Some screen, window, layer, and surface structures in directfb and Their Relationships

Address: http://blog.csdn.net/dotphoenix/archive/2009/11/03/4762623.aspx

Relationship between some major data types in directfb

Layer (layers)

Indicates an independent image buffer. Most embedded devices have multiple layers. They are blending by the hardware using the appropriate Alpha value and then displayed.

Surface)

Reserved memory area used to save pixel data. The drawing and blitting operations of directfb ultimately work on the surface (surfaces. the memory on the surface can be obtained from the video memory or from the system memory (system meomroy), which is determined by the given limits.

Primary Surface)

The special surface of the frame buffer of a specific layer. If the main surface is a single buffer, any operation that acts on this main layer will be seen directly on the screen.

The relationship between them is mainly one-to-one or one-to-many:

• 1 idirectfb (top layer) <--> N screens (screens)
• 1 screen <--> layer N (layers)
• Layer 1 <--> 1 primary surface)
• Layer 1 <--> N window (Windows)
• 1 window <--> 1 window Surface)
• Surface <--> N subsurface (subsurfaces)

Normally, a screen has a display layer, but DFB supports multiple instances.

Layers and screens)

Each screen can have one or more layers. Generally, a screen has only one layer, but some systems that support overlays support multiple layers because the hardware supports displaying one layer on the other.

Screens and windows)

You cannot directly create a window on the screen, but you can request an ID of the screen's primary layer and then request the idirectfb interface) you can use the layer interface to create a window.

Surfaces and windows)

Each window has a surface associated with it. The content on the surface is not immediately displayed on the screen, because the window manager is responsible for combining all the surfaces of the window to the main surface-based on the area and stack order to be refreshed. When there is a change, the flip () function will notify the window manager.

Surfaces and layers)

A layer also has a surface associated with it. This surface is the direct display of the screen memory of this layer. In exclusive mode, you can only access this surface. Otherwise, you can create only one window and use the window manager to draw the surface.