DirectFB官方已经不再维护，但目前还有不少用户使用DirectFB，该组件从某种程度上可以说是业界事实标准，之所以这么流行原因是DirectFB天生就是针对嵌入式设备而设计，以最小的资源来实现了最高的硬件加速性。如今IOT设备流行，需要一种在RAM和ROM占用均小图形显示组件，所以该项目从DirectFB-1.6.3拉出了一个分支，命名OpenDFB，该项目主要是通过对DirectFB代码进行重构和精简，旨在建立一个IOT轻量级设备的显示服务组件。
OpenDFB定位为IOT设备显示服务组件，因为DirectFB发展多年，一方面存在历史代码导致代码陈旧，另外一方面也存在发展中增加了很多背离最早轻量级设计目标的很多没有用的功能，OpenDFB出现就是为了解决这些问题，主要是通过明确显示服务的目标删除一些没有用的功能，甚至对外接口也会有些调整，目前调整的代码包括：
- 将directfb内部C++代码统一整改成纯C代码，避免代码膨胀，保持代码简洁；(done)
- 删除历史遗留的半吊子组件，包括++dfb, dvc, fusiondale, fusionsound, voodoo, input hub; (done)
- 显示服务需要强化显示功能，对于显示之外的功能进行删除，包括IDirectFBVideoProvider,IFusionSound,IFusionSoundMusicProvider,IWater；（done）
- 对外接口保留，但内部实现保留最简单实现，建议应用端实现， 包括Image provider, Font/Text. （done）
- 对于2D接口保留Blitter相关功能，对于其他矢量绘制等功能均删除. （done）
- 将游离directfb之外的库收编到内部直接编译，包括sawman, divine;（done）
- 将内核fusion机制使用socket来代替，避免依赖linux内核依赖，方便移植到其他RTOS。（doing）
OpenDFB关注以下功能，其他功能和规格均会被删除或不会被纳入
- 提供显示输出功能，包括图形和视频输出；
- 提供交互输入设备功能，包括按键，触摸，鼠标等输入设备对接；
- 提供窗口管理功能；
- 提供2D Blitter图形加速功能，其他绘制接口不会提供；
- 支持单进程和多进程架构；
Mandatory are - libc - libpthread - libm - libdl
For regenerating autofoo (./autogen.sh or autoreconf) - autoconf - automake - libtool - pkg-config
Optionally, depending on the configuration you want:
FBDev - Linux kernel 2.2.x or newer with working frame buffer device (check /proc/fb) for the fbdev system.
SDL - libSDL (Simple Direct Media Layer) for the sdl system.
X11 - libX11 (X11 client library) for the X11 system (libx11-dev and libxext-dev packages).
The following libraries are optional, but important (Debian package names):
Fonts - libfreetype6-dev for TrueType and other fonts
Images - libjpeg-dev for Joint Picture Expert Group images - libpng-dev for Portable Network Graphics
Extra - zlib1g-dev for compressed screenshot support (also needed by libpng)
The multi application core also requires <linux/fusion.h>, see the section "Running multiple DirectFB applications" for more details.
The build of the image and font providers can be disabled but we strongly suggest that you don't do this since the code examples and a lot of DirectFB applications depend on the functionality provided by them.
Depending on the DirectFB application you want to run, you need some or all of these:
- A working frame buffer device (check the output of 'fbset -i').
- A keyboard (if it works on the console, everything should be fine).
- A PS/2 or serial mouse for windowing. USB and ADB mice do also work via PS/2 emulation.
Using the single application core you always need access to /dev/tty0, /dev/fb0 and the mouse device (/dev/psaux, /dev/mouse). You can either run all DirectFB applications as root or allow users to access these devices. A reasonable way to do this is to add users to the group tty (or some other group) and allow this group to read and write the files in /dev:
crw-rw---- 1 root tty 29, 0 /dev/fb0
crw-rw---- 1 root tty 10, 1 /dev/psaux
crw-r----- 1 root tty 4, 0 /dev/tty0
If you are using the multi application core, only the master process needs access to all of these devices. Additional processes (slaves) just need access to /dev/fb0 and:
crw-rw---- 1 root fusion 29, 0 /dev/fusion/0
Note that the master creates a shared memory file, probably in '/dev/shm/fusion.0'. It's read/writeable for anyone matching the master process' user or group.
Some applications from the DirectFB-examples package have additional requirements:
- A video card supported by video4linux for df_video.
- A joystick for df_joystick.
With the default build of the DirectFB library, only one DirectFB application may be running. However you have the option to use the multi application core of DirectFB which allows multiple DirectFB applications to run at the same time within a session.
DirectFB applications communicate through a layer we call "Fusion". This layer was previously implemented completely in user space using semaphores and message queues. But since 0.9.15 the Fusion Kernel Device is required which implements critical parts of Fusion and thus lead to better performance and decent stability. To install this kernel module (only available for Linux yet), find the linux-fusion module in our CVS or GIT repository or on the DirectFB website. For DirectFB 1.4.x releases you should use linux-fusion 8.1.1 or newer.
Compile DirectFB with multi-application core enabled:
./configure --enable-multi
Make sure your Linux kernel supports tmpfs. This is explained in the kernel sources in Documentation/filesystems/tmpfs.txt. Mount a tmpfs filesystem as /dev/shm:
mount tmpfs /dev/shm -ttmpfs
Optionally a mount point can be specified via the "tmpfs" option, see directfbrc(5). The option has to be the same for all processes.
A good way to test the multi-application core is to install the lite toolkit and DFBTerm, a DirectFB terminal (both available in the DirectFB CVS/GIT repository). You can then start DirectFB applications from dfbterm.
- In the DirectFB directory type:
./configure <options>
make
make install (as superuser)
Use './configure --help' to get a list of possible configure options.
Imported options include:
--enable-multi Enables the Multi Application Core
--enable-debug Enables many debug messages and assertions
--enable-trace Enables run time stack trace information
Debugging and especially stack trace support are a performance
impact. It may be noticably slower in some areas, e.g. text drawing.
You may use the options "no-debug" and "no-trace" by default, e.g.
in '<prefix>/etc/directfbrc', and use "--dfb:debug,trace" on the command
line if needed.
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Make sure that "/lib" is listed in your /etc/ld.so.conf. The default prefix is "/usr/local". After adding it you have to run 'ldconfig' as superuser.
Alternatively, you can add the path to the environment variable LD_LIBRARY_PATH. This is useful for temporarily switching to another installed version.
-
You might want to copy fb.modes to /etc or merge it with your existing /etc/fb.modes file. The first entry will be used by default - copy other entries you may need.
-
If you want to use a serial mouse, create a link called /dev/mouse that points to serial device (e.g. /dev/ttyS0). Then add a line describing your mouse-protocol to /etc/directfbrc or ~/.directfbrc: "mouse-protocol=[ms|ms3|mouseman|mousesystems]".
-
If you are cross compiling and have installed the required libraries someplace other than /usr/local/lib be sure to add the bin directory for those libraries to the front of your 'PATH'.
For instance if you configured using: --prefix=/dfb/usr/local then be sure to export PATH=/dfb/usr/local/bin:$PATH before compiling and installing.
There are lots of things that can be configured. We try to ship DirectFB with reasonable defaults but you might have to tweak things. There are several ways to do this. You may edit the system-wide configuration file /etc/directfbrc or the user-specific $HOME/.directfbrc. There's a manual page called directfbrc(5) that documents all the settings. The same manual page also explains how DirectFB application can be configured via the command-line.
DirectFB's prefered way-of-working needs a Linux kernel with frame buffer support. Check the documentation in the kernel tree (/usr/src/linux/Documentation/fb/) on how to enable the frame buffer device for your graphics card.
The generic VESA frame buffer device does not support mode switching and you will not get hardware acceleration. To make DirectFB work with veasfb, you should add the following lines to /etc/lilo.conf:
append="video=vesa:ywrap,mtrr"
'ywrap' enables panning with wraparound. 'mtrr' enables setting caching type for the frame buffer to write-combining.
vga=791
This sets the mode on startup. 791 means 1024x768@16, 788 means 800x600@16.
All VESA Video Modes:
Bits 640x480 800x600 1024x768 1280x1024 1600x1200 8 769 771 773 775 796 16 785 788 791 794 798 32 786 789 792 795 799
Other frame buffer devices support mode switching. DirectFB will only support modes listed in your /etc/fb.modes file. By default the first entry found is used.
If you have a Matrox card you may want to try the vsync patch found in the patches directory that enables applications to "idle wait" for the vertical retrace.
Since DirectFB lacks a real window manager, we added a hack to the window stack to allow for basic window management. While pressing the (or Windows) key or alternatively you can do the following:
- Drag your mouse to move the focused window.
- Drag and press <Ctrl> to resize the focused window.
- Drag and press <Alt> to change the opacity of the focused window.
- Press C to close the focused window.
- Press A to lower the focused window to the bottom.
- Press X to cycle the focus through the windows.
- Press S to raise the lowest window to the top.
- Press P to enable and show the mouse cursor.
- Press R to rotate the focused window by 90 degree.
- Press E to focus the window currently under the mouse cursor,
useful in conjunction with 'X'.
- Press Escape to return from fullscreen mode to the desktop.
(currently not advisable if the fullscreen app is still flipping)
- Press F12 to redraw the whole window stack.
You might want to use the "capslock-meta" option (see directfbrc(5)) if you don't have a key.
A complete API reference documentation in HTML format is created during the build in the docs directory. You may also access the API reference as well as a concepts overview, tutorials and the FAQ online at https://github.com/openDFB/OpenDFB/wiki.