Appendix

graphics/ Directory Structure

The graphics capability consist both of components internal to the RTOS and of user-callable interfaces. In the NuttX kernel mode build there are some components of the graphics subsystem are callable in user mode and other components that are internal to the RTOS. The directory nuttx/graphics contains only those components that are internal to the RTOS. User callable functions must be part of a library that can be linked against user applications. This user callable interfaces are provided in sub-directories under nuttx/libnx.

libnx/nx

Common callable interfaces that are, logically, part of both nxmu and nxsu.

graphics/nxglib and libnx/nxglib

The NuttX tiny graphics library. The directory contains generic utilities support operations on primitive graphics objects and logic to rasterize directly into a framebuffer or through an LCD driver interface. It has no concept of windows (other than the one, framebuffer or LCD window).

graphics/nxbe

This is the back-end of a tiny windowing system. It can be used with either of two front-ends to complete a windowing system (see nxmu and nxsu below). It contains most of the important window management logic: clipping, window controls, window drawing, etc.

graphics/nxmu and libnx/nxmu

This is the NX multi user front end. When combined with the generic back-end (nxbe), it implements a multi-threaded, multi-user windowing system. The files in this directory present the window APIs described in include/nuttx/nx/nx.h. The multi-user front end includes a graphics server that executes on its own thread; multiple graphics clients then communicate with the server via a POSIX message queue to serialize window operations from many threads.

libnx/nxfonts

This is where the NXFONTS implementation resides. This is a relatively low-level set of charset set/glyph management APIs. See include/nuttx/nx/nxfonts.h.

libnx/nxtk

This is where the NXTOOLKIT implementation resides. This toolkit is built on top of NX and works with the multi-user NX front-end. See include/nuttx/nx/nxtk.h.

apps/graphics/NxWidgets

The NxWidgets code is provided as a separate package provided in the apps/ repository.

graphics/nxterm

The NxTerm driver is built on top of NX and works with the multi-user NX front-end. See include/nuttx/nx/nxterm.h.

NX Configuration Options

General Configuration Settings

CONFIG_NX

Enables overall support for graphics library and NX

CONFIG_NX_RAMBACKED

Enables RAM backed window support. If this option is selected, then windows may be optionally created with a RAM framebuffer backing up the window content. Rending into the window will result in rending into the backup framebuffer, then updating the physical display from the framebuffer.

The advantage of this option is that the application that manages window will no longer receive redraw() callbacks. Those calls normally occur, for example, when a window “above” moves exposing a portion of the window below. If this option is selected, then the system will redraw the exposed portion of the window from the backup framebuffer without intervention of the window applications. This greatly reduces the complexity of the application and performance of the window at the expense of increased memory usage.

An exception is the case when the window is resized to a wider and/or taller size. In that case, the redraw callback will till occur. It is necessary in that case to provide new graphic content for the extended window area.

Redraw requests in other cases are also suppressed: Changes to window position, size, etc.

NXGL Configuration Settings

CONFIG_NX_NPLANES:

Some YUV color formats requires support for multiple planes, one for each color component. Unless you have such special hardware, this value should be undefined or set to 1.

CONFIG_NX_DISABLE_1BPP, CONFIG_NX_DISABLE_2BPP, CONFIG_NX_DISABLE_4BPP, CONFIG_NX_DISABLE_8BPP CONFIG_NX_DISABLE_16BPP, CONFIG_NX_DISABLE_24BPP, and CONFIG_NX_DISABLE_32BPP:

NX supports a variety of pixel depths. You can save some memory by disabling support for unused color depths.

CONFIG_NX_PACKEDMSFIRST:

If a pixel depth of less than 8-bits is used, then NX needs to know if the pixels pack from the MS to LS or from LS to MS

CONFIG_NX_LCDDRIVER:

By default, NX builds to use a framebuffer driver (see include/nuttx/video/fb.h). If this option is defined, NX will build to use an LCD driver (see include/nuttx/lcd/lcd.h).

CONFIG_NX_ANTIALIASING:

Enable support for anti-aliasing when rendering lines as various orientations. This option is only available for use with frame buffer drivers and only with 16-, 24-, or 32-bit RGB color formats.

Configuration Settings

CONFIG_NX_XYINPUT:

Build in support for an X/Y input such as a mouse or a touscreen.

CONFIG_NX_KBD:

Build in support of keypad/keyboard input.

CONFIG_NX_WRITEONLY:

Define if the underlying graphics device does not support read operations. Automatically defined if CONFIG_NX_LCDDRIVER and CONFIG_LCD_NOGETRUN are defined.

NX Server Configuration Settings

CONFIG_NX_BLOCKING

Open the client message queues in blocking mode. In this case, nx_eventhandler() will not return until a message is received and processed.

CONFIG_NX_MXSERVERMSGS and CONFIG_NX_MXCLIENTMSGS

Specifies the maximum number of messages that can fit in the message queues. No additional resources are allocated, but this can be set to prevent flooding of the client or server with too many messages (CONFIG_PREALLOC_MQ_MSGS controls how many messages are pre-allocated).

NXTK Configuration Settings

CONFIG_NXTK_BORDERWIDTH:

Specifies the width of the border (in pixels) used with framed windows. The default is 4.

CONFIG_NXTK_BORDERCOLOR1, CONFIG_NXTK_BORDERCOLOR2, and CONFIG_NXTK_BORDERCOLOR3:

Specify the colors of the border used with framed windows.

CONFIG_NXTK_BORDERCOLOR2

The shadow side color and so is normally darker.

CONFIG_NXTK_BORDERCOLOR3

The shiny side color and so is normally brighter. The default is medium, dark, and light grey, respectively

CONFIG_NXTK_AUTORAISE:

If set, a window will be raised to the top if the mouse position is over a visible portion of the window. Default: A mouse button must be clicked over a visible portion of the window.

NXFONTS Configuration Settings

CONFIG_NXFONTS_CHARBITS:

The number of bits in the character set. Current options are only 7 and 8. The default is 7.

CONFIG_NXFONT_SANS17X22:

This option enables support for a tiny, 17x22 san serif font (font ID FONTID_SANS17X22 == 14).

CONFIG_NXFONT_SANS20X26:

This option enables support for a tiny, 20x26 san serif font (font ID FONTID_SANS20X26 == 15).

CONFIG_NXFONT_SANS23X27:

This option enables support for a tiny, 23x27 san serif font (font ID FONTID_SANS23X27 == 1).

CONFIG_NXFONT_SANS22X29:

This option enables support for a small, 22x29 san serif font (font ID FONTID_SANS22X29 == 2).

CONFIG_NXFONT_SANS28X37:

This option enables support for a medium, 28x37 san serif font (font ID FONTID_SANS28X37 == 3).

CONFIG_NXFONT_SANS39X48:

This option enables support for a large, 39x48 san serif font (font ID FONTID_SANS39X48 == 4).

CONFIG_NXFONT_SANS17X23B:

This option enables support for a tiny, 17x23 san serif bold font (font ID FONTID_SANS17X23B == 16).

CONFIG_NXFONT_SANS20X27B:

This option enables support for a tiny, 20x27 san serif bold font (font ID FONTID_SANS20X27B == 17).

CONFIG_NXFONT_SANS22X29B:

This option enables support for a small, 22x29 san serif bold font (font ID FONTID_SANS22X29B == 5).

CONFIG_NXFONT_SANS28X37B:

This option enables support for a medium, 28x37 san serif bold font (font ID FONTID_SANS28X37B == 6).

CONFIG_NXFONT_SANS40X49B:

This option enables support for a large, 40x49 san serif bold font (font ID FONTID_SANS40X49B == 7).

CONFIG_NXFONT_SERIF22X29:

This option enables support for a small, 22x29 font (with serifs) (font ID FONTID_SERIF22X29 == 8).

CONFIG_NXFONT_SERIF29X37:

This option enables support for a medium, 29x37 font (with serifs) (font ID FONTID_SERIF29X37 == 9).

CONFIG_NXFONT_SERIF38X48:

This option enables support for a large, 38x48 font (with serifs) (font ID FONTID_SERIF38X48 == 10).

CONFIG_NXFONT_SERIF22X28B:

This option enables support for a small, 27x38 bold font (with serifs) (font ID FONTID_SERIF22X28B == 11).

CONFIG_NXFONT_SERIF27X38B:

This option enables support for a medium, 27x38 bold font (with serifs) (font ID FONTID_SERIF27X38B == 12).

CONFIG_NXFONT_SERIF38X49B:

This option enables support for a large, 38x49 bold font (with serifs) (font ID FONTID_SERIF38X49B == 13).

NxTerm Configuration Settings

General NxTerm settings.

CONFIG_NXTERM:

Enables building of the NxTerm driver.

NxTerm output text/graphics options:

CONFIG_NXTERM_BPP:

Currently, NxTerm supports only a single pixel depth. This configuration setting must be provided to support that single pixel depth. Default: The smallest enabled pixel depth. (see CONFIG_NX_DISABLE_*BPP)

CONFIG_NXTERM_CURSORCHAR:

The bitmap code to use as the cursor. Default ‘_’

CONFIG_NXTERM_MXCHARS:

NxTerm needs to remember every character written to the console so that it can redraw the window. This setting determines the size of some internal memory allocations used to hold the character data. Default: 128.

CONFIG_NXTERM_CACHESIZE:

NxTerm supports caching of rendered fonts. This font caching is required for two reasons: (1) First, it improves text performance, but more importantly (2) it preserves the font memory. Since the NX server runs on a separate server thread, it requires that the rendered font memory persist until the server has a chance to render the font. Unfortunately, the font cache would be quite large if all fonts were saved. The CONFIG_NXTERM_CACHESIZE setting will control the size of the font cache (in number of glyphs). Only that number of the most recently used glyphs will be retained. Default: 16.

NOTE: There can still be a race condition between the NxTerm driver and the NX task. If you every see character corruption (especially when printing a lot of data or scrolling), then increasing the value of CONFIG_NXTERM_CACHESIZE is something that you should try. Alternatively, you can reduce the size of CONFIG_MQ_MAXMSGSIZE which will force NxTerm task to pace the server task. CONFIG_NXTERM_CACHESIZE should be larger than CONFIG_MQ_MAXMSGSIZE in any event.

CONFIG_NXTERM_LINESEPARATION:

This the space (in rows) between each row of test. Default: 0

CONFIG_NXTERM_NOWRAP:

By default, lines will wrap when the test reaches the right hand side of the window. This setting can be defining to change this behavior so that the text is simply truncated until a new line is encountered.

NxTerm input options:

CONFIG_NXTERM_NXKBDIN:

Take input from the NX keyboard input callback. By default, keyboard input is taken from stdin (/dev/console). If this option is set, then the interfacenxterm_kdbin() is enabled. That interface may be driven by window callback functions so that keyboard input only goes to the top window.

CONFIG_NXTERM_KBDBUFSIZE:

If CONFIG_NXTERM_NXKBDIN is enabled, then this value may be used to define the size of the per-window keyboard input buffer. Default: 16

CONFIG_NXTERM_NPOLLWAITERS:

The number of threads that can be waiting for read data available. Default: 4

Installing New Fonts

The BDF Font Converter. There is a tool called bdf-converter in the directory tools/.. The bdf-converter program be used to convert fonts in Bitmap Distribution Format (BDF) into fonts that can be used in the NX graphics system. The BDF format most well known as a font format traditionally used for X-11 bitmap fonts.

A Note about Font Copyrights: My understanding is that the underlying bitmap font data for traditional fonts cannot be copyrighted (the same is not true for scalable fonts). This is because a copyright covers only the form of delivery of the font and not the underlying font content and, at least for the traditional typefaces, the underlying font designs are ancient. There could be issues, however, if you convert from modern, trademarked images. However, remember that I am a programmer not an attorney and that my knowledge of font copyright issues is limited to what I glean by Googling.

Font Installation Steps, Below are general instructions for creating and installing a new font in the NX graphic system. The first two steps only apply if you are using the BDF font converter program.

1. Locate a font in BDF format. There are many good BDF bitmap fonts bundled with X-11. See this link, as an example,

2. Use the bdf-converter program to convert the BDF font to the NuttX font format. This will result in a C header file containing definitions. That header file should be installed at, for example, graphics/nxfonts/nxfonts_myfont.h.

The remaining steps apply however you managed to create the NuttX C font header file. After you have your C font header file, the next thing to do is to create a new NuttX configuration variable to select the font. For example, suppose you define the following variable: CONFIG_NXFONT_MYFONT. Then you would need to:

3. Define CONFIG_NXFONT_MYFONT=y in your NuttX configuration file.

A font ID number has to be assigned for each new font. The font IDs are defined in the file include/nuttx/nx/nxfonts.h. Those definitions have to be extended to support your new font. Look at how the font ID enabled by CONFIG_NXFONT_SANS23X27 is defined and add an ID for yournew font in a similar fashion:

4. include/nuttx/nx/nxfonts.h. Add you new font as a possible system default font:

   #if defined(CONFIG_NXFONT_SANS23X27)
   # define NXFONT_DEFAULT FONTID_SANS23X27
   #elif defined(CONFIG_NXFONT_MYFONT)
   # define NXFONT_DEFAULT FONTID_MYFONT
   #endif
   

   Then define the actual font ID. Make sure that the font ID value is unique:

   #if defined(CONFIG_NXFONT_SANS23X27)
   # define NXFONT_DEFAULT FONTID_SANS23X27
   #elif defined(CONFIG_NXFONT_MYFONT)
   # define NXFONT_DEFAULT FONTID_MYFONT
   #endif
   

New Add the font to the NX build system. There are several files that you have to modify to do this. Look how the build system uses the font CONFIG_NXFONT_SANS23X27 for examaples:

5. nuttx/graphics/Makefile. This file needs logic to auto-generate a C source file from the header file that you generated with the bdf-converter program. Notice NXFONTS_FONTID=2; this must be set to the same font ID value that you defined in the include/nuttx/nx/nxfonts.h file.

   genfontsources:
     ifeq ($(CONFIG_NXFONT_SANS23X27),y)
         @$(MAKE) -C nxfonts -f Makefile.sources NXFONTS_FONTID=1 EXTRAFLAGS=$(EXTRAFLAGS)
     endif
     ifeq ($(CONFIG_NXFONT_MYFONT),y)
         @$(MAKE) -C nxfonts -f Makefile.sources NXFONTS_FONTID=2 EXTRAFLAGS=$(EXTRAFLAGS)
     endif
   

6. nuttx/graphics/nxfonts/Make.defs. Set the make variable NXFSET_CSRCS. NXFSET_CSRCS determines the name of the font C file to build when NXFONTS_FONTID=2:

   ifeq ($(CONFIG_NXFONT_SANS23X27),y)
   NXFSET_CSRCS += nxfonts_bitmaps_sans23x27.c
   endif
   ifeq ($(CONFIG_NXFONT_MYFONT),y)
   NXFSET_CSRCS += nxfonts_bitmaps_myfont.c
   endif
   

7. nuttx/graphics/nxfonts/Makefile.sources. This is the Makefile used in step 5 that will actually generate the font C file. So, given your NXFONTS_FONTID=2, it needs to determine a prefix to use for auto-generated variable and function names and (again) the name of the autogenerated file to create (this must be the same name that was used in nuttx/graphics/nxfonts/Make.defs):

   ifeq ($(NXFONTS_FONTID),1)
   NXFONTS_PREFIX  := g_sans23x27_
   GEN_CSRC  = nxfonts_bitmaps_sans23x27.c
   endif
   ifeq ($(NXFONTS_FONTID),2)
   NXFONTS_PREFIX  := g_myfont_
   GEN_CSRC  = nxfonts_bitmaps_myfont.c
   endif
   

8. graphics/nxfonts/nxfonts_bitmaps.c. This is the file that contains the generic font structures. It is used as a “template&qout; file by nuttx/graphics/nxfonts/Makefile.sourcesto create your customized font data set at build time.

   #if NXFONTS_FONTID == 1
   #  include "nxfonts_sans23x27.h"
   #elif NXFONTS_FONTID == 2
   #  include "nxfonts_myfont.h"
   #else
   #  error "No font ID specified"
   #endif
   

   Where nxfonts_myfont.h is the NuttX font file that we generated in step 2 using the bdf-converter tool.

9. graphics/nxfonts/nxfonts_getfont.c. Finally, we need to extend the logic that does the run-time font lookups so that can find our new font. The lookup function is `NXHANDLE nxf_getfonthandle(enum nx_fontid_e fontid) <#nxfgetfonthandle>`__. Note that the lookup is based on the font ID that was defined in step 4. The new font information needs to be added to data structures used by that function:

   #ifdef CONFIG_NXFONT_SANS23X27
   extern const struct nx_fontpackage_s g_sans23x27_package;
   #endif
   #ifdef CONFIG_NXFONT_MYFONT
   extern const struct nx_fontpackage_s g_myfont_package;
   #endif
   
   static FAR const struct nx_fontpackage_s *g_fontpackages[] =
   {
   #ifdef CONFIG_NXFONT_SANS23X27
     &g_sans23x27_package,
   #endif
   #ifdef CONFIG_NXFONT_MYFONT
     &g_myfont_package,
   #endif
     NULL
   };
   

NX Test Coverage

apps/examples/nx. The primary test tool for debugging NX resides at apps/examples/nx.

Building apps/examples/nx. NX testing was performed using apps/examples/nx with the Linux/Cygwin-based NuttX simulator. Configuration files for building this test can be found in boards/sim/sim/sim/configs/nx and boards/sim/sim/sim/configs/nx11. There are two alternative configurations for building the simulation:

1. The configuration using the configuration file at boards/sim/sim/sim/configs/nx/defconfig. This default configuration exercises the NX logic a 8 BPP but provides no visual feedback. In this configuration, a very simple, simulated framebuffer driver is used that is based upon a simple region of memory posing as video memory. That default configuration can be built as follows:

   tools/configure.sh sim:nx
   make
   ./nuttx
   

2. The preferred configuration is at boards/sim/sim/sim/configs/nx11/defconfig. This configuration extends the test with a simulated framebuffer driver that uses an X window as a framebuffer. This is a superior test configuration because the X window appears at your desktop and you can see the NX output. This preferred configuration can be built as follows:

   tools/configure sim:nx11
   make
   ./nuttx
   

   Update: The sim target has suffered some bit-rot over the years and so the following caveats need to be added:

   • The X target builds under recent Cygwin configurations, but does not execute. (It fails inside of XOpenDisplay().

   • The X target does not build under current (9.09) Ubuntu distributions. I needed to make the following changes:

     The build will also fail to locate the X header files unless you install an X11 development package.

   • Refer to the SIM file for additional information.

Test Coverage. At present, apps/examples/nxt only exercises a subset of NX; the remainder is essentially untested. The following table describes the testing performed on each NX API:

NXGLIB API Test Coverage

Function	Special Setup/Notes	Verified
nxgl_rgb2yuv()	.	NO
nxgl_yuv2rgb()	.	NO
nxgl_rectcopy()	.	YES
nxgl_rectoffset()	.	YES
nxgl_vectoradd()	.	YES
nxgl_vectorsubtract()	.	YES
nxgl_rectintersect()	.	YES
nxgl_rectunion()	.	YES
nxgl_nonintersecting()	.	YES
nxgl_rectoverlap()	.	YES
nxgl_rectinside()	.	YES
nxgl_rectsize()	.	YES
nxgl_nullrect()	.	YES
nxgl_runoffset()	Verified by apps/examples/nxlines.	YES
nxgl_runcopy()	.	NO
nxgl_trapoffset()	Verified by apps/examples/nxlines.	YES
nxgl_trapcopy()	Verified by apps/examples/nxlines.	YES
nxgl_colorcopy	.	YES
nxgl_splitline	Verified using apps/examples/nxlines Generally works well, but has some accuracy/overflow problems wide lines that are nearly horizontal. There is a “fudge factor” that seems to eliminate the problem, but there could still be issues in some configurations.	YES
nxgl_circlepts	Verified by apps/examples/nxlines.	YES
nxgl_circletraps	Verified by apps/examples/nxlines.	YES

NX Server Callbacks Test Coverage

Function	Special Setup/Notes	Verified
redraw()	.	YES
position()	.	YES
mousein()	.	YES
kbdin()	.	YES

NX API Test Coverage

Function	Special Setup/Notes	Verified
nx_runinstance()	.	YES
nx_connectinstance()	.	YES
nx_disconnect()	.	YES
nx_eventhandler()	.	YES
nx_eventnotify()	This is not used in the current version of apps/examples/nx, was tested in a previous version)	NO
nx_openwindow()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file	YES
nx_closewindow()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file	YES
nx_requestbkgd()	Verified by apps/examples/nxtext and apps/examples/nxhello.	YES
nx_releasebkgd()	Verified by apps/examples/nxtext and apps/examples/nxhello.	YES
nx_getposition()	.	NO
nx_setposition()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file	YES
nx_setsize()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file	YES
nx_raise()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file	YES
nx_lower()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file	YES
nx_modal()	.	NO
nx_setvisibility()	Exercized using Twm4Nx	YES, Informally
nx_ishidden()	Exercized using Twm4Nx	YES, Informally
nx_fill()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file	YES
nx_getrectangle()	.	YES
nx_filltrapezoid()	Verified by apps/examples/nxlines.	YES
nx_drawline()	by apps/examples/nxlines.	YES
nx_drawcircle()	Verified by apps/examples/nxlines.	YES
nx_fillcircle()	Verified by apps/examples/nxlines.	YES
nx_setbgcolor()	.	YES
nx_move()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file	YES
nx_bitmap()	Change to CONFIG_EXAMPLES_NX_RAWWINDOWS=y in the <NuttX-Directory>/.config file.	YES
nx_kbdin()	.	YES
nx_mousein()	.	YES

NXTK API Test Coverage

Function	Special Setup/Notes	Verified
nxtk_openwindow()	.	YES
nxtk_closewindow()	.	YES
nxtk_getposition()	.	NO
nxtk_setposition()	.	YES
nxtk_setsize()	.	YES
nxtk_raise()	.	YES
nxtk_lower()	.	YES
nxtk_modal()	.	NO
nxtk_setvisibility()	Exercized using Twm4Nx	YES, informally
nxtk_ishidden()	Exercized using Twm4Nx	YES, informally
nxtk_fillwindow()	.	YES
nxtk_getwindow()	.	NO
nxtk_filltrapwindow()	.	NO
nxtk_drawlinewindow()	.	YES
nxtk_drawcirclewindow()	.	YES
nxtk_fillcirclewindow()	.	YES
nxtk_movewindow()	.	NO
nxtk_bitmapwindow()	.	YES
nxtk_opentoolbar()	.	YES
nxtk_closetoolbar()	.	YES
nxtk_filltoolbar()	.	YES
nxtk_gettoolbar()	.	NO
nxtk_filltraptoolbar()	.	NO
nxtk_drawlinetoolbar()	.	NO
nxtk_drawcircletoolbar()	.	NO
nxtk_fillcircletoolbar()	.	NO
nxtk_movetoolbar()	.	NO
nxtk_bitmaptoolbar()	.	NO

NXFONTS API Test Coverage

Function	Special Setup/Notes	Verified
nxf_getfonthandle()	.	YES
nxf_getfontset()	.	YES
nxf_getbitmap()	.	YES
nxf_convert_2bpp()	.	NO
nxf_convert_4bpp()	.	NO
nxf_convert_8bpp()	Use defconfig when building.	YES
nxf_convert_16bpp()	.	YES
nxf_convert_24bpp()	.	NO
nxf_convert_32bpp()	.	YES