTSTR lp. Window. Name. _In_ DWORD dw. Style. _In_ int x. In_ int y. In_ int n. Width. _In_ int n. Height. _In_opt_ HWND h. Wnd. Parent. _In_opt_ HMENU h. Menu. _In_opt_ HINSTANCE h. Instance. _In_opt_ LPVOID lp. Param. Parameterslp. Class. Name [in, optional]Type: LPCTSTRA null- terminated string or a class atom created by a previous call to the Register. Class or Register. Class. Ex function. The atom must be in the low- order word of lp. Class. Name; the high- order word must be zero. If lp. Class. Name is a string, it specifies the window class name. The class name can be any name registered with Register. Class or Register. Class. Ex, provided that the module that registers the class is also the module that creates the window. The class name can also be any of the predefined system class names. For a list of system class names, see the Remarks section. Window. Name [in, optional]Type: LPCTSTRThe window name. If the window style specifies a title bar, the window title pointed to by lp. Window. Name is displayed in the title bar. When using Create. Window to create controls, such as buttons, check boxes, and static controls, use lp. Window. Name to specify the text of the control. When creating a static control with the SS_ICON style, use lp. Window. Name to specify the icon name or identifier. To specify an identifier, use the syntax "#num". Style [in]Type: DWORDThe style of the window being created. This parameter can be a combination of the window style values, plus the control styles indicated in the Remarks section. Type: int. The initial horizontal position of the window. For an overlapped or pop- up window, the x parameter is the initial x- coordinate of the window's upper- left corner, in screen coordinates. For a child window, x is the x- coordinate of the upper- left corner of the window relative to the upper- left corner of the parent window's client area. If this parameter is set to CW_USEDEFAULT, the system selects the default position for the window's upper- left corner and ignores the y parameter. CW_USEDEFAULT is valid only for overlapped windows; if it is specified for a pop- up or child window, the x and y parameters are set to zero. Type: int. The initial vertical position of the window. For an overlapped or pop- up window, the y parameter is the initial y- coordinate of the window's upper- left corner, in screen coordinates. For a child window, y is the initial y- coordinate of the upper- left corner of the child window relative to the upper- left corner of the parent window's client area. For a list box, y is the initial y- coordinate of the upper- left corner of the list box's client area relative to the upper- left corner of the parent window's client area. If an overlapped window is created with the WS_VISIBLE style bit set and the x parameter is set to CW_USEDEFAULT, then the y parameter determines how the window is shown. If the y parameter is CW_USEDEFAULT, then the window manager calls Show. Window with the SW_SHOW flag after the window has been created. If the y parameter is some other value, then the window manager calls Show. Window with that value as the n. Cmd. Show parameter. Width [in]Type: int. The width, in device units, of the window. For overlapped windows, n. Width is either the window's width, in screen coordinates, or CW_USEDEFAULT. If n. Width is CW_USEDEFAULT, the system selects a default width and height for the window; the default width extends from the initial x- coordinate to the right edge of the screen, and the default height extends from the initial y- coordinate to the top of the icon area. CW_USEDEFAULT is valid only for overlapped windows; if CW_USEDEFAULT is specified for a pop- up or child window, n. Width and n. Height are set to zero. Height [in]Type: int. The height, in device units, of the window. For overlapped windows, n. Height is the window's height, in screen coordinates. If n. Width is set to CW_USEDEFAULT, the system ignores n. Height. h. Wnd. Parent [in, optional]Type: HWNDA handle to the parent or owner window of the window being created. To create a child window or an owned window, supply a valid window handle. This parameter is optional for pop- up windows. To create a message- only window, supply HWND_MESSAGE or a handle to an existing message- only window. Menu [in, optional]Type: HMENUA handle to a menu, or specifies a child- window identifier depending on the window style. For an overlapped or pop- up window, h. Menu identifies the menu to be used with the window; it can be NULL if the class menu is to be used. For a child window, h. Menu specifies the child- window identifier, an integer value used by a dialog box control to notify its parent about events. The application determines the child- window identifier; it must be unique for all child windows with the same parent window. Instance [in, optional]Type: HINSTANCEA handle to the instance of the module to be associated with the window. Param [in, optional]Type: LPVOIDA pointer to a value to be passed to the window through the CREATESTRUCT structure (lp. Create. Params member) pointed to by the l. Param param of the WM_CREATE message. This message is sent to the created window by this function before it returns. If an application calls Create. Window to create a MDI client window, lp. Param should point to a CLIENTCREATESTRUCT structure. If an MDI client window calls Create. Window to create an MDI child window, lp. Param should point to a MDICREATESTRUCT structure. Param may be NULL if no additional data is needed. Return value. Type: Type: HWNDIf the function succeeds, the return value is a handle to the new window. If the function fails, the return value is NULL. To get extended error information, call Get. Last. Error. This function typically fails for one of the following reasons: an invalid parameter valuethe system class was registered by a different module. The WH_CBT hook is installed and returns a failure codeif one of the controls in the dialog template is not registered, or its window window procedure fails WM_CREATE or WM_NCCREATERemarks. Before returning, Create. Window sends a WM_CREATE message to the window procedure. For overlapped, pop- up, and child windows, Create. Window sends WM_CREATE, WM_GETMINMAXINFO, and WM_NCCREATE messages to the window. The. l. Param parameter of the WM_CREATE message contains a pointer to a CREATESTRUCT structure. If the WS_VISIBLE style is specified, Create. Window sends the window all the messages required to activate and show the window. If the created window is a child window, its default position is at the bottom of the Z- order. If the created window is a top- level window, its default position is at the top of the Z- order (but beneath all topmost windows unless the created window is itself topmost). For information on controlling whether the Taskbar displays a button for the created window, see Managing Taskbar Buttons. For information on removing a window, see the Destroy. Window function. The following predefined system classes can be specified in the lp. Class. Name parameter. Note the corresponding control styles you can use in the dw. Style parameter. System class. Meaning. BUTTONDesignates a small rectangular child window that represents a button the user can click to turn it on or off. Button controls can be used alone or in groups, and they can either be labeled or appear without text. Button controls typically change appearance when the user clicks them. For more information, see Buttons. For a table of the button styles you can specify in the dw. Style parameter, see Button Styles. COMBOBOXDesignates a control consisting of a list box and a selection field similar to an edit control. When using this style, an application should either display the list box at all times or enable a drop- down list box. If the list box is visible, typing characters into the selection field highlights the first list box entry that matches the characters typed.
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