Implementing Scrollbars

Scrollbars can be useful whenever the display rectangle is larger than the window's client area. This is an alternative to making the displayed image fit the window.

If you are using the high-level LBitmapWindow (or derived) class, scrolling is handled automatically for you. You can enable/disable scrolling using the LBitmapWindow::EnableAutoScroll function.

If you are not using LBitmapWindow, the following instructions describe how to implement scrollbars, turning them on when they are required and turning them off when they are not.

1.

Modify the window style for your window to include the WS_VSCROLL and WS_HSCROLL styles.

2.

Add variables to your program that track the scroll range and position.

3.

In your function for processing the WM_SIZE message, you can add code to show or hide the scrollbars, as needed, and adjust the scrollbar ranges and positions.

4.

In your functions for processing WM_HSCROLL and WM_VSCROLL messages, add this code.

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