Position of child control..?

This is a discussion on Position of child control..? within the Windows Programming forums, part of the Platform Specific Boards category; This seems such a basic question but i cant find the answer anywhere. How do i get the position of ...

  1. #1
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    Position of child control..?

    This seems such a basic question but i cant find the answer anywhere. How do i get the position of a child control RELATIVE to its parent. GetClientRect does not return its position. It sets the left and top fields to 0 all the time. I want to get the same X and Y that i used when i call CreateWindowEx().

    EDIT: even more helpful would be to tell me how i can get the control in the below screenshot to automatically grow and shrink when the user grows and shrinks the window.

    [img=http://img146.imageshack.us/img146/7359/testoi5.th.jpg]
    Last edited by 39ster; 02-23-2008 at 01:53 AM.

  2. #2
    Registered User Codeplug's Avatar
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    http://msdn2.microsoft.com/en-us/library/ms632598.aspx
    See the example code in the "Creating, Enumerating, and Sizing Child Windows" section.

    FYI - There is also GetWindowRect() wich can be used to calculate the coordinates used in the CreateWindow() call.

    gg

  3. #3
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    Quote Originally Posted by Codeplug View Post
    http://msdn2.microsoft.com/en-us/library/ms632598.aspx
    See the example code in the "Creating, Enumerating, and Sizing Child Windows" section.

    FYI - There is also GetWindowRect() wich can be used to calculate the coordinates used in the CreateWindow() call.

    gg
    Thanks. I've tried using GetWindowRect() and MoveWindow() to automatically resize a child control in the WM_SIZE event. For some reason the X and Y are way off and instead of not moving the child at all (by making the X and Y in MoveWindow the same values you get from GetWindowRect()) the child control moves south-east until it goes way past the parents boundaries.

  4. #4
    Registered User Codeplug's Avatar
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    When you call MoveWindow() on child windows, the coordinate parameters are relative to the parent. So (0, 0) is the top-left point on the parent window.

    GetWindowRect() returns coordinates relative to the screen.

    gg

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    ...So GetWindowRect() cant be used to get the position you used in CreateWindow() ? It only works on the main window, not the children. I even tried this and the child still moves south east each time i resize the main window.

    Code:
    		RECT childRect, parentRect;
    		GetWindowRect(canvas.getHandle(), &childRect);
    		GetWindowRect(GetParent(canvas.getHandle()), &parentRect);
    
    		MoveWindow(canvas.getHandle(), childRect.left - parentRect.left,
                        childRect.top - parentRect.top, 50, 50, true);

  6. #6
    Registered User Codeplug's Avatar
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    Code:
    MoveWindow(canvas.getHandle(), childRect.left - parentRect.left,
               childRect.top - parentRect.top, 50, 50, TRUE);
    So that code should keep the canvas at the same X,Y and at 50x50.

    So when is this code being executed? During what message, ect...?

    gg

  7. #7
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    Yes the X and Y should stay the same. I put 50x50 there just for the example, it shoudnt really relate to the question as to why the canvas moves south east. I just want to resize the canvas without modifying the position. Its being executed in the WM_SIZE event.

  8. #8
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    I don't think you want to use MoveWindow, what you're trying to do is reposition it. I think SetWindowPos( ) would better suit your needs. You'd still use GetWindowRect on both on main and child, then use .right, -top, bottom or whatever it works itself out to successfully do the resize and repositioning of the control.

  9. #9
    Registered User Codeplug's Avatar
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    SetWindowPos() also requires client coordinates - either function works equally well.

    If you're using a framework, then there may be a specific "framework-way" of doing this. Here's a simple console app that has no problem resizing a child during WM_SIZE.

    Code:
    #include <windows.h>
    
    #include <iostream>
    using namespace std;
    
    LRESULT CALLBACK WinProc(HWND, UINT, WPARAM, LPARAM);
    
    int main()
    {
        const char *className = "WindowsApp";
    
        WNDCLASSA wincl = {0};
        wincl.hInstance = GetModuleHandle(0);
        wincl.lpszClassName = className;
        wincl.lpfnWndProc = WinProc;
        wincl.style = CS_DBLCLKS;    
        wincl.hIcon = LoadIcon(0, IDI_APPLICATION);
        wincl.hCursor = LoadCursor(0, IDC_ARROW);
        wincl.hbrBackground = (HBRUSH)COLOR_BACKGROUND;
    
        if (!RegisterClassA(&wincl))
            return 1;
    
        HWND hwndParent;
        hwndParent = CreateWindowA(className, "Windows App", 
                                   WS_OVERLAPPEDWINDOW | WS_VISIBLE,
                                   CW_USEDEFAULT, CW_USEDEFAULT,
                                   450, 375, HWND_DESKTOP, 0, 
                                   GetModuleHandle(0), 0);
        if (!hwndParent)
            return 1;
    
        RECT parentRect;
        GetWindowRect(hwndParent, &parentRect);
        int parentWidth = parentRect.right - parentRect.left;
        int parentHeight = parentRect.bottom - parentRect.top;
    
        HWND hwndChild;
        hwndChild = CreateWindowA("Button", "Button", WS_CHILD | WS_VISIBLE,
                                  10, 10,  parentWidth / 2, parentHeight / 2,
                                  hwndParent, 0, GetModuleHandle(0), 0);
        if (!hwndChild)
            return 1;
    
        MSG msg;
        BOOL bRet;
        for (;;)
        {
            bRet = GetMessage(&msg, 0, 0, 0);
            if ((bRet == 0) || (bRet == -1))
                break;
    
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }//while
    
        return (int)msg.wParam;
    }//main
    
    
    LRESULT CALLBACK WinProc(HWND hwnd, UINT msg, 
                             WPARAM wParam, LPARAM lParam)
    {
        switch(msg)
        {
            case WM_DESTROY:
            {
                PostQuitMessage(0);
                return 0;
            }//case
                
            case WM_SIZE:
            {
                cout << LOWORD(lParam) << ", " 
                     << HIWORD(lParam) << endl;
                
                RECT parentRect;
                GetWindowRect(hwnd, &parentRect);
                
                int parentWidth = parentRect.right - parentRect.left;
                int parentHeight = parentRect.bottom - parentRect.top;
                
                MoveWindow(GetWindow(hwnd, GW_CHILD), 
                           10, 10, parentWidth / 2, parentHeight / 2, 
                           TRUE); 
                return 0;
            }//case
        }//switch
    
        return DefWindowProc(hwnd, msg, wParam, lParam);
    }//WinProc
    gg

  10. #10
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    Ok this is how i decided to do it (btw im not using a framework. Its just a few classes i made to make the event handling easier):

    Code:
        CDlgMain(HWND hWnd): CWindowClass(hWnd)
        {
    
           .....
     	//Create a canvas
            canvas.create(CreateWindowEx(WS_EX_CLIENTEDGE,
                    "PANELCLASS",
                    "",
                    WS_CHILD | WS_VSCROLL | WS_HSCROLL,
                    0,
                    0,
                    0,
                    0,
                    getHandle(),
                    NULL,
                    CApplication::getHandle(),
                    NULL));
            //Create menu tab
            menuTab.create(CreateWindowEx(0, WC_TABCONTROL, "", WS_CHILD | TCS_MULTILINE, 0, 0, 0, 0,
                        getHandle(), NULL, CApplication::getHandle(), NULL));
            //Create map tab
            mapTab.create(CreateWindowEx(0, WC_TABCONTROL, "", WS_CHILD, 0, 0, 0, 0,
                        getHandle(), NULL, CApplication::getHandle(), NULL));
    
            //force the WM_SIZE message to be sent (to adjust the scroll bars on the canvas)
            canvas.sendSizeMessage();
            //force the WM_SIZE message to be sent to main window (to set the shape and position of some of the child windows)
            this->sendSizeMessage();
           .....
    
        }
    
        int onSize(const TSizeEvent& event)
        {
            int canvasWidth = event.width - 210;
            int canvasHeight = event.height - 76;
    
            //Autosize status bar and scroll bar
            statusBar.sendMessage(WM_SIZE, 0, 0);
    	toolBar.sendMessage(WM_SIZE, 0, 0);
    
            //Auto size the other stuff
    	MoveWindow(canvas.getHandle(), 206, 55, canvasWidth, canvasHeight, true);
            MoveWindow(menuTab.getHandle(), 14, 32, 188, event.height - 54, true);
            MoveWindow(mapTab.getHandle(), 206, 32, event.width - 210, 24, true);
    
            //Resize back buffer
            if(canvasWidth > backBuffer->w || canvasHeight > backBuffer->h)
    	{
                SDL_FreeSurface(backBuffer);
                backBuffer = SDL_CreateRGBSurface(SDL_SWSURFACE, canvasWidth, canvasHeight, 24, 0x00FF0000, 0x0000FF00, 0x000000FF, 0);
                updateCanvas(true);
    	}
            return 1;
        }
    Now i just dont even bother putting the size and position in CreateWindow

  11. #11
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    Ummmm.....

    ClientToScreen() will convert from the controls coods to the parents (given the right input).

    There is also a reverse, ScreenToClient().

    AdjustWindowRect() may also be useful.
    "Man alone suffers so excruciatingly in the world that he was compelled to invent laughter."
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  12. #12
    Registered User Codeplug's Avatar
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    I probably should have searched the forums.....

    SetWindowPos doesn't seem to work

    gg

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