[Video - 9 min] The Clip Object

Learn to create a clipping region like Google Maps using the Altia Clip object.



NOTE: As shown in the video, it is suggested that you use an "anchor" object in the bottom-left corner of your clip to prevent it from moving around.Here are a couple Q&A tips on the suggested format/usage of the anchor object:

1. Is there any bad combination of objects other than "dynamic (anchor) object in a Clip"?
An anchor object should be a single static object, not a combination of objects.  For minimal code size, a Rectangle with no scale/stretch/rotate/distort and no animation is a good choice.  A small solid color Raster (for example, 10 x 10) is another choice, but it uses more memory than a rectangle.  This is understood by looking in altia/altiaTypes.h.  Note the difference in number of elements for an Altia_Rect_type structure versus an Altia_Raster_type structure.  And the Raster also has some image bytes even though they should be few if the Raster is a solid color and 10 x 10.

2. Is there any other magic numbers, such like (0, 0)-(0, 0) means empty extent?
The Clip object is implemented in the DeepScreen source file altia/altiaLibClip.c.  From my analysis of this file, (0, 0)-(0, 0) is the only pattern that means an empty extent.


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