Programming C++Builder How to Draw Graphics and Make them Scrollable by Using the Graphic Controls in CBuilder?

How to draw on a graphic?

You don't need any components to manipulate your application't graphic objects. You can construct, draw on, save, and destroy graphic objects without ever drawing anything on screen. In fact, your applications rarely draw directly on a form. More often, an application operates on graphics and then uses an image control component to display the graphic on a form.

Once you move the application's drawing to the graphic in the image control, it is easy to add printing, clipboard, and loading and saving operations for any graphic objects. graphic objects can be bitmap files, drawings, icons or whatever other graphics classes that have been installed such as jpeg graphics.

Note: Because you are drawing on an offscreen image such as a TBitmap canvas, the image is not displayed until a control copies from a bitmap onto the control's canvas. That is, when drawing bitmaps and assigning them to an image control, the image appears only when the control has an opportunity to process its paint message. But if you are drawing directly onto the canvas property of a control, the picture object is displayed immediately.

How to make your graphics scrollable?

The graphic need not be the same size as the form: it can be either smaller or larger. By adding a scroll box control to the form and placing the graphic image inside it, you can display graphics that are much larger than the form or even larger than the screen. To add a scrollable graphic first you add a TScrollBox component and then you add the image control.

How to add an image control to your application?

An image control is a container component that allows you to display your bitmap objects. You use an image control to hold a bitmap that is not necessarily displayed all the time, or which an application needs to use to generate other pictures.

Note: Adding graphics to controls shows how to use graphics in controls.

How to place the control?

You can place an image control anywhere on a form. If you take advantage of the image control's ability to size itself to its picture, you need to set the top left corner only. If the image control is a nonvisible holder for a bitmap, you can place it anywhere, just as you would a nonvisual component.

If you drop the image control on a scroll box already aligned to the form's client area, this assures that the scroll box adds any scroll bars necessary to access offscreen portions of the image's picture. Then set the image control's properties.

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Programming - C++Builder