1.1 Overview

This document describes the tiny graphics support included in NuttX. It includes an overview description of that graphics support, detailed descriptions of the NuttX graphics APIs, and discussion of code organization, and OS configuration options.

Figure 1. This scren shot shows the final frame for the NuttX example at apps/examples/nx running on the simulated, Linux x86 platform with simulated framebuffer output to an X window. This picture shows to framed windows with (blank) toolbars. Each window has displayed text as received from the NX keyboard interface The second window has just been raised to the top of the display.

1.2 Objectives

The objective of this development was to provide a tiny windowing system in the spirit of X, but greatly scaled down and appropriate for most resource-limited embedded environments. The current NX implementation supports the general following, high-level features:

• Virtual Vertical Graphics Space. Windows that reside in a virtual, vertical space so that it makes sense to talk about one window being on top of another and obcuring the window below it.
• Client/Server Model. A standard client server/model was adopted. NX may be considered a server and other logic that presents the windows are NX clients.
• Single- and Multi-User Support. NX includes front-end logic to either a simple single-thread/single-user architecture or a separate NX server thread that can serve multiple NX client threads. In the single-user case, the NX server is simply a set of library calls; in the multi-user case, NX is a server thread/daemon the serializes graphics operations from multiple clients. Other some unique start-up/connection logic, the APIs supported by the single-user and multi-user front-ends are identical. Providing both front-ends is consistent with the NuttX commitment to scalability.
• Minimal Graphics Toolset. The actual implementation of the graphics operations is performed by common, back-end logic. This back-end supports only a primitive set of graphic and rendering operations.
• Device Interface. NX supports any graphics device either of two device interfaces:
  • Any device with random accesss video memory using the NuttX framebuffer driver interface (see include/nuttx/fb.h).
  • Any LCD-like device than can accept raster line runs through a parallel or serial interface (see include/nuttx/lcd/lcd.h). By default, NX is configured to use the frame buffer driver unless CONFIG_NX_LCDDRIVER is defined =y in your NuttX configuration file.
• Transparent to NX Client. The window client on "sees" the sub-window that is operates in and does not need to be concerned with the virtual, vertical space (other that to respond to redraw requests from NX when needed).
• Framed Windows and Toolbars. NX also adds the capability to support windows with frames and toolbars on top of the basic windowing support. These are windows such as those shown in the screenshot above. These framed windows sub-divide one one window into three relatively independent subwindows: A frame, the contained window and an (optional) toolbar window.
• Mouse Support. NX provides support for a mouse or other X/Y pointing devices. APIs are provided to allow external devices to give X/Y position information and mouse button presses to NX. NX will then provide the mouse input to the relevant window clients via callbacks. Client windows only receive the mouse input callback if the mouse is positioned over a visible portion of the client window; X/Y position is provided to the client in the relative coordinate system of the client window.
• Keyboard input. NX also supports keyboard/keypad devices. APIs are provided to allow external devices to give keypad information to NX. NX will then provide the mouse input to the top window on the display (the window that has the focus) via a callback function.

1.3 Organization

NX is organized into 6 (and perhaps someday 7 or 8) logical modules. These logical modules also correspond to the directory organization. That NuttX directory organization is discussed in Appendix B of this document. The logic modules are discussed in the following sub-paragraphs.

1.3.1 NX Graphics Library (NXGL)

NXGLIB is a standalone library that contains low-level graphics utilities and direct framebuffer or LCD rendering logic. NX is built on top NXGLIB.

1.3.2 NX (NXSU and NXMU)

NX is the tiny NuttX windowing system for raw windows (i.e., simple regions of graphics memory). NX includes both a small-footprint, single user implementaton (NXSU) and a somewhat larger multi-user implentation (NXMU as described below). Both conform to the same APIs as defined in include/nuttx/nx.h and, hence, are interchangable¹. NX can be used without NXWIDGETS and without NXTOOLKIT for raw window displays.

¹NXMU and NXSU are interchangeable other than (1) certain start-up and intialization APIs (as described below), and (2) timing. With NXSU, NX APIs execute immediately; with NXMU, NX APIs defer and serialize the operations and, hence, introduce different timing and potential race conditions that you would not experience with NXSU.

NXNULL? At one time, I also envisoned a NULL front-end that did not support windowing at all but, rather, simply provided the entire framebuffer or LCD memory as one dumb window. This has the advantage that the same NX APIs can be used on the one dumb window as for the other NX windows. This would be in the NuttX spirit of scalability.

However, the same end result can be obtained by using the nx_requestbkgd() API. It still may be possible to reduce the footprint in this usage case by developing and even thinner NXNULL front-end. That is a possible future development.

1.3.3 NX Tool Kit (NXTK)

NXTK is a s set of C graphics tools that provide higher-level window drawing operations. This is the module where the framed windows and toolbar logic is implemented. NXTK is built on top of NX and does not depend on NXWIDGETS.

1.3.4 NX Fonts Support (NXFONTS)

A set of C graphics tools for present (bitmap) font images. The font implementation is at a very low level or graphics operation, comparable to the logic in NXGLIB. NXFONTS does not depend on any NX module other than some utilities and types from NXGLIB.

1.3.5 NX Widgets (NXWIDGETS)

I had originally planned a high level, C++, object-oriented library for object-oriented access to graphics widgets. However, C++ compilers are not available for some of the targets supported by NuttX. So I have decided to implement the entire solution in C. That decision makes the solution somewhat more difficult to work with, but supports all platforms.

At this point, the amount of C in the implementation would make conversion to C++ a more difficult job. I leave the C++ widget interface to any contributor who may have an interest in such things.

2.1 NX Header Files

include/nuttx/nxglib.h

Describes the NXGLIB C interfaces

include/nuttx/nx.h

Describes the NX C interfaces

include/nutt/nxtk.h

Describe the NXTOOLKIT C interfaces

include/nutt/nxfont.h

Describe sthe NXFONT C interfaces

include/nuttx/nxwidgets.h

Will describe the NXWIDGETS classes (no longer planned)

2.2 NX Graphics Library (NXGL)

NXGL provides many APIs, some available for use internally by NX and others for use by applications as well. Only those APIs intended for application usage are documented here See include/nuttx/nxglib.h for the full set of APIs; those APIs might be of interest if you are rendering directly into framebuffer or LCD memory.

2.2.1 NXGL Types

nxgl_mxpixel_t. Holds one device pixel. NXGLIB will select the smallest size for the nxgl_mxpixel_t that just contains the pixel: byte if 16, 24, and 32 resolution support is disabled, uint16_t if 24, and 32 resolution support is disabled, or uint32_t.

nxgl_coord_t. A given coordinate is limited to the screen height an width. If either of those values exceed 32,767 pixels, then the following will have to need to change:

typedef int16_t nxgl_coord_t;

struct nxgl_point_s. Describes a point on the display:

struct nxgl_point_s
{
  nxgl_coord_t x;         /* X position, range: 0 to screen width - 1 */
  nxgl_coord_t y;         /* Y position, range: 0 to screen height - 1 */
};

struct nxgl_size_s. Describes the size of a rectangular region.

struct nxgl_size_s
{
  nxgl_coord_t w;        /* Width in pixels */
  nxgl_coord_t h;        /* Height in rows */
};

struct nxgl_rect_s. Describes a positioned rectangle on the display.

struct nxgl_rect_s
{
  struct nxgl_point_s pt1; /* Upper, left-hand corner */
  struct nxgl_point_s pt2; /* Lower, right-hand corner */
};

struct nxgl_run_s. Describes a run, i.e., a horizontal line. Note that the start/end positions have fractional precision. This is necessary for good joining of trapezoids when a more complex shape is decomposed into trapezoids

struct nxgl_run_s
{
  b16_t        x1;        /* Left X position, range: 0 to x2 */
  b16_t        x2;        /* Right X position, range: x1 to screen width - 1 */
  nxgl_coord_t y;         /* Top Y position, range: 0 to screen height - 1 */
};

struct nxgl_trapezoid_s. Describes a horizontal trapezoid on the display in terms the run at the top of the trapezoid and the run at the bottom

struct nxgl_trapezoid_s
{
  struct nxgl_run_s top;  /* Top run */
  struct nxgl_run_s bot;  /* bottom run */
};

2.2.1 nxgl_rgb2yuv()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_rgb2yuv(uint8_t r, uint8_t g, uint8_t b, uint8_t *y, uint8_t *u, uint8_t *v);

Description: Convert 8-bit RGB triplet to 8-bit YUV triplet.

2.2.2 nxgl_yuv2rgb()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_yuv2rgb(uint8_t y, uint8_t u, uint8_t v, uint8_t *r, uint8_t *g, uint8_t *b);

Description: Convert 8-bit RGB triplet to 8-bit YUV triplet.

2.2.3 nxgl_rectcopy()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_rectcopy(FAR struct nxgl_rect_s *dest,
                   FAR const struct nxgl_rect_s *src);

Description: This is essentially memcpy()for rectangles. We don't do structure assignments because some compilers are not good at that.

2.2.4 nxgl_rectoffset()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_rectoffset(FAR struct nxgl_rect_s *dest,
                     FAR const struct nxgl_rect_s *src,
                     nxgl_coord_t dx, nxgl_coord_t dy);

Description: Offset the rectangle position by the specified dx, dy values.

2.2.5 nxgl_vectoradd()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_vectoradd(FAR struct nxgl_point_s *dest,
                    FAR const struct nxgl_point_s *v1,
                    FAR const struct nxgl_point_s *v2);

Description: Add two 2x1 vectors and save the result to a third.

2.2.6 nxgl_vectorsubtract()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_vectsubtract(FAR struct nxgl_point_s *dest,
                       FAR const struct nxgl_point_s *v1,
                       FAR const struct nxgl_point_s *v2);

Description: Add subtract vector v2 from vector v1 and return the result in vector dest.

2.2.7 nxgl_rectintersect()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_rectintersect(FAR struct nxgl_rect_s *dest,
                        FAR const struct nxgl_rect_s *src1,
                        FAR const struct nxgl_rect_s *src2);

Description: Return the rectangle representing the intersection of the two rectangles.

2.2.8 nxgl_rectunion()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_rectunion(FAR struct nxgl_rect_s *dest,
                    FAR const struct nxgl_rect_s *src1,
                    FAR const struct nxgl_rect_s *src2);

Description: Given two rectanges, src1 and src2, return the larger rectangle that contains both, dest.

2.2.9 nxgl_nonintersecting()

Function Prototype:

#include <nuttx/nxglib.h>
nxgl_nonintersecting(FAR struct nxgl_rect_s result[4],
                     FAR const struct nxgl_rect_s *rect1,
                     FAR const struct nxgl_rect_s *rect2);

Description: Return the regions of rectangle rect1 that do not intersect with rect2. This will four rectangles, some of which may be degenerate (and can be picked off with nxgl_nullrect()).

2.2.10 nxgl_rectoverlap()

Function Prototype:

#include <nuttx/nxglib.h>
bool nxgl_rectoverlap(FAR struct nxgl_rect_s *rect1,
                      FAR struct nxgl_rect_s *rect2);

Description: Return true if the two rectangles overlap.

2.2.11 nxgl_rectinside()

Function Prototype:

#include <nuttx/nxglib.h>
bool nxgl_rectinside(FAR const struct nxgl_rect_s *rect,
                     FAR const struct nxgl_point_s *pt);

Description: Return true if the point pt lies within rect.

2.2.12 nxgl_rectsize()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_rectsize(FAR struct nxgl_size_s *size,
                   FAR const struct nxgl_rect_s *rect);

Description: Return the size of the specified rectangle.

2.2.13 nxgl_nullrect()

Function Prototype:

#include <nuttx/nxglib.h>
bool nxgl_nullrect(FAR const struct nxgl_rect_s *rect);

Description: Return true if the area of the retangle is <= 0.

2.2.14 nxgl_runoffset()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_runoffset(FAR struct nxgl_run_s *dest,
                    FAR const struct nxgl_run_s *src,
                    nxgl_coord_t dx, nxgl_coord_t dy);

Description: Offset the run position by the specified dx, dy values.

2.2.15 nxgl_runcopy()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_runcopy(FAR struct nxgl_run_s *dest,
                  FAR const struct nxgl_run_s *src);

Description: This is essentially memcpy()for runs. We don't do structure assignments because some compilers are not good at that.

2.2.16 nxgl_trapoffset()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_trapoffset(FAR struct nxgl_trapezoid_s *dest,
                     FAR const struct nxgl_trapezoid_s *src,
                     nxgl_coord_t dx, nxgl_coord_t dy);

Description: Offset the trapezoid position by the specified dx, dy values.

2.2.1 nxgl_trapcopy()

Function Prototype:

#include <nuttx/nxglib.h>
void nxgl_trapcopy(FAR struct nxgl_trapezoid_s *dest,
                   FAR const struct nxgl_trapezoid_s *src);

Description: This is essentially memcpy()for trapezoids. We don't do structure assignments because some compilers are not good at that.

2.2.1 nxgl_colorcopy

Function Prototype:

#include <nuttx/nxglib.h>
nxgl_colorcopy(nxgl_mxpixel_t dest[CONFIG_NX_NPLANES],
               const nxgl_mxpixel_t src[CONFIG_NX_NPLANES]);

Description: This is essentially memcpy()for colors. This does very little for us other than hide all of the conditional compilation for planar colors in one place.

2.3 NX

2.3.1 Pre-Processor Definitions

The default server message queue name used by the nx_run() macro:

#define NX_DEFAULT_SERVER_MQNAME "/dev/nxs"

Mouse button bits:

#define NX_MOUSE_NOBUTTONS    0x00
#define NX_MOUSE_LEFTBUTTON   0x01
#define NX_MOUSE_CENTERBUTTON 0x02
#define NX_MOUSE_RIGHTBUTTON  0x04

2.3.2 NX Types

The interface to the NX server is managed using a opaque handle:

typedef FAR void *NXHANDLE;

The interface to a specific window is managed using an opaque handle:

typedef FAR void *NXWINDOW;

These define callbacks that must be provided to nx_openwindow(). In the multi-user model, these callbacks will be invoked as part of the processing performed by nx_eventhandler().

struct nx_callback_s
{
  void (*redraw)(NXWINDOW hwnd, FAR const struct nxgl_rect_s *rect,
                 bool more, FAR void *arg);
  void (*position)(NXWINDOW hwnd, FAR const struct nxgl_size_s *size,
                   FAR const struct nxgl_point_s *pos,
                   FAR const struct nxgl_rect_s *bounds,
                   FAR void *arg);
#ifdef CONFIG_NX_MOUSE
  void (*mousein)(NXWINDOW hwnd, FAR const struct nxgl_point_s *pos,
                  uint8_t buttons, FAR void *arg);
#endif
#ifdef CONFIG_NX_KBD
  void (*kbdin)(NXWINDOW hwnd, uint8_t nch, FAR const uint8_t *ch, FAR void *arg);
#endif
};

2.3.3 NX Server Callbacks

2.3.3.1 redraw()

Callback Function Prototype:

void redraw(NXWINDOW hwnd, FAR const struct nxgl_rect_s *rect,
            bool more, FAR void *arg);

Description: NX requests that the client re-draw the portion of the window within with rectangle.

Input Parameters:

hwnd

The handle created by nx_openwindow() or nx_requestbkgd()

rect

The rectangle that needs to be re-drawn (in window relative coordinates)

more

true: More re-draw requests will follow

arg

User provided argument (see nx_openwindow())

Returned Value: None

2.3.3.2 position()

Callback Function Prototype:

void position(NXWINDOW hwnd, FAR const struct nxgl_size_s *size,
              FAR const struct nxgl_point_s *pos,
              FAR const struct nxgl_rect_s *bounds,
              FAR void *arg);

Description: The size or position of the window has changed (or the window was just created with zero size.

Input Parameters:

hwnd

The handle created by nx_openwindow() or nx_requestbkgd()

size

The size of the window

pos

The position of the upper left hand corner of the window on the overall display

bounds

The bounding rectangle that the describes the entire display

arg

User provided argument (see nx_openwindow())

Returned Value: None

2.3.3.3 mousein()

Callback Function Prototype:

#ifdef CONFIG_NX_MOUSE
void mousein(NXWINDOW hwnd, FAR const struct nxgl_point_s *pos,
             uint8_t buttons, FAR void *arg);
#endif

Description: New mouse data is available for the window

Input Parameters:

hwnd

The handle created by nx_openwindow() or nx_requestbkgd()

pos

The (x,y) position of the mouse

buttons

See NX_MOUSE_* definitions

arg

User provided argument (see nx_openwindow())

Returned Value: None

2.3.3.4 kbdin()

Callback Function Prototype:

#ifdef CONFIG_NX_KBD
void (*kbdin)(NXWINDOW hwnd, uint8_t nch, FAR const uint8_t *ch, FAR void *arg);
#endif

Description: New keyboard/keypad data is available for the window.

Input Parameters:

hwnd

The handle created by nx_openwindow() or nx_requestbkgd()

nch

The number of characters that are available in ch[]

ch

The array of characters

arg

User provided argument (see nx_openwindow())

Returned Value: None

2.3.4 nx_runinstance() (and nx_run() macro)

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#ifdef CONFIG_NX_MULTIUSER
int nx_runinstance(FAR const char *mqname, FAR struct fb_vtable_s *fb);
#define nx_run(fb) nx_runinstance(NX_DEFAULT_SERVER_MQNAME, dev)
#endif

Description: This is the server entry point. It does not return; the calling thread is dedicated to supporting NX server.

NOTE that multiple instances of the NX server may run at the same time, with different callback and message queue names. nx_run() is simply a macro that can be used when only one server instance is required. In that case, a default server name is used.

Multiple user mode only!

Input Parameters:

mqname

- The name for the server incoming message queue

dev

Framebuffer or LCD driver "object" to be used

Returned Value: This function usually does not return. If it does return, it will return ERROR and errno will be set appropriately.

2.3.5 nx_connectinstance() (and nx_connect() macro)

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#ifdef CONFIG_NX_MULTIUSER
NXHANDLE nx_connectinstance(FAR const char *svrmqname);
#define nx_connect(cb) nx_connectinstance(NX_DEFAULT_SERVER_MQNAME)
#endif

Description: Open a connection from a client to the NX server. One one client connection is normally needed per thread as each connection can host multiple windows.

NOTES:

• This function returns before the connection is fully instantiated. it is necessary to wait for the connection event before using the returned handle.
• Multiple instances of the NX server may run at the same time, each with different message queue names.
• nx_connect() is simply a macro that can be used when only one server instance is required. In that case, a default server name is used.

Multiple user mode only!

Input Parameters:

svrmqname

The name for the server incoming message queue

Returned Value:

Success: A non-NULL handle used with subsequent NX accesses
Failure: NULL is returned and errno is set appropriately.

2.3.6 nx_open()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#ifndef CONFIG_NX_MULTIUSER
NXHANDLE nx_open(FAR struct fb_vtable_s *dev);
#endif

Description: Create, initialize and return an NX handle for use in subsequent NX API calls. nx_open() is the single user equivalent of nx_connect() plus nx_run().

Single user mode only!

Input Parameters:

dev

Frame buffer or LCD driver "object" to be used.

cb

Callbacks used to process received NX server messages

Returned Value:

Success: A non-NULL handle used with subsequent NX accesses
Failure: NULL is returned and errno is set appropriately.

2.3.7 nx_disconnect()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#ifdef CONFIG_NX_MULTIUSER
void nx_disconnect(NXHANDLE handle);
#endif

Description: Disconnect a client from the NX server and/or free resources reserved by nx_connect()/nx_connectinstance(). nx_disconnect() is muliti-user equivalent of nx_close().

Multiple user mode only!

Input Parameters:

handle

The handle returned by nx_connect().

Returned Value: None.

2.3.8 nx_close()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#ifndef CONFIG_NX_MULTIUSER
void nx_close(NXHANDLE handle);
#endif

Description: Close the single user NX interface. nx_close is single-user equivalent of nx_disconnect().

Single user mode only!

Input Parameters:

handle

The handle returned by nx_open().

Returned Value: None

2.3.9 nx_eventhandler()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#ifdef CONFIG_NX_MULTIUSER
int nx_eventhandler(NXHANDLE handle);
#else
#  define nx_eventhandler(handle) (OK)
#endif

Description: The client code must call this function periodically to process incoming messages from the server. If CONFIG_NX_BLOCKING is defined, then this function not return until a server message is received.

When CONFIG_NX_BLOCKING is not defined, the client must exercise caution in the looping to assure that it does not eat up all of the CPU bandwidth calling nx_eventhandler repeatedly. nx_eventnotify() may be called to get a signal event whenever a new incoming server event is avaiable.

Input Parameters:

handle

The handle returned by nx_connect().

Returned Value:

• OK: No errors occurred. If CONFIG_NX_BLOCKING is defined, then one or more server messages were processed.
• ERROR: An error occurred and errno has been set appropriately. Of particular interest, it will return errno == EHOSTDOWN when the server is disconnected. After that event, the handle can no longer be used.

2.3.10 nx_eventnotify()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#if defined(CONFIG_NX_MULTIUSER) && !defined(CONFIG_DISABLE_SIGNALS)
int nx_eventnotify(NXHANDLE handle, int signo);
#else
#  define nx_eventnotify(handle, signo) (OK)
#endif

Description: Rather than calling nx_eventhandler() periodically, the client may register to receive a signal when a server event is available. The client can then call nv_eventhandler() only when incoming events are available.

The underlying implementation used mq_notifiy() and, as a result, the client must observe the rules for using mq_notifiy():

• Only one event is signaled. Upon receipt of the signal, if the client wishes further notifications, it must call nx_eventnotify() again.
• The signal will only be issued when the message queue transitions from empty to not empty.

Input Parameters:

handle

The handle returned by nx_connect().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.11 nx_openwindow()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

NXWINDOW nx_openwindow(NXHANDLE handle,
                       FAR const struct nx_callback_s *cb,
                       FAR void *arg);

Description: Create a new window.

Input Parameters:

handle

The handle returned by nx_connect() or nx_open().

cb

Callbacks used to process window events

arg

User provided value that will be returned with NX callbacks.

Returned Value:

Success: A non-NULL handle used with subsequent NX accesses
Failure: NULL is returned and errno is set appropriately.

2.3.12 nx_closewindow()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_closewindow(NXWINDOW hwnd);

Description: Destroy a window created by nx_openwindow() window.

Input Parameters:

hwnd

The handle returned by nx_openwindow() that identifies the window to be destroyed. This handle must not have been one returned by nx_requestbkgd().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.13 nx_requestbkgd()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_requestbkgd(NXHANDLE handle,
                   FAR const struct nx_callback_s *cb,
                   FAR void *arg);

Description: NX normally controls a separate window called the background window. It repaints the window as necessary using only a solid color fill. The background window always represents the entire screen and is always below other windows. It is useful for an application to control the background window in the following conditions:

• If you want to implement a windowless solution. The single screen can be used to creat a truly simple graphic environment. In this case, you should probably also de-select CONFIG_NX_MULTIUSER as well.
• When you want more on the background than a solid color. For example, if you want an image in the background, or animations in the background, or live video, etc.

This API only requests the handle of the background window. That handle will be returned asynchronously in a subsequent position and redraw callbacks.

Cautions:

• The following should never be called using the background window. They are guaranteed to cause severe crashes: nx_setposition(), nx_setsize(), nx_raise(), or nx_lower().
• Neither nx_requestbkgd() nor nx_releasebkgd () should be called more than once. Multiple instances of the background window are not supported.

Input Parameters:

handle

The handle returned by nx_connect() or nx_open().

cb

Callbacks to use for processing background window events

arg

User provided argument (see nx_openwindow())

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.14 nx_releasebkgd()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_releasebkgd(NXWINDOW hwnd);

Description: Release the background window previously acquired using nx_requestbkgd() and return control of the background to NX.

Input Parameters:

handle

The handle returned indirectly by nx_requestbkgd(). This handle must not have been one created by nx_openwindow().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.15 nx_getposition()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_getposition(NXWINDOW hwnd);

Description: Request the position and size information for the selected window. The values will be return asynchronously through the client callback function pointer.

Input Parameters:

hwnd

The handle returned by nx_openwindow() or nx_requestbkgd().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.16 nx_setposition()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_setposition(NXWINDOW hwnd, FAR struct nxgl_point_s *pos);

Description: Set the position and size for the selected window.

Input Parameters:

hwnd

The handle returned by nx_openwindow(). This handle must not have been created by nx_requestbkgd().

pos

The new position of the window

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.17 nx_setsize()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_setsize(NXWINDOW hwnd, FAR struct nxgl_size_s *size);

Description: Set the size of the selected window.

Input Parameters:

hwnd

The handle returned by nx_openwindow(). This handle must not have been created by nx_requestbkgd().

size

The new size of the window (in pixels).

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.18 nx_raise()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_raise(NXWINDOW hwnd);

Description: Bring the specified window to the top of the display.

Input Parameters:

hwnd

The handle returned by nx_openwindow(). This handle must not have been created by nx_requestbkgd().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.19 nx_lower()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_lower(NXWINDOW hwnd);

Description: Lower the specified window to the bottom of the display.

Input Parameters:

hwnd

The handle returned by nx_openwindow(). This handle must not have been created by nx_requestbkgd().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.20 nx_fill()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_fill(NXWINDOW hwnd, FAR const struct nxgl_rect_s *rect,
                   nxgl_mxpixel_t color[CONFIG_NX_NPLANES]);

Description: Fill the specified rectangle in the window with the specified color.

Input Parameters:

hwnd

The handle returned by nx_openwindow() or nx_requestbkgd()

rect

The location to be filled

color

The color to use in the fill

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.21 nx_filltrapezoid()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_filltrapezoid(NXWINDOW hwnd, FAR const struct nxgl_rect_s *clip,
                            FAR const struct nxgl_trapezoid_s *trap,
                            nxgl_mxpixel_t color[CONFIG_NX_NPLANES]);

Description: Fill the specified trapezoidal region in the window with the specified color.

Input Parameters:

hwnd

The handle returned by nx_openwindow() or nx_requestbkgd()

clip

Clipping rectangle relative to window (may be null)

trap

The trapezoidal region to be filled

color

The color to use in the fill

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.22 nx_setbgcolor()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_setbgcolor(NXHANDLE handle,
                  nxgl_mxpixel_t color[CONFIG_NX_NPLANES]);

Description: Set the color of the background.

Input Parameters:

handle

The handle created by nx_openwindow() or nx_requestbkgd()

color

The color to use in the background

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.23 nx_move()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_move(NXWINDOW hwnd, FAR const struct nxgl_rect_s *rect,
                   FAR const struct nxgl_point_s *offset);

Description: Move a rectangular region within the window.

Input Parameters:

hwnd

The handle returned by nx_openwindow() or nx_requestbkgd() that specifies the window within which the move is to be done

rect

Describes the (source) rectangular region to move

offset

The offset to move the region

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.24 nx_bitmap()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

int nx_bitmap(NXWINDOW hwnd, FAR const struct nxgl_rect_s *dest,
                     FAR const void *src[CONFIG_NX_NPLANES],
                     FAR const struct nxgl_point_s *origin,
                     unsigned int stride);

Description: Copy a rectangular region of a larger image into the rectangle in the specified window.

Input Parameters:

hwnd

The handle returned by nx_openwindow() or nx_requestbkgd() that specifies the window that will receive the bitmap image.

dest

Describes the rectangular on the display that will receive the bit map.

src

The start of the source image. This is an array source images of size CONFIG_NX_NPLANES (probably 1).

origin

The origin of the upper, left-most corner of the full bitmap. Both dest and origin are in window coordinates, however, the origin may lie outside of the display.

stride

The width of the full source image in bytes.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.25 nx_kbdin()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#ifdef CONFIG_NX_KBD
int nx_kbdchin(NXHANDLE handle, uint8_t ch);
int nx_kbdin(NXHANDLE handle, uint8_t nch, FAR const uint8_t *ch);
#endif

Description: Used by a thread or interrupt handler that manages some kind of keypad hardware to report text information to the NX server. That text data will be routed by the NX server to the appropriate window client.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.3.26 nx_mousein()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>

#ifdef CONFIG_NX_MOUSE
int nx_mousein(NXHANDLE handle, nxgl_coord_t x, nxgl_coord_t y, uint8_t buttons);
#endif

Description: Used by a thread or interrupt handler that manages some kind of pointing hardware to report new positional data to the NX server. That positional data will be routed by the NX server to the appropriate window client.

Input Parameters:

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4 NX Tool Kit (NXTK)

NXTK implements where the framed window. NX framed windows consist of three components within one NX window:

1. The window border,
2. The main client window area, and
3. A toolbar area

Each sub-window represents a region within one window. Figure 1 shows some simple NX framed windows. NXTK allows these sub-windows to be managed more-or-less independently:

• Each component has its own callbacks for redraw and position events as well as mouse and keyboard inputs. The client sub-window callbacks are registered when the framed window is created with a call to nxtk_openwindow(); Separate toolbar sub-window callbakcs are reigistered when the toolbar is added using nxtk_opentoolbar(). (NOTES: (1) only the client sub-window receives keyboard input and, (2) border callbacks are not currently accessible by the user).
All position informational provided within the callback is relative to the specific sub-window. That is, the origin (0,0) of the coordinate system for each sub-window begins at the top left corner of the subwindow. This means that toolbar logic need not be concerned about client window geometry (and vice versa) and, for example, common toolbar logic can be used with different windows.

2.4.1 NXTK Types()

This is the handle that can be used to access the window data region.

typedef FAR void *NXTKWINDOW;

2.4.2 nxtk_openwindow()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

NXTKWINDOW nxtk_openwindow(NXHANDLE handle,
                           FAR const struct nx_callback_s *cb,
                           FAR void *arg);

Description: Create a new, framed window.

Input Parameters:

handle

The handle returned by nx_connect() or nx_open().

cb

Callbacks used to process window events

arg

User provided argument (see nx_openwindow())

Returned Value:

Success: A non-NULL handle used with subsequent NXTK window accesses
Failure: NULL is returned and errno is set appropriately.

2.4.3 nxtk_closewindow()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_closewindow(NXTKWINDOW hfwnd);

Description: Close the window opened by nxtk_openwindow().

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.4 nxtk_getposition()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_getposition(NXTKWINDOW hfwnd);

Description: Request the position and size information for the selected framed window. The size/position for the client window and toolbar will be return asynchronously through the client callback function pointer.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.5 nxtk_setposition()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_setposition(NXTKWINDOW hfwnd, FAR struct nxgl_point_s *pos);

Description: Set the position for the selected client window. This position does not include the offsets for the borders nor for any toolbar. Those offsets will be added in to set the full window position.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

pos

The new position of the client sub-window

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.6 nxtk_setsize()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_setsize(NXTKWINDOW hfwnd, FAR struct nxgl_size_s *size);

Description: Set the size for the selected client window. This size does not include the sizes of the borders nor for any toolbar. Those sizes will be added in to set the full window size.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

size

The new size of the client sub-window.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.7 nxtk_raise()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_raise(NXTKWINDOW hfwnd);

Description: Bring the window containing the specified client sub-window to the top of the display.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow() specifying the window to be raised.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.8 nxtk_lower()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_lower(NXTKWINDOW hfwnd);

Description: Lower the window containing the specified client sub-window to the bottom of the display.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow() specifying the window to be lowered.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.9 nxtk_fillwindow()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_fillwindow(NXTKWINDOW hfwnd, FAR const struct nxgl_rect_s *rect,
                    nxgl_mxpixel_t color[CONFIG_NX_NPLANES]);

Description: Fill the specified rectangle in the client window with the specified color.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

rect

The location within the client window to be filled

color

The color to use in the fill

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.10 nxtk_filltrapwindow()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_filltrapwindow(NXTKWINDOW hfwnd,
                        FAR const struct nxgl_trapezoid_s *trap,
                        nxgl_mxpixel_t color[CONFIG_NX_NPLANES]);

Description: Fill the specified trapezoid in the client window with the specified color

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

trap

The trapezoidal region to be filled.

color

The color to use in the fill.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.11 nxtk_movewindow()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_movewindow(NXTKWINDOW hfwnd, FAR const struct nxgl_rect_s *rect,
                    FAR const struct nxgl_point_s *offset);

Description: Move a rectangular region within the client sub-window of a framed window.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow() specifying the client sub-window within which the move is to be done.

rect

Describes the rectangular region relative to the client sub-window to move.

offset

The offset to move the region

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.12 nxtk_bitmapwindow()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_bitmapwindow(NXTKWINDOW hfwnd,
                      FAR const struct nxgl_rect_s *dest,
                      FAR const void *src[CONFIG_NX_NPLANES],
                      FAR const struct nxgl_point_s *origin,
                      unsigned int stride);

Description: Copy a rectangular region of a larger image into the rectangle in the specified client sub-window.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow() specifying the client sub-window that will receive the bitmap.

dest

Describes the rectangular region on in the client sub-window will receive the bit map.

src

The start of the source image(s). This is an array source images of size CONFIG_NX_NPLANES (probably 1).

origin

The origin of the upper, left-most corner of the full bitmap. Both dest and origin are in sub-window coordinates, however, the origin may lie outside of the sub-window display.

stride

The width of the full source image in pixels.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.13 nxtk_opentoolbar()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_opentoolbar(NXTKWINDOW hfwnd, nxgl_coord_t height,
                     FAR const struct nx_callback_s *cb,
                     FAR void *arg);

Description: Create a tool bar at the top of the specified framed window.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

height

The requested height of the toolbar in pixels.

cb

Callbacks used to process toolbar events.

arg

User provided value that will be returned with toolbar callbacks.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.14 nxtk_closetoolbar()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_closetoolbar(NXTKWINDOW hfwnd);

Description: Remove the tool bar at the top of the specified framed window.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.15 nxtk_filltoolbar()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_filltoolbar(NXTKWINDOW hfwnd, FAR const struct nxgl_rect_s *rect,
                     nxgl_mxpixel_t color[CONFIG_NX_NPLANES]);

Description: Fill the specified rectangle in the toolbar sub-window with the specified color.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

rect

The location within the toolbar window to be filled.

color

The color to use in the fill.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.16 nxtk_filltraptoolbar()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_filltraptoolbar(NXTKWINDOW hfwnd, FAR const struct nxgl_trapezoid_s *trap,
                         nxgl_mxpixel_t color[CONFIG_NX_NPLANES]);

Description: Fill the specified trapezoid in the toolbar sub-window with the specified color.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

trap

The trapezoidal region to be filled

color

The color to use in the fill

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.17 nxtk_movetoolbar()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_movetoolbar(NXTKWINDOW hfwnd, FAR const struct nxgl_rect_s *rect,
                     FAR const struct nxgl_point_s *offset);

Description: Move a rectangular region within the toolbar sub-window of a framed window.

Input Parameters:

hfwnd

A handle identifying sub-window containing the toolbar within which the move is to be done. This handle must have previously been returned by nxtk_openwindow().

rect

Describes the rectangular region relative to the toolbar sub-window to move.

offset

The offset to move the region

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.4.18 nxtk_bitmaptoolbar()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nx.h>
#include <nuttx/nxtk.h>

int nxtk_bitmaptoolbar(NXTKWINDOW hfwnd,
                       FAR const struct nxgl_rect_s *dest,
                       FAR const void *src[CONFIG_NX_NPLANES],
                       FAR const struct nxgl_point_s *origin,
                       unsigned int stride);

Description: Copy a rectangular region of a larger image into the rectangle in the specified toolbar sub-window.

Input Parameters:

hfwnd

A handle previously returned by nxtk_openwindow().

dest

Describes the rectangular region on in the toolbar sub-window will receive the bit map.

src

The start of the source image.

origin

The origin of the upper, left-most corner of the full bitmap. Both dest and origin are in sub-window coordinates, however, the origin may lie outside of the sub-window display.

stride

The width of the full source image in bytes.

Returned Value: OK on success; ERROR on failure with errno set appropriately

2.5 NX Fonts Support (NXFONTS)

2.5.1 NXFONTS Types()

This structures provides the metrics for one glyph:

struct nx_fontmetric_s
{
  uint32_t stride   : 2;      /* Width of one font row in bytes */
  uint32_t width    : 6;      /* Width of the font in bits */
  uint32_t height   : 6;      /* Height of the font in rows */
  uint32_t xoffset  : 6;      /* Top, left-hand corner X-offset in pixels */
  uint32_t yoffset  : 6;      /* Top, left-hand corner y-offset in pixels */
  uint32_t unused   : 6;
};

This structure binds the glyph metrics to the glyph bitmap:

struct nx_fontbitmap_s
{
  struct nx_fontmetric_s metric; /* Character metrics */
  FAR const uint8_t *bitmap;     /* Pointer to the character bitmap */
};

This structure describes one contiguous grouping of glyphs that can be described by an array starting with encoding first and extending through (first + nchars - 1).

struct nx_fontset_s
{
  uint8_t  first;             /* First bitmap character code */
  uint8_t  nchars;            /* Number of bitmap character codes */
  FAR const struct nx_fontbitmap_s *bitmap;
};

This structure describes the overall fontset:

struct nx_font_s
{
  uint8_t  mxheight;          /* Max height of one glyph in rows */
  uint8_t  mxwidth;           /* Max width of any glyph in pixels */
  uint8_t  mxbits;            /* Max number of bits per character code */
  uint8_t  spwidth;           /* The width of a space in pixels */
};

2.5.2 nxf_getfonthandle()

Function Prototype:

#include <nuttx/nxfonts.h>

NXHANDLE nxf_getfonthandle(enum nx_fontid_e fontid);

Description: Given a numeric font ID, return a handle that may be subsequently be used to access the font data sets.

Input Parameters:

fontid

Identifies the font set to use

Returned Value: A handle that may be subsequently be used to access the font data sets.

2.5.3 nxf_getfontset()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nxfonts.h>

FAR const struct nx_font_s *nxf_getfontset(NXHANDLE handle);

Description: Return information about the current font set.

Input Parameters:

handle

A font handle previously returned by nxf_getfonthandle().

Returned Value: An instance of struct nx_font_s describing the font set.

2.5.4 nxf_getbitmap()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nxfonts.h>

FAR const struct nx_fontbitmap_s *nxf_getbitmap(NXHANDLE handle, uint16_t ch);

Description: Return font bitmap information for the selected character encoding.

Input Parameters:

ch

The char code for the requested bitmap.

handle

A font handle previously returned by nxf_getfonthandle().

Returned Value: An instance of struct nx_fontbitmap_s describing the glyph.

2.5.5 nxf_convert_*bpp()

Function Prototype:

#include <nuttx/nxglib.h>
#include <nuttx/nxfonts.h>

int nxf_convert_2bpp(FAR uint8_t *dest, uint16_t height,
                     uint16_t width, uint16_t stride,
                     FAR const struct nx_fontbitmap_s *bm,
                     nxgl_mxpixel_t color);
int nxf_convert_4bpp(FAR uint8_t *dest, uint16_t height,
                     uint16_t width, uint16_t stride,
                     FAR const struct nx_fontbitmap_s *bm,
                     nxgl_mxpixel_t color);
int nxf_convert_8bpp(FAR uint8_t *dest, uint16_t height,
                     uint16_t width, uint16_t stride,
                     FAR const struct nx_fontbitmap_s *bm,
                     nxgl_mxpixel_t color);
int nxf_convert_16bpp(FAR uint16_t *dest, uint16_t height,
                      uint16_t width, uint16_t stride,
                      FAR const struct nx_fontbitmap_s *bm,
                      nxgl_mxpixel_t color);
int nxf_convert_24bpp(FAR uint32_t *dest, uint16_t height,
                      uint16_t width, uint16_t stride,
                      FAR const struct nx_fontbitmap_s *bm,
                      nxgl_mxpixel_t color);
int nxf_convert_32bpp(FAR uint32_t *dest, uint16_t height,
                      uint16_t width, uint16_t stride,
                      FAR const struct nx_fontbitmap_s *bm,
                      nxgl_mxpixel_t color);

Description: Convert the 1BPP font to a new pixel depth.

Input Parameters:

dest

The destination buffer provided by the caller.

height

The max height of the returned char in rows.

width

The max width of the returned char in pixels.

stride

The width of the destination buffer in bytes.

bm

Describes the character glyph to convert

color

The color to use for '1' bits in the font bitmap (0 bits are transparent).

Returned Value: OK on success; ERROR on failure with errno set appropriately.

2.6 Sample Code

apps/examples/nx*. No sample code is provided in this document. However, examples can be found in the NuttX source tree at the follow locations: That example code is intended to test NX. Since it is test code, it is designed to exercise functionality and does not necessarily represent best NX coding practices.

• apps/examples/nx. This is a test of windows, optionally with toolbars. Two windows are created, re-sized, moved, raise lowered. Simulated mouse and keyboard input is provided.
• apps/examples/nxhello. This is intended to be simplest NX test: It simply displays the words "Hello, World!" centered on the display.
• apps/examples/nxtext. This illustrates how fonts may be managed to provide scrolling text windows. Pop-up windows are included to verify the clipping and re-drawing of the text display.

In its current form, the NX graphics system provides a low level of graphics and window support. Most of the complexity of manage redrawing and handling mouse and keyboard events must be implemented by the NX client code.

Building apps/examples/nx. Testing was performed using the Linux/Cygwin-based NuttX simulator. Instructions are provided for building that simulation are provided in Appendix C of this document.

graphics/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/nxsu

This is the NX single user front end. When combined with the generic back-end (nxbe), it implements a single threaded, single user windowing system. The files in this directory present the window APIs described in include/nuttx/nx.h. The single user front-end is selected when CONFIG_NX_MULTIUSER is not defined in the NuttX configuration file.

graphics/nxsu

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.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. The multi-user front-end is selected when CONFIG_NX_MULTIUSER is defined in the NuttX configuration file.

graphics/nxfonts

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

graphics/nxtk

This is where the NXTOOLKIT implementation resides. This toolkit is built on top of NX and works with either the single-user or multi-user NX version. See include/nuttx/nxtk.h.

graphics/nxwidgets

At one time, I planned to put NXWIDGETS implementation here, but not anymore.

B.1 General Configuration Settings

CONFIG_NX Enables overall support for graphics library and NX

B.2 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/fb.h). If this option is defined, NX will build to use an LCD driver (see include/nuttx/lcd/lcd.h).

B.3 NX Configuration Settings

CONFIG_NX_MOUSE:

Build in support for mouse input.

CONFIG_NX_KBD:

Build in support of keypad/keyboard input.

B.4 NX Multi-User (Only) Configuration Settings

CONFIG_NX_MULTIUSER:

Configures NX in multi-user mode.

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).

B.5 NXTK Configuration Settings

CONFIG_NXTK_BORDERWIDTH:

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

CONFIG_NXTK_BORDERCOLOR1 and CONFIG_NXTK_BORDERCOLOR2:

Specify the colors of the border used with framed windows.

CONFIG_NXTK_BORDERCOLOR2 is the shadow side color and so

is normally darker. The default is medium and dark 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.

B.6 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_SANS23X27:

At present, there is only one font, a 23x27 san serif font. But if there were were more, then this option would select that sans serif font.

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 configs/sim/nx. There are two alternative configurations for building the simulation:

1. The default configuration using the configuration file at configs/sim/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:

   cd <NuttX-Directory>/tools
   ./configure sim/nx
   cd  <NuttX-Directory>
   make
   ./nuttx
   

2. A preferred configuration extends the test with a simulated framebuffer driver that uses an X window as a framebuffer. This configuration uses the configuration file at configs/sim/nx/defconfig-x11. 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:

   cd <NuttX-Directory>/tools
   ./configure sim/nx
   cd  <NuttX-Directory>
   cp <NuttX-Directory>/configs/sim/nx/defconfig-x11 .config
   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 does not build under recent Cygwin configurations.
   • The X target does not build under current Ubuntu distributions; it fails to locate the X header files.
   • The sim target itself is broken under 64-bit Linux. This is because the sim target is based upon some assembly language setjmp/longjmp logic that only works on 32-bit systems.

     NOTE: There is a workaround in this case: You can build for 32-bit execution on a 64-bit machine by adding -m3 to the CFLAGS and -m32 -m elf_i386 to the LDFLAGS. See the patch file 0001-Quick-hacks-to-build-sim-nsh-ostest-on-x86_64-as-32-.patch that can be found in NuttX files.

Why isn't this configuration the default? Because not all systems the use NX support X.

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: