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Class to build a modeless dialog.


Class name:
(vBaseWindow,vCmdParent) ->vDialog


The vDialog class is used to build modeless dialogs. Since most dialogs will require a response to the commands they define, you will almost always derive your own subclass based on vDialog, and override the DialogCommand method to handle those commands. Note that vDialog is multiply derived from the vBaseWindow and the vCmdParent classes.


vDialog(vBaseWindow* parent)
vDialog(vApp* parent)
vDialog(vBaseWindow* parent, int isModal = 0, char* title = "")
vDialog(vApp* parent, int isModal = 0, char* title = "")

A dialog is constructed by calling it with a pointer to a vBaseWindow or vApp, which is usually the 'this' of the object that creates the vDialog. The isModal parameter indicates if the dialog should be modal or modeless. You would usually use the default of 0. The modal flag is used by the derived vModalDialog class. The title parameter can be used to set a title for your dialog (see SetDialogTitle for information on titles). If you create a derived dialog class, you might provide a parent and a title in your constructor, and provide the 0 for the isModal flag in the call to the vDialog constructor.

The constructor builds an empty dialog. The AddDialogCmds method must be called in order to build a useful dialog, which you would usually do from within the constructor of your derived dialog class.

IMPORTANT! When you derive your own vDialog objects, you should write constructors for both the vBaseWindow* and vApp* versions. These two different constructors allow dialogs to be used both from windows directly, and from the vApp code as well. Normally, you would construct a dialog from a window. Occasionally, it will be useful to build a dialog from the vApp that applies to all windows, and not just the window that constructed it.

void vDialog::AddDialogCmds(CommandObject* cList)

This method is used to add a list of commands to a dialog. It is called after the dialog object has been created. You can usually do this in the constructor for your derived Dialog class. This method is passed an array of CommandObject structures.

void vDialog::SetDialogTitle(char* title)

This can be used to dynamically change the title of any object derived from a vDialog object. Note that the title will not always be displayed. This depends on the host system. For example, the user can set up their X window manager to not show decorations on transient windows, which is how dialogs are implemented on X. You should write your applications to provide a meaningful title as they are often helpful when displayed.


This example shows the steps required to use a dialog object. Note that the example uses the vDialog class directly, and thus only uses the default behavior of responding to the OK button.


 #include <v/vdialog.h>
     CommandObject cmdList[] =           // list of the commands
         {C_Label, lbl1, 0, "Label",NoList,CA_MainMsg,isSens,0,0},
         {C_Button, M_OK, M_OK, " OK ", NoList,
             CA_DefaultButton, isSens,lbl1,0},
         {C_EndOfList,0,0,0,0,CA_None,0,0}  // This ends list
     vDialog curDialog(this,0,"Sample Dialog"); // create dialog instance
     curDialog.AddDialogCmds(cmdList);          // add the commands
     curDialog.ShowDialog("Sample modeless dialog."); // invoke

This example creates a simple modeless dialog with a label and an OK button placed below the label (see the description of layout control below). ShowDialog displays the dialog, and the vDialog::DialogCommand method will be invoked with the id (2) and value (M_OK) of the OK button when it is pressed.

Use the vModalDialog class to define modal dialogs.

The CommandObject structure includes the following:

    typedef struct CommandObject
        CmdType cmdType;    // what kind of item is this
        ItemVal cmdId;      // unique id for the item
        ItemVal retVal;     // initial value
                            //  depends on type of command
        char* title;        // string for label or title
        void* itemList;     // a list of stuff to use for the cmd
                            //  depends on type of command
        CmdAttribute attrs; // list of attributes of command
             Sensitive:1;   // if item is sensitive or not
        ItemVal cFrame;     // if item part of a frame
        ItemVal cRightOf;   // Item placed left of this id
        ItemVal cBelow;     // Item placed below this one
        int size;           // Used for size information
	char* tip;          // tool tip string
      } CommandObject;

Placements of command objects within the dialog box are controlled by the cRightOf and cBelow fields. By specifying where an object goes in relation to other command objects in the dialog (using their cmdId value), it is simple to get a very pleasing layout of the dialog. The exact spacing of command objects is controlled by the vDialog class, but the application can used C_Blank command objects to help control spacing. See [cmdobj.htm#CommandObject CommandObject] for more details.

The various types of command objects that can be added include (with suggested id prefix in parens):

    C_EndOfList:   Used to denote end of command list
    C_Blank:       filler to help RightOfs, Belows work (blk)
    C_BoxedLabel:  a label with a box (bxl)
    C_Button:      Button (btn)
    C_CheckBox:    Checked Item (chk)
    C_ColorButton: Colored button (cbt)
    C_ColorLabel:  Colored label (clb)
    C_ComboBox:    Popup combo list (cbx)
    C_Frame:       General purpose frame (frm)
    C_Icon:        a display only Icon (ico)
    C_IconButton:  a command button Icon (icb)
    C_Label:       Regular text label (lbl)
    C_List:        List of items (lst)
    C_ProgressBar: Bar to show progress (pbr)
    C_RadioButton: Radio button (rdb)
    C_Slider:      Slider to enter value (sld)
    C_Spinner:     Spinner value entry (spn)
    C_TextIn:      Text input field (txi)
    C_Text:        wrapping text out (txt)
    C_ToggleButton: a toggle button (tbt)
    C_ToggleFrame: a toggle frame (tfr)
    C_ToggleIconButton:  a toggle Icon button (tib)

These command values are passed to the vDialog::DialogCommand function, which you override to interpret commands. See [cmdobj.htm#Commands Command Objects] for more details about the commands.

virtual void CancelDialog()

This method is used to cancel any action that took place in the dialog. The values of any items in the dialog are reset to their original values, and the This method is automatically invoked when the user selects a button with the value M_Cancel and the DialogCommand method invoked as appropriate to reset values of check boxes and so on. CancelDialog can also be invoked by the application code.

virtual void CloseDialog()

The CloseDialog is used to close the dialog. It can be called by user code, and is automatically invoked if the user selects the M_Done or M_OK buttons and the user either doesn't override the DialogCommand or calls the default DialogCommand from any derived DialogCommand methods.

virtual void DialogCommand(ItemVal Id, ItemVal Val, CmdType Type)

This method is invoked when a user selects some command item of the dialog. The default DialogCommand method will normally be overridden by a user derived class. It is useful to call the default DialogCommand from the derived method for default handling of the M_Cancel and M_OK buttons.

The Id parameter is the value of the cmdId field of the CommandObject structure. The Val parameter is the retVal value, and the Type is the cmdType.

The user defined DialogCommand is where most of the work defined by the dialog is done. Typically the derived DialogCommand will have a switch statement with a case for each of the command cmdId values defined for items in the dialog.

void DialogDisplayed()

This method is called by the V runtime system after a dialog has actually been displayed on the screen. This method is especially useful to override to set values of dialog controls with SetValue and SetString.

It is important to understand that the dialog does not get displayed until ShowDialog or ShowModalDialog has been called. There is a very important practical limitation implied by this, especially for modal dialogs. The values of controls cannot be changed until the dialog has been displayed, even though the vDialog object may exist. Thus, you can't call SetValue or SetString until after you call ShowDialog for modeless dialogs, or ShowModalDialog for modal dialogs. Since ShowModalDialog does not return until the user has closed the dialog, you must override DialogDisplayed if you want to change the values of controls in a modal dialog dynamically.

For most applications, this is not a problem because the static definitions of controls in the CommandObject definition will be usually be what is needed. However, if you need to create a dialog that has those values changed at runtime, then the easiest way is to include the required SetValue and SetString calls inside the overridden DialogDisplayed.

void GetDialogPosition(int& left, int& top, int& width, int& height)

Returns the position and size of this dialog. These values reflect the actual position and size on the screen of the dialog. The intent of this method is to allow you to find out where a dialog is so position it so that it doesn't cover a window.

virtual int GetTextIn(ItemVal Id, char* str, int maxlen)

This method is called by the application to retrieve any text entered into any C_TextIn items included in the dialog box. It will usually be called after the dialog is closed. You call GetTextIn with the Id of the TextIn command, the address of a buffer (str), and the size of str in maxlen.

virtual int GetValue(ItemVal Id)

This method is called by the user code to retrieve values of command items, usually after the dialog is closed. The most typical use is to get the index of any item selected by the user in a C_List or C_ComboBox.

int IsDisplayed()

This returns true if the dialog object is currently displayed, and false if it isn't. Typically, it will make sense only to have a single displayed instance of any dialog, and your code will want to create only one instance of any dialog. Since modal dialogs allow the user to continue to interact with the parent window, you must prevent multiple calls to ShowDialog. One way would be to make the command that displays the dialog to be insensitive. IsDisplayed() is provided as an alternative method. You can check the IsDisplayed() status before calling ShowDialog.

virtual void SetDialogPosition(int left, int top)

Moves this dialog to the location left and top. This function can be used to move dialogs so they don't cover other windows.

virtual void SetValue(ItemVal Id, ItemVal val, ItemSetType type)

This method is used to change the state of dialog command items. The ItemSetType parameter is used to control what is set. Not all dialog command items can use all types of settings. The possibilities include:

Checked The Checked type is used to change the checked status of check boxes. V will normally handle checkboxes, but if you implement a command such as Check All, you can use SetValue to change the check state according to ItemVal val.

Sensitive The Sensitive type is used to change the sensitivity of a dialog command.

Value The Value type is used primarily to preselect the item specified by ItemVal val in a list or combo box list.

ChangeList, ChangeListPtr Lists, Combo Boxes, and Spinners use the itemList field of the defining CommandObject to specify an appropriate list. SetValue provides two ways to change the list values associated with these controls.

The key to using ChangeListPtr and ChangeList is an understanding of just how the controls use the list. When a list type control is instantiated, it keeps a private copy of the pointer to the original list as specified in the itemList field of the defining CommandObject.

So if you want to change the original list, then ChangeList is used. The original list may be longer or shorter, but it must be in the same place. Remember that a NULL entry marks the end of the list. So you could allocate a 100 item array, for example, and then reuse it to hold 0 to 100 items.

Call SetValue with type set to ChangeList. This will cause the list to be updated. Note that you must not change the itemList pointer used when you defined the list or combo box. The contents of the list can change, but the pointer must be the same. The val parameter is not used for ChangeList.

Sometimes, especially for regular list controls, a statically sized list just won't work. Using ChangeListPtr allows you to use dynamically created list, but with a small coding penalty. To use ChangeListPtr, you must first modify the contents of the itemList field of the original CommandObject definition to point to the new list. Then call SetValue with ChangeListPtr. Note that this will both update the pointer, and update the contents of the list. You don't need to call again with ChangeList.

The following illustrates using both types of list change:

  char* comboList[] = {
    "Bruce", "Katrina", "Risa", "Van", 0 };
  char* list1[] = {"1", "2", "3", 0};
  char* list2[] = {"A", "B", "C", "D", 0};

  // The definition of the dialog
  CommandObject ListExample[] = {

    // Change the contents of the combo list
    comboList[0] = "Wampler";  // Change Bruce to Wampler
    // Change to a new list entirely for list
    // Note that we have to change ListExample[1], the
    // original definition of the list control.
    ListExample[1].itemList = (void*)list2;  // change to list2

Note that this example uses static definitions of lists. It is perfectly fine to use completely dynamic lists: you just have to dynamically fill in the appropriate itemList field of the defining CommandObject.

Please see the description of DialogDisplayed for an important discussion of setting dialog control values.

virtual void SetString(ItemVal Id, char* str)

This method is called to set the string values of dialog items. This can include the labels on check boxes and radio buttons and labels, as well as the text value of a Text item.

Please see the description of DialogDisplayed for an important discussion of setting dialog control values.

virtual void ShowDialog(char* message)

After the dialog has been defined, it must then be displayed by calling the ShowDialog method. If a C_Label was defined with a CA_MainMsg attribute, then the message provided to ShowDialog will be used for that label.

ShowDialog returns to the calling code as soon as the dialog is displayed. It is up to the DialogCommand method to then handle command input to the dialog, and to close the dialog when done.

Please see the description of DialogDisplayed for an important discussion of setting dialog control values.

Derived Methods


Inherited Methods


See Also

vModalDialog, Command Objects