Introduction to PowerBuilder

Types of Windows

There are six types of windows available in PowerBuilder. They are all created in the same way, but each has a specific task for which it is used. You don't have to specify the window type before you create the window. The default window type is: "Main".

Main Window

A Main Window is a stand-alone window, which acts independent of all others. This type of window can be minimized, maximized and resized; they can also overlap and be overlapped by other windows. They are usually used:

	in single window applications,
	As sheets in MDI (Multiple Document Interface) applications. (We will explain about MDI concepts & programming in the comming sessions.

If you open say, 3 windows of type "Main", each window behaves independently. For the user, it looks as if they are 3 different applications. Closing of one window doesn't exit the application unless it is the last open window on the screen. Minimizing a window will display the minimized icon in the "Program Manager"; Under Windows 95, it would not be displayed anywhere.

Popup Window

A Popup Window is typically opened from another window, which is then said to be the popup window's parent window.

The popup window is dependent on its parent window, but it can also be displayed without opening it from the parent window.If you do not open the popup window from another window, it will behave like a main window.

Parent window will not overlap a popup window, but if a parent is minimized popup window will be hidden.

Response Window

A Response Window is the PowerBuilders equivalent of a Windows dialog box; it is used to accept response from the user, to display warnings and so on. A response window demands action from the user and once active remains active until the user answers.

If a window behaves in this manner it is said to be modal.

When a response window is opened, you neither can move to another window within the same application nor can you resize, minimize or maximize the opened response window. You can switch to any other application that you have opened under Windows, but when you return to the current application, the response window will still be active.

A typical example of where you might encounter this type of window is when you want to save a new document using your favorite word-processor. When you click on the save option, the word-processor can't save the file as the document is as still untitled and therefore displays a 'Save As' window, asking for the required information.

Until you answer this question, the word processor will not allow you to continue , unless you click on the Cancel button and throw away the whole idea of saving the document.

Child Window

As in "popup window", a Child Window can only be opened from another window, its parent. Even though you specify the window type as "child", it will behave like a main window, when opened directly, i.e. not opened from another window. "Directly" means from an application object, from a menu option and so on.

A child window can't be moved outside the parent window boundaries. If you try to move a child window outside its parent window limits, all the window area that you expect to see outside of parent window would disappear. To see the full window area again you need to move back the child window into the parent window.

On the other hand, if you move the parent window, the child window will maintain its relative position within the parent.

A child window can't have a menu associated with, but a child window can still have a title bar. When you minimize a child window, the minimized icon is displayed at the bottom of the parent window and when it is maximized, it occupies the entire parent window. A child window is never considered as an active window. It doesn't mean that you can't do anything in the child window. The interpretation of "never considered as an active window" is from programming and not from the end-user perspective. When you close a parent window, any children that are inside it are closed automatically.

MDI Frame Window

A MDI Frame Window allows you to open multiple windows as sheets inside it. We will explain PowerScript in the coming sessions. For better understanding: Open() is the function that you need to call to open a window programmatically. As explained in  "Main Window", when you use Open() function, the window behaves independently once open. If you open ten windows, it will look like they are ten different running applications. You feel as if all windows are independent and you can see Program Manager also.

You can use another function OpenSheet() which gives you the functionality of "developmental environment" of "PowerBuilder". When you first invoke PowerBuilder, you see a window, i.e. a PowerBuilder window. Within that you are opening all these painters. You can see that all these painters are open within the PowerBuilder window. You can't move a window outside the PowerBuilder window . When you close PowerBuilder window, all those painters that are open will close. In PowerBuilder terminology, all the windows that are open within the MDI window (in this example, PowerBuilder window it self), are called as "Sheets". Well, as a developer, we call them as painters. MS-Word is the good example for this.

When a window (sheet) inside the MDI Frame window minimizes, the minimized sheet icon is displayed at the bottom of the MDI Frame window.

MDI Frame with Microhelp

This window is exactly like an MDI Frame, except that it has an additional feature of a status bar at the bottom of the window. This status bar is used to display context-sensitive help like current time, etc..

PowerBuilder opening window is a good example of this type of window. When you move the mouse over the toolbar icons, microhelp is displayed on the status bar giving you an idea of what the icon stands for.

By resizing this window's workspace, not only are you defining your design area, but you are also defining the size of the window when the application is run. Clearly, if you have enabled the Maximize, Minimize and Resizable properties of the window, you will be able to alter this sizing at run-time, but when the window is initially opened, it will be displayed within these proportions.

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