From 7b52cc13af4e85f1ca2deb6b6c77de9c95ea0dcf Mon Sep 17 00:00:00 2001 From: scuri Date: Fri, 17 Oct 2008 06:10:33 +0000 Subject: First commit - moving from LuaForge to SourceForge --- html/en/internal.html | 207 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 207 insertions(+) create mode 100644 html/en/internal.html (limited to 'html/en/internal.html') diff --git a/html/en/internal.html b/html/en/internal.html new file mode 100644 index 0000000..d919b84 --- /dev/null +++ b/html/en/internal.html @@ -0,0 +1,207 @@ + + + + +Internal Architecture + + + + + +

Internal Architecture

+ +

Modularity

+ + +

Apart from the several drivers, the CD library is composed of a few modules, the public + header files cd.h and wd.h, those which implement the functions + independently from drivers, cd*.c and wd.c, and the header file cd_private.h, + apart from some other modules which implement non-exported specific functions. Such + modules are totally independent from the implemented drivers, as well as every driver + independs from one another, unless there is an intentional dependency.

+ + +

Linking

+ + +

Since the drivers independ from one another, we could create a library for each of + them. For the drivers provided with CD it was easy to include them in their own library, + thus simplifying the application's linking process. Note: Internally, the drivers are + called "context".

In order to establish this dependency, when creating a canvas in a given driver the + user must specify the driver to be used. This specification is done by means of a macro + which is actually a function with no parameter, which passes the function table from that + driver to the canvas creation function. For instance:

+ +

CD_PS (is in fact) cdContextPS()
+cdCreateCanvas(CD_PS, "teste.ps"); (will do) canvas->Line = context->Line

If the context function is not invoqued then that driver does not need to be +linked with the application. This is usefull if the application uses a custom +build of the CD library and usefull for additional drivers not included in the +main library, like IUP and PDF, that have external dependencies.

+ + + +

Structures

+ + +

The core implementation defines the structures declared in the cd.h header. + But declares an undefined structure called cdCtxCanvas. This structure is + defined in each driver according to their needs. But the first member of this + structure must be a pointer to the cdCanvas structure.

The drivers need not to implement all functions from the function table, + only a few are required.

Here is the definition of the cdContext and cdCanvas structures:

+ + + + + + + +

struct _cdContext
+{
+  unsigned long caps;
+
+  /* can NOT be NULL */
+  void (*CreateCanvas)(cdCanvas* canvas, void *data);
+  void (*InitTable)(cdCanvas* canvas);
+
+  /* can be NULL */
+  int (*Play)(cdCanvas* canvas, int xmin, int xmax, int ymin, int ymax, void *data); 
+  int (*RegisterCallback)(int cb, cdCallback func);
+};

struct _cdCanvas
+{
+  ...
+  void (*Line)(cdCtxCanvas* ctxcanvas, int x1, int y1, int x2, int y2);
+  void (*Rect)(cdCtxCanvas* ctxcanvas, int xmin, int xmax, int ymin, int ymax);
+  void (*Box)(cdCtxCanvas* ctxcanvas, int xmin, int xmax, int ymin, int ymax);
+  ...
+
+  ...
+  int mark_type, mark_size;
+  int line_style, line_width;
+  int interior_style, hatch_style;
+  ...
+
+  cdVectorFont* vector_font;
+  cdSimulation* simulation;
+  cdCtxCanvas* ctxcanvas;     // context dependent defintion
+  cdContext* context;
+};

+ + + +

Internally each driver defines its cdCtxCanvas strcuture:

struct _cdCtxCanvas 
+{
+  cdCanvas* canvas;
+
+  char* filename; 
+
+  int last_line_style;
+  int last_fill_mode;
+  FILE* file;
+};

Then it must implement the cdcreatecanvas and cdinittable functions:

/* In the driver implementation file */
+
+static void cdcreatecanvas(cdCanvas *canvas, void *data)
+{
+  cdCtxCanvas* ctxcanvas = (cdCtxCanvas *)malloc(sizeof(cdCtxCanvas));
+
+  // parse data parameters
+  ...
+
+  ctxcanvas->canvas = canvas;
+  canvas->ctxcanvas = ctxcanvas;
+
+  /* update canvas context */
+  canvas->w = (int)(w_mm * res);
+  canvas->h = (int)(h_mm * res);
+  canvas->w_mm = w_mm;
+  canvas->h_mm = h_mm;
+  canvas->bpp = 24;
+  canvas->xres = res;
+  canvas->yres = res;
+}
+
+static void cdinittable(cdCanvas* canvas)
+{
+  canvas->Flush = cdflush;
+  canvas->Clear = cdclear;
+  canvas->Pixel = cdpixel;
+  canvas->Line = cdline;
+  canvas->Poly = cdpoly;
+  ...
+ }
+
+static cdContext cdMetafileContext =
+{
+  CD_CAP_ALL & ~(CD_CAP_GETIMAGERGB|CD_CAP_IMAGESRV|CD_CAP_REGION|CD_CAP_FONTDIM|CD_CAP_TEXTSIZE),
+  cdcreatecanvas,
+  cdinittable,
+  cdplay,
+  cdregistercallback,
+};
+
+cdContext* cdContextMetafile(void)
+{
+  return &cdMetafileContext;
+}

To simplify driver administration, the context structure's linking is done as follows:

+ +

/* In the header file */
+#define CD_METAFILE cdContextMetafile()
+cdContext* cdContextMetafile(void)
+

+ + + + +

Attributes

+ + +

The query mechanism of an attribute is done in the core and does not + depends on the driver. Due to this fact, the attributes which are modified several times for the same + value are not updated in the drivers, thus saving processing. Similarly, if an attribute + modification in a driver was not successful, its value is not updated. Nevertheless, the + fact that a driver does not implement the attribute's modification function does not mean + that it rejects that attribute - the driver just does not need to do anything with this + attribute on that moment and will query it later, before drawing the primitive.

The creation of customized attributes for each driver is made generically, using + string-like attributes. A structure with the attribute's name and its set and get + functions must be declared, as in the example below:

+ +

static void set_fill_attrib(cdCtxCanvas* ctxcanvas, char* data)
+{
+  ctxcanvas->fill_attrib[0] = data[0];
+}
+
+static char* get_fill_attrib(cdCtxCanvas* ctxcanvas)
+{
+  return ctxcanvas->fill_attrib;
+}
+
+static cdAttribute fill_attrib =
+{
+  "SIMPENFILLPOLY",
+  set_fill_attrib,
+  get_fill_attrib
+};

+ +

At createcanvas in the driver:

+ +

ctxcanvas->fill_attrib[0] = '1';
+ctxcanvas->fill_attrib[1] = 0;
+
+cdRegisterAttribute(canvas, &fill_attrib);

+ +

, for instance, must exist, thus initializing the attribute and registering it in the + canvas' attribute list.

+ + + + -- cgit v1.2.3