Canvas Initialization

CD - Canvas Draw

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Canvas Initialization

cdCanvas *cdCreateCanvas(cdContext* ctx, void *data); [in C]

cd.CreateCanvas(ctx: number, data: string or userdata) -> (canvas: cdCanvas) [in Lua]

Creates a CD canvas for a virtual visualization surface (VVS). A VVS may be the canvas of a user-interface window, the page of a document sent to a printer, an offscreen image, the clipboard, a metafile, and so on. To create the canvas, it is necessary to specify the driver in which each canvas is implemented.

The driver is set by the driver variable with additional information provided in the data parameter. Even though it is possible to create more than one canvas with the same driver/data pair, this is not recommended, and its behavior is not specified. Each canvas maintains its own features.

In case of failure, a  NULL value is returned. The following predefined drivers are available:

Window-Base Drivers

Device-Based Drivers

Image-Based Drivers 

File-Based Drivers 

  • CD_CGM = Computer Graphics Metafile ISO (cdcgm.h).
  • CD_DGN = MicroStation Design File (cddgn.h).
  • CD_DXF = AutoCad Drawing Interchange File (cddxf.h).
  • CD_EMF = Microsoft Windows Enhanced Metafile (cdemf.h). Works only in MS Windows systems.
  • CD_METAFILE = Metafile Canvas Draw (cdmf.h).
  • CD_PS = PostScript File (cdps.h).
  • CD_WMF = Microsoft Windows Metafile (cdwmf.h).
cdCanvas* cdCreateCanvasf(cdContext *ctx, const char* format, ...); [in C]

[There is no equivalent in Lua]

Same as cdCreateCanvas, used in the case that the parameter data is a string composed by several parameters. This function can be used with parameters equivalent to the printf function from the default C library.

void cdKillCanvas(cdCanvas *canvas); [in C]

cd.KillCanvas(canvas: cdCanvas) [in Lua]

Destroys a previously created canvas. If this function is not called in Lua, the garbage collector will call it.

int cdCanvasActivate(cdCanvas *canvas); [in C]

canvas:Activate(canvas: cdCanvas) -> (status: number) [in Lua]

Activates a canvas for drawing. This is used only for a few drivers. Native Window and IUP drivers will update the canvas size if the window size has changed. Double Buffer driver will recreate the image buffer if the window canvas size has changed. In these cases the function MUST be called, for other drivers is useless. Returns CD_ERROR or CD_OK.

void cdCanvasDeactivate(cdCanvas* canvas); [in C]

canvas:Deactivate(canvas: cdCanvas) [in Lua]

Called when the application has finished drawing in the canvas. It is optional, but if used for the Native Window driver in Windows when the handle can not be retained, the drawing can only be done again after a cdCanvasActivate. On some drivers will simply call Flush.

int cdUseContextPlus(int use); [in C]

cd.UseContextPlus(use: number) -> (old_use: number) [in Lua]

Activates or deactivates the use of an external context for the next calls of the cdCreateCanvas function.

void cdInitContextPlus(void); [in C]

Initializes the context driver to use another context replacing the standard drivers.

cdContext* cdCanvasGetContext(cdCanvas *canvas); [in C]

canvas:GetContext(canvas: cdCanvas) -> (ctx: number) [in Lua]

Returns the context of a given canvas, which can be compared with the predefined contexts, such as "CD_PS".

int cdContextCaps(cdContext* ctx); [in C]

cd.ContextCaps(ctx: number) -> (caps: number) [in Lua]

Returns the resources available for that context. To verify if a given resource is available, perform a binary AND ('&.html with the following values:

CD_CAP_FLUSH
CD_CAP_CLEAR
CD_CAP_PLAY
CD_CAP_YAXIS - The Y axis has the same orientation as the CD axis.
CD_CAP_CLIPAREA
CD_CAP_CLIPPOLY - Usually is not implemented.
CD_CAP_MARK - Marks are implemented directly in the driver (they are usually simulated).
CD_CAP_RECT - Rectangles are implemented directly in the driver (they are usually simulated).
CD_CAP_VECTORTEXT - Vector text is implemented directly in the driver (it is usually simulated).
CD_CAP_IMAGERGB
CD_CAP_IMAGERGBA - If this is not implemented, but cdGetImageRGB is, then it is simulated using cdGetImageRGB and cdPutImageRGB.
CD_CAP_IMAGEMAP
CD_CAP_GETIMAGERGB
CD_CAP_IMAGESRV - Usually is only implemented in contexts of window graphics systems (Native Window and IUP).
CD_CAP_BACKGROUND
CD_CAP_BACKOPACITY
CD_CAP_WRITEMODE
CD_CAP_LINESTYLE
CD_CAP_LINEWITH
CD_CAP_WD - Functions of world coordinates are implemented directly in the driver (they are usually simulated).
CD_CAP_HATCH
CD_CAP_STIPPLE
CD_CAP_PATTERN
CD_CAP_FONT
CD_CAP_FONTDIM - If not defined, the function is implemented using an internal heuristics of the library.
CD_CAP_TEXTSIZE - If not defined, the function is implemented using an internal heuristics of the library.
CD_CAP_TEXTORIENTATION - Usually is not implemented.
CD_CAP_PALETTE - Usually is only implemented in contexts of window graphics systems (Native Window and IUP).

int cdCanvasSimulate(cdCanvas* canvas, int mode); [in C]

canvas:Simulate(mode: number) -> (old_mode: number) [in Lua]

Activates the simulation of one or more primitives. It is ignored for the canvas in the ImageRGB context, because in this case everything is already simulated. It also has no effect for primitives that are usually simulated. It returns the previous simulation, but does not include primitives that are usually simulated. The simulation can be activated at any moment. For instance, if a line simulation is required only for a situation, the simulation can be activated for the line to be drawn, and then deactivated.

If simulation is activated the driver transformation matrix is disabled.

See in the Simulation sub-driver the information on how each simulation is performed.

To activate a given simulation, perform a binary OR ('|.html using one or more of the following values (in Lua, the values must be added '+.html:

CD_SIM_NONE - Deactivates all kinds of simulation.
CD_SIM_LINE
CD_SIM_RECT
CD_SIM_BOX
CD_SIM_ARC
CD_SIM_SECTOR
CD_SIM_CHORD
CD_SIM_POLYLINE
CD_SIM_POLYGON
CD_SIM_TEXT
CD_SIM_ALL - Activates all simulation options.
CD_SIM_LINES - Combination of CD_SIM_LINE, CD_SIM_RECT, CD_SIM_ARC and CD_SIM_POLYLINE.
CD_SIM_FILLS - Combination of CD_SIM_BOX, CD_SIM_SECTOR, CD_SIM_CHORD and CD_SIM_POLYGON.

Extras

int cdlua_open(lua_State* L); [for Lua 5]

Initializes the CDLua binding. In Lua 5 the binding is lua state safe, this means that several states can be initialized any time.

int cdlua_close(lua_State* L); [for Lua 5]

Releases the memory allocated by the CDLua binding.

cdCanvas* cdlua_checkcanvas(lua_State* L, int pos); [for Lua 5]

Returns the canvas in the Lua stack at position pos. The function will call lua_error if there is not a valid canvas in the stack at the given position.

void cdlua_pushcanvas(lua_State* L, cdCanvas* canvas);

Pushes the given canvas into the stack.

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